Experimental encrypt-then-mac support.
Experimental support for encrypt then mac from
draft-gutmann-tls-encrypt-then-mac-02.txt
To enable it set the appropriate extension number (0x10 for the test server)
using e.g. -DTLSEXT_TYPE_encrypt_then_mac=0x10
For non-compliant peers (i.e. just about everything) this should have no
effect.
diff --git a/ssl/t1_lib.c b/ssl/t1_lib.c
index 2a3eaeb..a471995 100644
--- a/ssl/t1_lib.c
+++ b/ssl/t1_lib.c
@@ -1465,6 +1465,10 @@
ret += outlen;
}
}
+#ifdef TLSEXT_TYPE_encrypt_then_mac
+ s2n(TLSEXT_TYPE_encrypt_then_mac,ret);
+ s2n(0,ret);
+#endif
if ((extdatalen = ret-p-2) == 0)
return p;
@@ -1700,6 +1704,21 @@
}
}
}
+#ifdef TLSEXT_TYPE_encrypt_then_mac
+ if (s->s3->flags & TLS1_FLAGS_ENCRYPT_THEN_MAC)
+ {
+ /* Don't use encrypt_then_mac if AEAD: might want
+ * to disable for other ciphersuites too.
+ */
+ if (s->s3->tmp.new_cipher->algorithm_mac == SSL_AEAD)
+ s->s3->flags &= ~TLS1_FLAGS_ENCRYPT_THEN_MAC;
+ else
+ {
+ s2n(TLSEXT_TYPE_encrypt_then_mac,ret);
+ s2n(0,ret);
+ }
+ }
+#endif
if (s->s3->alpn_selected)
{
@@ -1934,6 +1953,10 @@
s->cert->pkeys[i].valid_flags = 0;
}
+#ifdef TLSEXT_TYPE_encrypt_then_mac
+ s->s3->flags &= ~TLS1_FLAGS_ENCRYPT_THEN_MAC;
+#endif
+
if (data >= (d+n-2))
goto ri_check;
n2s(data,len);
@@ -2452,6 +2475,10 @@
}
}
}
+#ifdef TLSEXT_TYPE_encrypt_then_mac
+ else if (type == TLSEXT_TYPE_encrypt_then_mac)
+ s->s3->flags |= TLS1_FLAGS_ENCRYPT_THEN_MAC;
+#endif
data+=size;
}
@@ -2538,6 +2565,10 @@
SSL_TLSEXT_HB_DONT_SEND_REQUESTS);
#endif
+#ifdef TLSEXT_TYPE_encrypt_then_mac
+ s->s3->flags &= ~TLS1_FLAGS_ENCRYPT_THEN_MAC;
+#endif
+
if (data >= (d+n-2))
goto ri_check;
@@ -2789,6 +2820,14 @@
}
}
}
+#ifdef TLSEXT_TYPE_encrypt_then_mac
+ else if (type == TLSEXT_TYPE_encrypt_then_mac)
+ {
+ /* Ignore if inappropriate ciphersuite */
+ if (s->s3->tmp.new_cipher->algorithm_mac != SSL_AEAD)
+ s->s3->flags |= TLS1_FLAGS_ENCRYPT_THEN_MAC;
+ }
+#endif
data += size;
}
