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Fix module configuration options in mbedtls_config.h #8161

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merged 6 commits into from
Sep 11, 2023
Merged

Fix module configuration options in mbedtls_config.h #8161

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a8861e0
Fix boolean options in the wrong section
gilles-peskine-arm Sep 5, 2023
da69eaa
TLS 1.3 support is mostly complete
gilles-peskine-arm Sep 5, 2023
d65ea42
Fix some TLS 1.3 settings that were required in mbedtls_config.h
gilles-peskine-arm Sep 5, 2023
ff2558a
Fix unused variable in some TLS 1.3 builds
gilles-peskine-arm Sep 5, 2023
f9e4caf
Comment out default definition
gilles-peskine-arm Sep 5, 2023
8673383
Modernize documentation of MBEDTLS_PLATFORM_ZEROIZE_ALT
gilles-peskine-arm Sep 7, 2023
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3 changes: 3 additions & 0 deletions ChangeLog.d/tls13-custom-config.txt
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Original file line number Diff line number Diff line change
@@ -0,0 +1,3 @@
Bugfix
* Fix undefined symbols in some builds using TLS 1.3 with a custom
configuration file.
181 changes: 89 additions & 92 deletions include/mbedtls/mbedtls_config.h
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Original file line number Diff line number Diff line change
Expand Up @@ -272,6 +272,45 @@
//#define MBEDTLS_PLATFORM_SETUP_TEARDOWN_ALT
//#define MBEDTLS_PLATFORM_MS_TIME_ALT

/**
* Uncomment the macro to let Mbed TLS use your alternate implementation of
* mbedtls_platform_gmtime_r(). This replaces the default implementation in
* platform_util.c.
*
* gmtime() is not a thread-safe function as defined in the C standard. The
* library will try to use safer implementations of this function, such as
* gmtime_r() when available. However, if Mbed TLS cannot identify the target
* system, the implementation of mbedtls_platform_gmtime_r() will default to
* using the standard gmtime(). In this case, calls from the library to
* gmtime() will be guarded by the global mutex mbedtls_threading_gmtime_mutex
* if MBEDTLS_THREADING_C is enabled. We recommend that calls from outside the
* library are also guarded with this mutex to avoid race conditions. However,
* if the macro MBEDTLS_PLATFORM_GMTIME_R_ALT is defined, Mbed TLS will
* unconditionally use the implementation for mbedtls_platform_gmtime_r()
* supplied at compile time.
*/
//#define MBEDTLS_PLATFORM_GMTIME_R_ALT

/**
* Uncomment the macro to let mbed TLS use your alternate implementation of
* mbedtls_platform_zeroize(). This replaces the default implementation in
* platform_util.c.
*
* mbedtls_platform_zeroize() is a widely used function across the library to
* zero a block of memory. The implementation is expected to be secure in the
* sense that it has been written to prevent the compiler from removing calls
* to mbedtls_platform_zeroize() as part of redundant code elimination
* optimizations. However, it is difficult to guarantee that calls to
* mbedtls_platform_zeroize() will not be optimized by the compiler as older
* versions of the C language standards do not provide a secure implementation
* of memset(). Therefore, MBEDTLS_PLATFORM_ZEROIZE_ALT enables users to
* configure their own implementation of mbedtls_platform_zeroize(), for
* example by using directives specific to their compiler, features from newer
* C standards (e.g using memset_s() in C11) or calling a secure memset() from
* their system (e.g explicit_bzero() in BSD).
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*/
//#define MBEDTLS_PLATFORM_ZEROIZE_ALT

/**
* \def MBEDTLS_DEPRECATED_WARNING
*
Expand Down Expand Up @@ -569,6 +608,20 @@
*/
//#define MBEDTLS_AES_ONLY_128_BIT_KEY_LENGTH

/*
* Disable plain C implementation for AES.
*
* When the plain C implementation is enabled, and an implementation using a
* special CPU feature (such as MBEDTLS_AESCE_C) is also enabled, runtime
* detection will be used to select between them.
*
* If only one implementation is present, runtime detection will not be used.
* This configuration will crash at runtime if running on a CPU without the
* necessary features. It will not build unless at least one of MBEDTLS_AESCE_C
* and/or MBEDTLS_AESNI_C is enabled & present in the build.
*/
//#define MBEDTLS_AES_USE_HARDWARE_ONLY

/**
* \def MBEDTLS_CAMELLIA_SMALL_MEMORY
*
Expand Down Expand Up @@ -692,6 +745,15 @@
*/
//#define MBEDTLS_CTR_DRBG_USE_128_BIT_KEY

/**
* Enable the verified implementations of ECDH primitives from Project Everest
* (currently only Curve25519). This feature changes the layout of ECDH
* contexts and therefore is a compatibility break for applications that access
* fields of a mbedtls_ecdh_context structure directly. See also
* MBEDTLS_ECDH_LEGACY_CONTEXT in include/mbedtls/ecdh.h.
*/
//#define MBEDTLS_ECDH_VARIANT_EVEREST_ENABLED

/**
* \def MBEDTLS_ECP_DP_SECP192R1_ENABLED
*
Expand Down Expand Up @@ -782,6 +844,28 @@
*/
//#define MBEDTLS_ECP_RESTARTABLE

/**
* Uncomment to enable using new bignum code in the ECC modules.
*
* \warning This is currently experimental, incomplete and therefore should not
* be used in production.
*/
//#define MBEDTLS_ECP_WITH_MPI_UINT

/**
* Uncomment to enable p256-m, which implements ECC key generation, ECDH,
* and ECDSA for SECP256R1 curves. This driver is used as an example to
* document how a third-party driver or software accelerator can be integrated
* to work alongside Mbed TLS.
*
* \warning p256-m has only been included to serve as a sample implementation
* of how a driver/accelerator can be integrated alongside Mbed TLS. It is not
* intended for use in production. p256-m files in Mbed TLS are not updated
* regularly, so they may not contain upstream fixes/improvements.
* DO NOT ENABLE/USE THIS MACRO IN PRODUCTION BUILDS!
*/
//#define MBEDTLS_P256M_EXAMPLE_DRIVER_ENABLED

/**
* \def MBEDTLS_ECDSA_DETERMINISTIC
*
Expand Down Expand Up @@ -1643,9 +1727,7 @@
*
* Enable support for TLS 1.3.
*
* \note The support for TLS 1.3 is not comprehensive yet, in particular
* pre-shared keys are not supported.
* See docs/architecture/tls13-support.md for a description of the TLS
* \note See docs/architecture/tls13-support.md for a description of the TLS
* 1.3 support that this option enables.
*
* Requires: MBEDTLS_SSL_KEEP_PEER_CERTIFICATE
Expand Down Expand Up @@ -3842,7 +3924,7 @@
//#define MBEDTLS_PSA_KEY_SLOT_COUNT 32

/* RSA OPTIONS */
#define MBEDTLS_RSA_GEN_KEY_MIN_BITS 1024 /**< Minimum RSA key size that can be generated in bits (Minimum possible value is 128 bits) */
//#define MBEDTLS_RSA_GEN_KEY_MIN_BITS 1024 /**< Minimum RSA key size that can be generated in bits (Minimum possible value is 128 bits) */

/* SSL Cache options */
//#define MBEDTLS_SSL_CACHE_DEFAULT_TIMEOUT 86400 /**< 1 day */
Expand Down Expand Up @@ -3973,7 +4055,7 @@
* This is not used in TLS 1.2.
*
*/
#define MBEDTLS_SSL_TLS1_3_TICKET_AGE_TOLERANCE 6000
//#define MBEDTLS_SSL_TLS1_3_TICKET_AGE_TOLERANCE 6000

/**
* \def MBEDTLS_SSL_TLS1_3_TICKET_NONCE_LENGTH
Expand All @@ -3982,7 +4064,7 @@
*
* This must be less than 256.
*/
#define MBEDTLS_SSL_TLS1_3_TICKET_NONCE_LENGTH 32
//#define MBEDTLS_SSL_TLS1_3_TICKET_NONCE_LENGTH 32

/**
* \def MBEDTLS_SSL_TLS1_3_DEFAULT_NEW_SESSION_TICKETS
Expand All @@ -3992,95 +4074,10 @@
* the MBEDTLS_SSL_SESSION_TICKETS option is enabled.
*
*/
#define MBEDTLS_SSL_TLS1_3_DEFAULT_NEW_SESSION_TICKETS 1
//#define MBEDTLS_SSL_TLS1_3_DEFAULT_NEW_SESSION_TICKETS 1

/* X509 options */
//#define MBEDTLS_X509_MAX_INTERMEDIATE_CA 8 /**< Maximum number of intermediate CAs in a verification chain. */
//#define MBEDTLS_X509_MAX_FILE_PATH_LEN 512 /**< Maximum length of a path/filename string in bytes including the null terminator character ('\0'). */

/**
* Uncomment the macro to let mbed TLS use your alternate implementation of
* mbedtls_platform_zeroize(). This replaces the default implementation in
* platform_util.c.
*
* mbedtls_platform_zeroize() is a widely used function across the library to
* zero a block of memory. The implementation is expected to be secure in the
* sense that it has been written to prevent the compiler from removing calls
* to mbedtls_platform_zeroize() as part of redundant code elimination
* optimizations. However, it is difficult to guarantee that calls to
* mbedtls_platform_zeroize() will not be optimized by the compiler as older
* versions of the C language standards do not provide a secure implementation
* of memset(). Therefore, MBEDTLS_PLATFORM_ZEROIZE_ALT enables users to
* configure their own implementation of mbedtls_platform_zeroize(), for
* example by using directives specific to their compiler, features from newer
* C standards (e.g using memset_s() in C11) or calling a secure memset() from
* their system (e.g explicit_bzero() in BSD).
*/
//#define MBEDTLS_PLATFORM_ZEROIZE_ALT

/**
* Uncomment the macro to let Mbed TLS use your alternate implementation of
* mbedtls_platform_gmtime_r(). This replaces the default implementation in
* platform_util.c.
*
* gmtime() is not a thread-safe function as defined in the C standard. The
* library will try to use safer implementations of this function, such as
* gmtime_r() when available. However, if Mbed TLS cannot identify the target
* system, the implementation of mbedtls_platform_gmtime_r() will default to
* using the standard gmtime(). In this case, calls from the library to
* gmtime() will be guarded by the global mutex mbedtls_threading_gmtime_mutex
* if MBEDTLS_THREADING_C is enabled. We recommend that calls from outside the
* library are also guarded with this mutex to avoid race conditions. However,
* if the macro MBEDTLS_PLATFORM_GMTIME_R_ALT is defined, Mbed TLS will
* unconditionally use the implementation for mbedtls_platform_gmtime_r()
* supplied at compile time.
*/
//#define MBEDTLS_PLATFORM_GMTIME_R_ALT

/**
* Enable the verified implementations of ECDH primitives from Project Everest
* (currently only Curve25519). This feature changes the layout of ECDH
* contexts and therefore is a compatibility break for applications that access
* fields of a mbedtls_ecdh_context structure directly. See also
* MBEDTLS_ECDH_LEGACY_CONTEXT in include/mbedtls/ecdh.h.
*/
//#define MBEDTLS_ECDH_VARIANT_EVEREST_ENABLED

/**
* Uncomment to enable p256-m, which implements ECC key generation, ECDH,
* and ECDSA for SECP256R1 curves. This driver is used as an example to
* document how a third-party driver or software accelerator can be integrated
* to work alongside Mbed TLS.
*
* \warning p256-m has only been included to serve as a sample implementation
* of how a driver/accelerator can be integrated alongside Mbed TLS. It is not
* intended for use in production. p256-m files in Mbed TLS are not updated
* regularly, so they may not contain upstream fixes/improvements.
* DO NOT ENABLE/USE THIS MACRO IN PRODUCTION BUILDS!
*/
//#define MBEDTLS_P256M_EXAMPLE_DRIVER_ENABLED


/**
* Uncomment to enable using new bignum code in the ECC modules.
*
* \warning This is currently experimental, incomplete and therefore should not
* be used in production.
*/
//#define MBEDTLS_ECP_WITH_MPI_UINT

/*
* Disable plain C implementation for AES.
*
* When the plain C implementation is enabled, and an implementation using a
* special CPU feature (such as MBEDTLS_AESCE_C) is also enabled, runtime
* detection will be used to select between them.
*
* If only one implementation is present, runtime detection will not be used.
* This configuration will crash at runtime if running on a CPU without the
* necessary features. It will not build unless at least one of MBEDTLS_AESCE_C
* and/or MBEDTLS_AESNI_C is enabled & present in the build.
*/
//#define MBEDTLS_AES_USE_HARDWARE_ONLY

/** \} name SECTION: Module configuration options */
12 changes: 12 additions & 0 deletions include/mbedtls/ssl.h
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Expand Up @@ -405,6 +405,18 @@
#define MBEDTLS_SSL_CID_TLS1_3_PADDING_GRANULARITY 16
#endif

#if !defined(MBEDTLS_SSL_TLS1_3_TICKET_AGE_TOLERANCE)
#define MBEDTLS_SSL_TLS1_3_TICKET_AGE_TOLERANCE 6000
#endif

#if !defined(MBEDTLS_SSL_TLS1_3_TICKET_NONCE_LENGTH)
#define MBEDTLS_SSL_TLS1_3_TICKET_NONCE_LENGTH 32
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The disadvantage of doing it this way is to change the default one now needs to make identical changes in two places

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Indeed. But in practice, I don't recall us changing the default for any of thse options in the past 6½ years.

Anyway, if we changed the organization, this pull request wouldn't be the place to do it. It would require some thought about the new design and backward compatibility.

#endif

#if !defined(MBEDTLS_SSL_TLS1_3_DEFAULT_NEW_SESSION_TICKETS)
#define MBEDTLS_SSL_TLS1_3_DEFAULT_NEW_SESSION_TICKETS 1
#endif

/** \} name SECTION: Module settings */

/*
Expand Down
2 changes: 2 additions & 0 deletions library/ssl_tls13_generic.c
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Expand Up @@ -837,6 +837,8 @@ int mbedtls_ssl_tls13_process_certificate(mbedtls_ssl_context *ssl)
ssl, MBEDTLS_SSL_HS_CERTIFICATE, buf, buf_len));

cleanup:
#else /* MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_EPHEMERAL_ENABLED */
(void) ssl;
#endif /* MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_EPHEMERAL_ENABLED */

MBEDTLS_SSL_DEBUG_MSG(2, ("<= parse certificate"));
Expand Down
8 changes: 7 additions & 1 deletion scripts/config.py
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Expand Up @@ -190,6 +190,7 @@ def realfull_adapter(_name, active, section):
EXCLUDE_FROM_FULL = frozenset([
#pylint: disable=line-too-long
'MBEDTLS_AES_ONLY_128_BIT_KEY_LENGTH', # interacts with CTR_DRBG_128_BIT_KEY
'MBEDTLS_AES_USE_HARDWARE_ONLY', # hardware dependency
'MBEDTLS_CTR_DRBG_USE_128_BIT_KEY', # interacts with ENTROPY_FORCE_SHA256
'MBEDTLS_DEPRECATED_REMOVED', # conflicts with deprecated options
'MBEDTLS_DEPRECATED_WARNING', # conflicts with deprecated options
Expand Down Expand Up @@ -233,7 +234,12 @@ def is_seamless_alt(name):
Exclude alternative implementations of library functions since they require
an implementation of the relevant functions and an xxx_alt.h header.
"""
if name in ('MBEDTLS_PLATFORM_SETUP_TEARDOWN_ALT', 'MBEDTLS_PLATFORM_MS_TIME_ALT'):
if name in (
'MBEDTLS_PLATFORM_GMTIME_R_ALT',
'MBEDTLS_PLATFORM_SETUP_TEARDOWN_ALT',
'MBEDTLS_PLATFORM_MS_TIME_ALT',
'MBEDTLS_PLATFORM_ZEROIZE_ALT',
):
# Similar to non-platform xxx_ALT, requires platform_alt.h
return False
return name.startswith('MBEDTLS_PLATFORM_')
Expand Down