+
+/* ----------------------------------------------------------------------
+ * The above is the MD5 algorithm itself. Now we implement the
+ * HMAC wrapper on it.
+ */
+
+static void *md5_make_context(void)
+{
+ return smalloc(2*sizeof(struct MD5Context));
+}
+
+static void md5_free_context(void *handle)
+{
+ sfree(handle);
+}
+
+static void md5_key_internal(void *handle, unsigned char *key, int len)
+{
+ struct MD5Context *keys = (struct MD5Context *)handle;
+ unsigned char foo[64];
+ int i;
+
+ memset(foo, 0x36, 64);
+ for (i = 0; i < len && i < 64; i++)
+ foo[i] ^= key[i];
+ MD5Init(&keys[0]);
+ MD5Update(&keys[0], foo, 64);
+
+ memset(foo, 0x5C, 64);
+ for (i = 0; i < len && i < 64; i++)
+ foo[i] ^= key[i];
+ MD5Init(&keys[0]);
+ MD5Update(&keys[0], foo, 64);
+
+ memset(foo, 0, 64); /* burn the evidence */
+}
+
+static void md5_key(void *handle, unsigned char *key)
+{
+ md5_key_internal(handle, key, 16);
+}
+
+static void md5_do_hmac(void *handle, unsigned char *blk, int len,
+ unsigned long seq, unsigned char *hmac)
+{
+ struct MD5Context *keys = (struct MD5Context *)handle;
+ 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 = keys[0]; /* structure copy */
+ MD5Update(&s, intermediate, 4);
+ MD5Update(&s, blk, len);
+ MD5Final(intermediate, &s);
+ s = keys[1]; /* structure copy */
+ MD5Update(&s, intermediate, 16);
+ MD5Final(hmac, &s);
+}
+
+static void md5_generate(void *handle, unsigned char *blk, int len,
+ unsigned long seq)
+{
+ md5_do_hmac(handle, blk, len, seq, blk + len);
+}
+
+static int md5_verify(void *handle, unsigned char *blk, int len,
+ unsigned long seq)
+{
+ unsigned char correct[16];
+ md5_do_hmac(handle, blk, len, seq, correct);
+ return !memcmp(correct, blk + len, 16);
+}
+
+const struct ssh_mac ssh_md5 = {
+ md5_make_context, md5_free_context, md5_key,
+ md5_generate, md5_verify,
+ "hmac-md5",
+ 16
+};