Description
This release of Mbed TLS provides bug fixes and minor enhancements. This release includes fixes for security issues.
Mbed TLS 2.28 is a long-time support branch. It will be supported with bug-fixes and security fixes until end of 2024.
Security Advisories
For full details, please see the following links:
https://tls.mbed.org/tech-updates/security-advisories/mbedtls-security-advisory-2021-12
Release Notes
API changes
- Some fields of mbedtls_ssl_session and mbedtls_ssl_config are in a
different order. This only affects applications that define such
structures directly or serialize them.
Requirement changes
- Sign-magnitude and one's complement representations for signed integers are
not supported. Two's complement is the only supported representation.
Removals
- Remove config option MBEDTLS_TLS_DEFAULT_ALLOW_SHA1_IN_CERTIFICATES,
which allowed SHA-1 in the default TLS configuration for certificate
signing. It was intended to facilitate the transition in environments
with SHA-1 certificates. SHA-1 is considered a weak message digest and
its use constitutes a security risk. - Remove the partial support for running unit tests via Greentea on Mbed OS,
which had been unmaintained since 2018.
Features
- The identifier of the CID TLS extension can be configured by defining
MBEDTLS_TLS_EXT_CID at compile time. - Warn if errors from certain functions are ignored. This is currently
supported on GCC-like compilers and on MSVC and can be configured through
the macro MBEDTLS_CHECK_RETURN. The warnings are always enabled
(where supported) for critical functions where ignoring the return
value is almost always a bug. Enable the new configuration option
MBEDTLS_CHECK_RETURN_WARNING to get warnings for other functions. This
is currently implemented in the AES, DES and md modules, and will be
extended to other modules in the future. - Add missing PSA macros declared by PSA Crypto API 1.0.0:
PSA_ALG_IS_SIGN_HASH, PSA_ALG_NONE, PSA_HASH_BLOCK_LENGTH, PSA_KEY_ID_NULL. - Add new API mbedtls_ct_memcmp for constant time buffer comparison.
- Add PSA API definition for ARIA.
Security
- Zeroize several intermediate variables used to calculate the expected
value when verifying a MAC or AEAD tag. This hardens the library in
case the value leaks through a memory disclosure vulnerability. For
example, a memory disclosure vulnerability could have allowed a
man-in-the-middle to inject fake ciphertext into a DTLS connection. - In psa_cipher_generate_iv() and psa_cipher_encrypt(), do not read back
from the output buffer. This fixes a potential policy bypass or decryption
oracle vulnerability if the output buffer is in memory that is shared with
an untrusted application. - Fix a double-free that happened after mbedtls_ssl_set_session() or
mbedtls_ssl_get_session() failed with MBEDTLS_ERR_SSL_ALLOC_FAILED
(out of memory). After that, calling mbedtls_ssl_session_free()
and mbedtls_ssl_free() would cause an internal session buffer to
be free()'d twice.
Bugfix
- Stop using reserved identifiers as local variables. Fixes #4630.
- The GNU makefiles invoke python3 in preference to python except on Windows.
The check was accidentally not performed when cross-compiling for Windows
on Linux. Fix this. Fixes #4774. - Prevent divide by zero if either of PSA_CIPHER_ENCRYPT_OUTPUT_SIZE() or
PSA_CIPHER_UPDATE_OUTPUT_SIZE() were called using an asymmetric key type. - Fix a parameter set but unused in psa_crypto_cipher.c. Fixes #4935.
- Don't use the obsolete header path sys/fcntl.h in unit tests.
These header files cause compilation errors in musl.
Fixes #4969. - Fix missing constraints on x86_64 and aarch64 assembly code
for bignum multiplication that broke some bignum operations with
(at least) Clang 12.
Fixes #4116, #4786, #4917, #4962. - Fix mbedtls_cipher_crypt: AES-ECB when MBEDTLS_USE_PSA_CRYPTO is enabled.
- Failures of alternative implementations of AES or DES single-block
functions enabled with MBEDTLS_AES_ENCRYPT_ALT, MBEDTLS_AES_DECRYPT_ALT,
MBEDTLS_DES_CRYPT_ECB_ALT or MBEDTLS_DES3_CRYPT_ECB_ALT were ignored.
This does not concern the implementation provided with Mbed TLS,
where this function cannot fail, or full-module replacements with
MBEDTLS_AES_ALT or MBEDTLS_DES_ALT. Reported by Armelle Duboc in #1092. - Some failures of HMAC operations were ignored. These failures could only
happen with an alternative implementation of the underlying hash module. - Fix the error returned by psa_generate_key() for a public key. Fixes #4551.
- Fix the build of sample programs when neither MBEDTLS_ERROR_C nor
MBEDTLS_ERROR_STRERROR_DUMMY is enabled. - Fix PSA_ALG_RSA_PSS verification accepting an arbitrary salt length.
This algorithm now accepts only the same salt length for verification
that it produces when signing, as documented. Use the new algorithm
PSA_ALG_RSA_PSS_ANY_SALT to accept any salt length. Fixes #4946. - The existing predicate macro name PSA_ALG_IS_HASH_AND_SIGN is now reserved
for algorithm values that fully encode the hashing step, as per the PSA
Crypto API specification. This excludes PSA_ALG_RSA_PKCS1V15_SIGN_RAW and
PSA_ALG_ECDSA_ANY. The new predicate macro PSA_ALG_IS_SIGN_HASH covers
all algorithms that can be used with psa_{sign,verify}_hash(), including
these two. - Fix issue in Makefile on Linux with SHARED=1, that caused shared libraries
not to list other shared libraries they need. - Fix a bug in mbedtls_gcm_starts() when the bit length of the iv
exceeds 2^32. Fixes #4884. - Fix an uninitialized variable warning in test_suite_ssl.function with GCC
version 11. - Fix the build when no SHA2 module is included. Fixes #4930.
- Fix the build when only the bignum module is included. Fixes #4929.
- Fix a potential invalid pointer dereference and infinite loop bugs in
pkcs12 functions when the password is empty. Fix the documentation to
better describe the inputs to these functions and their possible values.
Fixes #5136. - The key usage flags PSA_KEY_USAGE_SIGN_MESSAGE now allows the MAC
operations psa_mac_compute() and psa_mac_sign_setup(). - The key usage flags PSA_KEY_USAGE_VERIFY_MESSAGE now allows the MAC
operations psa_mac_verify() and psa_mac_verify_setup().
Changes
- Set config option MBEDTLS_TLS_DEFAULT_ALLOW_SHA1_IN_KEY_EXCHANGE to be
disabled by default. - Improve the performance of base64 constant-flow code. The result is still
slower than the original non-constant-flow implementation, but much faster
than the previous constant-flow implementation. Fixes #4814. - Indicate in the error returned if the nonce length used with
ChaCha20-Poly1305 is invalid, and not just unsupported. - The mbedcrypto library includes a new source code module constant_time.c,
containing various functions meant to resist timing side channel attacks.
This module does not have a separate configuration option, and functions
from this module will be included in the build as required. Currently
most of the interface of this module is private and may change at any
time.
Who should update
We recommend all users should update to take advantage of the bug fixes contained in this release at an appropriate point in their development lifecycle.
Checksum
The SHA256 hashes for the archives are:
6519579b836ed78cc549375c7c18b111df5717e86ca0eeff4cb64b2674f424cc mbedtls-2.28.0.tar.gz
80cf41f5f3f625436e3a800e9708e60a25206cd5d81968ba8dd9f3e8becd37e6 mbedtls-2.28.0.zip