Since the TLS 1.2 supported signature algorithms extension is less
sophisticaed in OpenSSL 1.0.1 this has to be done in two stages.
RSA+MD5 is removed from supported signature algorithms extension:
any compliant implementation should never use RSA+MD5 as a result.
To cover the case of a broken implementation using RSA+MD5 anyway
disable lookup of MD5 algorithm in TLS 1.2.
(I'd rather use an option, but it appears that the options field is
full.)
Now, we send the time in the gmt_unix_time field if the appropriate
one of these mode options is set, but randomize the field if the flag
is not set.
Instead, send random bytes.
While the gmt_unix_time record was added in an ostensible attempt to
mitigate the dangers of a bad RNG, its presence leaks the host's view
of the current time in the clear. This minor leak can help
fingerprint TLS instances across networks and protocols... and what's
worse, it's doubtful thet the gmt_unix_time record does any good at
all for its intended purpose, since:
* It's quite possible to open two TLS connections in one second.
* If the PRNG output is prone to repeat itself, ephemeral
* handshakes (and who knows what else besides) are broken.
This fix ensures that
* A HelloRequest is retransmitted if not responded by a ClientHello
* The HelloRequest "consumes" the sequence number 0. The subsequent
ServerHello uses the sequence number 1.
* The client also expects the sequence number of the ServerHello to
be 1 if a HelloRequest was received earlier.
This patch fixes the RFC violation.
(cherry picked from commit b62f4daac0)
The version check for DTLS1_VERSION was redundant as
DTLS1_VERSION > TLS1_1_VERSION, however we do need to
check for DTLS1_BAD_VER for compatibility.
PR:2984
(cherry picked from commit d980abb22e)
Now we set the current certificate to the one used by a server
there is no need to call ssl_get_server_send_cert which will
fail if we haven't sent a certificate yet.
Fix the calculation that checks there is enough room in a record
after removing padding and optional explicit IV. (by Steve)
For AEAD remove the correct number of padding bytes (by Andy)
MD5 should use little endian order. Fortunately the only ciphersuite
affected is EXP-RC2-CBC-MD5 (TLS_RSA_EXPORT_WITH_RC2_CBC_40_MD5) which
is a rarely used export grade ciphersuite.
We have to use EVP in FIPS mode so we can only partially mitigate
timing differences.
Make an extra call to EVP_DigestSignUpdate to hash additonal blocks
to cover any timing differences caused by removal of padding.
The previous CBC patch was bugged in that there was a path through enc()
in s3_pkt.c/d1_pkt.c which didn't set orig_len. orig_len would be left
at the previous value which could suggest that the packet was a
sufficient length when it wasn't.
This patch makes the decoding of SSLv3 and TLS CBC records constant
time. Without this, a timing side-channel can be used to build a padding
oracle and mount Vaudenay's attack.
This patch also disables the stitched AESNI+SHA mode pending a similar
fix to that code.
In order to be easy to backport, this change is implemented in ssl/,
rather than as a generic AEAD mode. In the future this should be changed
around so that HMAC isn't in ssl/, but crypto/ as FIPS expects.
This change adds CRYPTO_memcmp, which compares two vectors of bytes in
an amount of time that's independent of their contents. It also changes
several MAC compares in the code to use this over the standard memcmp,
which may leak information about the size of a matching prefix.
change the current certificate (in s->cert->key) to the one used and then
SSL_get_certificate and SSL_get_privatekey will automatically work.
Note for 1.0.1 and earlier also includes backport of the function
ssl_get_server_send_pkey.
