Mbed TLS 3.5.0

Description

This release of Mbed TLS provides new features, bug fixes and minor enhancements. This release includes fixes for security issues.

This release brings in significant code-size reductions, partly depending on configuration. In particular, the new options MBEDTLS_AES_ONLY_128_BIT_KEY_LENGTH and MBEDTLS_PSA_P256M_DRIVER_ENABLED may help you save code size.

Security Advisories

For full details, please see the following links:

• Buffer overread in TLS stream cipher suites
• Buffer overflow in TLS handshake parsing with ECDH

Release Notes

API changes

• Mbed TLS 3.4 introduced support for omitting the built-in implementation
  of ECDSA and/or EC J-PAKE when those are provided by a driver. However,
  there was a flaw in the logic checking if the built-in implementation, in
  that it failed to check if all the relevant curves were supported by the
  accelerator. As a result, it was possible to declare no curves as
  accelerated and still have the built-in implementation compiled out.
  Starting with this release, it is necessary to declare which curves are
  accelerated (using MBEDTLS_PSA_ACCEL_ECC_xxx macros), or they will be
  considered not accelerated, and the built-in implementation of the curves
  and any algorithm possible using them will be included in the build.
• Add new millisecond time type mbedtls_ms_time_t and mbedtls_ms_time()
  function, needed for TLS 1.3 ticket lifetimes. Alternative implementations
  can be created using an ALT interface.

Requirement changes

• Officially require Python 3.8 now that earlier versions are out of support.
• Minimum required Windows version is now Windows Vista, or
  Windows Server 2008.

New deprecations

• PSA_WANT_KEY_TYPE_xxx_KEY_PAIR and
  MBEDTLS_PSA_ACCEL_KEY_TYPE_xxx_KEY_PAIR, where xxx is either ECC or RSA,
  are now being deprecated in favor of PSA_WANT_KEY_TYPE_xxx_KEY_PAIR_yyy and
  MBEDTLS_PSA_ACCEL_KEY_TYPE_xxx_KEY_PAIR_yyy. Here yyy can be: BASIC,
  IMPORT, EXPORT, GENERATE, DERIVE. The goal is to have a finer detail about
  the capabilities of the PSA side for either key.
• MBEDTLS_CIPHER_BLKSIZE_MAX is deprecated in favor of
  MBEDTLS_MAX_BLOCK_LENGTH (if you intended what the name suggests:
  maximum size of any supported block cipher) or the new name
  MBEDTLS_CMAC_MAX_BLOCK_SIZE (if you intended the actual semantics:
  maximum size of a block cipher supported by the CMAC module).
• mbedtls_pkcs5_pbes2() and mbedtls_pkcs12_pbe() functions are now
  deprecated in favor of mbedtls_pkcs5_pbes2_ext() and
  mbedtls_pkcs12_pbe_ext() as they offer more security by checking
  for overflow of the output buffer and reporting the actual length
  of the output.

Features

• All modules that use hashes or HMAC can now take advantage of PSA Crypto
  drivers when MBEDTLS_PSA_CRYPTO_C is enabled and psa_crypto_init() has
  been called. Previously (in 3.3), this was restricted to a few modules,
  and only in builds where MBEDTLS_MD_C was disabled; in particular the
  entropy module was not covered which meant an external RNG had to be
  provided - these limitations are lifted in this version. A new set of
  feature macros, MBEDTLS_MD_CAN_xxx, has been introduced that can be used
  to check for availability of hash algorithms, regardless of whether
  they're provided by a built-in implementation, a driver or both. See
  docs/driver-only-builds.md.
• When a PSA driver for ECDH is present, it is now possible to disable
  MBEDTLS_ECDH_C in the build in order to save code size. For TLS 1.2
  key exchanges based on ECDH(E) to work, this requires
  MBEDTLS_USE_PSA_CRYPTO. Restartable/interruptible ECDHE operations in
  TLS 1.2 (ECDHE-ECDSA key exchange) are not supported in those builds yet,
  as PSA does not have an API for restartable ECDH yet.
• When all of ECDH, ECDSA and EC J-PAKE are either disabled or provided by
  a driver, it is possible to disable MBEDTLS_ECP_C (and MBEDTLS_BIGNUM_C
  if not required by another module) and still get support for ECC keys and
  algorithms in PSA, with some limitations. See docs/driver-only-builds.txt
  for details.
• Add parsing of directoryName subtype for subjectAltName extension in
  x509 certificates.
• Add support for server-side TLS version negotiation. If both TLS 1.2 and
  TLS 1.3 protocols are enabled, the TLS server now selects TLS 1.2 or
  TLS 1.3 depending on the capabilities and preferences of TLS clients.
  Fixes #6867.
• X.509 hostname verification now supports IPAddress Subject Alternate Names.
• Add support for reading and writing X25519 and X448
  public and private keys in RFC 8410 format using the existing PK APIs.
• When parsing X.509 certificates, support the extensions
  SignatureKeyIdentifier and AuthorityKeyIdentifier.
• Don't include the PSA dispatch functions for PAKEs (psa_pake_setup() etc)
  if no PAKE algorithms are requested
• Add support for the FFDH algorithm and DH key types in PSA, with
  parameters from RFC 7919. This includes a built-in implementation based
  on MBEDTLS_BIGNUM_C, and a driver dispatch layer enabling alternative
  implementations of FFDH through the driver entry points.
• It is now possible to generate certificates with SubjectAltNames.
  Currently supported subtypes: DnsName, UniformResourceIdentifier,
  IP address, OtherName, and DirectoryName, as defined in RFC 5280.
  See mbedtls_x509write_crt_set_subject_alternative_name for
  more information.
• X.509 hostname verification now partially supports URI Subject Alternate
  Names. Only exact matching, without any normalization procedures
  described in 7.4 of RFC5280, will result in a positive URI verification.
• Add function mbedtls_oid_from_numeric_string() to parse an OID from a
  string to a DER-encoded mbedtls_asn1_buf.
• Add SHA-3 family hash functions.
• Add support to restrict AES to 128-bit keys in order to save code size.
  A new configuration option, MBEDTLS_AES_ONLY_128_BIT_KEY_LENGTH, can be
  used to enable this feature.
• AES performance improvements. Uplift varies by platform,
  toolchain, optimisation flags and mode.
  Aarch64, gcc -Os and CCM, GCM and XTS benefit the most.
  On Aarch64, uplift is typically around 20 - 110%.
  When compiling with gcc -Os on Aarch64, AES-XTS improves
  by 4.5x.
• Add support for PBKDF2-HMAC through the PSA API.
• New symbols PSA_WANT_KEY_TYPE_xxx_KEY_PAIR_yyy and
  MBEDTLS_PSA_ACCEL_KEY_TYPE_xxx_KEY_PAIR_yyy (where xxx is either ECC, RSA
  or DH) were introduced in order to have finer accuracy in defining the
  PSA capabilities for each key. These capabilities, named yyy above, can be
  any of: BASIC, IMPORT, EXPORT, GENERATE, DERIVE.
  • DERIVE is only available for ECC keys, not for RSA or DH ones.
  • implementations are free to enable more than what it was strictly
    requested. For example BASIC internally enables IMPORT and EXPORT
    (useful for testing purposes), but this might change in the future.
• Add support for FFDH key exchange in TLS 1.3.
  This is automatically enabled as soon as PSA_WANT_ALG_FFDH
  and the ephemeral or psk-ephemeral key exchange mode are enabled.
  By default, all groups are offered; the list of groups can be
  configured using the existing API function mbedtls_ssl_conf_groups().
• Improve mbedtls_x509_time performance and reduce memory use.
• Reduce syscalls to time() during certificate verification.
• Allow MBEDTLS_CONFIG_FILE and MBEDTLS_USER_CONFIG_FILE to be set by
  setting the CMake variable of the same name at configuration time.
• Add getter (mbedtls_ssl_cache_get_timeout()) to access
  mbedtls_ssl_cache_context.timeout.
• Add getter (mbedtls_ssl_get_hostname()) to access
  mbedtls_ssl_context.hostname.
• Add getter (mbedtls_ssl_conf_get_endpoint()) to access
  mbedtls_ssl_config.endpoint.
• Support for "opaque" (PSA-held) ECC keys in the PK module has been
  extended: it is now possible to use mbedtls_pk_write_key_der(),
  mbedtls_pk_write_key_pem(), mbedtls_pk_check_pair(), and
  mbedtls_pk_verify() with opaque ECC keys (provided the PSA attributes
  allow it).
• The documentation of mbedtls_ecp_group now describes the optimized
  representation of A for some curves. Fixes #8045.
• Add a possibility to generate CSR's with RCF822 and directoryName subtype
  of subjectAltName extension in x509 certificates.
• Add support for PBKDF2-CMAC through the PSA API.
• New configuration option MBEDTLS_AES_USE_HARDWARE_ONLY introduced. When
  using CPU-accelerated AES (e.g., Arm Crypto Extensions), this option
  disables the plain C implementation and the run-time detection for the
  CPU feature, which reduces code size and avoids the vulnerability of the
  plain C implementation.
• Accept arbitrary AttributeType and AttributeValue in certificate
  Distinguished Names using RFC 4514 syntax.
• Applications using ECC over secp256r1 through the PSA API can use a
  new implementation with a much smaller footprint, but some minor
  usage restrictions. See the documentation of the new configuration
  option MBEDTLS_PSA_P256M_DRIVER_ENABLED for details.

Security

• Fix a case where potentially sensitive information held in memory would not
  be completely zeroized during TLS 1.2 handshake, in both server and client
  configurations.
• In configurations with ARIA or Camellia but not AES, the value of
  MBEDTLS_CIPHER_BLKSIZE_MAX was 8, rather than 16 as the name might
  suggest. This did not affect any library code, because this macro was
  only used in relation with CMAC which does not support these ciphers.
  This may affect application code that uses this macro.
• Developers using mbedtls_pkcs5_pbes2() or mbedtls_pkcs12_pbe() should
  review the size of the output buffer passed to this function, and note
  that the output after decryption may include CBC padding. Consider moving
  to the new functions mbedtls_pkcs5_pbes2_ext() or mbedtls_pkcs12_pbe_ext()
  which checks for overflow of the output buffer and reports the actual
  length of the output.
• Improve padding calculations in CBC decryption, NIST key unwrapping and
  RSA OAEP decryption. With the previous implementation, some compilers
  (notably recent versions of Clang and IAR) could produce non-constant
  time code, which could allow a padding oracle attack if the attacker
  has access to precise timing measurements.
• Updates to constant-time C code so that compilers are less likely to use
  conditional instructions, which can have an observable difference in
  timing. (Clang has been seen to do this.) Also introduce assembly
  implementations for 32- and 64-bit Arm and for x86 and x86-64, which are
  guaranteed not to use conditional instructions.
• Fix definition of MBEDTLS_MD_MAX_BLOCK_SIZE, which was too
  small when MBEDTLS_SHA384_C was defined and MBEDTLS_SHA512_C was
  undefined. Mbed TLS itself was unaffected by this, but user code
  which used MBEDTLS_MD_MAX_BLOCK_SIZE could be affected. The only
  release containing this bug was Mbed TLS 3.4.0.
• Fix a buffer overread when parsing short TLS application data records in
  null-cipher cipher suites. Credit to OSS-Fuzz.
• Fix a remotely exploitable heap buffer overflow in TLS handshake parsing.
  In TLS 1.3, all configurations are affected except PSK-only ones, and
  both clients and servers are affected.
  In TLS 1.2, the affected configurations are those with
  MBEDTLS_USE_PSA_CRYPTO and ECDH enabled but DHM and RSA disabled,
  and only servers are affected, not clients.
  Credit to OSS-Fuzz.

Bugfix

• Fix proper sizing for PSA_EXPORT_[KEY_PAIR/PUBLIC_KEY]_MAX_SIZE and
  PSA_SIGNATURE_MAX_SIZE buffers when at least one accelerated EC is bigger
  than all built-in ones and RSA is disabled.
  Resolves #6622.
• Add missing md.h includes to some of the external programs from
  the programs directory. Without this, even though the configuration
  was sufficient for a particular program to work, it would only print
  a message that one of the required defines is missing.
• Fix declaration of mbedtls_ecdsa_sign_det_restartable() function
  in the ecdsa.h header file. There was a build warning when the
  configuration macro MBEDTLS_ECDSA_SIGN_ALT was defined.
  Resolves #7407.
• Fix an error when MBEDTLS_ECDSA_SIGN_ALT is defined but not
  MBEDTLS_ECDSA_VERIFY_ALT, causing ecdsa verify to fail. Fixes #7498.
• Fix missing PSA initialization in sample programs when
  MBEDTLS_USE_PSA_CRYPTO is enabled.
• Fix the J-PAKE driver interface for user and peer to accept any values
  (previously accepted values were limited to "client" or "server").
• Fix clang and armclang compilation error when targeting certain Arm
  M-class CPUs (Cortex-M0, Cortex-M0+, Cortex-M1, Cortex-M23,
  SecurCore SC000). Fixes #1077.
• Fix "unterminated '#pragma clang attribute push'" in sha256/sha512.c when
  built with MBEDTLS_SHAxxx_USE_A64_CRYPTO_IF_PRESENT but don't have a
  way to detect the crypto extensions required. A warning is still issued.
• Fixed an issue that caused compile errors when using CMake and the IAR
  toolchain.
• Fix very high stack usage in SSL debug code. Reported by Maximilian
  Gerhardt in #7804.
• Fix a compilation failure in the constant_time module when
  building for arm64_32 (e.g., for watchos). Reported by Paulo
  Coutinho in #7787.
• Fix crypt_and_hash decryption fail when used with a stream cipher
  mode of operation due to the input not being multiple of block size.
  Resolves #7417.
• Fix a bug in which mbedtls_x509_string_to_names() would return success
  when given a invalid name string if it did not contain '=' or ','.
• Fix compilation warnings in aes.c, which prevented the
  example TF-M configuration in configs/ from building cleanly:
  tfm_mbedcrypto_config_profile_medium.h with
  crypto_config_profile_medium.h.
• In TLS 1.3, fix handshake failure when a client in its ClientHello
  proposes an handshake based on PSK only key exchange mode or at least
  one of the key exchange modes using ephemeral keys to a server that
  supports only the PSK key exchange mode.
• Fix CCM* with no tag being not supported in a build with CCM as the only
  symmetric encryption algorithm and the PSA configuration enabled.
• Fix the build with MBEDTLS_PSA_INJECT_ENTROPY. Fixes #7516.
• Fix a compilation error on some platforms when including mbedtls/ssl.h
  with all TLS support disabled. Fixes #6628.
• Fix x509 certificate generation to conform to RFC 5480 / RFC 5758 when
  using ECC key. The certificate was rejected by some crypto frameworks.
  Fixes #2924.
• Fix a potential corruption of the passed-in IV when mbedtls_aes_crypt_cbc()
  is called with zero length and padlock is not enabled.
• Fix compile failure due to empty enum in cipher_wrap.c, when building
  with a very minimal configuration. Fixes #7625.
• Fix some cases where mbedtls_mpi_mod_exp, RSA key construction or ECDSA
  signature can silently return an incorrect result in low memory conditions.
• Don't try to include MBEDTLS_PSA_CRYPTO_USER_CONFIG_FILE when
  MBEDTLS_PSA_CRYPTO_CONFIG is disabled.
• Fix IAR compiler warnings.
• Fix an issue when parsing an otherName subject alternative name into a
  mbedtls_x509_san_other_name struct. The type-id of the otherName was not
  copied to the struct. This meant that the struct had incomplete
  information about the otherName SAN and contained uninitialized memory.
• Fix the detection of HardwareModuleName otherName SANs. These were being
  detected by comparing the wrong field and the check was erroneously
  inverted.
• Fix a build error in some configurations with MBEDTLS_PSA_CRYPTO_CONFIG
  enabled, where some low-level modules required by requested PSA crypto
  features were not getting automatically enabled. Fixes #7420.
• Fix undefined symbols in some builds using TLS 1.3 with a custom
  configuration file.
• Fix log level for the got supported group message. Fixes #6765
• Functions in the ssl_cache module now return a negative MBEDTLS_ERR_xxx
  error code on failure. Before, they returned 1 to indicate failure in
  some cases involving a missing entry or a full cache.
• mbedtls_pk_parse_key() now rejects trailing garbage in encrypted keys.
• Fix the build with CMake when Everest or P256-m is enabled through
  a user configuration file or the compiler command line. Fixes #8165.

Changes

• Enable Arm / Thumb bignum assembly for most Arm platforms when
  compiling with gcc, clang or armclang and -O0.
• Enforce minimum RSA key size when generating a key
  to avoid accidental misuse.
• Use heap memory to allocate DER encoded RSA private key.
  This reduces stack usage significantly for RSA signature
  operations when MBEDTLS_PSA_CRYPTO_C is defined.
• Update Windows code to use BCryptGenRandom and wcslen, and
  ensure that conversions between size_t, ULONG, and int are
  always done safely. Original contribution by Kevin Kane #635, #730
  followed by Simon Butcher #1453.
• Users integrating their own PSA drivers should be aware that
  the file library/psa_crypto_driver_wrappers.c has been renamed
  to psa_crypto_driver_wrappers_no_static.c.
• When using CBC with the cipher module, the requirement to call
  mbedtls_cipher_set_padding_mode() is now enforced. Previously, omitting
  this call accidentally applied a default padding mode chosen at compile
  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

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