diff --git a/contrib/lax_der_privatekey_parsing.h b/contrib/lax_der_privatekey_parsing.h index 1a8ad8ae0c..3749e418fe 100644 --- a/contrib/lax_der_privatekey_parsing.h +++ b/contrib/lax_der_privatekey_parsing.h @@ -43,8 +43,7 @@ extern "C" { /** Export a private key in DER format. * * Returns: 1 if the private key was valid. - * Args: ctx: pointer to a context object, initialized for signing (cannot - * be NULL) + * Args: ctx: pointer to a context object (not secp256k1_context_static). * Out: privkey: pointer to an array for storing the private key in BER. * Should have space for 279 bytes, and cannot be NULL. * privkeylen: Pointer to an int where the length of the private key in diff --git a/doc/CHANGELOG.md b/doc/CHANGELOG.md index 08c42a2cab..a754e4e575 100644 --- a/doc/CHANGELOG.md +++ b/doc/CHANGELOG.md @@ -9,6 +9,13 @@ Each change falls into one of the following categories: Added, Changed, Deprecat ### Changed - Enable modules schnorrsig, extrakeys and ECDH by default in ./configure +### Deprecated + - Deprecated context flags `SECP256K1_CONTEXT_VERIFY` and `SECP256K1_CONTEXT_NONE`. Use `SECP256K1_CONTEXT_DEFAULT` instead. + - Renamed `secp256k1_context_no_precomp` to `secp256k1_context_static`. + +### Added + - Added `secp256k1_selftest`, to be used in conjunction with `secp256k1_context_static`. + ## [MAJOR.MINOR.PATCH] - YYYY-MM-DD ### Added/Changed/Deprecated/Removed/Fixed/Security diff --git a/examples/ecdh.c b/examples/ecdh.c index d7e8add361..f38cf02c22 100644 --- a/examples/ecdh.c +++ b/examples/ecdh.c @@ -11,7 +11,7 @@ #include #include -#include +#include #include #include "random.h" @@ -35,7 +35,8 @@ int main(void) { * a context with the SECP256K1_CONTEXT_SIGN flag. * (The docs for `secp256k1_ecdh` don't require any special context, just * some initialized context) */ - secp256k1_context* ctx = secp256k1_context_create(SECP256K1_CONTEXT_SIGN); + unsigned char mem[1000]; + secp256k1_context* ctx = secp256k1_context_preallocated_create(mem, SECP256K1_CONTEXT_SIGN); if (!fill_random(randomize, sizeof(randomize))) { printf("Failed to generate randomness\n"); return 1; @@ -109,7 +110,7 @@ int main(void) { print_hex(shared_secret1, sizeof(shared_secret1)); /* This will clear everything from the context and free the memory */ - secp256k1_context_destroy(ctx); + secp256k1_context_preallocated_destroy(ctx); /* It's best practice to try to clear secrets from memory after using them. * This is done because some bugs can allow an attacker to leak memory, for diff --git a/examples/ecdsa.c b/examples/ecdsa.c index 434c856ba0..decdb67f03 100644 --- a/examples/ecdsa.c +++ b/examples/ecdsa.c @@ -38,12 +38,8 @@ int main(void) { int return_val; secp256k1_pubkey pubkey; secp256k1_ecdsa_signature sig; - /* The specification in secp256k1.h states that `secp256k1_ec_pubkey_create` needs - * a context object initialized for signing and `secp256k1_ecdsa_verify` needs - * a context initialized for verification, which is why we create a context - * for both signing and verification with the SECP256K1_CONTEXT_SIGN and - * SECP256K1_CONTEXT_VERIFY flags. */ - secp256k1_context* ctx = secp256k1_context_create(SECP256K1_CONTEXT_SIGN | SECP256K1_CONTEXT_VERIFY); + /* Before we can call actual API functions, we need to create a "context". */ + secp256k1_context* ctx = secp256k1_context_create(SECP256K1_CONTEXT_DEFAULT); if (!fill_random(randomize, sizeof(randomize))) { printf("Failed to generate randomness\n"); return 1; diff --git a/examples/schnorr.c b/examples/schnorr.c index 82eb07d5d7..f4b79a4fc0 100644 --- a/examples/schnorr.c +++ b/examples/schnorr.c @@ -30,12 +30,8 @@ int main(void) { int return_val; secp256k1_xonly_pubkey pubkey; secp256k1_keypair keypair; - /* The specification in secp256k1_extrakeys.h states that `secp256k1_keypair_create` - * needs a context object initialized for signing. And in secp256k1_schnorrsig.h - * they state that `secp256k1_schnorrsig_verify` needs a context initialized for - * verification, which is why we create a context for both signing and verification - * with the SECP256K1_CONTEXT_SIGN and SECP256K1_CONTEXT_VERIFY flags. */ - secp256k1_context* ctx = secp256k1_context_create(SECP256K1_CONTEXT_SIGN | SECP256K1_CONTEXT_VERIFY); + /* Before we can call actual API functions, we need to create a "context". */ + secp256k1_context* ctx = secp256k1_context_create(SECP256K1_CONTEXT_DEFAULT); if (!fill_random(randomize, sizeof(randomize))) { printf("Failed to generate randomness\n"); return 1; diff --git a/include/secp256k1.h b/include/secp256k1.h index dddab346ae..b6810d5b13 100644 --- a/include/secp256k1.h +++ b/include/secp256k1.h @@ -5,34 +5,21 @@ extern "C" { #endif -#include +/** TODO Add some text that explains how the header files are organized */ -/* Unless explicitly stated all pointer arguments must not be NULL. +/** Opaque data structure that holds context information * - * The following rules specify the order of arguments in API calls: + * The primary purpose of context objects is to store randomization data for + * enhanced protection against side-channel leakage. This protection is only + * effective if the context is randomized after its creation. See + * secp256k1_context_create for creation of contexts and + * secp256k1_context_randomize for randomization. * - * 1. Context pointers go first, followed by output arguments, combined - * output/input arguments, and finally input-only arguments. - * 2. Array lengths always immediately follow the argument whose length - * they describe, even if this violates rule 1. - * 3. Within the OUT/OUTIN/IN groups, pointers to data that is typically generated - * later go first. This means: signatures, public nonces, secret nonces, - * messages, public keys, secret keys, tweaks. - * 4. Arguments that are not data pointers go last, from more complex to less - * complex: function pointers, algorithm names, messages, void pointers, - * counts, flags, booleans. - * 5. Opaque data pointers follow the function pointer they are to be passed to. - */ - -/** Opaque data structure that holds context information (precomputed tables etc.). - * - * The purpose of context structures is to cache large precomputed data tables - * that are expensive to construct, and also to maintain the randomization data - * for blinding. - * - * Do not create a new context object for each operation, as construction is - * far slower than all other API calls (~100 times slower than an ECDSA - * verification). + * A secondary purpose of context objects is to store pointers to callback + * functions that the library will call when certain error states arise. See + * secp256k1_context_set_error_callback as well as + * secp256k1_context_set_illegal_callback for details. Future library versions + * may use context objects for additional purposes. * * A constructed context can safely be used from multiple threads * simultaneously, but API calls that take a non-const pointer to a context @@ -45,7 +32,7 @@ extern "C" { */ typedef struct secp256k1_context_struct secp256k1_context; -/** Opaque data structure that holds rewriteable "scratch space" +/** Opaque data structure that holds rewritable "scratch space" * * The purpose of this structure is to replace dynamic memory allocations, * because we target architectures where this may not be available. It is @@ -58,177 +45,32 @@ typedef struct secp256k1_context_struct secp256k1_context; */ typedef struct secp256k1_scratch_space_struct secp256k1_scratch_space; -/** Opaque data structure that holds a parsed and valid public key. - * - * The exact representation of data inside is implementation defined and not - * guaranteed to be portable between different platforms or versions. It is - * however guaranteed to be 64 bytes in size, and can be safely copied/moved. - * If you need to convert to a format suitable for storage or transmission, - * use secp256k1_ec_pubkey_serialize and secp256k1_ec_pubkey_parse. To - * compare keys, use secp256k1_ec_pubkey_cmp. - */ -typedef struct { - unsigned char data[64]; -} secp256k1_pubkey; - -/** Opaque data structured that holds a parsed ECDSA signature. - * - * The exact representation of data inside is implementation defined and not - * guaranteed to be portable between different platforms or versions. It is - * however guaranteed to be 64 bytes in size, and can be safely copied/moved. - * If you need to convert to a format suitable for storage, transmission, or - * comparison, use the secp256k1_ecdsa_signature_serialize_* and - * secp256k1_ecdsa_signature_parse_* functions. - */ -typedef struct { - unsigned char data[64]; -} secp256k1_ecdsa_signature; - -/** A pointer to a function to deterministically generate a nonce. - * - * Returns: 1 if a nonce was successfully generated. 0 will cause signing to fail. - * Out: nonce32: pointer to a 32-byte array to be filled by the function. - * In: msg32: the 32-byte message hash being verified (will not be NULL) - * key32: pointer to a 32-byte secret key (will not be NULL) - * algo16: pointer to a 16-byte array describing the signature - * algorithm (will be NULL for ECDSA for compatibility). - * data: Arbitrary data pointer that is passed through. - * attempt: how many iterations we have tried to find a nonce. - * This will almost always be 0, but different attempt values - * are required to result in a different nonce. - * - * Except for test cases, this function should compute some cryptographic hash of - * the message, the algorithm, the key and the attempt. - */ -typedef int (*secp256k1_nonce_function)( - unsigned char *nonce32, - const unsigned char *msg32, - const unsigned char *key32, - const unsigned char *algo16, - void *data, - unsigned int attempt -); - -# if !defined(SECP256K1_GNUC_PREREQ) -# if defined(__GNUC__)&&defined(__GNUC_MINOR__) -# define SECP256K1_GNUC_PREREQ(_maj,_min) \ - ((__GNUC__<<16)+__GNUC_MINOR__>=((_maj)<<16)+(_min)) -# else -# define SECP256K1_GNUC_PREREQ(_maj,_min) 0 -# endif -# endif - -# if (!defined(__STDC_VERSION__) || (__STDC_VERSION__ < 199901L) ) -# if SECP256K1_GNUC_PREREQ(2,7) -# define SECP256K1_INLINE __inline__ -# elif (defined(_MSC_VER)) -# define SECP256K1_INLINE __inline -# else -# define SECP256K1_INLINE -# endif -# else -# define SECP256K1_INLINE inline -# endif - -/** When this header is used at build-time the SECP256K1_BUILD define needs to be set - * to correctly setup export attributes and nullness checks. This is normally done - * by secp256k1.c but to guard against this header being included before secp256k1.c - * has had a chance to set the define (e.g. via test harnesses that just includes - * secp256k1.c) we set SECP256K1_NO_BUILD when this header is processed without the - * BUILD define so this condition can be caught. - */ -#ifndef SECP256K1_BUILD -# define SECP256K1_NO_BUILD -#endif - -/** At secp256k1 build-time DLL_EXPORT is defined when building objects destined - * for a shared library, but not for those intended for static libraries. - */ - -#ifndef SECP256K1_API -# if defined(_WIN32) -# if defined(SECP256K1_BUILD) && defined(DLL_EXPORT) -# define SECP256K1_API __declspec(dllexport) -# else -# define SECP256K1_API -# endif -# elif defined(__GNUC__) && (__GNUC__ >= 4) && defined(SECP256K1_BUILD) -# define SECP256K1_API __attribute__ ((visibility ("default"))) -# else -# define SECP256K1_API -# endif -#endif - -/**Warning attributes - * NONNULL is not used if SECP256K1_BUILD is set to avoid the compiler optimizing out - * some paranoid null checks. */ -# if defined(__GNUC__) && SECP256K1_GNUC_PREREQ(3, 4) -# define SECP256K1_WARN_UNUSED_RESULT __attribute__ ((__warn_unused_result__)) -# else -# define SECP256K1_WARN_UNUSED_RESULT -# endif -# if !defined(SECP256K1_BUILD) && defined(__GNUC__) && SECP256K1_GNUC_PREREQ(3, 4) -# define SECP256K1_ARG_NONNULL(_x) __attribute__ ((__nonnull__(_x))) -# else -# define SECP256K1_ARG_NONNULL(_x) -# endif - -/** Attribute for marking functions, types, and variables as deprecated */ -#if !defined(SECP256K1_BUILD) && defined(__has_attribute) -# if __has_attribute(__deprecated__) -# define SECP256K1_DEPRECATED(_msg) __attribute__ ((__deprecated__(_msg))) -# else -# define SECP256K1_DEPRECATED(_msg) -# endif -#else -# define SECP256K1_DEPRECATED(_msg) -#endif - -/** All flags' lower 8 bits indicate what they're for. Do not use directly. */ -#define SECP256K1_FLAGS_TYPE_MASK ((1 << 8) - 1) -#define SECP256K1_FLAGS_TYPE_CONTEXT (1 << 0) -#define SECP256K1_FLAGS_TYPE_COMPRESSION (1 << 1) -/** The higher bits contain the actual data. Do not use directly. */ -#define SECP256K1_FLAGS_BIT_CONTEXT_VERIFY (1 << 8) -#define SECP256K1_FLAGS_BIT_CONTEXT_SIGN (1 << 9) -#define SECP256K1_FLAGS_BIT_CONTEXT_DECLASSIFY (1 << 10) -#define SECP256K1_FLAGS_BIT_COMPRESSION (1 << 8) - -/** Flags to pass to secp256k1_context_create, secp256k1_context_preallocated_size, and - * secp256k1_context_preallocated_create. */ -#define SECP256K1_CONTEXT_VERIFY (SECP256K1_FLAGS_TYPE_CONTEXT | SECP256K1_FLAGS_BIT_CONTEXT_VERIFY) -#define SECP256K1_CONTEXT_SIGN (SECP256K1_FLAGS_TYPE_CONTEXT | SECP256K1_FLAGS_BIT_CONTEXT_SIGN) -#define SECP256K1_CONTEXT_DECLASSIFY (SECP256K1_FLAGS_TYPE_CONTEXT | SECP256K1_FLAGS_BIT_CONTEXT_DECLASSIFY) -#define SECP256K1_CONTEXT_NONE (SECP256K1_FLAGS_TYPE_CONTEXT) - -/** Flag to pass to secp256k1_ec_pubkey_serialize. */ -#define SECP256K1_EC_COMPRESSED (SECP256K1_FLAGS_TYPE_COMPRESSION | SECP256K1_FLAGS_BIT_COMPRESSION) -#define SECP256K1_EC_UNCOMPRESSED (SECP256K1_FLAGS_TYPE_COMPRESSION) - -/** Prefix byte used to tag various encoded curvepoints for specific purposes */ -#define SECP256K1_TAG_PUBKEY_EVEN 0x02 -#define SECP256K1_TAG_PUBKEY_ODD 0x03 -#define SECP256K1_TAG_PUBKEY_UNCOMPRESSED 0x04 -#define SECP256K1_TAG_PUBKEY_HYBRID_EVEN 0x06 -#define SECP256K1_TAG_PUBKEY_HYBRID_ODD 0x07 - -/** A simple secp256k1 context object with no precomputed tables. These are useful for - * type serialization/parsing functions which require a context object to maintain - * API consistency, but currently do not require expensive precomputations or dynamic - * allocations. - */ -SECP256K1_API extern const secp256k1_context *secp256k1_context_no_precomp; +#include "secp256k1_main.h" /** Create a secp256k1 context object (in dynamically allocated memory). * * This function uses malloc to allocate memory. It is guaranteed that malloc is * called at most once for every call of this function. If you need to avoid dynamic - * memory allocation entirely, see the functions in secp256k1_preallocated.h. + * memory allocation entirely, see secp256k1_context_static and the functions in + * secp256k1_preallocated.h. * * Returns: a newly created context object. - * In: flags: which parts of the context to initialize. + * In: flags: Always set to SECP256K1_CONTEXT_DEFAULT (see below). + * + * Currently, the only valid non-deprecated flag is SECP256K1_CONTEXT_DEFAULT, which + * will create a context sufficient for all functionality currently offered by the + * library. All other (deprecated) flags will be treated as equivalent to the + * SECP256K1_CONTEXT_DEFAULT flag. Though the flags parameter primarily exists + * for historical reasons, future versions of the library may introduce new flags. * - * See also secp256k1_context_randomize. + * If the context is intended to be used for API functions that perform computations + * involving secret keys, e.g., signing and public key generation, then it is highly + * recommended to call secp256k1_context_randomize on the context before calling + * those API functions. This will provide enhanced protection against side-channel + * leakage, see secp256k1_context_randomize for details. + * + * Do not create a new context object for each operation, as construction and + * randomization can take non-negligible time. */ SECP256K1_API secp256k1_context* secp256k1_context_create( unsigned int flags @@ -264,577 +106,6 @@ SECP256K1_API void secp256k1_context_destroy( secp256k1_context* ctx ) SECP256K1_ARG_NONNULL(1); -/** Set a callback function to be called when an illegal argument is passed to - * an API call. It will only trigger for violations that are mentioned - * explicitly in the header. - * - * The philosophy is that these shouldn't be dealt with through a - * specific return value, as calling code should not have branches to deal with - * the case that this code itself is broken. - * - * On the other hand, during debug stage, one would want to be informed about - * such mistakes, and the default (crashing) may be inadvisable. - * When this callback is triggered, the API function called is guaranteed not - * to cause a crash, though its return value and output arguments are - * undefined. - * - * When this function has not been called (or called with fn==NULL), then the - * default handler will be used. The library provides a default handler which - * writes the message to stderr and calls abort. This default handler can be - * replaced at link time if the preprocessor macro - * USE_EXTERNAL_DEFAULT_CALLBACKS is defined, which is the case if the build - * has been configured with --enable-external-default-callbacks. Then the - * following two symbols must be provided to link against: - * - void secp256k1_default_illegal_callback_fn(const char* message, void* data); - * - void secp256k1_default_error_callback_fn(const char* message, void* data); - * The library can call these default handlers even before a proper callback data - * pointer could have been set using secp256k1_context_set_illegal_callback or - * secp256k1_context_set_error_callback, e.g., when the creation of a context - * fails. In this case, the corresponding default handler will be called with - * the data pointer argument set to NULL. - * - * Args: ctx: an existing context object. - * In: fun: a pointer to a function to call when an illegal argument is - * passed to the API, taking a message and an opaque pointer. - * (NULL restores the default handler.) - * data: the opaque pointer to pass to fun above, must be NULL for the default handler. - * - * See also secp256k1_context_set_error_callback. - */ -SECP256K1_API void secp256k1_context_set_illegal_callback( - secp256k1_context* ctx, - void (*fun)(const char* message, void* data), - const void* data -) SECP256K1_ARG_NONNULL(1); - -/** Set a callback function to be called when an internal consistency check - * fails. The default is crashing. - * - * This can only trigger in case of a hardware failure, miscompilation, - * memory corruption, serious bug in the library, or other error would can - * otherwise result in undefined behaviour. It will not trigger due to mere - * incorrect usage of the API (see secp256k1_context_set_illegal_callback - * for that). After this callback returns, anything may happen, including - * crashing. - * - * Args: ctx: an existing context object. - * In: fun: a pointer to a function to call when an internal error occurs, - * taking a message and an opaque pointer (NULL restores the - * default handler, see secp256k1_context_set_illegal_callback - * for details). - * data: the opaque pointer to pass to fun above, must be NULL for the default handler. - * - * See also secp256k1_context_set_illegal_callback. - */ -SECP256K1_API void secp256k1_context_set_error_callback( - secp256k1_context* ctx, - void (*fun)(const char* message, void* data), - const void* data -) SECP256K1_ARG_NONNULL(1); - -/** Create a secp256k1 scratch space object. - * - * Returns: a newly created scratch space. - * Args: ctx: an existing context object. - * In: size: amount of memory to be available as scratch space. Some extra - * (<100 bytes) will be allocated for extra accounting. - */ -SECP256K1_API SECP256K1_WARN_UNUSED_RESULT secp256k1_scratch_space* secp256k1_scratch_space_create( - const secp256k1_context* ctx, - size_t size -) SECP256K1_ARG_NONNULL(1); - -/** Destroy a secp256k1 scratch space. - * - * The pointer may not be used afterwards. - * Args: ctx: a secp256k1 context object. - * scratch: space to destroy - */ -SECP256K1_API void secp256k1_scratch_space_destroy( - const secp256k1_context* ctx, - secp256k1_scratch_space* scratch -) SECP256K1_ARG_NONNULL(1); - -/** Parse a variable-length public key into the pubkey object. - * - * Returns: 1 if the public key was fully valid. - * 0 if the public key could not be parsed or is invalid. - * Args: ctx: a secp256k1 context object. - * Out: pubkey: pointer to a pubkey object. If 1 is returned, it is set to a - * parsed version of input. If not, its value is undefined. - * In: input: pointer to a serialized public key - * inputlen: length of the array pointed to by input - * - * This function supports parsing compressed (33 bytes, header byte 0x02 or - * 0x03), uncompressed (65 bytes, header byte 0x04), or hybrid (65 bytes, header - * byte 0x06 or 0x07) format public keys. - */ -SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_pubkey_parse( - const secp256k1_context* ctx, - secp256k1_pubkey* pubkey, - const unsigned char *input, - size_t inputlen -) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3); - -/** Serialize a pubkey object into a serialized byte sequence. - * - * Returns: 1 always. - * Args: ctx: a secp256k1 context object. - * Out: output: a pointer to a 65-byte (if compressed==0) or 33-byte (if - * compressed==1) byte array to place the serialized key - * in. - * In/Out: outputlen: a pointer to an integer which is initially set to the - * size of output, and is overwritten with the written - * size. - * In: pubkey: a pointer to a secp256k1_pubkey containing an - * initialized public key. - * flags: SECP256K1_EC_COMPRESSED if serialization should be in - * compressed format, otherwise SECP256K1_EC_UNCOMPRESSED. - */ -SECP256K1_API int secp256k1_ec_pubkey_serialize( - const secp256k1_context* ctx, - unsigned char *output, - size_t *outputlen, - const secp256k1_pubkey* pubkey, - unsigned int flags -) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(4); - -/** Compare two public keys using lexicographic (of compressed serialization) order - * - * Returns: <0 if the first public key is less than the second - * >0 if the first public key is greater than the second - * 0 if the two public keys are equal - * Args: ctx: a secp256k1 context object. - * In: pubkey1: first public key to compare - * pubkey2: second public key to compare - */ -SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_pubkey_cmp( - const secp256k1_context* ctx, - const secp256k1_pubkey* pubkey1, - const secp256k1_pubkey* pubkey2 -) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3); - -/** Parse an ECDSA signature in compact (64 bytes) format. - * - * Returns: 1 when the signature could be parsed, 0 otherwise. - * Args: ctx: a secp256k1 context object - * Out: sig: a pointer to a signature object - * In: input64: a pointer to the 64-byte array to parse - * - * The signature must consist of a 32-byte big endian R value, followed by a - * 32-byte big endian S value. If R or S fall outside of [0..order-1], the - * encoding is invalid. R and S with value 0 are allowed in the encoding. - * - * After the call, sig will always be initialized. If parsing failed or R or - * S are zero, the resulting sig value is guaranteed to fail validation for any - * message and public key. - */ -SECP256K1_API int secp256k1_ecdsa_signature_parse_compact( - const secp256k1_context* ctx, - secp256k1_ecdsa_signature* sig, - const unsigned char *input64 -) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3); - -/** Parse a DER ECDSA signature. - * - * Returns: 1 when the signature could be parsed, 0 otherwise. - * Args: ctx: a secp256k1 context object - * Out: sig: a pointer to a signature object - * In: input: a pointer to the signature to be parsed - * inputlen: the length of the array pointed to be input - * - * This function will accept any valid DER encoded signature, even if the - * encoded numbers are out of range. - * - * After the call, sig will always be initialized. If parsing failed or the - * encoded numbers are out of range, signature validation with it is - * guaranteed to fail for every message and public key. - */ -SECP256K1_API int secp256k1_ecdsa_signature_parse_der( - const secp256k1_context* ctx, - secp256k1_ecdsa_signature* sig, - const unsigned char *input, - size_t inputlen -) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3); - -/** Serialize an ECDSA signature in DER format. - * - * Returns: 1 if enough space was available to serialize, 0 otherwise - * Args: ctx: a secp256k1 context object - * Out: output: a pointer to an array to store the DER serialization - * In/Out: outputlen: a pointer to a length integer. Initially, this integer - * should be set to the length of output. After the call - * it will be set to the length of the serialization (even - * if 0 was returned). - * In: sig: a pointer to an initialized signature object - */ -SECP256K1_API int secp256k1_ecdsa_signature_serialize_der( - const secp256k1_context* ctx, - unsigned char *output, - size_t *outputlen, - const secp256k1_ecdsa_signature* sig -) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(4); - -/** Serialize an ECDSA signature in compact (64 byte) format. - * - * Returns: 1 - * Args: ctx: a secp256k1 context object - * Out: output64: a pointer to a 64-byte array to store the compact serialization - * In: sig: a pointer to an initialized signature object - * - * See secp256k1_ecdsa_signature_parse_compact for details about the encoding. - */ -SECP256K1_API int secp256k1_ecdsa_signature_serialize_compact( - const secp256k1_context* ctx, - unsigned char *output64, - const secp256k1_ecdsa_signature* sig -) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3); - -/** Verify an ECDSA signature. - * - * Returns: 1: correct signature - * 0: incorrect or unparseable signature - * Args: ctx: a secp256k1 context object, initialized for verification. - * In: sig: the signature being verified. - * msghash32: the 32-byte message hash being verified. - * The verifier must make sure to apply a cryptographic - * hash function to the message by itself and not accept an - * msghash32 value directly. Otherwise, it would be easy to - * create a "valid" signature without knowledge of the - * secret key. See also - * https://bitcoin.stackexchange.com/a/81116/35586 for more - * background on this topic. - * pubkey: pointer to an initialized public key to verify with. - * - * To avoid accepting malleable signatures, only ECDSA signatures in lower-S - * form are accepted. - * - * If you need to accept ECDSA signatures from sources that do not obey this - * rule, apply secp256k1_ecdsa_signature_normalize to the signature prior to - * validation, but be aware that doing so results in malleable signatures. - * - * For details, see the comments for that function. - */ -SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ecdsa_verify( - const secp256k1_context* ctx, - const secp256k1_ecdsa_signature *sig, - const unsigned char *msghash32, - const secp256k1_pubkey *pubkey -) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(4); - -/** Convert a signature to a normalized lower-S form. - * - * Returns: 1 if sigin was not normalized, 0 if it already was. - * Args: ctx: a secp256k1 context object - * Out: sigout: a pointer to a signature to fill with the normalized form, - * or copy if the input was already normalized. (can be NULL if - * you're only interested in whether the input was already - * normalized). - * In: sigin: a pointer to a signature to check/normalize (can be identical to sigout) - * - * With ECDSA a third-party can forge a second distinct signature of the same - * message, given a single initial signature, but without knowing the key. This - * is done by negating the S value modulo the order of the curve, 'flipping' - * the sign of the random point R which is not included in the signature. - * - * Forgery of the same message isn't universally problematic, but in systems - * where message malleability or uniqueness of signatures is important this can - * cause issues. This forgery can be blocked by all verifiers forcing signers - * to use a normalized form. - * - * The lower-S form reduces the size of signatures slightly on average when - * variable length encodings (such as DER) are used and is cheap to verify, - * making it a good choice. Security of always using lower-S is assured because - * anyone can trivially modify a signature after the fact to enforce this - * property anyway. - * - * The lower S value is always between 0x1 and - * 0x7FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF5D576E7357A4501DDFE92F46681B20A0, - * inclusive. - * - * No other forms of ECDSA malleability are known and none seem likely, but - * there is no formal proof that ECDSA, even with this additional restriction, - * is free of other malleability. Commonly used serialization schemes will also - * accept various non-unique encodings, so care should be taken when this - * property is required for an application. - * - * The secp256k1_ecdsa_sign function will by default create signatures in the - * lower-S form, and secp256k1_ecdsa_verify will not accept others. In case - * signatures come from a system that cannot enforce this property, - * secp256k1_ecdsa_signature_normalize must be called before verification. - */ -SECP256K1_API int secp256k1_ecdsa_signature_normalize( - const secp256k1_context* ctx, - secp256k1_ecdsa_signature *sigout, - const secp256k1_ecdsa_signature *sigin -) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(3); - -/** An implementation of RFC6979 (using HMAC-SHA256) as nonce generation function. - * If a data pointer is passed, it is assumed to be a pointer to 32 bytes of - * extra entropy. - */ -SECP256K1_API extern const secp256k1_nonce_function secp256k1_nonce_function_rfc6979; - -/** A default safe nonce generation function (currently equal to secp256k1_nonce_function_rfc6979). */ -SECP256K1_API extern const secp256k1_nonce_function secp256k1_nonce_function_default; - -/** Create an ECDSA signature. - * - * Returns: 1: signature created - * 0: the nonce generation function failed, or the secret key was invalid. - * Args: ctx: pointer to a context object, initialized for signing. - * Out: sig: pointer to an array where the signature will be placed. - * In: msghash32: the 32-byte message hash being signed. - * seckey: pointer to a 32-byte secret key. - * noncefp: pointer to a nonce generation function. If NULL, - * secp256k1_nonce_function_default is used. - * ndata: pointer to arbitrary data used by the nonce generation function - * (can be NULL). If it is non-NULL and - * secp256k1_nonce_function_default is used, then ndata must be a - * pointer to 32-bytes of additional data. - * - * The created signature is always in lower-S form. See - * secp256k1_ecdsa_signature_normalize for more details. - */ -SECP256K1_API int secp256k1_ecdsa_sign( - const secp256k1_context* ctx, - secp256k1_ecdsa_signature *sig, - const unsigned char *msghash32, - const unsigned char *seckey, - secp256k1_nonce_function noncefp, - const void *ndata -) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(4); - -/** Verify an ECDSA secret key. - * - * A secret key is valid if it is not 0 and less than the secp256k1 curve order - * when interpreted as an integer (most significant byte first). The - * probability of choosing a 32-byte string uniformly at random which is an - * invalid secret key is negligible. - * - * Returns: 1: secret key is valid - * 0: secret key is invalid - * Args: ctx: pointer to a context object. - * In: seckey: pointer to a 32-byte secret key. - */ -SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_seckey_verify( - const secp256k1_context* ctx, - const unsigned char *seckey -) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2); - -/** Compute the public key for a secret key. - * - * Returns: 1: secret was valid, public key stores. - * 0: secret was invalid, try again. - * Args: ctx: pointer to a context object, initialized for signing. - * Out: pubkey: pointer to the created public key. - * In: seckey: pointer to a 32-byte secret key. - */ -SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_pubkey_create( - const secp256k1_context* ctx, - secp256k1_pubkey *pubkey, - const unsigned char *seckey -) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3); - -/** Negates a secret key in place. - * - * Returns: 0 if the given secret key is invalid according to - * secp256k1_ec_seckey_verify. 1 otherwise - * Args: ctx: pointer to a context object - * In/Out: seckey: pointer to the 32-byte secret key to be negated. If the - * secret key is invalid according to - * secp256k1_ec_seckey_verify, this function returns 0 and - * seckey will be set to some unspecified value. - */ -SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_seckey_negate( - const secp256k1_context* ctx, - unsigned char *seckey -) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2); - -/** Same as secp256k1_ec_seckey_negate, but DEPRECATED. Will be removed in - * future versions. */ -SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_privkey_negate( - const secp256k1_context* ctx, - unsigned char *seckey -) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) - SECP256K1_DEPRECATED("Use secp256k1_ec_seckey_negate instead"); - -/** Negates a public key in place. - * - * Returns: 1 always - * Args: ctx: pointer to a context object - * In/Out: pubkey: pointer to the public key to be negated. - */ -SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_pubkey_negate( - const secp256k1_context* ctx, - secp256k1_pubkey *pubkey -) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2); - -/** Tweak a secret key by adding tweak to it. - * - * Returns: 0 if the arguments are invalid or the resulting secret key would be - * invalid (only when the tweak is the negation of the secret key). 1 - * otherwise. - * Args: ctx: pointer to a context object. - * In/Out: seckey: pointer to a 32-byte secret key. If the secret key is - * invalid according to secp256k1_ec_seckey_verify, this - * function returns 0. seckey will be set to some unspecified - * value if this function returns 0. - * In: tweak32: pointer to a 32-byte tweak. If the tweak is invalid according to - * secp256k1_ec_seckey_verify, this function returns 0. For - * uniformly random 32-byte arrays the chance of being invalid - * is negligible (around 1 in 2^128). - */ -SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_seckey_tweak_add( - const secp256k1_context* ctx, - unsigned char *seckey, - const unsigned char *tweak32 -) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3); - -/** Same as secp256k1_ec_seckey_tweak_add, but DEPRECATED. Will be removed in - * future versions. */ -SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_privkey_tweak_add( - const secp256k1_context* ctx, - unsigned char *seckey, - const unsigned char *tweak32 -) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) - SECP256K1_DEPRECATED("Use secp256k1_ec_seckey_tweak_add instead"); - -/** Tweak a public key by adding tweak times the generator to it. - * - * Returns: 0 if the arguments are invalid or the resulting public key would be - * invalid (only when the tweak is the negation of the corresponding - * secret key). 1 otherwise. - * Args: ctx: pointer to a context object initialized for validation. - * In/Out: pubkey: pointer to a public key object. pubkey will be set to an - * invalid value if this function returns 0. - * In: tweak32: pointer to a 32-byte tweak. If the tweak is invalid according to - * secp256k1_ec_seckey_verify, this function returns 0. For - * uniformly random 32-byte arrays the chance of being invalid - * is negligible (around 1 in 2^128). - */ -SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_pubkey_tweak_add( - const secp256k1_context* ctx, - secp256k1_pubkey *pubkey, - const unsigned char *tweak32 -) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3); - -/** Tweak a secret key by multiplying it by a tweak. - * - * Returns: 0 if the arguments are invalid. 1 otherwise. - * Args: ctx: pointer to a context object. - * In/Out: seckey: pointer to a 32-byte secret key. If the secret key is - * invalid according to secp256k1_ec_seckey_verify, this - * function returns 0. seckey will be set to some unspecified - * value if this function returns 0. - * In: tweak32: pointer to a 32-byte tweak. If the tweak is invalid according to - * secp256k1_ec_seckey_verify, this function returns 0. For - * uniformly random 32-byte arrays the chance of being invalid - * is negligible (around 1 in 2^128). - */ -SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_seckey_tweak_mul( - const secp256k1_context* ctx, - unsigned char *seckey, - const unsigned char *tweak32 -) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3); - -/** Same as secp256k1_ec_seckey_tweak_mul, but DEPRECATED. Will be removed in - * future versions. */ -SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_privkey_tweak_mul( - const secp256k1_context* ctx, - unsigned char *seckey, - const unsigned char *tweak32 -) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) - SECP256K1_DEPRECATED("Use secp256k1_ec_seckey_tweak_mul instead"); - -/** Tweak a public key by multiplying it by a tweak value. - * - * Returns: 0 if the arguments are invalid. 1 otherwise. - * Args: ctx: pointer to a context object initialized for validation. - * In/Out: pubkey: pointer to a public key object. pubkey will be set to an - * invalid value if this function returns 0. - * In: tweak32: pointer to a 32-byte tweak. If the tweak is invalid according to - * secp256k1_ec_seckey_verify, this function returns 0. For - * uniformly random 32-byte arrays the chance of being invalid - * is negligible (around 1 in 2^128). - */ -SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_pubkey_tweak_mul( - const secp256k1_context* ctx, - secp256k1_pubkey *pubkey, - const unsigned char *tweak32 -) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3); - -/** Updates the context randomization to protect against side-channel leakage. - * Returns: 1: randomization successfully updated or nothing to randomize - * 0: error - * Args: ctx: pointer to a context object. - * In: seed32: pointer to a 32-byte random seed (NULL resets to initial state) - * - * While secp256k1 code is written to be constant-time no matter what secret - * values are, it's possible that a future compiler may output code which isn't, - * and also that the CPU may not emit the same radio frequencies or draw the same - * amount power for all values. - * - * This function provides a seed which is combined into the blinding value: that - * blinding value is added before each multiplication (and removed afterwards) so - * that it does not affect function results, but shields against attacks which - * rely on any input-dependent behaviour. - * - * This function has currently an effect only on contexts initialized for signing - * because randomization is currently used only for signing. However, this is not - * guaranteed and may change in the future. It is safe to call this function on - * contexts not initialized for signing; then it will have no effect and return 1. - * - * You should call this after secp256k1_context_create or - * secp256k1_context_clone (and secp256k1_context_preallocated_create or - * secp256k1_context_clone, resp.), and you may call this repeatedly afterwards. - */ -SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_context_randomize( - secp256k1_context* ctx, - const unsigned char *seed32 -) SECP256K1_ARG_NONNULL(1); - -/** Add a number of public keys together. - * - * Returns: 1: the sum of the public keys is valid. - * 0: the sum of the public keys is not valid. - * Args: ctx: pointer to a context object. - * Out: out: pointer to a public key object for placing the resulting public key. - * In: ins: pointer to array of pointers to public keys. - * n: the number of public keys to add together (must be at least 1). - */ -SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_pubkey_combine( - const secp256k1_context* ctx, - secp256k1_pubkey *out, - const secp256k1_pubkey * const * ins, - size_t n -) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3); - -/** Compute a tagged hash as defined in BIP-340. - * - * This is useful for creating a message hash and achieving domain separation - * through an application-specific tag. This function returns - * SHA256(SHA256(tag)||SHA256(tag)||msg). Therefore, tagged hash - * implementations optimized for a specific tag can precompute the SHA256 state - * after hashing the tag hashes. - * - * Returns: 1 always. - * Args: ctx: pointer to a context object - * Out: hash32: pointer to a 32-byte array to store the resulting hash - * In: tag: pointer to an array containing the tag - * taglen: length of the tag array - * msg: pointer to an array containing the message - * msglen: length of the message array - */ -SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_tagged_sha256( - const secp256k1_context* ctx, - unsigned char *hash32, - const unsigned char *tag, - size_t taglen, - const unsigned char *msg, - size_t msglen -) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(5); - #ifdef __cplusplus } #endif diff --git a/include/secp256k1_ecdh.h b/include/secp256k1_ecdh.h index c8577984b1..621dcae8d8 100644 --- a/include/secp256k1_ecdh.h +++ b/include/secp256k1_ecdh.h @@ -1,8 +1,6 @@ #ifndef SECP256K1_ECDH_H #define SECP256K1_ECDH_H -#include "secp256k1.h" - #ifdef __cplusplus extern "C" { #endif diff --git a/include/secp256k1_extrakeys.h b/include/secp256k1_extrakeys.h index 09cbeaaa80..5dc7111231 100644 --- a/include/secp256k1_extrakeys.h +++ b/include/secp256k1_extrakeys.h @@ -1,8 +1,6 @@ #ifndef SECP256K1_EXTRAKEYS_H #define SECP256K1_EXTRAKEYS_H -#include "secp256k1.h" - #ifdef __cplusplus extern "C" { #endif @@ -108,7 +106,7 @@ SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_xonly_pubkey_from_pubke * invalid (only when the tweak is the negation of the corresponding * secret key). 1 otherwise. * - * Args: ctx: pointer to a context object initialized for verification. + * Args: ctx: pointer to a context object. * Out: output_pubkey: pointer to a public key to store the result. Will be set * to an invalid value if this function returns 0. * In: internal_pubkey: pointer to an x-only pubkey to apply the tweak to. @@ -137,7 +135,7 @@ SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_xonly_pubkey_tweak_add( * * Returns: 0 if the arguments are invalid or the tweaked pubkey is not the * result of tweaking the internal_pubkey with tweak32. 1 otherwise. - * Args: ctx: pointer to a context object initialized for verification. + * Args: ctx: pointer to a context object. * In: tweaked_pubkey32: pointer to a serialized xonly_pubkey. * tweaked_pk_parity: the parity of the tweaked pubkey (whose serialization * is passed in as tweaked_pubkey32). This must match the @@ -159,7 +157,7 @@ SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_xonly_pubkey_tweak_add_ * * Returns: 1: secret was valid, keypair is ready to use * 0: secret was invalid, try again with a different secret - * Args: ctx: pointer to a context object, initialized for signing. + * Args: ctx: pointer to a context object (not secp256k1_context_static). * Out: keypair: pointer to the created keypair. * In: seckey: pointer to a 32-byte secret key. */ @@ -228,7 +226,7 @@ SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_keypair_xonly_pub( * invalid (only when the tweak is the negation of the keypair's * secret key). 1 otherwise. * - * Args: ctx: pointer to a context object initialized for verification. + * Args: ctx: pointer to a context object. * In/Out: keypair: pointer to a keypair to apply the tweak to. Will be set to * an invalid value if this function returns 0. * In: tweak32: pointer to a 32-byte tweak. If the tweak is invalid according diff --git a/include/secp256k1_main.h b/include/secp256k1_main.h new file mode 100644 index 0000000000..b4188a8bff --- /dev/null +++ b/include/secp256k1_main.h @@ -0,0 +1,812 @@ +#ifndef SECP256K1_MAIN_H +#define SECP256K1_MAIN_H + +#ifdef __cplusplus +extern "C" { +#endif + +#include + +/** Unless explicitly stated all pointer arguments must not be NULL. + * + * The following rules specify the order of arguments in API calls: + * + * 1. Context pointers go first, followed by output arguments, combined + * output/input arguments, and finally input-only arguments. + * 2. Array lengths always immediately follow the argument whose length + * they describe, even if this violates rule 1. + * 3. Within the OUT/OUTIN/IN groups, pointers to data that is typically generated + * later go first. This means: signatures, public nonces, secret nonces, + * messages, public keys, secret keys, tweaks. + * 4. Arguments that are not data pointers go last, from more complex to less + * complex: function pointers, algorithm names, messages, void pointers, + * counts, flags, booleans. + * 5. Opaque data pointers follow the function pointer they are to be passed to. + */ + +/** Opaque data structure that holds a parsed and valid public key. + * + * The exact representation of data inside is implementation defined and not + * guaranteed to be portable between different platforms or versions. It is + * however guaranteed to be 64 bytes in size, and can be safely copied/moved. + * If you need to convert to a format suitable for storage or transmission, + * use secp256k1_ec_pubkey_serialize and secp256k1_ec_pubkey_parse. To + * compare keys, use secp256k1_ec_pubkey_cmp. + */ +typedef struct { + unsigned char data[64]; +} secp256k1_pubkey; + +/** Opaque data structured that holds a parsed ECDSA signature. + * + * The exact representation of data inside is implementation defined and not + * guaranteed to be portable between different platforms or versions. It is + * however guaranteed to be 64 bytes in size, and can be safely copied/moved. + * If you need to convert to a format suitable for storage, transmission, or + * comparison, use the secp256k1_ecdsa_signature_serialize_* and + * secp256k1_ecdsa_signature_parse_* functions. + */ +typedef struct { + unsigned char data[64]; +} secp256k1_ecdsa_signature; + +/** A pointer to a function to deterministically generate a nonce. + * + * Returns: 1 if a nonce was successfully generated. 0 will cause signing to fail. + * Out: nonce32: pointer to a 32-byte array to be filled by the function. + * In: msg32: the 32-byte message hash being verified (will not be NULL) + * key32: pointer to a 32-byte secret key (will not be NULL) + * algo16: pointer to a 16-byte array describing the signature + * algorithm (will be NULL for ECDSA for compatibility). + * data: Arbitrary data pointer that is passed through. + * attempt: how many iterations we have tried to find a nonce. + * This will almost always be 0, but different attempt values + * are required to result in a different nonce. + * + * Except for test cases, this function should compute some cryptographic hash of + * the message, the algorithm, the key and the attempt. + */ +typedef int (*secp256k1_nonce_function)( + unsigned char *nonce32, + const unsigned char *msg32, + const unsigned char *key32, + const unsigned char *algo16, + void *data, + unsigned int attempt +); + +# if !defined(SECP256K1_GNUC_PREREQ) +# if defined(__GNUC__)&&defined(__GNUC_MINOR__) +# define SECP256K1_GNUC_PREREQ(_maj,_min) \ + ((__GNUC__<<16)+__GNUC_MINOR__>=((_maj)<<16)+(_min)) +# else +# define SECP256K1_GNUC_PREREQ(_maj,_min) 0 +# endif +# endif + +# if (!defined(__STDC_VERSION__) || (__STDC_VERSION__ < 199901L) ) +# if SECP256K1_GNUC_PREREQ(2,7) +# define SECP256K1_INLINE __inline__ +# elif (defined(_MSC_VER)) +# define SECP256K1_INLINE __inline +# else +# define SECP256K1_INLINE +# endif +# else +# define SECP256K1_INLINE inline +# endif + +/* When this header is used at build-time the SECP256K1_BUILD define needs to be set + * to correctly setup export attributes and nullness checks. This is normally done + * by secp256k1.c but to guard against this header being included before secp256k1.c + * has had a chance to set the define (e.g. via test harnesses that just includes + * secp256k1.c) we set SECP256K1_NO_BUILD when this header is processed without the + * BUILD define so this condition can be caught. + */ +#ifndef SECP256K1_BUILD +# define SECP256K1_NO_BUILD +#endif + +/** At secp256k1 build-time DLL_EXPORT is defined when building objects destined + * for a shared library, but not for those intended for static libraries. + */ + +#ifndef SECP256K1_API +# if defined(_WIN32) +# if defined(SECP256K1_BUILD) && defined(DLL_EXPORT) +# define SECP256K1_API __declspec(dllexport) +# else +# define SECP256K1_API +# endif +# elif defined(__GNUC__) && (__GNUC__ >= 4) && defined(SECP256K1_BUILD) +# define SECP256K1_API __attribute__ ((visibility ("default"))) +# else +# define SECP256K1_API +# endif +#endif + +/* Warning attributes + * NONNULL is not used if SECP256K1_BUILD is set to avoid the compiler optimizing out + * some paranoid null checks. */ +# if defined(__GNUC__) && SECP256K1_GNUC_PREREQ(3, 4) +# define SECP256K1_WARN_UNUSED_RESULT __attribute__ ((__warn_unused_result__)) +# else +# define SECP256K1_WARN_UNUSED_RESULT +# endif +# if !defined(SECP256K1_BUILD) && defined(__GNUC__) && SECP256K1_GNUC_PREREQ(3, 4) +# define SECP256K1_ARG_NONNULL(_x) __attribute__ ((__nonnull__(_x))) +# else +# define SECP256K1_ARG_NONNULL(_x) +# endif + +/* Attribute for marking functions, types, and variables as deprecated */ +#if !defined(SECP256K1_BUILD) && defined(__has_attribute) +# if __has_attribute(__deprecated__) +# define SECP256K1_DEPRECATED(_msg) __attribute__ ((__deprecated__(_msg))) +# else +# define SECP256K1_DEPRECATED(_msg) +# endif +#else +# define SECP256K1_DEPRECATED(_msg) +#endif + +/* All flags' lower 8 bits indicate what they're for. Do not use directly. */ +#define SECP256K1_FLAGS_TYPE_MASK ((1 << 8) - 1) +#define SECP256K1_FLAGS_TYPE_CONTEXT (1 << 0) +#define SECP256K1_FLAGS_TYPE_COMPRESSION (1 << 1) +/* The higher bits contain the actual data. Do not use directly. */ +#define SECP256K1_FLAGS_BIT_CONTEXT_VERIFY (1 << 8) +#define SECP256K1_FLAGS_BIT_CONTEXT_SIGN (1 << 9) +#define SECP256K1_FLAGS_BIT_CONTEXT_DEFAULT (1 << 9) /* DEFAULT is really just an alias for the deprecated SIGN */ +#define SECP256K1_FLAGS_BIT_CONTEXT_DECLASSIFY (1 << 10) +#define SECP256K1_FLAGS_BIT_COMPRESSION (1 << 8) + +/** Context flags to pass to secp256k1_context_create, secp256k1_context_preallocated_size, and + * secp256k1_context_preallocated_create. */ +#define SECP256K1_CONTEXT_DEFAULT (SECP256K1_FLAGS_TYPE_CONTEXT | SECP256K1_FLAGS_BIT_CONTEXT_DEFAULT) + +/** Deprecated context flags. These flags are treated equivalent to SECP256K1_CONTEXT_DEFAULT. */ +#define SECP256K1_CONTEXT_VERIFY (SECP256K1_FLAGS_TYPE_CONTEXT | SECP256K1_FLAGS_BIT_CONTEXT_VERIFY) +#define SECP256K1_CONTEXT_SIGN (SECP256K1_FLAGS_TYPE_CONTEXT | SECP256K1_FLAGS_BIT_CONTEXT_SIGN) +#define SECP256K1_CONTEXT_NONE (SECP256K1_FLAGS_TYPE_CONTEXT) + +/* Testing flag. Do not use. */ +#define SECP256K1_CONTEXT_DECLASSIFY (SECP256K1_FLAGS_TYPE_CONTEXT | SECP256K1_FLAGS_BIT_CONTEXT_DECLASSIFY) + +/** Flag to pass to secp256k1_ec_pubkey_serialize. */ +#define SECP256K1_EC_COMPRESSED (SECP256K1_FLAGS_TYPE_COMPRESSION | SECP256K1_FLAGS_BIT_COMPRESSION) +#define SECP256K1_EC_UNCOMPRESSED (SECP256K1_FLAGS_TYPE_COMPRESSION) + +/** Prefix byte used to tag various encoded curvepoints for specific purposes */ +#define SECP256K1_TAG_PUBKEY_EVEN 0x02 +#define SECP256K1_TAG_PUBKEY_ODD 0x03 +#define SECP256K1_TAG_PUBKEY_UNCOMPRESSED 0x04 +#define SECP256K1_TAG_PUBKEY_HYBRID_EVEN 0x06 +#define SECP256K1_TAG_PUBKEY_HYBRID_ODD 0x07 + +/** A built-in constant secp256k1 context object with static storage duration, to be + * used in conjunction with secp256k1_selftest. + * + * This context object offers *only limited functionality* , i.e., it cannot be used + * for API functions that perform computations involving secret keys, e.g., signing + * and public key generation. If this restriction applies to a specific API function, + * it is mentioned in its documentation. See secp256k1_context_create if you need a + * full context object that supports all functionality offered by the library. + * + * It is highly recommended to call secp256k1_selftest before using this context. + */ +SECP256K1_API extern const secp256k1_context *secp256k1_context_static; + +/** Deprecated alias for secp256k1_context_static. */ +SECP256K1_API extern const secp256k1_context *secp256k1_context_no_precomp +SECP256K1_DEPRECATED("Use secp256k1_context_static instead"); + +/** Perform basic self tests (to be used in conjunction with secp256k1_context_static) + * + * This function performs self tests that detect some serious usage errors and + * similar conditions, e.g., when the library is compiled for the wrong endianness. + * This is a last resort measure to be used in production. The performed tests are + * very rudimentary and are not intended as a replacement for running the test + * binaries. + * + * It is highly recommended to call this before using secp256k1_context_static. + * It is not necessary to call this function before using a context created with + * secp256k1_context_create (or secp256k1_context_preallocated_create), which will + * take care of performing the self tests. + * + * If the tests fail, this function will call the default error handler to abort the + * program (see secp256k1_context_set_error_callback). + */ +SECP256K1_API void secp256k1_selftest(void); + + +/** Set a callback function to be called when an illegal argument is passed to + * an API call. It will only trigger for violations that are mentioned + * explicitly in the header. + * + * The philosophy is that these shouldn't be dealt with through a + * specific return value, as calling code should not have branches to deal with + * the case that this code itself is broken. + * + * On the other hand, during debug stage, one would want to be informed about + * such mistakes, and the default (crashing) may be inadvisable. + * When this callback is triggered, the API function called is guaranteed not + * to cause a crash, though its return value and output arguments are + * undefined. + * + * When this function has not been called (or called with fn==NULL), then the + * default handler will be used. The library provides a default handler which + * writes the message to stderr and calls abort. This default handler can be + * replaced at link time if the preprocessor macro + * USE_EXTERNAL_DEFAULT_CALLBACKS is defined, which is the case if the build + * has been configured with --enable-external-default-callbacks. Then the + * following two symbols must be provided to link against: + * - void secp256k1_default_illegal_callback_fn(const char* message, void* data); + * - void secp256k1_default_error_callback_fn(const char* message, void* data); + * The library can call these default handlers even before a proper callback data + * pointer could have been set using secp256k1_context_set_illegal_callback or + * secp256k1_context_set_error_callback, e.g., when the creation of a context + * fails. In this case, the corresponding default handler will be called with + * the data pointer argument set to NULL. + * + * Args: ctx: an existing context object. + * In: fun: a pointer to a function to call when an illegal argument is + * passed to the API, taking a message and an opaque pointer. + * (NULL restores the default handler.) + * data: the opaque pointer to pass to fun above, must be NULL for the default handler. + * + * See also secp256k1_context_set_error_callback. + */ +SECP256K1_API void secp256k1_context_set_illegal_callback( + secp256k1_context* ctx, + void (*fun)(const char* message, void* data), + const void* data +) SECP256K1_ARG_NONNULL(1); + +/** Set a callback function to be called when an internal consistency check + * fails. + * + * The default callback writes an error message to stderr and calls abort + * to abort the program. + * + * This can only trigger in case of a hardware failure, miscompilation, + * memory corruption, serious bug in the library, or other error would can + * otherwise result in undefined behaviour. It will not trigger due to mere + * incorrect usage of the API (see secp256k1_context_set_illegal_callback + * for that). After this callback returns, anything may happen, including + * crashing. + * + * Args: ctx: an existing context object. + * In: fun: a pointer to a function to call when an internal error occurs, + * taking a message and an opaque pointer (NULL restores the + * default handler, see secp256k1_context_set_illegal_callback + * for details). + * data: the opaque pointer to pass to fun above, must be NULL for the default handler. + * + * See also secp256k1_context_set_illegal_callback. + */ +SECP256K1_API void secp256k1_context_set_error_callback( + secp256k1_context* ctx, + void (*fun)(const char* message, void* data), + const void* data +) SECP256K1_ARG_NONNULL(1); + +/** Create a secp256k1 scratch space object. + * + * Returns: a newly created scratch space. + * Args: ctx: an existing context object. + * In: size: amount of memory to be available as scratch space. Some extra + * (<100 bytes) will be allocated for extra accounting. + */ +SECP256K1_API SECP256K1_WARN_UNUSED_RESULT secp256k1_scratch_space* secp256k1_scratch_space_create( + const secp256k1_context* ctx, + size_t size +) SECP256K1_ARG_NONNULL(1); + +/** Destroy a secp256k1 scratch space. + * + * The pointer may not be used afterwards. + * Args: ctx: a secp256k1 context object. + * scratch: space to destroy + */ +SECP256K1_API void secp256k1_scratch_space_destroy( + const secp256k1_context* ctx, + secp256k1_scratch_space* scratch +) SECP256K1_ARG_NONNULL(1); + +/** Parse a variable-length public key into the pubkey object. + * + * Returns: 1 if the public key was fully valid. + * 0 if the public key could not be parsed or is invalid. + * Args: ctx: a secp256k1 context object. + * Out: pubkey: pointer to a pubkey object. If 1 is returned, it is set to a + * parsed version of input. If not, its value is undefined. + * In: input: pointer to a serialized public key + * inputlen: length of the array pointed to by input + * + * This function supports parsing compressed (33 bytes, header byte 0x02 or + * 0x03), uncompressed (65 bytes, header byte 0x04), or hybrid (65 bytes, header + * byte 0x06 or 0x07) format public keys. + */ +SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_pubkey_parse( + const secp256k1_context* ctx, + secp256k1_pubkey* pubkey, + const unsigned char *input, + size_t inputlen +) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3); + +/** Serialize a pubkey object into a serialized byte sequence. + * + * Returns: 1 always. + * Args: ctx: a secp256k1 context object. + * Out: output: a pointer to a 65-byte (if compressed==0) or 33-byte (if + * compressed==1) byte array to place the serialized key + * in. + * In/Out: outputlen: a pointer to an integer which is initially set to the + * size of output, and is overwritten with the written + * size. + * In: pubkey: a pointer to a secp256k1_pubkey containing an + * initialized public key. + * flags: SECP256K1_EC_COMPRESSED if serialization should be in + * compressed format, otherwise SECP256K1_EC_UNCOMPRESSED. + */ +SECP256K1_API int secp256k1_ec_pubkey_serialize( + const secp256k1_context* ctx, + unsigned char *output, + size_t *outputlen, + const secp256k1_pubkey* pubkey, + unsigned int flags +) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(4); + +/** Compare two public keys using lexicographic (of compressed serialization) order + * + * Returns: <0 if the first public key is less than the second + * >0 if the first public key is greater than the second + * 0 if the two public keys are equal + * Args: ctx: a secp256k1 context object. + * In: pubkey1: first public key to compare + * pubkey2: second public key to compare + */ +SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_pubkey_cmp( + const secp256k1_context* ctx, + const secp256k1_pubkey* pubkey1, + const secp256k1_pubkey* pubkey2 +) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3); + +/** Parse an ECDSA signature in compact (64 bytes) format. + * + * Returns: 1 when the signature could be parsed, 0 otherwise. + * Args: ctx: a secp256k1 context object + * Out: sig: a pointer to a signature object + * In: input64: a pointer to the 64-byte array to parse + * + * The signature must consist of a 32-byte big endian R value, followed by a + * 32-byte big endian S value. If R or S fall outside of [0..order-1], the + * encoding is invalid. R and S with value 0 are allowed in the encoding. + * + * After the call, sig will always be initialized. If parsing failed or R or + * S are zero, the resulting sig value is guaranteed to fail verification for + * any message and public key. + */ +SECP256K1_API int secp256k1_ecdsa_signature_parse_compact( + const secp256k1_context* ctx, + secp256k1_ecdsa_signature* sig, + const unsigned char *input64 +) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3); + +/** Parse a DER ECDSA signature. + * + * Returns: 1 when the signature could be parsed, 0 otherwise. + * Args: ctx: a secp256k1 context object + * Out: sig: a pointer to a signature object + * In: input: a pointer to the signature to be parsed + * inputlen: the length of the array pointed to be input + * + * This function will accept any valid DER encoded signature, even if the + * encoded numbers are out of range. + * + * After the call, sig will always be initialized. If parsing failed or the + * encoded numbers are out of range, signature verification with it is + * guaranteed to fail for every message and public key. + */ +SECP256K1_API int secp256k1_ecdsa_signature_parse_der( + const secp256k1_context* ctx, + secp256k1_ecdsa_signature* sig, + const unsigned char *input, + size_t inputlen +) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3); + +/** Serialize an ECDSA signature in DER format. + * + * Returns: 1 if enough space was available to serialize, 0 otherwise + * Args: ctx: a secp256k1 context object + * Out: output: a pointer to an array to store the DER serialization + * In/Out: outputlen: a pointer to a length integer. Initially, this integer + * should be set to the length of output. After the call + * it will be set to the length of the serialization (even + * if 0 was returned). + * In: sig: a pointer to an initialized signature object + */ +SECP256K1_API int secp256k1_ecdsa_signature_serialize_der( + const secp256k1_context* ctx, + unsigned char *output, + size_t *outputlen, + const secp256k1_ecdsa_signature* sig +) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(4); + +/** Serialize an ECDSA signature in compact (64 byte) format. + * + * Returns: 1 + * Args: ctx: a secp256k1 context object + * Out: output64: a pointer to a 64-byte array to store the compact serialization + * In: sig: a pointer to an initialized signature object + * + * See secp256k1_ecdsa_signature_parse_compact for details about the encoding. + */ +SECP256K1_API int secp256k1_ecdsa_signature_serialize_compact( + const secp256k1_context* ctx, + unsigned char *output64, + const secp256k1_ecdsa_signature* sig +) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3); + +/** Verify an ECDSA signature. + * + * Returns: 1: correct signature + * 0: incorrect or unparseable signature + * Args: ctx: a secp256k1 context object. + * In: sig: the signature being verified. + * msghash32: the 32-byte message hash being verified. + * The verifier must make sure to apply a cryptographic + * hash function to the message by itself and not accept an + * msghash32 value directly. Otherwise, it would be easy to + * create a "valid" signature without knowledge of the + * secret key. See also + * https://bitcoin.stackexchange.com/a/81116/35586 for more + * background on this topic. + * pubkey: pointer to an initialized public key to verify with. + * + * To avoid accepting malleable signatures, only ECDSA signatures in lower-S + * form are accepted. + * + * If you need to accept ECDSA signatures from sources that do not obey this + * rule, apply secp256k1_ecdsa_signature_normalize to the signature prior to + * verification, but be aware that doing so results in malleable signatures. + * + * For details, see the comments for that function. + */ +SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ecdsa_verify( + const secp256k1_context* ctx, + const secp256k1_ecdsa_signature *sig, + const unsigned char *msghash32, + const secp256k1_pubkey *pubkey +) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(4); + +/** Convert a signature to a normalized lower-S form. + * + * Returns: 1 if sigin was not normalized, 0 if it already was. + * Args: ctx: a secp256k1 context object + * Out: sigout: a pointer to a signature to fill with the normalized form, + * or copy if the input was already normalized. (can be NULL if + * you're only interested in whether the input was already + * normalized). + * In: sigin: a pointer to a signature to check/normalize (can be identical to sigout) + * + * With ECDSA a third-party can forge a second distinct signature of the same + * message, given a single initial signature, but without knowing the key. This + * is done by negating the S value modulo the order of the curve, 'flipping' + * the sign of the random point R which is not included in the signature. + * + * Forgery of the same message isn't universally problematic, but in systems + * where message malleability or uniqueness of signatures is important this can + * cause issues. This forgery can be blocked by all verifiers forcing signers + * to use a normalized form. + * + * The lower-S form reduces the size of signatures slightly on average when + * variable length encodings (such as DER) are used and is cheap to verify, + * making it a good choice. Security of always using lower-S is assured because + * anyone can trivially modify a signature after the fact to enforce this + * property anyway. + * + * The lower S value is always between 0x1 and + * 0x7FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF5D576E7357A4501DDFE92F46681B20A0, + * inclusive. + * + * No other forms of ECDSA malleability are known and none seem likely, but + * there is no formal proof that ECDSA, even with this additional restriction, + * is free of other malleability. Commonly used serialization schemes will also + * accept various non-unique encodings, so care should be taken when this + * property is required for an application. + * + * The secp256k1_ecdsa_sign function will by default create signatures in the + * lower-S form, and secp256k1_ecdsa_verify will not accept others. In case + * signatures come from a system that cannot enforce this property, + * secp256k1_ecdsa_signature_normalize must be called before verification. + */ +SECP256K1_API int secp256k1_ecdsa_signature_normalize( + const secp256k1_context* ctx, + secp256k1_ecdsa_signature *sigout, + const secp256k1_ecdsa_signature *sigin +) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(3); + +/** An implementation of RFC6979 (using HMAC-SHA256) as nonce generation function. + * If a data pointer is passed, it is assumed to be a pointer to 32 bytes of + * extra entropy. + */ +SECP256K1_API extern const secp256k1_nonce_function secp256k1_nonce_function_rfc6979; + +/** A default safe nonce generation function (currently equal to secp256k1_nonce_function_rfc6979). */ +SECP256K1_API extern const secp256k1_nonce_function secp256k1_nonce_function_default; + +/** Create an ECDSA signature. + * + * Returns: 1: signature created + * 0: the nonce generation function failed, or the secret key was invalid. + * Args: ctx: pointer to a context object (not secp256k1_context_static). + * Out: sig: pointer to an array where the signature will be placed. + * In: msghash32: the 32-byte message hash being signed. + * seckey: pointer to a 32-byte secret key. + * noncefp: pointer to a nonce generation function. If NULL, + * secp256k1_nonce_function_default is used. + * ndata: pointer to arbitrary data used by the nonce generation function + * (can be NULL). If it is non-NULL and + * secp256k1_nonce_function_default is used, then ndata must be a + * pointer to 32-bytes of additional data. + * + * The created signature is always in lower-S form. See + * secp256k1_ecdsa_signature_normalize for more details. + */ +SECP256K1_API int secp256k1_ecdsa_sign( + const secp256k1_context* ctx, + secp256k1_ecdsa_signature *sig, + const unsigned char *msghash32, + const unsigned char *seckey, + secp256k1_nonce_function noncefp, + const void *ndata +) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(4); + +/** Verify an ECDSA secret key. + * + * A secret key is valid if it is not 0 and less than the secp256k1 curve order + * when interpreted as an integer (most significant byte first). The + * probability of choosing a 32-byte string uniformly at random which is an + * invalid secret key is negligible. + * + * Returns: 1: secret key is valid + * 0: secret key is invalid + * Args: ctx: pointer to a context object. + * In: seckey: pointer to a 32-byte secret key. + */ +SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_seckey_verify( + const secp256k1_context* ctx, + const unsigned char *seckey +) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2); + +/** Compute the public key for a secret key. + * + * Returns: 1: secret was valid, public key stores. + * 0: secret was invalid, try again. + * Args: ctx: pointer to a context object (not secp256k1_context_static). + * Out: pubkey: pointer to the created public key. + * In: seckey: pointer to a 32-byte secret key. + */ +SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_pubkey_create( + const secp256k1_context* ctx, + secp256k1_pubkey *pubkey, + const unsigned char *seckey +) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3); + +/** Negates a secret key in place. + * + * Returns: 0 if the given secret key is invalid according to + * secp256k1_ec_seckey_verify. 1 otherwise + * Args: ctx: pointer to a context object + * In/Out: seckey: pointer to the 32-byte secret key to be negated. If the + * secret key is invalid according to + * secp256k1_ec_seckey_verify, this function returns 0 and + * seckey will be set to some unspecified value. + */ +SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_seckey_negate( + const secp256k1_context* ctx, + unsigned char *seckey +) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2); + +/** Same as secp256k1_ec_seckey_negate, but DEPRECATED. Will be removed in + * future versions. */ +SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_privkey_negate( + const secp256k1_context* ctx, + unsigned char *seckey +) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) + SECP256K1_DEPRECATED("Use secp256k1_ec_seckey_negate instead"); + +/** Negates a public key in place. + * + * Returns: 1 always + * Args: ctx: pointer to a context object + * In/Out: pubkey: pointer to the public key to be negated. + */ +SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_pubkey_negate( + const secp256k1_context* ctx, + secp256k1_pubkey *pubkey +) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2); + +/** Tweak a secret key by adding tweak to it. + * + * Returns: 0 if the arguments are invalid or the resulting secret key would be + * invalid (only when the tweak is the negation of the secret key). 1 + * otherwise. + * Args: ctx: pointer to a context object. + * In/Out: seckey: pointer to a 32-byte secret key. If the secret key is + * invalid according to secp256k1_ec_seckey_verify, this + * function returns 0. seckey will be set to some unspecified + * value if this function returns 0. + * In: tweak32: pointer to a 32-byte tweak. If the tweak is invalid according to + * secp256k1_ec_seckey_verify, this function returns 0. For + * uniformly random 32-byte arrays the chance of being invalid + * is negligible (around 1 in 2^128). + */ +SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_seckey_tweak_add( + const secp256k1_context* ctx, + unsigned char *seckey, + const unsigned char *tweak32 +) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3); + +/** Same as secp256k1_ec_seckey_tweak_add, but DEPRECATED. Will be removed in + * future versions. */ +SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_privkey_tweak_add( + const secp256k1_context* ctx, + unsigned char *seckey, + const unsigned char *tweak32 +) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) + SECP256K1_DEPRECATED("Use secp256k1_ec_seckey_tweak_add instead"); + +/** Tweak a public key by adding tweak times the generator to it. + * + * Returns: 0 if the arguments are invalid or the resulting public key would be + * invalid (only when the tweak is the negation of the corresponding + * secret key). 1 otherwise. + * Args: ctx: pointer to a context object. + * In/Out: pubkey: pointer to a public key object. pubkey will be set to an + * invalid value if this function returns 0. + * In: tweak32: pointer to a 32-byte tweak. If the tweak is invalid according to + * secp256k1_ec_seckey_verify, this function returns 0. For + * uniformly random 32-byte arrays the chance of being invalid + * is negligible (around 1 in 2^128). + */ +SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_pubkey_tweak_add( + const secp256k1_context* ctx, + secp256k1_pubkey *pubkey, + const unsigned char *tweak32 +) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3); + +/** Tweak a secret key by multiplying it by a tweak. + * + * Returns: 0 if the arguments are invalid. 1 otherwise. + * Args: ctx: pointer to a context object. + * In/Out: seckey: pointer to a 32-byte secret key. If the secret key is + * invalid according to secp256k1_ec_seckey_verify, this + * function returns 0. seckey will be set to some unspecified + * value if this function returns 0. + * In: tweak32: pointer to a 32-byte tweak. If the tweak is invalid according to + * secp256k1_ec_seckey_verify, this function returns 0. For + * uniformly random 32-byte arrays the chance of being invalid + * is negligible (around 1 in 2^128). + */ +SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_seckey_tweak_mul( + const secp256k1_context* ctx, + unsigned char *seckey, + const unsigned char *tweak32 +) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3); + +/** Same as secp256k1_ec_seckey_tweak_mul, but DEPRECATED. Will be removed in + * future versions. */ +SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_privkey_tweak_mul( + const secp256k1_context* ctx, + unsigned char *seckey, + const unsigned char *tweak32 +) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) + SECP256K1_DEPRECATED("Use secp256k1_ec_seckey_tweak_mul instead"); + +/** Tweak a public key by multiplying it by a tweak value. + * + * Returns: 0 if the arguments are invalid. 1 otherwise. + * Args: ctx: pointer to a context object. + * In/Out: pubkey: pointer to a public key object. pubkey will be set to an + * invalid value if this function returns 0. + * In: tweak32: pointer to a 32-byte tweak. If the tweak is invalid according to + * secp256k1_ec_seckey_verify, this function returns 0. For + * uniformly random 32-byte arrays the chance of being invalid + * is negligible (around 1 in 2^128). + */ +SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_pubkey_tweak_mul( + const secp256k1_context* ctx, + secp256k1_pubkey *pubkey, + const unsigned char *tweak32 +) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3); + +/** Randomizes the context to provide enhanced protection against side-channel leakage. + * + * Returns: 1: randomization successful (or called on copy of secp256k1_context_static) + * 0: error + * Args: ctx: pointer to a context object. + * In: seed32: pointer to a 32-byte random seed (NULL resets to initial state) + * + * While secp256k1 code is written and tested to be constant-time no matter what + * secret values are, it is possible that a compiler may output code which is not, + * and also that the CPU may not emit the same radio frequencies or draw the same + * amount of power for all values. Randomization of the context shields against + * side-channel observations which aim to exploit secret-dependent behaviour in + * certain computations which involve secret keys. + * + * It is highly recommended to call this function on contexts returned from + * secp256k1_context_create or secp256k1_context_clone (or from the corresponding + * functions in secp256k1_preallocated.h) before using these contexts to call API + * functions that perform computations involving secret keys, e.g., signing and + * public key generation. It is possible to call this function more than once on + * the same context, and doing so before every few computations involving secret + * keys is recommended as a defense-in-depth measure. + * + * Currently, the random seed is mainly used for blinding multiplications of a + * secret scalar with the elliptic curve base point. Multiplications of this + * kind are performed by exactly those API functions which are documented to + * require a context that is not the secp256k1_context_static. As a rule of thumb, + * these are all functions which take a secret key (or a keypair) as an input. + * A notable exception to that rule is the ECDH module, which relies on a different + * kind of elliptic curve point multiplication and thus does not benefit from + * enhanced protection against side-channel leakage currently. + * + * It is safe call this function on a copy of secp256k1_context_static in writable + * memory (e.g., obtained via secp256k1_context_clone). In that case, this + * function is guaranteed to return 1, but the call will have no effect because + * the static context (or a copy thereof) is not meant to be randomized. + */ +SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_context_randomize( + secp256k1_context* ctx, + const unsigned char *seed32 +) SECP256K1_ARG_NONNULL(1); + +/** Add a number of public keys together. + * + * Returns: 1: the sum of the public keys is valid. + * 0: the sum of the public keys is not valid. + * Args: ctx: pointer to a context object. + * Out: out: pointer to a public key object for placing the resulting public key. + * In: ins: pointer to array of pointers to public keys. + * n: the number of public keys to add together (must be at least 1). + */ +SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_pubkey_combine( + const secp256k1_context* ctx, + secp256k1_pubkey *out, + const secp256k1_pubkey * const * ins, + size_t n +) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3); + +/** Compute a tagged hash as defined in BIP-340. + * + * This is useful for creating a message hash and achieving domain separation + * through an application-specific tag. This function returns + * SHA256(SHA256(tag)||SHA256(tag)||msg). Therefore, tagged hash + * implementations optimized for a specific tag can precompute the SHA256 state + * after hashing the tag hashes. + * + * Returns: 1 always. + * Args: ctx: pointer to a context object + * Out: hash32: pointer to a 32-byte array to store the resulting hash + * In: tag: pointer to an array containing the tag + * taglen: length of the tag array + * msg: pointer to an array containing the message + * msglen: length of the message array + */ +SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_tagged_sha256( + const secp256k1_context* ctx, + unsigned char *hash32, + const unsigned char *tag, + size_t taglen, + const unsigned char *msg, + size_t msglen +) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(5); + +#ifdef __cplusplus +} +#endif + +#endif /* SECP256K1_MAIN_H */ diff --git a/include/secp256k1_preallocated.h b/include/secp256k1_preallocated.h index d2d9014f02..e9a2d3a48f 100644 --- a/include/secp256k1_preallocated.h +++ b/include/secp256k1_preallocated.h @@ -1,12 +1,16 @@ #ifndef SECP256K1_PREALLOCATED_H #define SECP256K1_PREALLOCATED_H -#include "secp256k1.h" - #ifdef __cplusplus extern "C" { #endif +/* See secp256k1.h */ +typedef struct secp256k1_context_struct secp256k1_context; +typedef struct secp256k1_scratch_space_struct secp256k1_scratch_space; + +#include "secp256k1_main.h" + /* The module provided by this header file is intended for settings in which it * is not possible or desirable to rely on dynamic memory allocation. It provides * functions for creating, cloning, and destroying secp256k1 context objects in a @@ -58,6 +62,8 @@ SECP256K1_API size_t secp256k1_context_preallocated_size( * bytes, as detailed above. * flags: which parts of the context to initialize. * + * See secp256k1_context_create (in secp256k1.h) for further details. + * * See also secp256k1_context_randomize (in secp256k1.h) * and secp256k1_context_preallocated_destroy. */ diff --git a/include/secp256k1_recovery.h b/include/secp256k1_recovery.h index 0e2847db96..6d0f5dbacc 100644 --- a/include/secp256k1_recovery.h +++ b/include/secp256k1_recovery.h @@ -1,8 +1,6 @@ #ifndef SECP256K1_RECOVERY_H #define SECP256K1_RECOVERY_H -#include "secp256k1.h" - #ifdef __cplusplus extern "C" { #endif @@ -72,7 +70,7 @@ SECP256K1_API int secp256k1_ecdsa_recoverable_signature_serialize_compact( * * Returns: 1: signature created * 0: the nonce generation function failed, or the secret key was invalid. - * Args: ctx: pointer to a context object, initialized for signing. + * Args: ctx: pointer to a context object (not secp256k1_context_static). * Out: sig: pointer to an array where the signature will be placed. * In: msghash32: the 32-byte message hash being signed. * seckey: pointer to a 32-byte secret key. @@ -94,7 +92,7 @@ SECP256K1_API int secp256k1_ecdsa_sign_recoverable( * * Returns: 1: public key successfully recovered (which guarantees a correct signature). * 0: otherwise. - * Args: ctx: pointer to a context object, initialized for verification. + * Args: ctx: pointer to a context object. * Out: pubkey: pointer to the recovered public key. * In: sig: pointer to initialized signature that supports pubkey recovery. * msghash32: the 32-byte message hash assumed to be signed. diff --git a/include/secp256k1_schnorrsig.h b/include/secp256k1_schnorrsig.h index 5fedcb07b0..ebfcf56249 100644 --- a/include/secp256k1_schnorrsig.h +++ b/include/secp256k1_schnorrsig.h @@ -1,7 +1,6 @@ #ifndef SECP256K1_SCHNORRSIG_H #define SECP256K1_SCHNORRSIG_H -#include "secp256k1.h" #include "secp256k1_extrakeys.h" #ifdef __cplusplus @@ -106,7 +105,7 @@ typedef struct { * signatures from being valid in multiple contexts by accident. * * Returns 1 on success, 0 on failure. - * Args: ctx: pointer to a context object, initialized for signing. + * Args: ctx: pointer to a context object (not secp256k1_context_static). * Out: sig64: pointer to a 64-byte array to store the serialized signature. * In: msg32: the 32-byte message being signed. * keypair: pointer to an initialized keypair. @@ -161,7 +160,7 @@ SECP256K1_API int secp256k1_schnorrsig_sign_custom( * * Returns: 1: correct signature * 0: incorrect signature - * Args: ctx: a secp256k1 context object, initialized for verification. + * Args: ctx: a secp256k1 context object. * In: sig64: pointer to the 64-byte signature to verify. * msg: the message being verified. Can only be NULL if msglen is 0. * msglen: length of the message diff --git a/src/modules/extrakeys/tests_impl.h b/src/modules/extrakeys/tests_impl.h index c8a99f4466..6130043bfb 100644 --- a/src/modules/extrakeys/tests_impl.h +++ b/src/modules/extrakeys/tests_impl.h @@ -359,7 +359,7 @@ void test_keypair(void) { secp256k1_context *none = api_test_context(SECP256K1_CONTEXT_NONE, &ecount); secp256k1_context *sign = api_test_context(SECP256K1_CONTEXT_SIGN, &ecount); secp256k1_context *verify = api_test_context(SECP256K1_CONTEXT_VERIFY, &ecount); - secp256k1_context *sttc = secp256k1_context_clone(secp256k1_context_no_precomp); + secp256k1_context *sttc = secp256k1_context_clone(secp256k1_context_static); secp256k1_context_set_error_callback(sttc, counting_illegal_callback_fn, &ecount); secp256k1_context_set_illegal_callback(sttc, counting_illegal_callback_fn, &ecount); diff --git a/src/modules/recovery/tests_impl.h b/src/modules/recovery/tests_impl.h index abf62f7f3a..3791227ae6 100644 --- a/src/modules/recovery/tests_impl.h +++ b/src/modules/recovery/tests_impl.h @@ -34,7 +34,7 @@ void test_ecdsa_recovery_api(void) { secp256k1_context *sign = secp256k1_context_create(SECP256K1_CONTEXT_SIGN); secp256k1_context *vrfy = secp256k1_context_create(SECP256K1_CONTEXT_VERIFY); secp256k1_context *both = secp256k1_context_create(SECP256K1_CONTEXT_SIGN | SECP256K1_CONTEXT_VERIFY); - secp256k1_context *sttc = secp256k1_context_clone(secp256k1_context_no_precomp); + secp256k1_context *sttc = secp256k1_context_clone(secp256k1_context_static); secp256k1_pubkey pubkey; secp256k1_pubkey recpubkey; secp256k1_ecdsa_signature normal_sig; diff --git a/src/modules/schnorrsig/tests_impl.h b/src/modules/schnorrsig/tests_impl.h index 25840b8fa7..2d79071045 100644 --- a/src/modules/schnorrsig/tests_impl.h +++ b/src/modules/schnorrsig/tests_impl.h @@ -132,7 +132,7 @@ void test_schnorrsig_api(void) { secp256k1_context *sign = secp256k1_context_create(SECP256K1_CONTEXT_SIGN); secp256k1_context *vrfy = secp256k1_context_create(SECP256K1_CONTEXT_VERIFY); secp256k1_context *both = secp256k1_context_create(SECP256K1_CONTEXT_SIGN | SECP256K1_CONTEXT_VERIFY); - secp256k1_context *sttc = secp256k1_context_clone(secp256k1_context_no_precomp); + secp256k1_context *sttc = secp256k1_context_clone(secp256k1_context_static); int ecount; secp256k1_context_set_error_callback(none, counting_illegal_callback_fn, &ecount); diff --git a/src/secp256k1.c b/src/secp256k1.c index 05daad2d1c..e390941bf9 100644 --- a/src/secp256k1.c +++ b/src/secp256k1.c @@ -18,7 +18,6 @@ #define SECP256K1_BUILD #include "../include/secp256k1.h" -#include "../include/secp256k1_preallocated.h" #include "assumptions.h" #include "util.h" @@ -64,13 +63,20 @@ struct secp256k1_context_struct { int declassify; }; -static const secp256k1_context secp256k1_context_no_precomp_ = { +static const secp256k1_context secp256k1_context_static_ = { { 0 }, { secp256k1_default_illegal_callback_fn, 0 }, { secp256k1_default_error_callback_fn, 0 }, 0 }; -const secp256k1_context *secp256k1_context_no_precomp = &secp256k1_context_no_precomp_; +const secp256k1_context *secp256k1_context_static = &secp256k1_context_static_; +const secp256k1_context *secp256k1_context_no_precomp = &secp256k1_context_static_; + +void secp256k1_selftest(void) { + if (!secp256k1_selftest_passes()) { + secp256k1_callback_call(&default_error_callback, "self test failed"); + } +} size_t secp256k1_context_preallocated_size(unsigned int flags) { size_t ret = sizeof(secp256k1_context); @@ -96,9 +102,7 @@ secp256k1_context* secp256k1_context_preallocated_create(void* prealloc, unsigne size_t prealloc_size; secp256k1_context* ret; - if (!secp256k1_selftest()) { - secp256k1_callback_call(&default_error_callback, "self test failed"); - } + secp256k1_selftest(); prealloc_size = secp256k1_context_preallocated_size(flags); if (prealloc_size == 0) { @@ -150,7 +154,7 @@ secp256k1_context* secp256k1_context_clone(const secp256k1_context* ctx) { } void secp256k1_context_preallocated_destroy(secp256k1_context* ctx) { - ARG_CHECK_NO_RETURN(ctx != secp256k1_context_no_precomp); + ARG_CHECK_NO_RETURN(ctx != secp256k1_context_static); if (ctx != NULL) { secp256k1_ecmult_gen_context_clear(&ctx->ecmult_gen_ctx); } @@ -164,7 +168,7 @@ void secp256k1_context_destroy(secp256k1_context* ctx) { } void secp256k1_context_set_illegal_callback(secp256k1_context* ctx, void (*fun)(const char* message, void* data), const void* data) { - ARG_CHECK_NO_RETURN(ctx != secp256k1_context_no_precomp); + ARG_CHECK_NO_RETURN(ctx != secp256k1_context_static); if (fun == NULL) { fun = secp256k1_default_illegal_callback_fn; } @@ -173,7 +177,7 @@ void secp256k1_context_set_illegal_callback(secp256k1_context* ctx, void (*fun)( } void secp256k1_context_set_error_callback(secp256k1_context* ctx, void (*fun)(const char* message, void* data), const void* data) { - ARG_CHECK_NO_RETURN(ctx != secp256k1_context_no_precomp); + ARG_CHECK_NO_RETURN(ctx != secp256k1_context_static); if (fun == NULL) { fun = secp256k1_default_error_callback_fn; } diff --git a/src/selftest.h b/src/selftest.h index 52f1b8442e..d083ac9524 100644 --- a/src/selftest.h +++ b/src/selftest.h @@ -25,7 +25,7 @@ static int secp256k1_selftest_sha256(void) { return secp256k1_memcmp_var(out, output32, 32) == 0; } -static int secp256k1_selftest(void) { +static int secp256k1_selftest_passes(void) { return secp256k1_selftest_sha256(); } diff --git a/src/tests.c b/src/tests.c index 6d61dc811e..8ee77802a5 100644 --- a/src/tests.c +++ b/src/tests.c @@ -16,7 +16,6 @@ #include "secp256k1.c" #include "../include/secp256k1.h" -#include "../include/secp256k1_preallocated.h" #include "testrand_impl.h" #include "util.h" @@ -141,6 +140,11 @@ void random_scalar_order_b32(unsigned char *b32) { secp256k1_scalar_get_b32(b32, &num); } +void run_selftest_tests(void) { + /* Test public API */ + secp256k1_selftest(); +} + void run_context_tests(int use_prealloc) { secp256k1_pubkey pubkey; secp256k1_pubkey zero_pubkey; @@ -164,12 +168,18 @@ void run_context_tests(int use_prealloc) { secp256k1_scalar msg, key, nonce; secp256k1_scalar sigr, sigs; + /* Check that SECP256K1_CONTEXT_DEFAULT is just an alias of the deprecated SECP256K1_CONTEXT_SIGN. */ + CHECK(SECP256K1_CONTEXT_DEFAULT == SECP256K1_CONTEXT_SIGN); + + /* Check that deprecated secp256k1_context_no_precomp is an alias to secp256k1_context_static. */ + CHECK(secp256k1_context_no_precomp == secp256k1_context_static); + if (use_prealloc) { none_prealloc = malloc(secp256k1_context_preallocated_size(SECP256K1_CONTEXT_NONE)); sign_prealloc = malloc(secp256k1_context_preallocated_size(SECP256K1_CONTEXT_SIGN)); vrfy_prealloc = malloc(secp256k1_context_preallocated_size(SECP256K1_CONTEXT_VERIFY)); both_prealloc = malloc(secp256k1_context_preallocated_size(SECP256K1_CONTEXT_SIGN | SECP256K1_CONTEXT_VERIFY)); - sttc_prealloc = malloc(secp256k1_context_preallocated_clone_size(secp256k1_context_no_precomp)); + sttc_prealloc = malloc(secp256k1_context_preallocated_clone_size(secp256k1_context_static)); CHECK(none_prealloc != NULL); CHECK(sign_prealloc != NULL); CHECK(vrfy_prealloc != NULL); @@ -179,13 +189,13 @@ void run_context_tests(int use_prealloc) { sign = secp256k1_context_preallocated_create(sign_prealloc, SECP256K1_CONTEXT_SIGN); vrfy = secp256k1_context_preallocated_create(vrfy_prealloc, SECP256K1_CONTEXT_VERIFY); both = secp256k1_context_preallocated_create(both_prealloc, SECP256K1_CONTEXT_SIGN | SECP256K1_CONTEXT_VERIFY); - sttc = secp256k1_context_preallocated_clone(secp256k1_context_no_precomp, sttc_prealloc); + sttc = secp256k1_context_preallocated_clone(secp256k1_context_static, sttc_prealloc); } else { none = secp256k1_context_create(SECP256K1_CONTEXT_NONE); sign = secp256k1_context_create(SECP256K1_CONTEXT_SIGN); vrfy = secp256k1_context_create(SECP256K1_CONTEXT_VERIFY); both = secp256k1_context_create(SECP256K1_CONTEXT_SIGN | SECP256K1_CONTEXT_VERIFY); - sttc = secp256k1_context_clone(secp256k1_context_no_precomp); + sttc = secp256k1_context_clone(secp256k1_context_static); } memset(&zero_pubkey, 0, sizeof(zero_pubkey)); @@ -5799,7 +5809,7 @@ void run_ec_pubkey_parse_test(void) { ecount = 0; VG_UNDEF(&pubkey, sizeof(pubkey)); CHECK(secp256k1_ec_pubkey_parse(ctx, &pubkey, pubkeyc, 65) == 1); - CHECK(secp256k1_ec_pubkey_parse(secp256k1_context_no_precomp, &pubkey, pubkeyc, 65) == 1); + CHECK(secp256k1_ec_pubkey_parse(secp256k1_context_static, &pubkey, pubkeyc, 65) == 1); VG_CHECK(&pubkey, sizeof(pubkey)); CHECK(ecount == 0); VG_UNDEF(&ge, sizeof(ge)); @@ -7385,6 +7395,7 @@ int main(int argc, char **argv) { secp256k1_testrand_init(argc > 2 ? argv[2] : NULL); /* initialize */ + run_selftest_tests(); run_context_tests(0); run_context_tests(1); run_scratch_tests();