1 files changed, 51 insertions, 0 deletions
diff --git a/lib/sha256.c b/lib/sha256.c
index 827bd9a872b..c2e77c854b9 100644
--- a/lib/sha256.c
+++ b/lib/sha256.c
@@ -264,3 +264,54 @@ void sha256_finish(sha256_context * ctx, uint8_t digest[32])
 	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;
+}