This setting belongs to the individual connection, not to a configuration
shared by many connections. (If a default value is desired, that can be handled
by the application code that calls mbedtls_ssl_set_mtu().)
There are at least two ways in which this matters:
- per-connection settings can be adjusted if MTU estimates become available
during the lifetime of the connection
- it is at least conceivable that a server might recognize restricted clients
based on range of IPs and immediately set a lower MTU for them. This is much
easier to do with a per-connection setting than by maintaining multiple
near-duplicated ssl_config objects that differ only by the MTU setting.
The standard HKDF security guarantees only hold if `mbedtls_hkdf()` is
used or if `mbedtls_hkdf_extract()` and `mbedtls_hkdf_expand()` are
called in succession carefully and an equivalent way.
Making `mbedtls_hkdf_extract()` and `mbedtls_hkdf_expand()` static would
prevent any misuse, but doing so would require the TLS 1.3 stack to
break abstraction and bypass the module API.
To reduce the risk of misuse we add warnings to the function
descriptions.
In ecp_mul_comb(), if (!p_eq_g && grp->T == NULL) and then ecp_precompute_comb() fails (which can
happen due to OOM), then the new array of points T will be leaked (as it's newly allocated, but
hasn't been asigned to grp->T yet).
Symptom was a memory leak in ECDHE key exchange under low memory conditions.
The basis for the Lucky 13 family of attacks is for an attacker to be able to
distinguish between (long) valid TLS-CBC padding and invalid TLS-CBC padding.
Since our code sets padlen = 0 for invalid padding, the length of the input to
the HMAC function, and the location where we read the MAC, give information
about that.
A local attacker could gain information about that by observing via a
cache attack whether the bytes at the end of the record (at the location of
would-be padding) have been read during MAC verification (computation +
comparison).
Let's make sure they're always read.
The basis for the Lucky 13 family of attacks is for an attacker to be able to
distinguish between (long) valid TLS-CBC padding and invalid TLS-CBC padding.
Since our code sets padlen = 0 for invalid padding, the length of the input to
the HMAC function gives information about that.
Information about this length (modulo the MD/SHA block size) can be deduced
from how much MD/SHA padding (this is distinct from TLS-CBC padding) is used.
If MD/SHA padding is read from a (static) buffer, a local attacker could get
information about how much is used via a cache attack targeting that buffer.
Let's get rid of this buffer. Now the only buffer used is the internal MD/SHA
one, which is always read fully by the process() function.
Fix Documentation error in `mbedtls_ssl_get_session`.
This function supports deep copying of the session,
and the peer certificate is not lost anymore, Resolves#926
* development: (180 commits)
Change the library version to 2.11.0
Fix version in ChangeLog for fix for #552
Add ChangeLog entry for clang version fix. Issue #1072
Compilation warning fixes on 32b platfrom with IAR
Revert "Turn on MBEDTLS_SSL_ASYNC_PRIVATE by default"
Fix for missing len var when XTS config'd and CTR not
ssl_server2: handle mbedtls_x509_dn_gets failure
Fix harmless use of uninitialized memory in ssl_parse_encrypted_pms
SSL async tests: add a few test cases for error in decrypt
Fix memory leak in ssl_server2 with SNI + async callback
SNI + SSL async callback: make all keys async
ssl_async_resume: free the operation context on error
ssl_server2: get op_name from context in ssl_async_resume as well
Clarify "as directed here" in SSL async callback documentation
SSL async callbacks documentation: clarify resource cleanup
Async callback: use mbedtls_pk_check_pair to compare keys
Rename mbedtls_ssl_async_{get,set}_data for clarity
Fix copypasta in the async callback documentation
SSL async callback: cert is not always from mbedtls_ssl_conf_own_cert
ssl_async_set_key: detect if ctx->slots overflows
...
* development: (182 commits)
Change the library version to 2.11.0
Fix version in ChangeLog for fix for #552
Add ChangeLog entry for clang version fix. Issue #1072
Compilation warning fixes on 32b platfrom with IAR
Revert "Turn on MBEDTLS_SSL_ASYNC_PRIVATE by default"
Fix for missing len var when XTS config'd and CTR not
ssl_server2: handle mbedtls_x509_dn_gets failure
Fix harmless use of uninitialized memory in ssl_parse_encrypted_pms
SSL async tests: add a few test cases for error in decrypt
Fix memory leak in ssl_server2 with SNI + async callback
SNI + SSL async callback: make all keys async
ssl_async_resume: free the operation context on error
ssl_server2: get op_name from context in ssl_async_resume as well
Clarify "as directed here" in SSL async callback documentation
SSL async callbacks documentation: clarify resource cleanup
Async callback: use mbedtls_pk_check_pair to compare keys
Rename mbedtls_ssl_async_{get,set}_data for clarity
Fix copypasta in the async callback documentation
SSL async callback: cert is not always from mbedtls_ssl_conf_own_cert
ssl_async_set_key: detect if ctx->slots overflows
...
Fix compilation warnings with IAR toolchain, on 32 bit platform.
Reported by rahmanih in #683
This is based on work by Ron Eldor in PR #750, some of which was independently
fixed by Azim Khan and already merged in PR #1646.
