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Add fall-back to hash-based KDF for internal ECP DRBG

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The dependency on a DRBG module was perhaps a bit strict for LTS branches, so
let's have an option that works with no DRBG when at least one SHA module is
present.

This changes the internal API of ecp_drbg_seed() by adding the size of the
MPI as a parameter. Re-computing the size from the number of limbs doesn't
work too well here as we're writing out to a fixed-size buffer and for some
curves (P-521) that would round up too much. Using mbedtls_mpi_get_len() is
not entirely satisfactory either as it would mean using a variable-length
encoding, with could open side channels.

Signed-off-by: Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com>
This commit is contained in:
Manuel Pégourié-Gonnard 2020-06-16 12:51:42 +02:00
parent 99bf33fa81
commit 6d61498e05
3 changed files with 279 additions and 10 deletions
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63
tests/scripts/all.sh
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@ -814,6 +814,69 @@ component_test_no_hmac_drbg () {
# so there's little value in running those lengthy tests here.
}
component_test_no_drbg_all_hashes () {
# this tests the internal ECP DRBG using a KDF based on SHA-512
msg "build: Default minus DRBGs"
scripts/config.pl unset MBEDTLS_CTR_DRBG_C
scripts/config.pl unset MBEDTLS_HMAC_DRBG_C
scripts/config.pl unset MBEDTLS_ECDSA_DETERMINISTIC # requires HMAC_DRBG
scripts/config.pl unset MBEDTLS_PSA_CRYPTO_C # requires a DRBG
scripts/config.pl unset MBEDTLS_PSA_CRYPTO_STORAGE_C # requires PSA Crypto
CC=gcc cmake -D CMAKE_BUILD_TYPE:String=Asan .
make
msg "test: Default minus DRBGs"
make test
# no SSL tests as they all depend on having a DRBG
}
component_test_no_drbg_no_sha512 () {
# this tests the internal ECP DRBG using a KDF based on SHA-256
msg "build: Default minus DRBGs minus SHA-512"
scripts/config.pl unset MBEDTLS_CTR_DRBG_C
scripts/config.pl unset MBEDTLS_HMAC_DRBG_C
scripts/config.pl unset MBEDTLS_ECDSA_DETERMINISTIC # requires HMAC_DRBG
scripts/config.pl unset MBEDTLS_PSA_CRYPTO_C # requires a DRBG
scripts/config.pl unset MBEDTLS_PSA_CRYPTO_STORAGE_C # requires PSA Crypto
scripts/config.pl unset MBEDTLS_SHA512_C
CC=gcc cmake -D CMAKE_BUILD_TYPE:String=Asan .
make
msg "test: Default minus DRBGs minus SHA-512"
make test
# no SSL tests as they all depend on having a DRBG
}
component_test_no_drbg_no_sha2 () {
# this tests the internal ECP DRBG using a KDF based on SHA-1
msg "build: Default minus DRBGs minus SHA-2"
scripts/config.pl unset MBEDTLS_CTR_DRBG_C
scripts/config.pl unset MBEDTLS_HMAC_DRBG_C
scripts/config.pl unset MBEDTLS_ECDSA_DETERMINISTIC # requires HMAC_DRBG
scripts/config.pl unset MBEDTLS_PSA_CRYPTO_C # requires a DRBG
scripts/config.pl unset MBEDTLS_PSA_CRYPTO_STORAGE_C # requires PSA Crypto
scripts/config.pl unset MBEDTLS_SHA512_C
scripts/config.pl unset MBEDTLS_SHA256_C
scripts/config.pl unset MBEDTLS_ENTROPY_C # requires SHA-2
scripts/config.pl unset MBEDTLS_PSA_CRYPTO_C # requires Entropy
scripts/config.pl unset MBEDTLS_PSA_CRYPTO_STORAGE_C # requires PSA Crypto
scripts/config.pl unset MBEDTLS_PSA_CRYPTO_SE_C # requires PSA Crypto
scripts/config.pl unset MBEDTLS_USE_PSA_CRYPTO # requires PSA Crypto
scripts/config.pl unset MBEDTLS_SSL_PROTO_TLS1_2 # requires SHA-2
CC=gcc cmake -D CMAKE_BUILD_TYPE:String=Asan .
make
msg "test: Default minus DRBGs minus SHA-2"
make test
# no SSL tests as they all depend on having a DRBG
}
component_test_ecp_no_internal_rng () {
msg "build: Default plus ECP_NO_INTERNAL_RNG minus DRBG modules"
scripts/config.pl set MBEDTLS_ECP_NO_INTERNAL_RNG