From db94fb06861141b95741de8dc0bcdeb94a34945c Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Manuel=20P=C3=A9gouri=C3=A9-Gonnard?= Date: Thu, 21 May 2026 10:57:49 +0200 Subject: [PATCH] Add tests for x25519 non-standard/invalid inputs MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit We want to reject small order points for two reasons: - Those give rise to side channels attacks where the underlying field arithmetic is not constant time (which our bignum isn't so far), see the "May the Fourth" paper mentioned in ecp. - Those force the shared secret to be all-bytes zero, which is bad for protocols that might require contributory behaviour. Honest peers will never send low-order points anyway. While at it, test that we are clipping the input to 255 bits (ie, that we are unsetting bit 256) as required by the RFC. Again, honest peers will never send strings with bit 256 set. But the RFC says to accept such strings anyway, so that's what we do. Signed-off-by: Manuel Pégourié-Gonnard --- tests/suites/test_suite_psa_crypto.data | 77 +++++++++++++++++++++++++ 1 file changed, 77 insertions(+) diff --git a/tests/suites/test_suite_psa_crypto.data b/tests/suites/test_suite_psa_crypto.data index a5fb4c712b..db3824078a 100644 --- a/tests/suites/test_suite_psa_crypto.data +++ b/tests/suites/test_suite_psa_crypto.data @@ -7294,6 +7294,83 @@ PSA (raw) key agreement: X25519 (RFC 7748: Bob) depends_on:PSA_WANT_ALG_ECDH:PSA_WANT_KEY_TYPE_ECC_KEY_PAIR_DERIVE:PSA_WANT_ECC_MONTGOMERY_255 key_agreement:PSA_ALG_ECDH:PSA_KEY_TYPE_ECC_KEY_PAIR(PSA_ECC_FAMILY_MONTGOMERY):"5dab087e624a8a4b79e17f8b83800ee66f3bb1292618b6fd1c2f8b27ff88e0eb":"8520f0098930a754748b7ddcb43ef75a0dbf3a0d26381af4eba4a98eaa9b4e6a":"4a5d9d5ba4ce2de1728e3bf480350f25e07e21c947d19e3376f09b3c1e161742":PSA_SUCCESS +# RFC 7748 says we need clip the input to 255 bits, see decodeUCoordinate(). +# Check we indeed do that: same inputs as above except bit 256 is set in the +# peer's public key (little endian, so that's the MSB of the last byte). +PSA (raw) key agreement: X25519 (RFC 7748: Alice with bit 256 set) +depends_on:PSA_WANT_ALG_ECDH:PSA_WANT_KEY_TYPE_ECC_KEY_PAIR_DERIVE:PSA_WANT_ECC_MONTGOMERY_255 +key_agreement:PSA_ALG_ECDH:PSA_KEY_TYPE_ECC_KEY_PAIR(PSA_ECC_FAMILY_MONTGOMERY):"77076d0a7318a57d3c16c17251b26645df4c2f87ebc0992ab177fba51db92c2a":"de9edb7d7b7dc1b4d35b61c2ece435373f8343c85b78674dadfc7e146f882bcf":"4a5d9d5ba4ce2de1728e3bf480350f25e07e21c947d19e3376f09b3c1e161742":PSA_SUCCESS + +PSA (raw) key agreement: X25519 (RFC 7748: Bob with bit 256 set) +depends_on:PSA_WANT_ALG_ECDH:PSA_WANT_KEY_TYPE_ECC_KEY_PAIR_DERIVE:PSA_WANT_ECC_MONTGOMERY_255 +key_agreement:PSA_ALG_ECDH:PSA_KEY_TYPE_ECC_KEY_PAIR(PSA_ECC_FAMILY_MONTGOMERY):"5dab087e624a8a4b79e17f8b83800ee66f3bb1292618b6fd1c2f8b27ff88e0eb":"8520f0098930a754748b7ddcb43ef75a0dbf3a0d26381af4eba4a98eaa9b4eea":"4a5d9d5ba4ce2de1728e3bf480350f25e07e21c947d19e3376f09b3c1e161742":PSA_SUCCESS + +# BEGIN list from https://cr.yp.to/ecdh.html#validate +PSA (raw) key agreement: X25519 (peer key is 0) +depends_on:PSA_WANT_ALG_ECDH:PSA_WANT_KEY_TYPE_ECC_KEY_PAIR_DERIVE:PSA_WANT_ECC_MONTGOMERY_255 +key_agreement:PSA_ALG_ECDH:PSA_KEY_TYPE_ECC_KEY_PAIR(PSA_ECC_FAMILY_MONTGOMERY):"5dab087e624a8a4b79e17f8b83800ee66f3bb1292618b6fd1c2f8b27ff88e0eb":"0000000000000000000000000000000000000000000000000000000000000000":"":PSA_ERROR_INVALID_ARGUMENT + +PSA (raw) key agreement: X25519 (peer key is 1) +depends_on:PSA_WANT_ALG_ECDH:PSA_WANT_KEY_TYPE_ECC_KEY_PAIR_DERIVE:PSA_WANT_ECC_MONTGOMERY_255 +key_agreement:PSA_ALG_ECDH:PSA_KEY_TYPE_ECC_KEY_PAIR(PSA_ECC_FAMILY_MONTGOMERY):"5dab087e624a8a4b79e17f8b83800ee66f3bb1292618b6fd1c2f8b27ff88e0eb":"0100000000000000000000000000000000000000000000000000000000000000":"":PSA_ERROR_INVALID_ARGUMENT + +# this is x25519_bad_point_1 in ecp.c +PSA (raw) key agreement: X25519 (peer key is bad_point_1) +depends_on:PSA_WANT_ALG_ECDH:PSA_WANT_KEY_TYPE_ECC_KEY_PAIR_DERIVE:PSA_WANT_ECC_MONTGOMERY_255 +key_agreement:PSA_ALG_ECDH:PSA_KEY_TYPE_ECC_KEY_PAIR(PSA_ECC_FAMILY_MONTGOMERY):"5dab087e624a8a4b79e17f8b83800ee66f3bb1292618b6fd1c2f8b27ff88e0eb":"e0eb7a7c3b41b8ae1656e3faf19fc46ada098deb9c32b1fd866205165f49b800":"":PSA_ERROR_INVALID_ARGUMENT + +# this is x25519_bad_point_2 in ecp.c +PSA (raw) key agreement: X25519 (peer key is bad_point_2) +depends_on:PSA_WANT_ALG_ECDH:PSA_WANT_KEY_TYPE_ECC_KEY_PAIR_DERIVE:PSA_WANT_ECC_MONTGOMERY_255 +key_agreement:PSA_ALG_ECDH:PSA_KEY_TYPE_ECC_KEY_PAIR(PSA_ECC_FAMILY_MONTGOMERY):"5dab087e624a8a4b79e17f8b83800ee66f3bb1292618b6fd1c2f8b27ff88e0eb":"5f9c95bca3508c24b1d0b1559c83ef5b04445cc4581c8e86d8224eddd09f1157":"":PSA_ERROR_INVALID_ARGUMENT + +PSA (raw) key agreement: X25519 (peer key is p-1) +depends_on:PSA_WANT_ALG_ECDH:PSA_WANT_KEY_TYPE_ECC_KEY_PAIR_DERIVE:PSA_WANT_ECC_MONTGOMERY_255 +key_agreement:PSA_ALG_ECDH:PSA_KEY_TYPE_ECC_KEY_PAIR(PSA_ECC_FAMILY_MONTGOMERY):"5dab087e624a8a4b79e17f8b83800ee66f3bb1292618b6fd1c2f8b27ff88e0eb":"ecffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff7f":"":PSA_ERROR_INVALID_ARGUMENT + +PSA (raw) key agreement: X25519 (peer key is p) +depends_on:PSA_WANT_ALG_ECDH:PSA_WANT_KEY_TYPE_ECC_KEY_PAIR_DERIVE:PSA_WANT_ECC_MONTGOMERY_255 +key_agreement:PSA_ALG_ECDH:PSA_KEY_TYPE_ECC_KEY_PAIR(PSA_ECC_FAMILY_MONTGOMERY):"5dab087e624a8a4b79e17f8b83800ee66f3bb1292618b6fd1c2f8b27ff88e0eb":"edffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff7f":"":PSA_ERROR_INVALID_ARGUMENT + +PSA (raw) key agreement: X25519 (peer key is p+1) +depends_on:PSA_WANT_ALG_ECDH:PSA_WANT_KEY_TYPE_ECC_KEY_PAIR_DERIVE:PSA_WANT_ECC_MONTGOMERY_255 +key_agreement:PSA_ALG_ECDH:PSA_KEY_TYPE_ECC_KEY_PAIR(PSA_ECC_FAMILY_MONTGOMERY):"5dab087e624a8a4b79e17f8b83800ee66f3bb1292618b6fd1c2f8b27ff88e0eb":"eeffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff7f":"":PSA_ERROR_INVALID_ARGUMENT +# END list from https://cr.yp.to/ecdh.html#validate +# Further values in that list are larger that 2^256, and per RFC 7748 +# we clip the input to 255 bits, that is, set bit 256 to zero. +# So, what's actually useful to test is 2^256 + x (aka x | (1 << 256)) +# where x is any of the values above. (Reminder: little-endian.) + +PSA (raw) key agreement: X25519 (peer key is 2^256 + 0) +depends_on:PSA_WANT_ALG_ECDH:PSA_WANT_KEY_TYPE_ECC_KEY_PAIR_DERIVE:PSA_WANT_ECC_MONTGOMERY_255 +key_agreement:PSA_ALG_ECDH:PSA_KEY_TYPE_ECC_KEY_PAIR(PSA_ECC_FAMILY_MONTGOMERY):"5dab087e624a8a4b79e17f8b83800ee66f3bb1292618b6fd1c2f8b27ff88e0eb":"0000000000000000000000000000000000000000000000000000000000000080":"":PSA_ERROR_INVALID_ARGUMENT + +PSA (raw) key agreement: X25519 (peer key is 2^256 + 1) +depends_on:PSA_WANT_ALG_ECDH:PSA_WANT_KEY_TYPE_ECC_KEY_PAIR_DERIVE:PSA_WANT_ECC_MONTGOMERY_255 +key_agreement:PSA_ALG_ECDH:PSA_KEY_TYPE_ECC_KEY_PAIR(PSA_ECC_FAMILY_MONTGOMERY):"5dab087e624a8a4b79e17f8b83800ee66f3bb1292618b6fd1c2f8b27ff88e0eb":"0100000000000000000000000000000000000000000000000000000000000080":"":PSA_ERROR_INVALID_ARGUMENT + +# this is x25519_bad_point_1 in ecp.c +PSA (raw) key agreement: X25519 (peer key is 2^256 + bad_point_1) +depends_on:PSA_WANT_ALG_ECDH:PSA_WANT_KEY_TYPE_ECC_KEY_PAIR_DERIVE:PSA_WANT_ECC_MONTGOMERY_255 +key_agreement:PSA_ALG_ECDH:PSA_KEY_TYPE_ECC_KEY_PAIR(PSA_ECC_FAMILY_MONTGOMERY):"5dab087e624a8a4b79e17f8b83800ee66f3bb1292618b6fd1c2f8b27ff88e0eb":"e0eb7a7c3b41b8ae1656e3faf19fc46ada098deb9c32b1fd866205165f49b880":"":PSA_ERROR_INVALID_ARGUMENT + +# this is x25519_bad_point_2 in ecp.c +PSA (raw) key agreement: X25519 (peer key is 2^256 + bad_point_2) +depends_on:PSA_WANT_ALG_ECDH:PSA_WANT_KEY_TYPE_ECC_KEY_PAIR_DERIVE:PSA_WANT_ECC_MONTGOMERY_255 +key_agreement:PSA_ALG_ECDH:PSA_KEY_TYPE_ECC_KEY_PAIR(PSA_ECC_FAMILY_MONTGOMERY):"5dab087e624a8a4b79e17f8b83800ee66f3bb1292618b6fd1c2f8b27ff88e0eb":"5f9c95bca3508c24b1d0b1559c83ef5b04445cc4581c8e86d8224eddd09f11d7":"":PSA_ERROR_INVALID_ARGUMENT + +PSA (raw) key agreement: X25519 (peer key is 2^256 + p-1) +depends_on:PSA_WANT_ALG_ECDH:PSA_WANT_KEY_TYPE_ECC_KEY_PAIR_DERIVE:PSA_WANT_ECC_MONTGOMERY_255 +key_agreement:PSA_ALG_ECDH:PSA_KEY_TYPE_ECC_KEY_PAIR(PSA_ECC_FAMILY_MONTGOMERY):"5dab087e624a8a4b79e17f8b83800ee66f3bb1292618b6fd1c2f8b27ff88e0eb":"ecffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff":"":PSA_ERROR_INVALID_ARGUMENT + +PSA (raw) key agreement: X25519 (peer key is 2^256 + p) +depends_on:PSA_WANT_ALG_ECDH:PSA_WANT_KEY_TYPE_ECC_KEY_PAIR_DERIVE:PSA_WANT_ECC_MONTGOMERY_255 +key_agreement:PSA_ALG_ECDH:PSA_KEY_TYPE_ECC_KEY_PAIR(PSA_ECC_FAMILY_MONTGOMERY):"5dab087e624a8a4b79e17f8b83800ee66f3bb1292618b6fd1c2f8b27ff88e0eb":"edffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff":"":PSA_ERROR_INVALID_ARGUMENT + +PSA (raw) key agreement: X25519 (peer key is 2^256 + p+1) +depends_on:PSA_WANT_ALG_ECDH:PSA_WANT_KEY_TYPE_ECC_KEY_PAIR_DERIVE:PSA_WANT_ECC_MONTGOMERY_255 +key_agreement:PSA_ALG_ECDH:PSA_KEY_TYPE_ECC_KEY_PAIR(PSA_ECC_FAMILY_MONTGOMERY):"5dab087e624a8a4b79e17f8b83800ee66f3bb1292618b6fd1c2f8b27ff88e0eb":"eeffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff":"":PSA_ERROR_INVALID_ARGUMENT + # see generating script in commit message PSA (raw) key agreement: X25519 (shared secret with MSB 0) depends_on:PSA_WANT_ALG_ECDH:PSA_WANT_KEY_TYPE_ECC_KEY_PAIR_DERIVE:PSA_WANT_ECC_MONTGOMERY_255