_tagged_sha256 simply cannot have invalid inputs.
The other functions could in some sense have invalid inputs but only in
violation of the type system. For example, a pubkey could be invalid but
invalid objects of type secp256k1_pubkey either can't be obtained
via the API or will be caught by an ARG_CHECK when calling pubkey_load.
This is consistent with similar functions in the public API, e.g.,
_ec_pubkey_negate or _ec_pubkey_serialize.
BIP340's default signing algorithm always requires an aux_rnd argument,
but permits using an all-zero one when no randomness is available.
Make secp256k1_schnorrsig_sign follow this even when aux_rnd32==NULL,
by treating the same as if an all-zero byte array was provided as
input.
adec5a16383f1704d80d7c767b2a65d9221cee08 Add missing null check for ctx and input keys in the public API (Elichai Turkel)
f4edfc758142d6e100ca5d086126bf532b8a7020 Improve consistency for NULL arguments in the public interface (Elichai Turkel)
Pull request description:
I went over the public API and added missing explanations on when a pointer can be null and when it cannot,
and added some missing checks for null ctx and null pubkey pointers.
Open questions IMHO:
1. Can `secp256k1_context_create` return NULL? right now it could return null if you replaced the callbacks at compile time to ones that do return(unlike the default ones which never return).
2. Related to the first, should we document that the callbacks should never return? (in the tests we use returning callbacks but we can violate our own API) right now we say the following:
> After this callback returns, anything may happen, including crashing.
Is this enough to document answer `no` for the first question and just saying that if the callback returned then you violated the API so `secp256k1_context_create` can return NULL even though it is promised not to?
Right now we AFAICT we never check if it returns null
Another nit I'm not sure about is wording `(does nothing if NULL)`/`(ignored if NULL)`/`(can be NULL)`
More missing docs:
1. Documenting the `data` argument to the default nonce functions
ACKs for top commit:
ariard:
ACK adec5a16
jonasnick:
ACK adec5a16383f1704d80d7c767b2a65d9221cee08
Tree-SHA512: 6fe785776b7e451e9e8cae944987f927b1eb2e2d404dfcb1b0ceb0a30bda4ce16469708920269417e5ada09739723a430e270dea1868fe7d12ccd5699dde5976
unsigned char foo[4] = "abcd" is not valid C++ because the string
literal "abcd" does not fit into foo due to the terminating NUL
character. This is valid in C, it will just omit the NUL character.
Fixes#962.
Varlen message support for the default sign function comes from recommending
tagged_sha256. sign_custom on the other hand gets the ability to directly sign
message of any length. This also implies signing and verification support for
the empty message (NULL) with msglen 0.
Tests for variable lengths follow in a later commit.
This makes the default sign function easier to use while allowing more granular
control through sign_custom.
Tests for sign_custom follow in a later commit.
0881633dfd0c530a915cf63be295f00841c94cc4 secp256k1.h: clarify that by default arguments must be != NULL (Jonas Nick)
Pull request description:
The same file says that the illegal callback will only triger for violations
explicitly mentioned, which is not true without this commit because we often
don't mention that an argument is not allowed to be NULL.
This line is extracted from #783 in the hope that it gets merged faster because other PRs depend on it.
ACKs for top commit:
gmaxwell:
ACK 0881633dfd0c530a915cf63be295f00841c94cc4
real-or-random:
ACK 0881633dfd0c530a915cf63be295f00841c94cc4
Tree-SHA512: ecdc6954a1c21c333da5b03db51f50a0e53984aaef69cc697adaddc96b276da23e342037f476d21742632f6ec02bfa0574f837a5b5791f5985f4c355037176fa
The same file says that the illegal callback will only triger for violations
explicitly mentioned, which is not true without this commit because we often
don't mention that an argument is not allowed to be NULL.
33cb3c2b1fc3f3fe46c6d0eab118248ea86c1f06 Add secret key extraction from keypair to constant time tests (Elichai Turkel)
36d9dc1e8e6e3b15d805f04c973a8784a78880f6 Add seckey extraction from keypair to the extrakeys tests (Elichai Turkel)
fc96aa73f5c7f62452847a31821890ff1f72a5a4 Add a function to extract the secretkey from a keypair (Elichai Turkel)
Pull request description:
With schnorrsig if you need to tweak the secret key (for BIP32) you must use the keypair API to get compatible secret/public keys which you do by calling `secp256k1_keypair_xonly_tweak_add()`, but after that there's no currently a way to extract the secret key back for storage.
so I added a `secp256k1_keypair_seckey` function to extract the key
ACKs for top commit:
jonasnick:
ACK 33cb3c2b1fc3f3fe46c6d0eab118248ea86c1f06
real-or-random:
ACK 33cb3c2b1fc3f3fe46c6d0eab118248ea86c1f06 code inspection, tests pass
Tree-SHA512: 11212db38c8b87a87e2dc35c4d6993716867b45215b94b20522b1b3164ca63d4c6bf5192a6bff0e9267b333779cc8164844c56669a94e9be72df9ef025ffcfd4
