The buffer to receive messages is initialised to 16k. If a message is
received that is larger than that then the buffer is "realloc'd". This can
cause the location of the underlying buffer to change. Anything that is
referring to the old location will be referring to free'd data. In the
recent commit c1ef7c97 (master) and 4b390b6c (1.1.0) the point in the code
where the message buffer is grown was changed. However s->init_msg was not
updated to point at the new location.
CVE-2016-6309
Reviewed-by: Emilia Käsper <emilia@openssl.org>
We actually construct a HelloVerifyRequest in two places with common code
pulled into a single function. This one commit handles both places.
Reviewed-by: Rich Salz <rsalz@openssl.org>
Russian GOST ciphersuites are vulnerable to the KCI attack because they use
long-term keys to establish the connection when ssl client authorization is
on. This change brings the GOST implementation into line with the latest
specs in order to avoid the attack. It should not break backwards
compatibility.
Reviewed-by: Rich Salz <rsalz@openssl.org>
Reviewed-by: Matt Caswell <matt@openssl.org>
This issue is very similar to CVE-2016-6307 described in the previous
commit. The underlying defect is different but the security analysis and
impacts are the same except that it impacts DTLS.
A DTLS message includes 3 bytes for its length in the header for the
message.
This would allow for messages up to 16Mb in length. Messages of this length
are excessive and OpenSSL includes a check to ensure that a peer is sending
reasonably sized messages in order to avoid too much memory being consumed
to service a connection. A flaw in the logic of version 1.1.0 means that
memory for the message is allocated too early, prior to the excessive
message length check. Due to way memory is allocated in OpenSSL this could
mean an attacker could force up to 21Mb to be allocated to service a
connection. This could lead to a Denial of Service through memory
exhaustion. However, the excessive message length check still takes place,
and this would cause the connection to immediately fail. Assuming that the
application calls SSL_free() on the failed conneciton in a timely manner
then the 21Mb of allocated memory will then be immediately freed again.
Therefore the excessive memory allocation will be transitory in nature.
This then means that there is only a security impact if:
1) The application does not call SSL_free() in a timely manner in the
event that the connection fails
or
2) The application is working in a constrained environment where there
is very little free memory
or
3) The attacker initiates multiple connection attempts such that there
are multiple connections in a state where memory has been allocated for
the connection; SSL_free() has not yet been called; and there is
insufficient memory to service the multiple requests.
Except in the instance of (1) above any Denial Of Service is likely to
be transitory because as soon as the connection fails the memory is
subsequently freed again in the SSL_free() call. However there is an
increased risk during this period of application crashes due to the lack
of memory - which would then mean a more serious Denial of Service.
This issue does not affect TLS users.
Issue was reported by Shi Lei (Gear Team, Qihoo 360 Inc.).
CVE-2016-6308
Reviewed-by: Richard Levitte <levitte@openssl.org>
A TLS message includes 3 bytes for its length in the header for the message.
This would allow for messages up to 16Mb in length. Messages of this length
are excessive and OpenSSL includes a check to ensure that a peer is sending
reasonably sized messages in order to avoid too much memory being consumed
to service a connection. A flaw in the logic of version 1.1.0 means that
memory for the message is allocated too early, prior to the excessive
message length check. Due to way memory is allocated in OpenSSL this could
mean an attacker could force up to 21Mb to be allocated to service a
connection. This could lead to a Denial of Service through memory
exhaustion. However, the excessive message length check still takes place,
and this would cause the connection to immediately fail. Assuming that the
application calls SSL_free() on the failed conneciton in a timely manner
then the 21Mb of allocated memory will then be immediately freed again.
Therefore the excessive memory allocation will be transitory in nature.
This then means that there is only a security impact if:
1) The application does not call SSL_free() in a timely manner in the
event that the connection fails
or
2) The application is working in a constrained environment where there
is very little free memory
or
3) The attacker initiates multiple connection attempts such that there
are multiple connections in a state where memory has been allocated for
the connection; SSL_free() has not yet been called; and there is
insufficient memory to service the multiple requests.
Except in the instance of (1) above any Denial Of Service is likely to
be transitory because as soon as the connection fails the memory is
subsequently freed again in the SSL_free() call. However there is an
increased risk during this period of application crashes due to the lack
of memory - which would then mean a more serious Denial of Service.
This issue does not affect DTLS users.
Issue was reported by Shi Lei (Gear Team, Qihoo 360 Inc.).
CVE-2016-6307
Reviewed-by: Richard Levitte <levitte@openssl.org>
All the other functions that take an argument for the number of bytes
use convenience macros for this purpose. We should do the same with
WPACKET_put_bytes().
Reviewed-by: Rich Salz <rsalz@openssl.org>
Makes the logic a little bit clearer.
Reviewed-by: Andy Polyakov <appro@openssl.org>
Reviewed-by: Rich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/1571)
Updated the construction code to use the new function. Also added some
convenience macros for WPACKET_sub_memcpy().
Reviewed-by: Rich Salz <rsalz@openssl.org>
A few style tweaks here and there. The main change is that curr and
packet_len are now offsets into the buffer to account for the fact that
the pointers can change if the buffer grows. Also dropped support for the
WPACKET_set_packet_len() function. I thought that was going to be needed
but so far it hasn't been. It doesn't really work any more due to the
offsets change.
Reviewed-by: Rich Salz <rsalz@openssl.org>
The function tls_construct_cert_status() is called by both TLS and DTLS
code. However it only ever constructed a TLS message header for the message
which obviously failed in DTLS.
Reviewed-by: Rich Salz <rsalz@openssl.org>
DTLS can handle out of order record delivery. Additionally since
handshake messages can be bigger than will fit into a single packet, the
messages can be fragmented across multiple records (as with normal TLS).
That means that the messages can arrive mixed up, and we have to
reassemble them. We keep a queue of buffered messages that are "from the
future", i.e. messages we're not ready to deal with yet but have arrived
early. The messages held there may not be full yet - they could be one
or more fragments that are still in the process of being reassembled.
The code assumes that we will eventually complete the reassembly and
when that occurs the complete message is removed from the queue at the
point that we need to use it.
However, DTLS is also tolerant of packet loss. To get around that DTLS
messages can be retransmitted. If we receive a full (non-fragmented)
message from the peer after previously having received a fragment of
that message, then we ignore the message in the queue and just use the
non-fragmented version. At that point the queued message will never get
removed.
Additionally the peer could send "future" messages that we never get to
in order to complete the handshake. Each message has a sequence number
(starting from 0). We will accept a message fragment for the current
message sequence number, or for any sequence up to 10 into the future.
However if the Finished message has a sequence number of 2, anything
greater than that in the queue is just left there.
So, in those two ways we can end up with "orphaned" data in the queue
that will never get removed - except when the connection is closed. At
that point all the queues are flushed.
An attacker could seek to exploit this by filling up the queues with
lots of large messages that are never going to be used in order to
attempt a DoS by memory exhaustion.
I will assume that we are only concerned with servers here. It does not
seem reasonable to be concerned about a memory exhaustion attack on a
client. They are unlikely to process enough connections for this to be
an issue.
A "long" handshake with many messages might be 5 messages long (in the
incoming direction), e.g. ClientHello, Certificate, ClientKeyExchange,
CertificateVerify, Finished. So this would be message sequence numbers 0
to 4. Additionally we can buffer up to 10 messages in the future.
Therefore the maximum number of messages that an attacker could send
that could get orphaned would typically be 15.
The maximum size that a DTLS message is allowed to be is defined by
max_cert_list, which by default is 100k. Therefore the maximum amount of
"orphaned" memory per connection is 1500k.
Message sequence numbers get reset after the Finished message, so
renegotiation will not extend the maximum number of messages that can be
orphaned per connection.
As noted above, the queues do get cleared when the connection is closed.
Therefore in order to mount an effective attack, an attacker would have
to open many simultaneous connections.
Issue reported by Quan Luo.
CVE-2016-2179
Reviewed-by: Richard Levitte <levitte@openssl.org>
Run util/openssl-format-source on ssl/
Some comments and hand-formatted tables were fixed up
manually by disabling auto-formatting.
Reviewed-by: Rich Salz <rsalz@openssl.org>
When handling ECDH check to see if the curve is "custom" (X25519 is
currently the only curve of this type) and instead of setting a curve
NID just allocate a key of appropriate type.
Reviewed-by: Rich Salz <rsalz@openssl.org>
DTLSv1_client_method() is deprecated, but it was the only way to obtain
DTLS1_BAD_VER support. The SSL_OP_CISCO_ANYCONNECT hack doesn't work with
DTLS_client_method(), and it's relatively non-trivial to make it work without
expanding the hack into lots of places.
So deprecate SSL_OP_CISCO_ANYCONNECT with DTLSv1_client_method(), and make
it work with SSL_CTX_set_{min,max}_proto_version(DTLS1_BAD_VER) instead.
Reviewed-by: Rich Salz <rsalz@openssl.org>
Reviewed-by: Matt Caswell <matt@openssl.org>
The Change Cipher Spec message in this ancient pre-standard version of DTLS
that Cisco are unfortunately still using in their products, is 3 bytes.
Allow it.
Reviewed-by: Rich Salz <rsalz@openssl.org>
Reviewed-by: Matt Caswell <matt@openssl.org>
This is adapted from BoringSSL commit 2f87112b963.
This fixes a number of bugs where the existence of bbio was leaked in the
public API and broke things.
- SSL_get_wbio returned the bbio during the handshake. It must always return
the BIO the consumer configured. In doing so, some internal accesses of
SSL_get_wbio should be switched to ssl->wbio since those want to see bbio.
- The logic in SSL_set_rfd, etc. (which I doubt is quite right since
SSL_set_bio's lifetime is unclear) would get confused once wbio got
wrapped. Those want to compare to SSL_get_wbio.
- If SSL_set_bio was called mid-handshake, bbio would get disconnected and
lose state. It forgets to reattach the bbio afterwards. Unfortunately,
Conscrypt does this a lot. It just never ended up calling it at a point
where the bbio would cause problems.
- Make more explicit the invariant that any bbio's which exist are always
attached. Simplify a few things as part of that.
RT#4572
Reviewed-by: Richard Levitte <levitte@openssl.org>
Fix some indentation at the same time
Reviewed-by: Matt Caswell <matt@openssl.org>
Reviewed-by: Rich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/1292)
- Always process ALPN (previously there was an early return in the
certificate status handling)
- Don't send a duplicate alert. Previously, both
ssl_check_clienthello_tlsext_late and its caller would send an
alert. Consolidate alert sending code in the caller.
Reviewed-by: Rich Salz <rsalz@openssl.org>
Continuing from the previous commit. Refactor tls_process_key_exchange() to
split out into a separate function the ECDHE aspects.
Reviewed-by: Richard Levitte <levitte@openssl.org>
Continuing from the previous commit. Refactor tls_process_key_exchange() to
split out into a separate function the DHE aspects.
Reviewed-by: Richard Levitte <levitte@openssl.org>
Continuing from the previous commit. Refactor tls_process_key_exchange() to
split out into a separate function the SRP aspects.
Reviewed-by: Richard Levitte <levitte@openssl.org>
The tls_process_key_exchange() function is too long. This commit starts
the process of splitting it up by moving the PSK preamble code to a
separate function.
Reviewed-by: Richard Levitte <levitte@openssl.org>
The function tls_process_key_exchange() is too long. This commit moves
the PSK preamble processing out to a separate function.
Reviewed-by: Richard Levitte <levitte@openssl.org>
If the SSL_SESS_CACHE_NO_INTERNAL_STORE cache mode is used then we weren't
removing sessions from the external cache, e.g. if an alert occurs the
session is supposed to be automatically removed.
Reviewed-by: Richard Levitte <levitte@openssl.org>
Don't call strncpy with strlen of the source as the length. Don't call
strlen multiple times. Eventually we will want to replace this with a proper
PACKET style handling (but for construction of PACKETs instead of just
reading them as it is now). For now though this is safe because
PSK_MAX_IDENTITY_LEN will always fit into the destination buffer.
This addresses an OCAP Audit issue.
Reviewed-by: Richard Levitte <levitte@openssl.org>
Continuing previous commit to break up the
tls_construct_client_key_exchange() function. This splits out the SRP
code.
Reviewed-by: Richard Levitte <levitte@openssl.org>
Continuing previous commit to break up the
tls_construct_client_key_exchange() function. This splits out the GOST
code.
Reviewed-by: Richard Levitte <levitte@openssl.org>
Continuing previous commit to break up the
tls_construct_client_key_exchange() function. This splits out the ECDHE
code.
Reviewed-by: Richard Levitte <levitte@openssl.org>
Continuing previous commit to break up the
tls_construct_client_key_exchange() function. This splits out the DHE
code.
Reviewed-by: Richard Levitte <levitte@openssl.org>
The tls_construct_client_key_exchange() function is too long. This splits
out the construction of the PSK pre-amble into a separate function as well
as the RSA construction.
Reviewed-by: Richard Levitte <levitte@openssl.org>
Continuing from the previous commits, this splits out the GOST code into
a separate function from the process CKE code.
Reviewed-by: Richard Levitte <levitte@openssl.org>
Continuing from the previous commits, this splits out the ECDHE code into
a separate function from the process CKE code.
Reviewed-by: Richard Levitte <levitte@openssl.org>
Continuing from the previous commit, this splits out the DHE code into
a separate function from the process CKE code.
Reviewed-by: Richard Levitte <levitte@openssl.org>
The tls_process_client_key_exchange() function is far too long. This
splits out the PSK preamble processing, and the RSA processing into
separate functions.
Reviewed-by: Richard Levitte <levitte@openssl.org>
In preparation for splitting this function up into smaller functions this
commit reduces the scope of some of the variables to only be in scope for
the algorithm specific parts. In some cases that makes the error handling
more verbose than it needs to be - but we'll clean that up in a later
commit.
Reviewed-by: Richard Levitte <levitte@openssl.org>
The logic testing whether a CKE message is allowed or not was a little
difficult to follow. This tries to clean it up.
Reviewed-by: Emilia Käsper <emilia@openssl.org>
The static function key_exchange_expected() used to return -1 on error.
Commit 361a119127 changed that so that it can never fail. This means that
some tidy up can be done to simplify error handling in callers of that
function.
Reviewed-by: Emilia Käsper <emilia@openssl.org>
Having received a ClientKeyExchange message instead of a Certificate we
know that we are not going to receive a CertificateVerify message. This
means we can free up the handshake_buffer. However we better call
ssl3_digest_cached_records() instead of just freeing it up, otherwise we
later try and use it anyway and a core dump results. This could happen,
for example, in SSLv3 where we send a CertificateRequest but the client
sends no Certificate message at all. This is valid in SSLv3 (in TLS
clients are required to send an empty Certificate message).
Found using the BoringSSL test suite.
Reviewed-by: Emilia Käsper <emilia@openssl.org>
In TLS if the server sends a CertificateRequest and the client does not
provide one, if the server cannot continue it should send a
HandshakeFailure alert. In SSLv3 the same should happen, but instead we
were sending an UnexpectedMessage alert. This is incorrect - the message
isn't unexpected - it is valid for the client not to send one - its just
that we cannot continue without one.
Reviewed-by: Emilia Käsper <emilia@openssl.org>
Move the preparation of the client certificate to be post processing work
after reading the CertificateRequest message rather than pre processing
work prior to writing the Certificate message. As part of preparing the
client certificate we may discover that we do not have one available. If
we are also talking SSLv3 then we won't send the Certificate message at
all. However, if we don't discover this until we are about to send the
Certificate message it is too late and we send an empty one anyway. This
is wrong for SSLv3.
Reviewed-by: Emilia Käsper <emilia@openssl.org>
The set0 setters take ownership of their arguments, so the values should
be set to NULL to avoid a double-free in the cleanup block should
ssl_security(SSL_SECOP_TMP_DH) fail. Found by BoringSSL's WeakDH test.
Reviewed-by: Kurt Roeckx <kurt@openssl.org>
Reviewed-by: Rich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/1299)
We calculate the size required for the ServerKeyExchange message and then
call BUF_MEM_grow_clean() on the buffer. However we fail to take account of
2 bytes required for the signature algorithm and 2 bytes for the signature
length, i.e. we could overflow by 4 bytes. In reality this won't happen
because the buffer is pre-allocated to a large size that means it should be
big enough anyway.
Addresses an OCAP Audit issue.
Reviewed-by: Rich Salz <rsalz@openssl.org>
Reviewed-by: Andy Polyakov <appro@openssl.org>
Reviewed-by: Kurt Roeckx <kurt@openssl.org>
Reviewed-by: Rich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/1264)
Using RSA_PKCS1_PADDING with RSA_private_decrypt is inherently unsafe.
The API requires writing output on success and touching the error queue
on error. Thus, although the padding check itself is constant-time as of
294d1e36c2, and the logic after the
decryption in the SSL code is constant-time as of
adb46dbc6d, the API boundary in the middle
still leaks whether the padding check succeeded, giving us our
much-loved Bleichenbacher padding oracle.
Instead, PKCS#1 padding must be handled by the caller which uses
RSA_NO_PADDING, in timing-sensitive code integrated with the
Bleichenbacher mitigation. Removing PKCS#1 padding in constant time is
actually much simpler when the expected length is a constant (and if
it's not a constant, avoiding a padding oracle seems unlikely), so just
do it inline.
Signed-off-by: Kurt Roeckx <kurt@roeckx.be>
Reviewed-by: Rich Salz <rsalz@openssl.org>
GH: #1222
When session tickets are used, it's possible that SNI might swtich the
SSL_CTX on an SSL. Normally, this is not a problem, because the
initial_ctx/session_ctx are used for all session ticket/id processes.
However, when the SNI callback occurs, it's possible that the callback
may update the options in the SSL from the SSL_CTX, and this could
cause SSL_OP_NO_TICKET to be set. If this occurs, then two bad things
can happen:
1. The session ticket TLSEXT may not be written when the ticket expected
flag is set. The state machine transistions to writing the ticket, and
the client responds with an error as its not expecting a ticket.
2. When creating the session ticket, if the ticket key cb returns 0
the crypto/hmac contexts are not initialized, and the code crashes when
trying to encrypt the session ticket.
To fix 1, if the ticket TLSEXT is not written out, clear the expected
ticket flag.
To fix 2, consider a return of 0 from the ticket key cb a recoverable
error, and write a 0 length ticket and continue. The client-side code
can explicitly handle this case.
Fix these two cases, and add unit test code to validate ticket behavior.
Reviewed-by: Emilia Käsper <emilia@openssl.org>
Reviewed-by: Rich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/1098)
The ssl3_init_finished_mac() function can fail, in which case we need to
propagate the error up through the stack.
RT#3198
Reviewed-by: Rich Salz <rsalz@openssl.org>
In the new state machine if using nbio and we get the header of a
handshake message is one record with the body in the next, with an nbio
event in the middle, then the connection was failing. This is because
s->init_num was getting reset. We should only reset it after we have
read the whole message.
RT#4394
Reviewed-by: Andy Polyakov <appro@openssl.org>
ChangeCipherSpec messages have a defined value. They also may not occur
in the middle of a handshake message. The current logic will accept a
ChangeCipherSpec with value 2. It also would accept up to three bytes of
handshake data before the ChangeCipherSpec which it would discard
(because s->init_num gets reset).
Instead, require that s->init_num is 0 when a ChangeCipherSpec comes in.
RT#4391
Reviewed-by: Andy Polyakov <appro@openssl.org>
Reviewed-by: Matt Caswell <matt@openssl.org>
The write BIO for handshake messages is bufferred so that we only write
out to the network when we have a complete flight. There was some
complexity in the buffering logic so that we switched buffering on and
off at various points through out the handshake. The only real reason to
do this was historically it complicated the state machine when you wanted
to flush because you had to traverse through the "flush" state (in order
to cope with NBIO). Where we knew up front that there was only going to
be one message in the flight we switched off buffering to avoid that.
In the new state machine there is no longer a need for a flush state so
it is simpler just to have buffering on for the whole handshake. This
also gives us the added benefit that we can simply call flush after every
flight even if it only has one message in it. This means that BIO authors
can implement their own buffering strategies and not have to be aware of
the state of the SSL object (previously they would have to switch off
their own buffering during the handshake because they could not rely on
a flush being received when they really needed to write data out). This
last point addresses GitHub Issue #322.
Reviewed-by: Andy Polyakov <appro@openssl.org>
Set ctx->error = X509_V_ERR_OUT_OF_MEM when verificaiton cannot
continue due to malloc failure. Also, when X509_verify_cert()
returns <= 0 make sure that the verification status does not remain
X509_V_OK, as a last resort set it it to X509_V_ERR_UNSPECIFIED,
just in case some code path returns an error without setting an
appropriate value of ctx->error.
Reviewed-by: Richard Levitte <levitte@openssl.org>
This involves providing more session ticket key data, for both the cipher and
the digest
Signed-off-by: Kurt Roeckx <kurt@roeckx.be>
Reviewed-by: Matt Caswell <matt@openssl.org>
GH: #515, MR: #2153
The current limit of 2^14 bytes is too low (e.g. RFC 5246 specifies the
maximum size of just the extensions field to be 2^16-1), and may cause
bogus failures.
RT#4063
Reviewed-by: Kurt Roeckx <kurt@openssl.org>
Reviewed-by: Rich Salz <rsalz@openssl.org>
Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/413)
Per RFC 4507, section 3.3:
This message [NewSessionTicket] MUST be sent if the
server included a SessionTicket extension in the ServerHello. This
message MUST NOT be sent if the server did not include a
SessionTicket extension in the ServerHello.
The presence of the NewSessionTicket message should be determined
entirely from the ServerHello without probing.
RT#4389
Reviewed-by: Emilia Käsper <emilia@openssl.org>
Reviewed-by: Matt Caswell <matt@openssl.org>
