+
+/* ----------------------------------------------------------------------
+ * The above is the MD5 algorithm itself. Now we implement the
+ * HMAC wrapper on it.
+ */
+
+static struct MD5Context md5_cs_mac_s1, md5_cs_mac_s2;
+static struct MD5Context md5_sc_mac_s1, md5_sc_mac_s2;
+
+static void md5_key(struct MD5Context *s1, struct MD5Context *s2,
+ unsigned char *key, int len)
+{
+ unsigned char foo[64];
+ int i;
+
+ memset(foo, 0x36, 64);
+ for (i = 0; i < len && i < 64; i++)
+ foo[i] ^= key[i];
+ MD5Init(s1);
+ MD5Update(s1, foo, 64);
+
+ memset(foo, 0x5C, 64);
+ for (i = 0; i < len && i < 64; i++)
+ foo[i] ^= key[i];
+ MD5Init(s2);
+ MD5Update(s2, foo, 64);
+
+ memset(foo, 0, 64); /* burn the evidence */
+}
+
+static void md5_cskey(unsigned char *key)
+{
+ md5_key(&md5_cs_mac_s1, &md5_cs_mac_s2, key, 16);
+}
+
+static void md5_sckey(unsigned char *key)
+{
+ md5_key(&md5_sc_mac_s1, &md5_sc_mac_s2, key, 16);
+}
+
+static void md5_do_hmac(struct MD5Context *s1, struct MD5Context *s2,
+ unsigned char *blk, int len, unsigned long seq,
+ unsigned char *hmac)
+{
+ struct MD5Context s;
+ unsigned char intermediate[16];
+
+ intermediate[0] = (unsigned char) ((seq >> 24) & 0xFF);
+ intermediate[1] = (unsigned char) ((seq >> 16) & 0xFF);
+ intermediate[2] = (unsigned char) ((seq >> 8) & 0xFF);
+ intermediate[3] = (unsigned char) ((seq) & 0xFF);
+
+ s = *s1; /* structure copy */
+ MD5Update(&s, intermediate, 4);
+ MD5Update(&s, blk, len);
+ MD5Final(intermediate, &s);
+ s = *s2; /* structure copy */
+ MD5Update(&s, intermediate, 16);
+ MD5Final(hmac, &s);
+}
+
+static void md5_generate(unsigned char *blk, int len, unsigned long seq)
+{
+ md5_do_hmac(&md5_cs_mac_s1, &md5_cs_mac_s2, blk, len, seq, blk + len);
+}
+
+static int md5_verify(unsigned char *blk, int len, unsigned long seq)
+{
+ unsigned char correct[16];
+ md5_do_hmac(&md5_sc_mac_s1, &md5_sc_mac_s2, blk, len, seq, correct);
+ return !memcmp(correct, blk + len, 16);
+}
+
+const struct ssh_mac ssh_md5 = {
+ md5_cskey, md5_sckey,
+ md5_generate,
+ md5_verify,
+ "hmac-md5",
+ 16
+};