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/**********************************************************************
* Copyright (c) 2014, 2015 Pieter Wuille *
* Distributed under the MIT software license, see the accompanying *
* file COPYING or http://www.opensource.org/licenses/mit-license.php.*
**********************************************************************/
/* This file contains code snippets that parse DER private keys 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.
*
* It also contains code to serialize private keys in a compatible
* manner.
*
* These functions are meant for compatibility with applications
* that require BER encoded keys. When working with secp256k1-specific
* code, the simple 32-byte private keys normally used by the
* library are sufficient.
*/
#ifndef _SECP256K1_CONTRIB_BER_PRIVATEKEY_H_
#define _SECP256K1_CONTRIB_BER_PRIVATEKEY_H_
#include <string.h>
#include <secp256k1.h>
/** Export a private key in DER format.
*
* Returns: 1 if the private key was valid.
* Args: ctx: pointer to a context object, initialized for signing (cannot
* be NULL)
* Out: privkey: pointer to an array for storing the private key in BER.
* Should have space for 279 bytes, and cannot be NULL.
* privkeylen: Pointer to an int where the length of the private key in
* privkey will be stored.
* In: seckey: pointer to a 32-byte secret key to export.
* compressed: 1 if the key should be exported in
* compressed format, 0 otherwise
*
* This function is purely meant for compatibility with applications that
* require BER encoded keys. When working with secp256k1-specific code, the
* simple 32-byte private keys are sufficient.
*
* Note that this function does not guarantee correct DER output. It is
* guaranteed to be parsable by secp256k1_ec_privkey_import_der
*/
static SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_privkey_export_der(
const secp256k1_context* ctx,
unsigned char *privkey,
size_t *privkeylen,
const unsigned char *seckey,
int compressed
) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(4);
/** Import a private key in DER format.
* Returns: 1 if a private key was extracted.
* Args: ctx: pointer to a context object (cannot be NULL).
* Out: seckey: pointer to a 32-byte array for storing the private key.
* (cannot be NULL).
* In: privkey: pointer to a private key in DER format (cannot be NULL).
* privkeylen: length of the DER private key pointed to be privkey.
*
* This function will accept more than just strict DER, and even allow some BER
* violations. The public key stored inside the DER-encoded private key is not
* verified for correctness, nor are the curve parameters. Use this function
* only if you know in advance it is supposed to contain a secp256k1 private
* key.
*/
static SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_privkey_import_der(
const secp256k1_context* ctx,
unsigned char *seckey,
const unsigned char *privkey,
size_t privkeylen
) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
static int secp256k1_eckey_privkey_parse(secp256k1_scalar *key, const unsigned char *privkey, size_t privkeylen) {
unsigned char c[32] = {0};
const unsigned char *end = privkey + privkeylen;
int lenb = 0;
int len = 0;
int overflow = 0;
/* sequence header */
if (end < privkey+1 || *privkey != 0x30) {
return 0;
}
privkey++;
/* sequence length constructor */
if (end < privkey+1 || !(*privkey & 0x80)) {
return 0;
}
lenb = *privkey & ~0x80; privkey++;
if (lenb < 1 || lenb > 2) {
return 0;
}
if (end < privkey+lenb) {
return 0;
}
/* sequence length */
len = privkey[lenb-1] | (lenb > 1 ? privkey[lenb-2] << 8 : 0);
privkey += lenb;
if (end < privkey+len) {
return 0;
}
/* sequence element 0: version number (=1) */
if (end < privkey+3 || privkey[0] != 0x02 || privkey[1] != 0x01 || privkey[2] != 0x01) {
return 0;
}
privkey += 3;
/* sequence element 1: octet string, up to 32 bytes */
if (end < privkey+2 || privkey[0] != 0x04 || privkey[1] > 0x20 || end < privkey+2+privkey[1]) {
return 0;
}
memcpy(c + 32 - privkey[1], privkey + 2, privkey[1]);
secp256k1_scalar_set_b32(key, c, &overflow);
memset(c, 0, 32);
return !overflow;
}
static int secp256k1_eckey_privkey_serialize(const secp256k1_ecmult_gen_context *ctx, unsigned char *privkey, size_t *privkeylen, const secp256k1_scalar *key, int compressed) {
secp256k1_gej rp;
secp256k1_ge r;
size_t pubkeylen = 0;
secp256k1_ecmult_gen(ctx, &rp, key);
secp256k1_ge_set_gej(&r, &rp);
if (compressed) {
static const unsigned char begin[] = {
0x30,0x81,0xD3,0x02,0x01,0x01,0x04,0x20
};
static const unsigned char middle[] = {
0xA0,0x81,0x85,0x30,0x81,0x82,0x02,0x01,0x01,0x30,0x2C,0x06,0x07,0x2A,0x86,0x48,
0xCE,0x3D,0x01,0x01,0x02,0x21,0x00,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
0xFF,0xFF,0xFE,0xFF,0xFF,0xFC,0x2F,0x30,0x06,0x04,0x01,0x00,0x04,0x01,0x07,0x04,
0x21,0x02,0x79,0xBE,0x66,0x7E,0xF9,0xDC,0xBB,0xAC,0x55,0xA0,0x62,0x95,0xCE,0x87,
0x0B,0x07,0x02,0x9B,0xFC,0xDB,0x2D,0xCE,0x28,0xD9,0x59,0xF2,0x81,0x5B,0x16,0xF8,
0x17,0x98,0x02,0x21,0x00,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
0xFF,0xFF,0xFF,0xFF,0xFE,0xBA,0xAE,0xDC,0xE6,0xAF,0x48,0xA0,0x3B,0xBF,0xD2,0x5E,
0x8C,0xD0,0x36,0x41,0x41,0x02,0x01,0x01,0xA1,0x24,0x03,0x22,0x00
};
unsigned char *ptr = privkey;
memcpy(ptr, begin, sizeof(begin)); ptr += sizeof(begin);
secp256k1_scalar_get_b32(ptr, key); ptr += 32;
memcpy(ptr, middle, sizeof(middle)); ptr += sizeof(middle);
if (!secp256k1_eckey_pubkey_serialize(&r, ptr, &pubkeylen, 1)) {
return 0;
}
ptr += pubkeylen;
*privkeylen = ptr - privkey;
} else {
static const unsigned char begin[] = {
0x30,0x82,0x01,0x13,0x02,0x01,0x01,0x04,0x20
};
static const unsigned char middle[] = {
0xA0,0x81,0xA5,0x30,0x81,0xA2,0x02,0x01,0x01,0x30,0x2C,0x06,0x07,0x2A,0x86,0x48,
0xCE,0x3D,0x01,0x01,0x02,0x21,0x00,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
0xFF,0xFF,0xFE,0xFF,0xFF,0xFC,0x2F,0x30,0x06,0x04,0x01,0x00,0x04,0x01,0x07,0x04,
0x41,0x04,0x79,0xBE,0x66,0x7E,0xF9,0xDC,0xBB,0xAC,0x55,0xA0,0x62,0x95,0xCE,0x87,
0x0B,0x07,0x02,0x9B,0xFC,0xDB,0x2D,0xCE,0x28,0xD9,0x59,0xF2,0x81,0x5B,0x16,0xF8,
0x17,0x98,0x48,0x3A,0xDA,0x77,0x26,0xA3,0xC4,0x65,0x5D,0xA4,0xFB,0xFC,0x0E,0x11,
0x08,0xA8,0xFD,0x17,0xB4,0x48,0xA6,0x85,0x54,0x19,0x9C,0x47,0xD0,0x8F,0xFB,0x10,
0xD4,0xB8,0x02,0x21,0x00,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
0xFF,0xFF,0xFF,0xFF,0xFE,0xBA,0xAE,0xDC,0xE6,0xAF,0x48,0xA0,0x3B,0xBF,0xD2,0x5E,
0x8C,0xD0,0x36,0x41,0x41,0x02,0x01,0x01,0xA1,0x44,0x03,0x42,0x00
};
unsigned char *ptr = privkey;
memcpy(ptr, begin, sizeof(begin)); ptr += sizeof(begin);
secp256k1_scalar_get_b32(ptr, key); ptr += 32;
memcpy(ptr, middle, sizeof(middle)); ptr += sizeof(middle);
if (!secp256k1_eckey_pubkey_serialize(&r, ptr, &pubkeylen, 0)) {
return 0;
}
ptr += pubkeylen;
*privkeylen = ptr - privkey;
}
return 1;
}
static int secp256k1_ec_privkey_export_der(const secp256k1_context* ctx, unsigned char *privkey, size_t *privkeylen, const unsigned char *seckey, int compressed) {
secp256k1_scalar key;
int ret = 0;
VERIFY_CHECK(ctx != NULL);
ARG_CHECK(seckey != NULL);
ARG_CHECK(privkey != NULL);
ARG_CHECK(privkeylen != NULL);
ARG_CHECK(secp256k1_ecmult_gen_context_is_built(&ctx->ecmult_gen_ctx));
secp256k1_scalar_set_b32(&key, seckey, NULL);
ret = secp256k1_eckey_privkey_serialize(&ctx->ecmult_gen_ctx, privkey, privkeylen, &key, compressed);
secp256k1_scalar_clear(&key);
return ret;
}
static int secp256k1_ec_privkey_import_der(const secp256k1_context* ctx, unsigned char *seckey, const unsigned char *privkey, size_t privkeylen) {
secp256k1_scalar key;
int ret = 0;
ARG_CHECK(seckey != NULL);
ARG_CHECK(privkey != NULL);
(void)ctx;
ret = secp256k1_eckey_privkey_parse(&key, privkey, privkeylen);
if (ret) {
secp256k1_scalar_get_b32(seckey, &key);
}
secp256k1_scalar_clear(&key);
return ret;
}
#endif