Fix pk_write with EC key to use a constant size for the private value #314
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Add pk_write test cases where the ASN.1 INTEGER encoding of the private value would not have the mandatory size for the OCTET STRING that contains the value. ec_256_long_prv.pem is a random secp256r1 private key, selected so that the private value is >= 2^255, i.e. the top bit of the first byte is set (which would cause the INTEGER encoding to have an extra leading 0 byte). ec_521_short_prv.pem is a random secp521r1 private key, selected so that the private value is < 2^519, i.e. the first byte is 0 and the top bit of the second byte is 0 (which would cause the INTEGER encoding to have one less 0 byte at the start).
When writing a private EC key, use a constant size for the private value, as specified in RFC 5915. Previously, the value was written as an ASN.1 INTEGER, which caused the size of the key to leak about 1 bit of information on average, and could cause the value to be 1 byte too large for the output buffer.
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AndrzejKurek
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New CI run with repaired CI: https://jenkins-internal.mbed.com/job/mbed-crypto-pr/job/PR-314-merge/2/ → passed. Good to merge. |
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* ARMmbed#292: Make psa_close_key(0) and psa_destroy_key(0) succeed * ARMmbed#299: Allow xxx_drbg_set_entropy_len before xxx_drbg_seed * ARMmbed#259: Check `len` against buffers size upper bound in PSA tests * ARMmbed#288: Add ECDSA tests with hash and key of different lengths * ARMmbed#305: CTR_DRBG: grab a nonce from the entropy source if needed * ARMmbed#316: Stop transactions from being reentrant * ARMmbed#317: getting_started: Make it clear that keys are passed in * ARMmbed#314: Fix pk_write with EC key to use a constant size for the private value * ARMmbed#298: Test a build without any asymmetric cryptography * ARMmbed#284: Fix some possibly-undefined variable warnings * ARMmbed#315: Define MBEDTLS_PK_SIGNATURE_MAX_SIZE * ARMmbed#318: Finish side-porting commits from mbedtls-restricted that missed the split
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When writing a private EC key, use a constant size for the private value, as specified in RFC 5915. Previously, the value was written as an ASN.1 INTEGER, which caused the size of the key to leak about 1 bit of information on average and could cause the value to be 1 byte too large for the output buffer.
These changes were previously applied to Mbed TLS 2.7, 2.16 and development (released in 2.19), but got lost during the split of Mbed TLS and Mbed Crypto. This is a straightforward side-port of https://github.com/ARMmbed/mbedtls-restricted/pull/503 and https://github.com/ARMmbed/mbedtls-restricted/pull/508 (private links: these were pull requests for a security fix which was quarantined until release).
Fix Mbed-TLS/mbedtls#1028
Internal ref: IOTCRYPT-969