HMAC signing for http push

common/hmac.c

@@ -0,0 +1,65 @@
+/*
+ * nodewatcher-agent - remote monitoring daemon
+ *
+ * Copyright (C) 2017 Anej Placer <[email protected]>
+ *
+ * This program is free software: you can redistribute it and/or modify it
+ * under the terms of the GNU Affero General Public License as published by the
+ * Free Software Foundation, either version 3 of the License, or (at your
+ * option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Affero General Public License
+ * for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+#include <nodewatcher-agent/hmac.h>
+
+void sha256(const BYTE *text, BYTE *buf)
+{
+    SHA256_CTX ctx;
+    sha256_init(&ctx);
+    sha256_update(&ctx, text, strlen((char*) text));
+    sha256_final(&ctx, buf);
+}
+
+void hmac_sha256(BYTE *key, int key_len, const BYTE *data, int data_len, BYTE *hmac_out)
+{
+    BYTE key_buf[SHA256_BLOCK_SIZE] = {0};
+
+    if (key_len > SHA256_BLOCK_SIZE) {
+        sha256(key, key_buf); 
+    }
+    if (key_len < SHA256_BLOCK_SIZE) {
+       memcpy(key_buf, key, key_len);
+    }
+
+    for (int i = 0; i < SHA256_BLOCK_SIZE; i++) {
+        key_buf[i] ^= 0x36;
+    }
+
+    size_t buf_size = SHA256_BLOCK_SIZE + data_len;
+    BYTE *in_buf = (BYTE*) malloc(buf_size);
+    memset(in_buf, 0x00, buf_size);
+    memcpy(in_buf, key_buf, SHA256_BLOCK_SIZE);
+    memcpy(in_buf + SHA256_BLOCK_SIZE, data, data_len);
+    memset(hmac_out, 0x00, SHA256_HASH_SIZE);
+    sha256(in_buf, hmac_out);
+
+    for (int i = 0; i < SHA256_BLOCK_SIZE; i++) {
+        key_buf[i] ^= 0x36 ^ 0x5c;
+    }
+
+    buf_size = SHA256_BLOCK_SIZE + SHA256_HASH_SIZE + 1;
+    in_buf = (BYTE*) realloc(in_buf, buf_size);
+    memset(in_buf, 0x00, buf_size);
+    memcpy(in_buf, key_buf, SHA256_BLOCK_SIZE);
+    memcpy(in_buf + SHA256_BLOCK_SIZE, hmac_out, SHA256_HASH_SIZE);
+    memset(hmac_out, 0x00, SHA256_HASH_SIZE);
+    sha256(in_buf, hmac_out);
+
+    free(in_buf);
+}

common/sha256.c

@@ -0,0 +1,159 @@
+/*********************************************************************
+* Filename:   sha256.c
+* Author:     Brad Conte (brad AT bradconte.com)
+* Copyright:
+* Disclaimer: This code is presented "as is" without any guarantees.
+* Details:    Implementation of the SHA-256 hashing algorithm.
+              SHA-256 is one of the three algorithms in the SHA2
+              specification. The others, SHA-384 and SHA-512, are not
+              offered in this implementation.
+              Algorithm specification can be found here:
+               * http://csrc.nist.gov/publications/fips/fips180-2/fips180-2withchangenotice.pdf
+              This implementation uses little endian byte order.
+*********************************************************************/
+
+/*************************** HEADER FILES ***************************/
+#include <nodewatcher-agent/sha256.h>
+
+#include <stdlib.h>
+#include <memory.h>
+
+/****************************** MACROS ******************************/
+#define ROTLEFT(a,b) (((a) << (b)) | ((a) >> (32-(b))))
+#define ROTRIGHT(a,b) (((a) >> (b)) | ((a) << (32-(b))))
+
+#define CH(x,y,z) (((x) & (y)) ^ (~(x) & (z)))
+#define MAJ(x,y,z) (((x) & (y)) ^ ((x) & (z)) ^ ((y) & (z)))
+#define EP0(x) (ROTRIGHT(x,2) ^ ROTRIGHT(x,13) ^ ROTRIGHT(x,22))
+#define EP1(x) (ROTRIGHT(x,6) ^ ROTRIGHT(x,11) ^ ROTRIGHT(x,25))
+#define SIG0(x) (ROTRIGHT(x,7) ^ ROTRIGHT(x,18) ^ ((x) >> 3))
+#define SIG1(x) (ROTRIGHT(x,17) ^ ROTRIGHT(x,19) ^ ((x) >> 10))
+
+/**************************** VARIABLES *****************************/
+static const WORD k[64] = {
+	0x428a2f98,0x71374491,0xb5c0fbcf,0xe9b5dba5,0x3956c25b,0x59f111f1,0x923f82a4,0xab1c5ed5,
+	0xd807aa98,0x12835b01,0x243185be,0x550c7dc3,0x72be5d74,0x80deb1fe,0x9bdc06a7,0xc19bf174,
+	0xe49b69c1,0xefbe4786,0x0fc19dc6,0x240ca1cc,0x2de92c6f,0x4a7484aa,0x5cb0a9dc,0x76f988da,
+	0x983e5152,0xa831c66d,0xb00327c8,0xbf597fc7,0xc6e00bf3,0xd5a79147,0x06ca6351,0x14292967,
+	0x27b70a85,0x2e1b2138,0x4d2c6dfc,0x53380d13,0x650a7354,0x766a0abb,0x81c2c92e,0x92722c85,
+	0xa2bfe8a1,0xa81a664b,0xc24b8b70,0xc76c51a3,0xd192e819,0xd6990624,0xf40e3585,0x106aa070,
+	0x19a4c116,0x1e376c08,0x2748774c,0x34b0bcb5,0x391c0cb3,0x4ed8aa4a,0x5b9cca4f,0x682e6ff3,
+	0x748f82ee,0x78a5636f,0x84c87814,0x8cc70208,0x90befffa,0xa4506ceb,0xbef9a3f7,0xc67178f2
+};
+
+/*********************** FUNCTION DEFINITIONS ***********************/
+void sha256_transform(SHA256_CTX *ctx, const BYTE data[])
+{
+	WORD a, b, c, d, e, f, g, h, i, j, t1, t2, m[64];
+
+	for (i = 0, j = 0; i < 16; ++i, j += 4)
+		m[i] = (data[j] << 24) | (data[j + 1] << 16) | (data[j + 2] << 8) | (data[j + 3]);
+	for ( ; i < 64; ++i)
+		m[i] = SIG1(m[i - 2]) + m[i - 7] + SIG0(m[i - 15]) + m[i - 16];
+
+	a = ctx->state[0];
+	b = ctx->state[1];
+	c = ctx->state[2];
+	d = ctx->state[3];
+	e = ctx->state[4];
+	f = ctx->state[5];
+	g = ctx->state[6];
+	h = ctx->state[7];
+
+	for (i = 0; i < 64; ++i) {
+		t1 = h + EP1(e) + CH(e,f,g) + k[i] + m[i];
+		t2 = EP0(a) + MAJ(a,b,c);
+		h = g;
+		g = f;
+		f = e;
+		e = d + t1;
+		d = c;
+		c = b;
+		b = a;
+		a = t1 + t2;
+	}
+
+	ctx->state[0] += a;
+	ctx->state[1] += b;
+	ctx->state[2] += c;
+	ctx->state[3] += d;
+	ctx->state[4] += e;
+	ctx->state[5] += f;
+	ctx->state[6] += g;
+	ctx->state[7] += h;
+}
+
+void sha256_init(SHA256_CTX *ctx)
+{
+	ctx->datalen = 0;
+	ctx->bitlen = 0;
+	ctx->state[0] = 0x6a09e667;
+	ctx->state[1] = 0xbb67ae85;
+	ctx->state[2] = 0x3c6ef372;
+	ctx->state[3] = 0xa54ff53a;
+	ctx->state[4] = 0x510e527f;
+	ctx->state[5] = 0x9b05688c;
+	ctx->state[6] = 0x1f83d9ab;
+	ctx->state[7] = 0x5be0cd19;
+}
+
+void sha256_update(SHA256_CTX *ctx, const BYTE data[], size_t len)
+{
+	WORD i;
+
+	for (i = 0; i < len; ++i) {
+		ctx->data[ctx->datalen] = data[i];
+		ctx->datalen++;
+		if (ctx->datalen == 64) {
+			sha256_transform(ctx, ctx->data);
+			ctx->bitlen += 512;
+			ctx->datalen = 0;
+		}
+	}
+}
+
+void sha256_final(SHA256_CTX *ctx, BYTE hash[])
+{
+	WORD i;
+
+	i = ctx->datalen;
+
+	// Pad whatever data is left in the buffer.
+	if (ctx->datalen < 56) {
+		ctx->data[i++] = 0x80;
+		while (i < 56)
+			ctx->data[i++] = 0x00;
+	}
+	else {
+		ctx->data[i++] = 0x80;
+		while (i < 64)
+			ctx->data[i++] = 0x00;
+		sha256_transform(ctx, ctx->data);
+		memset(ctx->data, 0, 56);
+	}
+
+	// Append to the padding the total message's length in bits and transform.
+	ctx->bitlen += ctx->datalen * 8;
+	ctx->data[63] = ctx->bitlen;
+	ctx->data[62] = ctx->bitlen >> 8;
+	ctx->data[61] = ctx->bitlen >> 16;
+	ctx->data[60] = ctx->bitlen >> 24;
+	ctx->data[59] = ctx->bitlen >> 32;
+	ctx->data[58] = ctx->bitlen >> 40;
+	ctx->data[57] = ctx->bitlen >> 48;
+	ctx->data[56] = ctx->bitlen >> 56;
+	sha256_transform(ctx, ctx->data);
+
+	// Since this implementation uses little endian byte ordering and SHA uses big endian,
+	// reverse all the bytes when copying the final state to the output hash.
+	for (i = 0; i < 4; ++i) {
+		hash[i]      = (ctx->state[0] >> (24 - i * 8)) & 0x000000ff;
+		hash[i + 4]  = (ctx->state[1] >> (24 - i * 8)) & 0x000000ff;
+		hash[i + 8]  = (ctx->state[2] >> (24 - i * 8)) & 0x000000ff;
+		hash[i + 12] = (ctx->state[3] >> (24 - i * 8)) & 0x000000ff;
+		hash[i + 16] = (ctx->state[4] >> (24 - i * 8)) & 0x000000ff;
+		hash[i + 20] = (ctx->state[5] >> (24 - i * 8)) & 0x000000ff;
+		hash[i + 24] = (ctx->state[6] >> (24 - i * 8)) & 0x000000ff;
+		hash[i + 28] = (ctx->state[7] >> (24 - i * 8)) & 0x000000ff;
+	}
+}

include/nodewatcher-agent/hmac.h

@@ -0,0 +1,30 @@
+/*
+ * nodewatcher-agent - remote monitoring daemon
+ *
+ * Copyright (C) 2017 Anej Placer <[email protected]>
+ *
+ * This program is free software: you can redistribute it and/or modify it
+ * under the terms of the GNU Affero General Public License as published by the
+ * Free Software Foundation, either version 3 of the License, or (at your
+ * option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Affero General Public License
+ * for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+#ifndef NODEWATCHER_AGENT_HMAC_H
+#define NODEWATCHER_AGENT_HMAC_H
+
+#include <nodewatcher-agent/sha256.h>
+
+#define SHA256_HASH_SIZE 32
+#define SHA256_BLOCK_SIZE 64
+
+void sha256(const BYTE *text, BYTE *buf);
+void hmac_sha256(BYTE *key, int key_len, const BYTE *data, int data_len, BYTE *hmac_out);
+
+#endif   // NODEWATCHER_AGENT_HMAC_H

include/nodewatcher-agent/sha256.h

@@ -0,0 +1,31 @@
+/*********************************************************************
+* Filename:   sha256.h
+* Author:     Brad Conte (brad AT bradconte.com)
+* Copyright:
+* Disclaimer: This code is presented "as is" without any guarantees.
+* Details:    Defines the API for the corresponding SHA1 implementation.
+*********************************************************************/
+
+#ifndef SHA256_H
+#define SHA256_H
+
+/*************************** HEADER FILES ***************************/
+#include <stddef.h>
+
+/**************************** DATA TYPES ****************************/
+typedef unsigned char BYTE;             // 8-bit byte
+typedef unsigned int  WORD;             // 32-bit word, change to "long" for 16-bit machines
+
+typedef struct {
+	BYTE data[64];
+	WORD datalen;
+	unsigned long long bitlen;
+	WORD state[8];
+} SHA256_CTX;
+
+/*********************** FUNCTION DECLARATIONS **********************/
+void sha256_init(SHA256_CTX *ctx);
+void sha256_update(SHA256_CTX *ctx, const BYTE data[], size_t len);
+void sha256_final(SHA256_CTX *ctx, BYTE hash[]);
+
+#endif   // SHA256_H

modules/http_push.c

@@ -19,9 +19,11 @@
 #include <nodewatcher-agent/module.h>
 #include <nodewatcher-agent/json.h>
 #include <nodewatcher-agent/utils.h>
+#include <nodewatcher-agent/hmac.h>
 
 #include <syslog.h>
 #include <curl.h>
+#include <strings.h>
 
 /* Timestamp when last successful push occurred. */
 static time_t last_push_at = 0;
@@ -49,6 +51,7 @@ static int nw_http_push_start_acquire_data(struct nodewatcher_module *module,
 
   /* Get the configured URL from UCI. */
   char *url = nw_uci_get_string(uci, "nodewatcher.@agent[0].push_url");
+
   if (url) {
     /* Collect all the module data and perform the push. */
     json_object *data = nw_module_get_output();
@@ -61,30 +64,66 @@ static int nw_http_push_start_acquire_data(struct nodewatcher_module *module,
           /* Default. */
           timeout = 5;
         }
+
+        const char* data_string = json_object_to_json_string(data);
+
         curl_easy_setopt(curl, CURLOPT_TIMEOUT, timeout);
         curl_easy_setopt(curl, CURLOPT_FAILONERROR, 1);
         curl_easy_setopt(curl, CURLOPT_URL, url);
         curl_easy_setopt(curl, CURLOPT_POST, 1);
-        curl_easy_setopt(curl, CURLOPT_POSTFIELDS, json_object_to_json_string(data));
+        curl_easy_setopt(curl, CURLOPT_POSTFIELDS, data_string);
+
+        const char *auth_type = nw_uci_get_string(uci, "nodewatcher.@agent[0].push_authentication_method");
+
+        if (strcasecmp(auth_type, "hmac") == 0) {
+          const char *hmac_key = nw_uci_get_string(uci, "nodewatcher.@agent[0].hmac_key");
+
+          if (hmac_key) {
+            unsigned char hmac_out[SHA256_HASH_SIZE];
+            hmac_sha256((unsigned char*) hmac_key, strlen(hmac_key), (unsigned char*) data_string, strlen(data_string), hmac_out);
+
+            char signature[SHA256_HASH_SIZE + 1] = {0};
+
+            if (nw_base64_encode(hmac_out, SHA256_HASH_SIZE, signature, SHA256_HASH_SIZE) == 0) {
+              char signature_header[26+sizeof(signature)] = {0};
+              strcat(strcpy(signature_header, "X-Nodewatcher-Signature: "), signature);
+
+              struct curl_slist *chunk = NULL;
+              chunk = curl_slist_append(chunk, "X-Nodewatcher-Signature-Algorithm: hmac-sha256");
+              chunk = curl_slist_append(chunk, signature_header);
+              curl_easy_setopt(curl, CURLOPT_HTTPHEADER, chunk);
+            }
+          }
+
+          free((char*) hmac_key);
+
+        } else {
+
 #if LIBCURL_VERSION_NUM >= 0x072700
-        /* Pin server-side public key when configured. */
-        char *server_pubkey = nw_uci_get_string(uci, "nodewatcher.@agent[0].push_server_pubkey");
-        if (server_pubkey) {
-          curl_easy_setopt(curl, CURLOPT_SSL_VERIFYPEER, 0);
-          curl_easy_setopt(curl, CURLOPT_PINNEDPUBLICKEY, server_pubkey);
-          free(server_pubkey);
-        }
+          /* Pin server-side public key when configured. */
+          char *server_pubkey = nw_uci_get_string(uci, "nodewatcher.@agent[0].push_server_pubkey");
+
+          if (server_pubkey) {
+            curl_easy_setopt(curl, CURLOPT_SSL_VERIFYPEER, 0);
+            curl_easy_setopt(curl, CURLOPT_PINNEDPUBLICKEY, server_pubkey);
+            free(server_pubkey);
+          }
 #endif
-        /* Setup client authentication when configured. */
-        char *client_certificate = nw_uci_get_string(uci, "nodewatcher.@agent[0].push_client_certificate");
-        char *client_key = nw_uci_get_string(uci, "nodewatcher.@agent[0].push_client_key");
-        if (client_certificate && client_key) {
-          curl_easy_setopt(curl, CURLOPT_SSLCERT, client_certificate);
-          curl_easy_setopt(curl, CURLOPT_SSLKEY, client_key);
+          /* Setup client authentication when configured. */
+          char *client_certificate = nw_uci_get_string(uci, "nodewatcher.@agent[0].push_client_certificate");
+          char *client_key = nw_uci_get_string(uci, "nodewatcher.@agent[0].push_client_key");
+
+          if (client_certificate && client_key) {
+            curl_easy_setopt(curl, CURLOPT_SSLCERT, client_certificate);
+            curl_easy_setopt(curl, CURLOPT_SSLKEY, client_key);
+          }
+
+          free(client_certificate);
+          free(client_key);
         }
 
-        free(client_certificate);
-        free(client_key);
+        free((char*) data_string);
+        free((char*) auth_type);
 
         /* Provide a buffer to store errors in. */
         char errbuf[CURL_ERROR_SIZE];