Previously, MAC validation for an incoming record proceeded as follows:
1) Make a copy of the MAC contained in the record;
2) Compute the expected MAC in place, overwriting the presented one;
3) Compare both.
This resulted in a record buffer overflow if truncated MAC was used, as in this
case the record buffer only reserved 10 bytes for the MAC, but the MAC
computation routine in 2) always wrote a full digest.
For specially crafted records, this could be used to perform a controlled write of
up to 6 bytes past the boundary of the heap buffer holding the record, thereby
corrupting the heap structures and potentially leading to a crash or remote code
execution.
This commit fixes this by making the following change:
1) Compute the expected MAC in a temporary buffer that has the size of the
underlying message digest.
2) Compare to this to the MAC contained in the record, potentially
restricting to the first 10 bytes if truncated HMAC is used.
A similar fix is applied to the encryption routine `ssl_encrypt_buf`.
Previously, if `POLARSSL_SSL_RENEGOTIATION` was disabled, incoming handshake
messages in `ssl_read` (expecting application data) lead to the connection being
closed. This commit fixes this, restricting the
`POLARSSL_SSL_RENEGOTIATION`-guard to the code-paths responsible for accepting
renegotiation requests and aborting renegotiation attempts after too many
unexpected records have been received.
This commit fixes the following case: If a client is both expecting a
SERVER_HELLO and has an application data record that's partially
processed in flight (that's the situation the client gets into after
receiving a ServerHelloRequest followed by ApplicationData), a
subsequent call to ssl_read will set keep_current_message = 1
when seeing the unexpected application data, but not reset it to 0
after the application data has been processed. This commit fixes this.
This commit adds a hard assertion to mbedtls_ssl_read_record
triggering if both ssl->in_hslen and ssl->in_offt are not 0. This
should never happen, and if it does, there's no sensible way of
telling whether the previous message was a handshake or an application
data message.
There are situations in which it is not clear what message to expect
next. For example, the message following the ServerHello might be
either a Certificate, a ServerKeyExchange or a CertificateRequest. We
deal with this situation in the following way: Initially, the message
processing function for one of the allowed message types is called,
which fetches and decodes a new message. If that message is not the
expected one, the function returns successfully (instead of throwing
an error as usual for unexpected messages), and the handshake
continues to the processing function for the next possible message. To
not have this function fetch a new message, a flag in the SSL context
structure is used to indicate that the last message was retained for
further processing, and if that's set, the following processing
function will not fetch a new record.
This commit simplifies the usage of this message-retaining parameter
by doing the check within the record-fetching routine instead of the
specific message-processing routines. The code gets cleaner this way
and allows retaining messages to be used in other situations as well
without much effort. This will be used in the next commits.
This commit changes the behaviour of mbedtls_ssl_parse_certificate
to make the two authentication modes SSL_VERIFY_REQUIRED and
SSL_VERIFY_OPTIONAL be in the following relationship:
Mode == SSL_VERIFY_REQUIRED
<=> Mode == SSL_VERIFY_OPTIONAL + check verify result
Also, it changes the behaviour to perform the certificate chain
verification even if the trusted CA chain is empty. Previously, the
function failed in this case, even when using optional verification,
which was brought up in #864.
This commit changes `ssl_parse_signature_algorithms_ext` to remember
one suitable ( := supported by client and by our config ) hash
algorithm per signature algorithm.
It also modifies the ciphersuite checking function
`ssl_ciphersuite_match` to refuse a suite if there
is no suitable hash algorithm.
Finally, it adds the corresponding entry to the ChangeLog.
In a USENIX WOOT '16 paper the authors warn about a security risk
of random Initialisation Vectors (IV) repeating values.
The MBEDTLS_SSL_AEAD_RANDOM_IV feature is affected by this risk and
it isn't compliant with RFC5116. Furthermore, strictly speaking it
is a different cipher suite from the TLS (RFC5246) point of view.
Removing the MBEDTLS_SSL_AEAD_RANDOM_IV feature to resolve the above
problems.
Hanno Böck, Aaron Zauner, Sean Devlin, Juraj Somorovsky and Philipp
Jovanovic, "Nonce-Disrespecting Adversaries: Practical Forgery Attacks
on GCM in TLS", USENIX WOOT '16
* mbedtls-1.3:
Add ChangeLog entry for previous commit
cert_write : fix "Destination buffer is too small" error
Add ChangeLog entry for previous two commits
Test certificate "Server1 SHA1, key_usage" reissued.
Fix boolean values according to DER specs
Fix typo in an OID name
Disable reportedly broken assembly of Sparc(64)
ECHDE-PSK does not use a certificate
Actually ignore most non-fatal alerts
Not a security issue as here we know the buffer is large enough (unless
something else if badly wrong in the code), and the value cast to int is less
than 2^16 (again, unless issues elsewhere).
Still changing to a more correct check as a matter of principle
backport of bc5e508
* rasp/mem-leak:
Fix another potential memory leak found by find-mem-leak.cocci.
Add a rule for another type of memory leak to find-mem-leak.cocci.
Fix a potential memory leak found by find-mem-leak.cocci.
Add a semantic patch to find potential memory leaks.
Fix whitespace of 369e6c20.
Apply the semantic patch rm-malloc-cast.cocci.
Add a semantic patch to remove casts of malloc.
Conflicts:
programs/ssl/ssl_server2.c
