Add __msan_unpoison for X25519 assembly output buffers#30021
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alexey-milovidov wants to merge 1 commit intoopenssl:masterfrom
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Add __msan_unpoison for X25519 assembly output buffers#30021alexey-milovidov wants to merge 1 commit intoopenssl:masterfrom
alexey-milovidov wants to merge 1 commit intoopenssl:masterfrom
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x25519_scalar_mult and fe_tobytes may dispatch to assembly implementations (e.g. x25519-x86_64.s) that MemorySanitizer cannot instrument. As a result, output buffers written by the assembly appear uninitialized to MSan, causing false positives when subsequent code reads them (e.g. CRYPTO_memcmp in ossl_x25519). Add __msan_unpoison annotations after assembly writes in ossl_x25519 and ossl_x25519_public_from_private, following the same pattern already used in sha3.c, bn_intern.c, and eng_rdrand.c.
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Note: this means usually you use a secret value in a non-constant time function, |
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x25519_scalar_multandfe_tobytesmay dispatch to assemblyimplementations (e.g.
x25519-x86_64.s) that MemorySanitizercannot instrument. As a result, output buffers written by the
assembly appear uninitialized to MSan, causing false positives
when subsequent code reads them (e.g.
CRYPTO_memcmpinossl_x25519).This adds
__msan_unpoisonannotations after assembly writes inossl_x25519andossl_x25519_public_from_private, following thesame pattern already used in
sha3.c,bn_intern.c, andeng_rdrand.c.The issue was discovered while testing ClickHouse's SSH protocol
support with MSan: the libssh library calls
EVP_PKEY_deriveforX25519 key exchange, and the shared secret buffer produced by the
assembly implementation triggers a false
use-of-uninitialized-valuereport in
BN_bin2bn.