The macro constant `MBEDTLS_SSL_MAC_ADD` defined in `ssl_internal.h`
defines an upper bound for the amount of space needed for the record
authentication tag. Its definition distinguishes between the
presence of an ARC4 or CBC ciphersuite suite, in which case the maximum
size of an enabled SHA digest is used; otherwise, `MBEDTLS_SSL_MAC_ADD`
is set to 16 to accomodate AEAD authentication tags.
This assignment has a flaw in the situation where confidentiality is
not needed and the NULL cipher is in use. In this case, the
authentication tag also uses a SHA digest, but the definition of
`MBEDTLS_SSL_MAC_ADD` doesn't guarantee enough space.
The present commit fixes this by distinguishing between the presence
of *some* ciphersuite using a MAC, including those using a NULL cipher.
For that, the previously internal macro `SSL_SOME_MODES_USE_MAC` from
`ssl_tls.c` is renamed and moved to the public macro
`MBEDTLS_SOME_MODES_USE_MAC` defined in `ssl_internal.h`.
Prior to this commit, the security parameter struct `ssl_transform`
contained a `ciphersuite_info` field pointing to the information
structure for the negotiated ciphersuite. However, the only
information extracted from that structure that was used in the core
encryption and decryption functions `ssl_encrypt_buf`/`ssl_decrypt_buf`
was the authentication tag length in case of an AEAD cipher.
The present commit removes the `ciphersuite_info` field from the
`ssl_transform` structure and adds an explicit `taglen` field
for AEAD authentication tag length.
This is in accordance with the principle that the `ssl_transform`
structure should contain the raw parameters needed for the record
encryption and decryption functions to work, but not the higher-level
information that gave rise to them. For example, the `ssl_transform`
structure implicitly contains the encryption/decryption keys within
their cipher contexts, but it doesn't contain the SSL master or
premaster secrets. Likewise, it contains an explicit `maclen`, while
the status of the 'Truncated HMAC' extension -- which determines the
value of `maclen` when the `ssl_transform` structure is created in
`ssl_derive_keys` -- is not contained in `ssl_transform`.
The `ciphersuite_info` pointer was used in other places outside
the encryption/decryption functions during the handshake, and for
these functions to work, this commit adds a `ciphersuite_info` pointer
field to the handshake-local `ssl_handshake_params` structure.
The `ssl_transform` security parameter structure contains opaque
cipher contexts for use by the record encryption/decryption functions
`ssl_decrypt_buf`/`ssl_encrypt_buf`, while the underlying key material
is configured once in `ssl_derive_keys` and is not explicitly dealt with
anymore afterwards. In particular, the key length is not needed
explicitly by the encryption/decryption functions but is nonetheless
stored in an explicit yet superfluous `keylen` field in `ssl_transform`.
This commit removes this field.
* public/mbedtls-2.16: (40 commits)
Clarify comment mangled by an earlier refactoring
Add an "out-of-box" component
Run ssl-opt.sh on 32-bit runtime
Fix typo in data_file generator code
Give credit to OSS-Fuzz for #2404
Remove ssl_cert_test sample app
Fix the proxy seed in Travis runs
Update library version to 2.16.1
Fix errors in AEAD test function
x509.c: Fix potential memory leak in X.509 self test
Remove Circle CI script
Fix ChangeLog entry ordering
Fix typo
Add non-regression test for buffer overflow
Improve documentation of mbedtls_mpi_write_string()
Adapt ChangeLog
Fix 1-byte buffer overflow in mbedtls_mpi_write_string()
Change Perl to Python in test builds
Fix default port number information
Silence pylint
...
requires_config_enabled doesn't support multiple config options.
Tests having multiple configuration dependencies must be prefixed
with multiple invocations of requires_config_enabled instead.
Run ssl-opt.sh on x86_32 with ASan. This may detect bugs that only
show up on 32-bit platforms, for example due to size_t overflow.
For this component, turn off some memory management features that are
not useful, potentially slow, and may reduce ASan's effectiveness at
catching buffer overflows.
