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Add tests for x25519 non-standard/invalid inputs

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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 <[email protected]>
This commit is contained in:
Manuel Pégourié-Gonnard
2026-05-28 12:24:29 +02:00
parent 72991252c8
commit db94fb0686
1 changed files with 77 additions and 0 deletions
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tests/suites/test_suite_psa_crypto.data
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@@ -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