1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
|
/***********************************************************************
* Copyright (c) 2015 Pieter Wuille *
* Distributed under the MIT software license, see the accompanying *
* file COPYING or https://www.opensource.org/licenses/mit-license.php.*
***********************************************************************/
/****
* Please do not link this file directly. It is not part of the libsecp256k1
* project and does not promise any stability in its API, functionality or
* presence. Projects which use this code should instead copy this header
* and its accompanying .c file directly into their codebase.
****/
/* This file defines a function that parses DER with various errors and
* violations. This is not a part of the library itself, because the allowed
* violations are chosen arbitrarily and do not follow or establish any
* standard.
*
* In many places it matters that different implementations do not only accept
* the same set of valid signatures, but also reject the same set of signatures.
* The only means to accomplish that is by strictly obeying a standard, and not
* accepting anything else.
*
* Nonetheless, sometimes there is a need for compatibility with systems that
* use signatures which do not strictly obey DER. The snippet below shows how
* certain violations are easily supported. You may need to adapt it.
*
* Do not use this for new systems. Use well-defined DER or compact signatures
* instead if you have the choice (see secp256k1_ecdsa_signature_parse_der and
* secp256k1_ecdsa_signature_parse_compact).
*
* The supported violations are:
* - All numbers are parsed as nonnegative integers, even though X.609-0207
* section 8.3.3 specifies that integers are always encoded as two's
* complement.
* - Integers can have length 0, even though section 8.3.1 says they can't.
* - Integers with overly long padding are accepted, violation section
* 8.3.2.
* - 127-byte long length descriptors are accepted, even though section
* 8.1.3.5.c says that they are not.
* - Trailing garbage data inside or after the signature is ignored.
* - The length descriptor of the sequence is ignored.
*
* Compared to for example OpenSSL, many violations are NOT supported:
* - Using overly long tag descriptors for the sequence or integers inside,
* violating section 8.1.2.2.
* - Encoding primitive integers as constructed values, violating section
* 8.3.1.
*/
#ifndef SECP256K1_CONTRIB_LAX_DER_PARSING_H
#define SECP256K1_CONTRIB_LAX_DER_PARSING_H
/* #include secp256k1.h only when it hasn't been included yet.
This enables this file to be #included directly in other project
files (such as tests.c) without the need to set an explicit -I flag,
which would be necessary to locate secp256k1.h. */
#ifndef SECP256K1_H
#include <secp256k1.h>
#endif
#ifdef __cplusplus
extern "C" {
#endif
/** Parse a signature in "lax DER" format
*
* Returns: 1 when the signature could be parsed, 0 otherwise.
* Args: ctx: a secp256k1 context object
* Out: sig: pointer to a signature object
* In: input: pointer to the signature to be parsed
* inputlen: the length of the array pointed to be input
*
* This function will accept any valid DER encoded signature, even if the
* encoded numbers are out of range. In addition, it will accept signatures
* which violate the DER spec in various ways. Its purpose is to allow
* validation of the Bitcoin blockchain, which includes non-DER signatures
* from before the network rules were updated to enforce DER. Note that
* the set of supported violations is a strict subset of what OpenSSL will
* accept.
*
* 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.
*/
int ecdsa_signature_parse_der_lax(
const secp256k1_context* ctx,
secp256k1_ecdsa_signature* sig,
const unsigned char *input,
size_t inputlen
) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
#ifdef __cplusplus
}
#endif
#endif /* SECP256K1_CONTRIB_LAX_DER_PARSING_H */
|
