completed set4, challenge 28

1 files changed, 28 insertions, 0 deletions

diff --git a/lib/lib4.c b/lib/lib4.c
index 475efe9..5b7ec7d 100644
--- a/lib/lib4.c
+++ b/lib/lib4.c
@@ -20,3 +20,31 @@ int aes_ctr_edit(char *ciphertext, int ciphertext_length, int offset, char *newt
 	aes_ctr(plaintext, ciphertext_length, ciphertext, key, nonce);
 	return 0;
 }
+
+void sha1_hmac(unsigned int *mac, unsigned char *message, unsigned int msg_len, unsigned char *key,
+		unsigned int key_len)
+{
+	char *res = malloc(msg_len + key_len);
+
+	memcpy(res, key, key_len);
+	memcpy(&res[key_len], message, msg_len);
+
+	SHA1Context sh;
+
+	SHA1Reset(&sh);
+	SHA1Input(&sh, res, (msg_len + key_len));
+	SHA1Result(&sh);
+
+	memcpy(mac, &(sh.Message_Digest), 20);
+}
+
+int sha1_hmac_verify(unsigned int *mac, unsigned char *msg, unsigned int msg_len,
+		unsigned char *key, unsigned int key_len)
+{
+	unsigned int com_mac[5];
+
+	sha1_hmac(com_mac, msg, msg_len, key, key_len);
+
+	return !memcmp(com_mac, mac, 20);
+
+}