David Woodhouse [Wed, 28 Sep 2016 13:31:22 +0000 (14:31 +0100)]
Call ENGINE_init() before trying to use keys from engine
Things like 'openssl s_client' only ever worked with keys from an engine
which provided a default generic method for some key type — because it
called ENGINE_set_default() and that ended up being an implicit
initialisation and functional refcount.
But an engine which doesn't provide generic methods doesn't get
initialised, and then when you try to use it you get an error:
cannot load client certificate private key file from engine 140688147056384:error:26096075:engine routines:ENGINE_load_private_key:not initialised:crypto/engine/eng_pkey.c:66:
unable to load client certificate private key file
cf. https://github.com/OpenSC/libp11/issues/107 (in which we discover
that engine_pkcs11 *used* to provide generic methods that OpenSSL would
try to use for ephemeral DH keys when negotiating ECDHE cipher suites in
TLS, and that didn't work out very well.)
Reviewed-by: Richard Levitte <levitte@openssl.org> Reviewed-by: Rich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/1640)
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: Richard Levitte <levitte@openssl.org> Reviewed-by: Matt Caswell <matt@openssl.org>
Matt Caswell [Fri, 9 Sep 2016 09:53:39 +0000 (10:53 +0100)]
Fix a mem leak in NPN handling
If a server sent multiple NPN extensions in a single ClientHello then a
mem leak can occur. This will only happen where the client has requested
NPN in the first place. It does not occur during renegotiation. Therefore
the maximum that could be leaked in a single connection with a malicious
server is 64k (the maximum size of the ServerHello extensions section). As
this is client side, only occurs if NPN has been requested and does not
occur during renegotiation this is unlikely to be exploitable.
Matt Caswell [Fri, 9 Sep 2016 09:08:45 +0000 (10:08 +0100)]
Fix OCSP Status Request extension unbounded memory growth
A malicious client can send an excessively large OCSP Status Request
extension. If that client continually requests renegotiation,
sending a large OCSP Status Request extension each time, then there will
be unbounded memory growth on the server. This will eventually lead to a
Denial Of Service attack through memory exhaustion. Servers with a
default configuration are vulnerable even if they do not support OCSP.
Builds using the "no-ocsp" build time option are not affected.
I have also checked other extensions to see if they suffer from a similar
problem but I could not find any other issues.
Matt Caswell [Wed, 21 Sep 2016 13:48:16 +0000 (14:48 +0100)]
Don't allow too many consecutive warning alerts
Certain warning alerts are ignored if they are received. This can mean that
no progress will be made if one peer continually sends those warning alerts.
Implement a count so that we abort the connection if we receive too many.
Grow TLS/DTLS 16 bytes more than strictly necessary as a precaution against
OOB reads. In most cases this will have no effect because the message buffer
will be large enough already.
There were some unexpected side effects to this commit, e.g. in SSLv3 a
warning alert gets sent "no_certificate" if a client does not send a
Certificate during Client Auth. With the above commit this causes the
connection to abort, which is incorrect. There may be some other edge cases
like this so we need to have a rethink on this.
Richard Levitte [Tue, 6 Sep 2016 15:39:35 +0000 (17:39 +0200)]
VMS: only use _realloc32 with /POINTER_SIZE=32
This fixes the following error when building with no particular pointer size
is specified (implied 32 bit):
static void *(*realloc_func) (void *, size_t) = realloc;
................................................^
%CC-E-UNDECLARED, In the initializer for realloc_func, "_realloc32" is not declared.
at line number 93 in file DEV:[OPENSSL102.crypto]mem.c;1
Matt Caswell [Thu, 8 Sep 2016 13:32:27 +0000 (14:32 +0100)]
Add some sanity checks around usage of t_fromb64()
The internal SRP function t_fromb64() converts from base64 to binary. It
does not validate that the size of the destination is sufficiently large -
that is up to the callers. In some places there was such a check, but not
in others.
Add an argument to t_fromb64() to provide the size of the destination
buffer and validate that we don't write too much data. Also add some sanity
checks to the callers where appropriate.
Matt Caswell [Mon, 12 Sep 2016 10:04:51 +0000 (11:04 +0100)]
Abort on unrecognised warning alerts
A peer continually sending unrecognised warning alerts could mean that we
make no progress on a connection. We should abort rather than continuing if
we receive an unrecognised warning alert.
David Woodhouse [Wed, 7 Sep 2016 15:53:18 +0000 (16:53 +0100)]
Avoid EVP_PKEY_cmp() crash on EC keys without public component
Some hardware devices don't provide the public EC_POINT data. The only
way for X509_check_private_key() to validate that the key matches a
given certificate is to actually perform a sign operation and then
verify it using the public key in the certificate.
Maybe that can come later, as discussed in issue 1532. But for now let's
at least make it fail gracefully and not crash.
GH: 1532
Reviewed-by: Richard Levitte <levitte@openssl.org> Reviewed-by: Rich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/1547)
(cherry picked from commit 92ed7fa575a80955f3bb6efefca9bf576a953586)
Never output -0; make "negative zero" an impossibility.
Do better checking on BN_rand top/bottom requirements and #bits.
Update doc.
Ignoring trailing garbage in BN_asc2bn.
Port this commit from boringSSL: https://boringssl.googlesource.com/boringssl/+/899b9b19a4cd3fe526aaf5047ab9234cdca19f7d%5E!/
Ensure |BN_div| never gives negative zero in the no_branch code.
Have |bn_correct_top| fix |bn->neg| if the input is zero so that we
don't have negative zeros lying around.
Matt Caswell [Tue, 30 Aug 2016 14:06:01 +0000 (15:06 +0100)]
Ensure the CertStatus message adds a DTLS message header where needed
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.
Richard Levitte [Fri, 26 Aug 2016 07:59:55 +0000 (09:59 +0200)]
Improve the definition of STITCHED_CALL in e_rc4_hmac_md5.c
The definition of STITCHED_CALL relies on OPENSSL_NO_ASM. However,
when a configuration simply lacks the assembler implementation for RC4
(which is where we have implemented the stitched call), OPENSSL_NO_ASM
isn't implemented. Better, then, to rely on specific macros that
indicated that RC4 (and MD5) are implemented in assembler.
For this to work properly, we must also make sure Configure adds the
definition of RC4_ASM among the C flags.
David Woodhouse [Tue, 2 Aug 2016 21:54:46 +0000 (22:54 +0100)]
Fix ubsan 'left shift of negative value -1' error in satsub64be()
Baroque, almost uncommented code triggers behaviour which is undefined
by the C standard. You might quite reasonably not care that the code was
broken on ones-complement machines, but if we support a ubsan build then
we need to at least pretend to care.
It looks like the special-case code for 64-bit big-endian is going to
behave differently (and wrongly) on wrap-around, because it treats the
values as signed. That seems wrong, and allows replay and other attacks.
Surely you need to renegotiate and start a new epoch rather than
wrapping around to sequence number zero again?
David Woodhouse [Fri, 8 Jul 2016 19:46:07 +0000 (20:46 +0100)]
Fix SSL_export_keying_material() for DTLS1_BAD_VER
Commit d8e8590e ("Fix missing return value checks in SCTP") made the
DTLS handshake fail, even for non-SCTP connections, if
SSL_export_keying_material() fails. Which it does, for DTLS1_BAD_VER.
Apply the trivial fix to make it succeed, since there's no real reason
why it shouldn't even though we never need it.
Andy Polyakov [Wed, 24 Aug 2016 15:13:09 +0000 (17:13 +0200)]
ec/asm/ecp_nistz256-x86_64.pl: /cmovb/cmovc/ as nasm doesn't recognize cmovb.
Reviewed-by: Richard Levitte <levitte@openssl.org> Reviewed-by: Matt Caswell <matt@openssl.org>
(cherry picked from commit d3034d31e7c04b334dd245504dd4f56e513ca115)
If a ticket callback changes the HMAC digest to SHA512 the existing
sanity checks are not sufficient and an attacker could perform a DoS
attack with a malformed ticket. Add additional checks based on
HMAC size.
Kazuki Yamaguchi [Sun, 21 Aug 2016 17:36:36 +0000 (02:36 +0900)]
Fix overflow check in BN_bn2dec()
Fix an off by one error in the overflow check added by 07bed46f332fc
("Check for errors in BN_bn2dec()").
Reviewed-by: Stephen Henson <steve@openssl.org> Reviewed-by: Matt Caswell <matt@openssl.org>
(cherry picked from commit 099e2968ed3c7d256cda048995626664082b1b30)
Richard Levitte [Mon, 22 Aug 2016 08:17:27 +0000 (10:17 +0200)]
VMS: Use strict refdef extern model when building library object files
Most of the time, this isn't strictly needed. However, in the default
extern model (called relaxed refdef), symbols are treated as weak
common objects unless they are initialised. The librarian doesn't
include weak symbols in the (static) libraries, which renders them
invisible when linking a program with said those libraries, which is a
problem at times.
Using the strict refdef model is much more like standard C on all
other platforms, and thereby avoid the issues that come with the
relaxed refdef model.
Note: this doesn't apply to VAX C. It's possible that this will make
OpenSSL building with VAX C difficult some time in the future if it
isn't already. However, VAX C is a very old compiler that we don't
expect to see too often, as DEC C (a.k.a VMS C) should have replaced
it a long time ago.
In that case, the second command wants to read a certificate request
from stdin, because -x509 wasn't fully flagged as being for creating
something new. This changes makes it fully flagged.
Andy Polyakov [Wed, 16 Mar 2016 22:33:53 +0000 (23:33 +0100)]
bn/asm/x86[_64]-mont*.pl: implement slightly alternative page-walking.
Original strategy for page-walking was adjust stack pointer and then
touch pages in order. This kind of asks for double-fault, because
if touch fails, then signal will be delivered to frame above adjusted
stack pointer. But touching pages prior adjusting stack pointer would
upset valgrind. As compromise let's adjust stack pointer in pages,
touching top of the stack. This still asks for double-fault, but at
least prevents corruption of neighbour stack if allocation is to
overstep the guard page.
Also omit predict-non-taken hints as they reportedly trigger illegal
instructions in some VM setups.
Richard Levitte [Mon, 22 Aug 2016 12:02:31 +0000 (14:02 +0200)]
ssltestlib: Tell compiler we don't care about the value when we don't
In mempacket_test_read(), we've already fetched the top value of the
stack, so when we shift the stack, we don't care for the value. The
compiler needs to be told, or it will complain harshly when we tell it
to be picky.
Matt Caswell [Thu, 30 Jun 2016 14:06:27 +0000 (15:06 +0100)]
Prevent DTLS Finished message injection
Follow on from CVE-2016-2179
The investigation and analysis of CVE-2016-2179 highlighted a related flaw.
This commit fixes a security "near miss" in the buffered message handling
code. Ultimately this is not currently believed to be exploitable due to
the reasons outlined below, and therefore there is no CVE for this on its
own.
The issue this commit fixes is a MITM attack where the attacker can inject
a Finished message into the handshake. In the description below it is
assumed that the attacker injects the Finished message for the server to
receive it. The attack could work equally well the other way around (i.e
where the client receives the injected Finished message).
The MITM requires the following capabilities:
- The ability to manipulate the MTU that the client selects such that it
is small enough for the client to fragment Finished messages.
- The ability to selectively drop and modify records sent from the client
- The ability to inject its own records and send them to the server
The MITM forces the client to select a small MTU such that the client
will fragment the Finished message. Ideally for the attacker the first
fragment will contain all but the last byte of the Finished message,
with the second fragment containing the final byte.
During the handshake and prior to the client sending the CCS the MITM
injects a plaintext Finished message fragment to the server containing
all but the final byte of the Finished message. The message sequence
number should be the one expected to be used for the real Finished message.
OpenSSL will recognise that the received fragment is for the future and
will buffer it for later use.
After the client sends the CCS it then sends its own Finished message in
two fragments. The MITM causes the first of these fragments to be
dropped. The OpenSSL server will then receive the second of the fragments
and reassemble the complete Finished message consisting of the MITM
fragment and the final byte from the real client.
The advantage to the attacker in injecting a Finished message is that
this provides the capability to modify other handshake messages (e.g.
the ClientHello) undetected. A difficulty for the attacker is knowing in
advance what impact any of those changes might have on the final byte of
the handshake hash that is going to be sent in the "real" Finished
message. In the worst case for the attacker this means that only 1 in
256 of such injection attempts will succeed.
It may be possible in some situations for the attacker to improve this such
that all attempts succeed. For example if the handshake includes client
authentication then the final message flight sent by the client will
include a Certificate. Certificates are ASN.1 objects where the signed
portion is DER encoded. The non-signed portion could be BER encoded and so
the attacker could re-encode the certificate such that the hash for the
whole handshake comes to a different value. The certificate re-encoding
would not be detectable because only the non-signed portion is changed. As
this is the final flight of messages sent from the client the attacker
knows what the complete hanshake hash value will be that the client will
send - and therefore knows what the final byte will be. Through a process
of trial and error the attacker can re-encode the certificate until the
modified handhshake also has a hash with the same final byte. This means
that when the Finished message is verified by the server it will be
correct in all cases.
In practice the MITM would need to be able to perform the same attack
against both the client and the server. If the attack is only performed
against the server (say) then the server will not detect the modified
handshake, but the client will and will abort the connection.
Fortunately, although OpenSSL is vulnerable to Finished message
injection, it is not vulnerable if *both* client and server are OpenSSL.
The reason is that OpenSSL has a hard "floor" for a minimum MTU size
that it will never go below. This minimum means that a Finished message
will never be sent in a fragmented form and therefore the MITM does not
have one of its pre-requisites. Therefore this could only be exploited
if using OpenSSL and some other DTLS peer that had its own and separate
Finished message injection flaw.
The fix is to ensure buffered messages are cleared on epoch change.
Reviewed-by: Richard Levitte <levitte@openssl.org>
Matt Caswell [Thu, 30 Jun 2016 12:17:08 +0000 (13:17 +0100)]
Fix DTLS buffered message DoS attack
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>
Matt Caswell [Tue, 5 Jul 2016 11:04:37 +0000 (12:04 +0100)]
Fix DTLS replay protection
The DTLS implementation provides some protection against replay attacks
in accordance with RFC6347 section 4.1.2.6.
A sliding "window" of valid record sequence numbers is maintained with
the "right" hand edge of the window set to the highest sequence number we
have received so far. Records that arrive that are off the "left" hand
edge of the window are rejected. Records within the window are checked
against a list of records received so far. If we already received it then
we also reject the new record.
If we have not already received the record, or the sequence number is off
the right hand edge of the window then we verify the MAC of the record.
If MAC verification fails then we discard the record. Otherwise we mark
the record as received. If the sequence number was off the right hand edge
of the window, then we slide the window along so that the right hand edge
is in line with the newly received sequence number.
Records may arrive for future epochs, i.e. a record from after a CCS being
sent, can arrive before the CCS does if the packets get re-ordered. As we
have not yet received the CCS we are not yet in a position to decrypt or
validate the MAC of those records. OpenSSL places those records on an
unprocessed records queue. It additionally updates the window immediately,
even though we have not yet verified the MAC. This will only occur if
currently in a handshake/renegotiation.
This could be exploited by an attacker by sending a record for the next
epoch (which does not have to decrypt or have a valid MAC), with a very
large sequence number. This means the right hand edge of the window is
moved very far to the right, and all subsequent legitimate packets are
dropped causing a denial of service.
A similar effect can be achieved during the initial handshake. In this
case there is no MAC key negotiated yet. Therefore an attacker can send a
message for the current epoch with a very large sequence number. The code
will process the record as normal. If the hanshake message sequence number
(as opposed to the record sequence number that we have been talking about
so far) is in the future then the injected message is bufferred to be
handled later, but the window is still updated. Therefore all subsequent
legitimate handshake records are dropped. This aspect is not considered a
security issue because there are many ways for an attacker to disrupt the
initial handshake and prevent it from completing successfully (e.g.
injection of a handshake message will cause the Finished MAC to fail and
the handshake to be aborted). This issue comes about as a result of trying
to do replay protection, but having no integrity mechanism in place yet.
Does it even make sense to have replay protection in epoch 0? That
issue isn't addressed here though.
This addressed an OCAP Audit issue.
CVE-2016-2181
Reviewed-by: Richard Levitte <levitte@openssl.org>
Matt Caswell [Tue, 5 Jul 2016 10:52:43 +0000 (11:52 +0100)]
Add DTLS replay protection test
Injects a record from epoch 1 during epoch 0 handshake, with a record
sequence number in the future, to test that the record replay protection
feature works as expected. This is described more fully in the next commit.
Reviewed-by: Richard Levitte <levitte@openssl.org>
Matt Caswell [Tue, 5 Jul 2016 10:46:26 +0000 (11:46 +0100)]
Fix DTLS unprocessed records bug
During a DTLS handshake we may get records destined for the next epoch
arrive before we have processed the CCS. In that case we can't decrypt or
verify the record yet, so we buffer it for later use. When we do receive
the CCS we work through the queue of unprocessed records and process them.
Unfortunately the act of processing wipes out any existing packet data
that we were still working through. This includes any records from the new
epoch that were in the same packet as the CCS. We should only process the
buffered records if we've not got any data left.
Reviewed-by: Richard Levitte <levitte@openssl.org>
If an oversize BIGNUM is presented to BN_bn2dec() it can cause
BN_div_word() to fail and not reduce the value of 't' resulting
in OOB writes to the bn_data buffer and eventually crashing.
Fix by checking return value of BN_div_word() and checking writes
don't overflow buffer.