lib: sha256: add feature sha256_hmac
Adds the support of the hmac based on sha256.
This implementation is based on rfc2104.
Signed-off-by: Philippe Reynes <philippe.reynes@softathome.com>
Reviewed-by: Raymond Mao <raymond.mao@linaro.org>
diff --git a/lib/sha256.c b/lib/sha256.c
index 827bd9a..c2e77c8 100644
--- a/lib/sha256.c
+++ b/lib/sha256.c
@@ -264,3 +264,54 @@
PUT_UINT32_BE(ctx->state[6], digest, 24);
PUT_UINT32_BE(ctx->state[7], digest, 28);
}
+
+int sha256_hmac(const unsigned char *key, int keylen,
+ const unsigned char *input, unsigned int ilen,
+ unsigned char *output)
+{
+ int i;
+ sha256_context ctx;
+ unsigned char keybuf[64];
+ unsigned char k_ipad[64];
+ unsigned char k_opad[64];
+ unsigned char tmpbuf[32];
+ int keybuf_len;
+
+ if (keylen > 64) {
+ sha256_starts(&ctx);
+ sha256_update(&ctx, key, keylen);
+ sha256_finish(&ctx, keybuf);
+
+ keybuf_len = 32;
+ } else {
+ memset(keybuf, 0, sizeof(keybuf));
+ memcpy(keybuf, key, keylen);
+ keybuf_len = keylen;
+ }
+
+ memset(k_ipad, 0x36, 64);
+ memset(k_opad, 0x5C, 64);
+
+ for (i = 0; i < keybuf_len; i++) {
+ k_ipad[i] ^= keybuf[i];
+ k_opad[i] ^= keybuf[i];
+ }
+
+ sha256_starts(&ctx);
+ sha256_update(&ctx, k_ipad, sizeof(k_ipad));
+ sha256_update(&ctx, input, ilen);
+ sha256_finish(&ctx, tmpbuf);
+
+ sha256_starts(&ctx);
+ sha256_update(&ctx, k_opad, sizeof(k_opad));
+ sha256_update(&ctx, tmpbuf, sizeof(tmpbuf));
+ sha256_finish(&ctx, output);
+
+ memset(k_ipad, 0, sizeof(k_ipad));
+ memset(k_opad, 0, sizeof(k_opad));
+ memset(tmpbuf, 0, sizeof(tmpbuf));
+ memset(keybuf, 0, sizeof(keybuf));
+ memset(&ctx, 0, sizeof(sha256_context));
+
+ return 0;
+}