Add Message-Authenticator support

src/include/krb5/krb5.hin

@@ -1516,6 +1516,10 @@ krb5_k_verify_checksum_iov(krb5_context context, krb5_cksumtype cksumtype,
 krb5_error_code KRB5_CALLCONV
 krb5_k_prf(krb5_context context, krb5_key key, krb5_data *input, krb5_data *output);
 
+krb5_error_code
+krb5_krad_hmacmd5_checksum(const krb5_data *secret, const krb5_crypto_iov *data,
+                           size_t num_data, krb5_data *output);
+
 #ifdef KRB5_OLD_CRYPTO
 /*
  * old cryptosystem routine prototypes.  These are now layered

src/lib/crypto/krb/checksum_hmac_md5.c

@@ -92,3 +92,53 @@ krb5_error_code krb5int_hmacmd5_checksum(const struct krb5_cksumtypes *ctp,
     free(hash_iov);
     return ret;
 }
+
+krb5_error_code
+krb5_krad_hmacmd5_checksum(const krb5_data *secret, const krb5_crypto_iov *data,
+                           size_t num_data, krb5_data *output)
+{
+    krb5_error_code ret;
+    const struct krb5_hash_provider *hash;
+    krb5_keyblock key = {0};
+    krb5_data hashed_secret = empty_data();
+    krb5_crypto_iov iov;
+
+    hash = &krb5int_hash_md5;
+
+    if (secret->length > hash->blocksize) {
+        /* Secret is too long, hash it to shrink it to 16 bits
+         * (see RFC2104 section 3). */
+        hashed_secret.length = hash->hashsize;
+        ret = alloc_data(&hashed_secret, hash->hashsize);
+        if (ret)
+            goto cleanup;
+
+        iov.flags = KRB5_CRYPTO_TYPE_DATA;
+        iov.data = *secret;
+
+        ret = hash->hash(&iov, 1, &hashed_secret);
+        if (ret)
+            goto cleanup;
+
+        secret = &hashed_secret;
+    }
+
+    key.length = secret->length;
+    key.contents = malloc(key.length);
+    if (!key.contents) {
+        ret = ENOMEM;
+        goto cleanup;
+    }
+
+    ret = k5_rand2key_direct(secret, &key);
+    if (ret)
+        goto cleanup;
+
+    ret = krb5int_hmac_keyblock(hash, &key, data, num_data, output);
+
+cleanup:
+    zapfree(hashed_secret.data, hashed_secret.length);
+    zapfree(key.contents, key.length);
+
+    return ret;
+}

src/lib/crypto/libk5crypto.exports

@@ -103,3 +103,4 @@ krb5_c_prfplus
 krb5_c_derive_prfplus
 k5_enctype_to_ssf
 krb5int_c_deprecated_enctype
+krb5_krad_hmacmd5_checksum

src/lib/krad/attr.c

@@ -122,6 +122,23 @@ static const attribute_record attributes[UCHAR_MAX] = {
     {"NAS-Port-Type", 4, 4, NULL, NULL},
     {"Port-Limit", 4, 4, NULL, NULL},
     {"Login-LAT-Port", 1, MAX_ATTRSIZE, NULL, NULL},
+    {NULL, 0, 0, NULL, NULL}, /* Reserved for tunnelling */
+    {NULL, 0, 0, NULL, NULL}, /* Reserved for tunnelling */
+    {NULL, 0, 0, NULL, NULL}, /* Reserved for tunnelling */
+    {NULL, 0, 0, NULL, NULL}, /* Reserved for tunnelling */
+    {NULL, 0, 0, NULL, NULL}, /* Reserved for tunnelling */
+    {NULL, 0, 0, NULL, NULL}, /* Reserved for tunnelling */
+    {NULL, 0, 0, NULL, NULL}, /* Reserved for Apple Remote Access Protocol */
+    {NULL, 0, 0, NULL, NULL}, /* Reserved for Apple Remote Access Protocol */
+    {NULL, 0, 0, NULL, NULL}, /* Reserved for Apple Remote Access Protocol */
+    {NULL, 0, 0, NULL, NULL}, /* Reserved for Apple Remote Access Protocol */
+    {NULL, 0, 0, NULL, NULL}, /* Reserved for Apple Remote Access Protocol */
+    {NULL, 0, 0, NULL, NULL}, /* Password-Retry */
+    {NULL, 0, 0, NULL, NULL}, /* Prompt */
+    {NULL, 0, 0, NULL, NULL}, /* Connect-Info */
+    {NULL, 0, 0, NULL, NULL}, /* Configuration-Token */
+    {NULL, 0, 0, NULL, NULL}, /* EAP-Message */
+    {"Message-Authenticator", MD5_DIGEST_SIZE, MD5_DIGEST_SIZE, NULL, NULL},
 };
 
 /* Encode User-Password attribute. */

src/lib/krad/attrset.c

@@ -164,34 +164,75 @@ krad_attrset_copy(const krad_attrset *set, krad_attrset **copy)
     return 0;
 }
 
+static krb5_error_code
+iter_attr_encode(krb5_context ctx, const char *secret,
+                 const unsigned char *auth, krad_attr type,
+                 const krb5_data *data, unsigned char outbuf[MAX_ATTRSETSIZE],
+                 size_t *i)
+{
+    unsigned char buffer[MAX_ATTRSIZE];
+    size_t attrlen;
+    krb5_error_code retval;
+
+    retval = kr_attr_encode(ctx, secret, auth, type, data, buffer, &attrlen);
+    if (retval)
+        return retval;
+
+    if (*i + attrlen + 2 > MAX_ATTRSETSIZE)
+        return EMSGSIZE;
+
+    outbuf[(*i)++] = type;
+    outbuf[(*i)++] = attrlen + 2;
+    memcpy(outbuf + *i, buffer, attrlen);
+    *i += attrlen;
+
+    return 0;
+}
+
 krb5_error_code
 kr_attrset_encode(const krad_attrset *set, const char *secret,
                   const unsigned char *auth,
                   unsigned char outbuf[MAX_ATTRSETSIZE], size_t *outlen)
 {
-    unsigned char buffer[MAX_ATTRSIZE];
     krb5_error_code retval;
-    size_t i = 0, attrlen;
+    krad_attr msgauth_type;
+    const krb5_data *msgauth;
+    size_t i = 0;
     attr *a;
 
     if (set == NULL) {
         *outlen = 0;
         return 0;
     }
 
-    K5_TAILQ_FOREACH(a, &set->list, list) {
-        retval = kr_attr_encode(set->ctx, secret, auth, a->type, &a->attr,
-                                buffer, &attrlen);
+    msgauth_type = krad_attr_name2num("Message-Authenticator");
+
+    msgauth = krad_attrset_get(set, msgauth_type, 0);
+    if (msgauth) {
+        /* Write Message-Authenticator as first attribute.
+         *
+         * draft-ietf-radext-deprecating-radius-03 (section 5.2.4):
+         *   Servers MUST add Message-Authenticator as the first attribute in
+         *   all responses to Access-Request packets.
+         *
+         * draft-ietf-radext-deprecating-radius-03 (section 5.2.1):
+         *   The Message-Authenticator SHOULD be the first attribute in all
+         *   Access-Request packets.
+         */
+        retval = iter_attr_encode(set->ctx, secret, auth, msgauth_type, msgauth,
+                                  outbuf, &i);
         if (retval != 0)
             return retval;
+    }
 
-        if (i + attrlen + 2 > MAX_ATTRSETSIZE)
-            return EMSGSIZE;
+    K5_TAILQ_FOREACH(a, &set->list, list) {
+        if (a->type == msgauth_type)
+            continue;
 
-        outbuf[i++] = a->type;
-        outbuf[i++] = attrlen + 2;
-        memcpy(&outbuf[i], buffer, attrlen);
-        i += attrlen;
+        retval = iter_attr_encode(set->ctx, secret, auth, a->type, &a->attr,
+                                  outbuf, &i);
+        if (retval != 0)
+            return retval;
     }
 
     *outlen = i;

src/lib/krad/internal.h

@@ -43,6 +43,8 @@
 #define UCHAR_MAX 255
 #endif
 
+#define MD5_DIGEST_SIZE 16
+
 /* RFC 2865 */
 #define MAX_ATTRSIZE (UCHAR_MAX - 2)
 #define MAX_ATTRSETSIZE (KRAD_PACKET_SIZE_MAX - 20)