Make LTC_ECCSIG_RFC7518 strict (again) #447
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sjaeckel
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Oct 7, 2018
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My personal preference would be to not have relaxed API's for security critical stuff!
src/headers/tomcrypt_pk.h
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| /* raw R, S values - both values strictly padded to the size of the curve order*/ | ||
| LTC_ECCSIG_RFC7518 = 0x1, | ||
| /* raw R, S values - without strict padding check (used just for verification) */ | ||
| LTC_ECCSIG_RFC7518_RELAXED = 0x2, |
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if we really change it, would it probably make more sense to make this enum (at least partially) a bitfield and relaxed is a flag (e.g. 0x80) where there's currently only a relaxed implementation of RFC 7518?
| 0x01,0x8a,0x79,0xb3,0xe0,0x26,0x3d,0x91,0xa8,0xba,0x90,0x62,0x2d,0xf6,0xf2,0xf0 | ||
| }; | ||
| const unsigned char sig1[] = { 0x05, 0x01 }; | ||
| /* msg+pub2+sig2 test vector is from wycheproof - ecdsa_webcrypto_test (incorrect size of signature) */ |
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shouldn't this testcase stay in there for the relaxed api where it was okay before?
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changed to the strict approach |
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This is basically a revert of my PR - Less strict ecc_verify_hash_ex (as it was before ecc_recover_key) #443
It enforces the strict verification mode for
LTC_ECCSIG_RFC7518but allow relaxed variant viaLTC_ECCSIG_RFC7518_RELAXED.I have changed my mind after investigation the latest wycheproof test suit. it seems that since approx. a yar ago wycheproof guys (=google) did change the status of some "acceptable" cases to "invalid". In other words what is declared today as "acceptable" is a candidate for tomorrow's "invalid".
So my new proposal is either enforce the strict length validation (the size of the signature should always be twice the number of bytes of the size of the order) or this PR.
Cc: @sjaeckel @rmw42