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Previously the length of the SM2 plaintext could be incorrectly calculated. The plaintext length was calculated by taking the ciphertext length and taking off an "overhead" value. The overhead value was assumed to have a "fixed" element of 10 bytes. This is incorrect since in some circumstances it can be more than 10 bytes. Additionally the overhead included the length of two integers C1x and C1y, which were assumed to be the same length as the field size (32 bytes for the SM2 curve). However in some cases these integers can have an additional padding byte when the msb is set, to disambiguate them from negative integers. Additionally the integers can also be less than 32 bytes in length in some cases. If the calculated overhead is incorrect and larger than the actual value this can result in the calculated plaintext length being too small. Applications are likely to allocate buffer sizes based on this and therefore a buffer overrun can occur. CVE-2021-3711 Issue reported by John Ouyang. Reviewed-by: Paul Dale <pauli@openssl.org> Reviewed-by: Nicola Tuveri <nic.tuv@gmail.com> |
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| build.info | ||
| rsa_enc.c | ||
| sm2_enc.c | ||