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Validate peer ECDH public key before shared-secret in key agreement #1061

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Validate peer ECDH public key before shared-secret in key agreement #1061

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6 changes: 6 additions & 0 deletions src/internal.c
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Original file line number Diff line number Diff line change
Expand Up @@ -12522,6 +12522,9 @@ static int KeyAgreeEcdh_server(WOLFSSH* ssh, byte hashId, byte* f, word32* fSz)
ssh->handshake->eSz,
pubKey, primeId);

if (ret == 0)

@aidangarske aidangarske Jul 9, 2026

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🟡 [Medium] Pure ECDH server validation lacks direct handshake coverage
💡 SUGGEST test

The PR adds wc_ecc_check_key(pubKey) to the pure ECDH server path after importing the client public value. The existing tests/kex.c end-to-end KEX coverage exercises DH and the hybrid ML-KEM variants, including the ECC ML-KEM branch touched by this PR, but it does not run a full ecdh-sha2-nistp* handshake through KeyAgreeEcdh_server. That leaves the newly added validation call in the pure ECDH server path without direct success-path coverage in the KEX test, so backend/config-specific behavior changes in wc_ecc_check_key would be easier to miss.

Recommendation: Consider adding an end-to-end pure ECDH KEX success test (e.g. wolfSSH_KexTest_Connect("ecdh-sha2-nistp256") guarded by WOLFSSH_NO_ECDH_SHA2_NISTP256, similar to the existing ML-KEM KEX cases) so both PR-modified server paths are exercised by the test suite.

ret = wc_ecc_check_key(pubKey);

if (ret == 0)
ret = wc_ecc_make_key_ex(ssh->rng,
wc_ecc_get_curve_size_from_id(primeId),
Expand Down Expand Up @@ -12845,6 +12848,9 @@ static int KeyAgreeEcdhMlKem_server(WOLFSSH* ssh, byte hashId,
ssh->handshake->eSz - length_publickey,
pubKey, primeId);
}
if (ret == 0) {
ret = wc_ecc_check_key(pubKey);
}
if (ret == 0) {
ret = wc_ecc_make_key_ex(ssh->rng,
wc_ecc_get_curve_size_from_id(primeId),
Expand Down
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