mbedTLS v2.23.0 Release Notes

Release Date: 2020-07-01 // about 1 year ago
  • Description

    ๐Ÿš€ This release of Mbed TLS provides bug fixes and minor enhancements. This release includes fixes for security issues and the most severe one is described in more detail in a security advisory.

    0๏ธโƒฃ Default behavior changes

    • In the experimental PSA secure element interface, change the encoding of key lifetimes to encode a persistence level and the location. Although C prototypes do not effectively change, code calling psa_register_se_driver() must be modified to pass the driver's location instead of the keys' lifetime. If the library is upgraded on an existing device, keys created with the old lifetime value will not be readable or removable through Mbed TLS after the upgrade.

    ๐Ÿ”‹ Features

    • ๐Ÿ†• New functions in the error module return constant strings for high- and low-level error codes, complementing mbedtls_strerror() which constructs a string for any error code, including compound ones, but requires a writable buffer. Contributed by Gaurav Aggarwal in #3176.
    • The new utility programs/ssl/ssl_context_info prints a human-readable dump of an SSL context saved with mbedtls_ssl_context_save().
    • โž• Add support for midipix, a POSIX layer for Microsoft Windows.
    • Add new mbedtls_x509_crt_parse_der_with_ext_cb() routine which allows parsing unsupported certificate extensions via user provided callback. Contributed by Nicola Di Lieto [email protected] in #3243 as a solution to #3241.
    • Pass the "certificate policies" extension to the callback supplied to mbedtls_x509_crt_parse_der_with_ext_cb() if it contains unsupported policies (#3419).
    • โž• Added support to entropy_poll for the kern.arandom syscall supported on some BSD systems. Contributed by Nia Alarie in #3423.
    • โž• Add support for Windows 2000 in net_sockets. Contributed by opatomic. #3239

    ๐Ÿ”’ Security

    • ๐Ÿ›  Fix a side channel vulnerability in modular exponentiation that could reveal an RSA private key used in a secure enclave. Noticed by Sangho Lee, Ming-Wei Shih, Prasun Gera, Taesoo Kim and Hyesoon Kim (Georgia Institute of Technology); and Marcus Peinado (Microsoft Research). Reported by Raoul Strackx (Fortanix) in #3394.
    • Fix side channel in mbedtls_ecp_check_pub_priv() and mbedtls_pk_parse_key() / mbedtls_pk_parse_keyfile() (when loading a private key that didn't include the uncompressed public key), as well as mbedtls_ecp_mul() / mbedtls_ecp_mul_restartable() when called with a NULL f_rng argument. An attacker with access to precise enough timing and memory access information (typically an untrusted operating system attacking a secure enclave) could fully recover the ECC private key. Found and reported by Alejandro Cabrera Aldaya and Billy Brumley.
    • Fix issue in Lucky 13 counter-measure that could make it ineffective when hardware accelerators were used (using one of the MBEDTLS_SHAxxx_ALT macros). This would cause the original Lucky 13 attack to be possible in those configurations, allowing an active network attacker to recover plaintext after repeated timing measurements under some conditions. Reported and fix suggested by Luc Perneel in #3246.

    ๐Ÿ›  Bugfix

    • ๐Ÿ›  Fix the Visual Studio Release x64 build configuration for mbedtls itself. Completes a previous fix in Mbed TLS 2.19 that only fixed the build for the example programs. Reported in #1430 and fix contributed by irwir.
    • ๐Ÿ›  Fix undefined behavior in X.509 certificate parsing if the pathLenConstraint basic constraint value is equal to INT_MAX. The actual effect with almost every compiler is the intended behavior, so this is unlikely to be exploitable anywhere. #3192
    • ๐Ÿ›  Fix issue with a detected HW accelerated record error not being exposed due to shadowed variable. Contributed by Sander Visser in #3310.
    • Avoid NULL pointer dereferencing if mbedtls_ssl_free() is called with a NULL pointer argument. Contributed by Sander Visser in #3312.
    • Fix potential linker errors on dual world platforms by inlining mbedtls_gcc_group_to_psa(). This allows the pk.c module to link separately from psa_crypto.c. Fixes #3300.
    • โœ‚ Remove dead code in X.509 certificate parsing. Contributed by irwir in #2855.
    • ๐Ÿ›  Include asn1.h in error.c. Fixes #3328 reported by David Hu.
    • Fix potential memory leaks in ecp_randomize_jac() and ecp_randomize_mxz() when PRNG function fails. Contributed by Jonas Lejeune in #3318.
    • โœ‚ Remove unused macros from MSVC projects. Reported in #3297 and fix submitted in #3333 by irwir.
    • Add additional bounds checks in ssl_write_client_hello() preventing output buffer overflow if the configuration declared a buffer that was too small.
    • Set _POSIX_C_SOURCE to at least 200112L in C99 code. Reported in #3420 and fix submitted in #3421 by Nia Alarie.
    • Fix building library/net_sockets.c and the ssl_mail_client program on NetBSD. Contributed by Nia Alarie in #3422.
    • ๐Ÿ›  Fix false positive uninitialised variable reported by cpp-check. Contributed by Sander Visser in #3311.
    • Update iv and len context pointers manually when reallocating buffers using the MBEDTLS_SSL_VARIABLE_BUFFER_LENGTH feature. This caused issues when receiving a connection with CID, when these fields were shifted in ssl_parse_record_header().

    ๐Ÿ”„ Changes

    • ๐Ÿ›  Fix warnings about signedness issues in format strings. The build is now clean of -Wformat-signedness warnings. Contributed by Kenneth Soerensen in #3153.
    • ๐Ÿ›  Fix minor performance issue in operations on Curve25519 caused by using a suboptimal modular reduction in one place. Found and fix contributed by Aurelien Jarno in #3209.
    • Combine identical cases in switch statements in md.c. Contributed by irwir in #3208.
    • Simplify a bounds check in ssl_write_certificate_request(). Contributed by irwir in #3150.
    • Unify the example programs termination to call mbedtls_exit() instead of using a return command. This has been done to enable customization of the behavior in bare metal environments.
    • Fix mbedtls_x509_dn_gets to escape non-ASCII characters as "?". Contributed by Koh M. Nakagawa in #3326.
    • ๐Ÿ‘‰ Use FindPython3 when cmake version >= 3.15.0
    • Abort the ClientHello writing function as soon as some extension doesn't fit into the record buffer. Previously, such extensions were silently dropped. As a consequence, the TLS handshake now fails when the output buffer is not large enough to hold the ClientHello.
    • ๐Ÿ— The unit tests now rely on header files in tests/include/test and source files in tests/src. When building with make or cmake, the files in tests/src are compiled and the resulting object linked into each test executable.
    • The ECP module, enabled by MBEDTLS_ECP_C, now depends on MBEDTLS_CTR_DRBG_C or MBEDTLS_HMAC_DRBG_C for some side-channel coutermeasures. If side channels are not a concern, this dependency can be avoided by enabling the new option MBEDTLS_ECP_NO_INTERNAL_RNG.
    • Align MSVC error flag with GCC and Clang. Contributed by Carlos Gomes Martinho. #3147
    • Remove superfluous assignment in mbedtls_ssl_parse_certificate(). Reported in #3182 and fix submitted by irwir. #3217
    • ๐Ÿ›  Fix typo in XTS tests. Reported and fix submitted by Kxuan. #3319

    โšก๏ธ Who should update

    ๐Ÿš€ We recommend all affected users should update to take advantage of the bug fixes contained in this release at an appropriate point in their development lifecycle.


    The SHA256 hashes for the archives are:

    9933fe6b5991d5308e183a5a07454f76d7054721ba269d0c3811b227cb629e7a mbedtls-2.23.0.tar.gz
    bbf9c3cc6b7603f2f15bbba7badcf6cf188a9d5aaa63c4df2d61213f459c2f5f mbedtls-2.23.0.zip