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