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Rewrite ECDSA signature parsing code

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There are now 2 encoding formats supported: 64-byte "compact" and DER.
The latter is strict: the data has to be exact DER, though the values
inside don't need to be valid.
This commit is contained in:
Pieter Wuille
2015-09-28 17:40:21 +02:00
parent fa57f1bdf1
commit 3bb9c44719
7 changed files with 502 additions and 60 deletions
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43
include/secp256k1.h
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@@ -271,6 +271,27 @@ SECP256K1_API int secp256k1_ec_pubkey_serialize(
unsigned int flags
) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(4);
/** Parse an ECDSA signature in compact (64 bytes) format.
*
* Returns: 1 when the signature could be parsed, 0 otherwise.
* Args: ctx: a secp256k1 context object
* Out: sig: a pointer to a signature object
* In: input64: a pointer to the 64-byte array to parse
*
* The signature must consist of a 32-byte big endian R value, followed by a
* 32-byte big endian S value. If R or S fall outside of [0..order-1], the
* encoding is invalid. R and S with value 0 are allowed in the encoding.
*
* After the call, sig will always be initialized. If parsing failed or R or
* S are zero, the resulting sig value is guaranteed to fail validation for any
* message and public key.
*/
SECP256K1_API int secp256k1_ecdsa_signature_parse_compact(
const secp256k1_context* ctx,
secp256k1_ecdsa_signature* sig,
const unsigned char *input64
) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
/** Parse a DER ECDSA signature.
*
* Returns: 1 when the signature could be parsed, 0 otherwise.
@@ -279,7 +300,12 @@ SECP256K1_API int secp256k1_ec_pubkey_serialize(
* In: input: a pointer to the signature to be parsed
* inputlen: the length of the array pointed to be input
*
* Note that this function also supports some violations of DER and even BER.
* This function will accept any valid DER encoded signature, even if the
* encoded numbers are out of range.
*
* After the call, sig will always be initialized. If parsing failed or the
* encoded numbers are out of range, signature validation with it is
* guaranteed to fail for every message and public key.
*/
SECP256K1_API int secp256k1_ecdsa_signature_parse_der(
const secp256k1_context* ctx,
@@ -306,6 +332,21 @@ SECP256K1_API int secp256k1_ecdsa_signature_serialize_der(
const secp256k1_ecdsa_signature* sig
) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(4);
/** Serialize an ECDSA signature in compact (64 byte) format.
*
* Returns: 1
* Args: ctx: a secp256k1 context object
* Out: output64: a pointer to a 64-byte array to store the compact serialization
* In: sig: a pointer to an initialized signature object
*
* See secp256k1_ecdsa_signature_parse_compact for details about the encoding.
*/
SECP256K1_API int secp256k1_ecdsa_signature_serialize_compact(
const secp256k1_context* ctx,
unsigned char *output64,
const secp256k1_ecdsa_signature* sig
) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
/** Verify an ECDSA signature.
*
* Returns: 1: correct signature

2
include/secp256k1_recovery.h
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@@ -65,7 +65,7 @@ SECP256K1_API int secp256k1_ecdsa_recoverable_signature_serialize_compact(
unsigned char *output64,
int *recid,
const secp256k1_ecdsa_recoverable_signature* sig
) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(4);
) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(4);
/** Create a recoverable ECDSA signature.
*