| // SPDX-License-Identifier: BSD-2-Clause |
| /* LibTomCrypt, modular cryptographic library -- Tom St Denis |
| * |
| * LibTomCrypt is a library that provides various cryptographic |
| * algorithms in a highly modular and flexible manner. |
| * |
| * The library is free for all purposes without any express |
| * guarantee it works. |
| */ |
| #include "tomcrypt_private.h" |
| |
| /** |
| @file der_decode_integer.c |
| ASN.1 DER, decode an integer, Tom St Denis |
| */ |
| |
| |
| #ifdef LTC_DER |
| |
| /** |
| Read a mp_int integer |
| @param in The DER encoded data |
| @param inlen Size of DER encoded data |
| @param num The first mp_int to decode |
| @return CRYPT_OK if successful |
| */ |
| int der_decode_integer(const unsigned char *in, unsigned long inlen, void *num) |
| { |
| unsigned long x, y; |
| int err; |
| |
| LTC_ARGCHK(num != NULL); |
| LTC_ARGCHK(in != NULL); |
| |
| /* min DER INTEGER is 0x02 01 00 == 0 */ |
| if (inlen < (1 + 1 + 1)) { |
| return CRYPT_INVALID_PACKET; |
| } |
| |
| /* ok expect 0x02 when we AND with 0001 1111 [1F] */ |
| x = 0; |
| if ((in[x++] & 0x1F) != 0x02) { |
| return CRYPT_INVALID_PACKET; |
| } |
| |
| /* get the length of the data */ |
| inlen -= x; |
| if ((err = der_decode_asn1_length(in + x, &inlen, &y)) != CRYPT_OK) { |
| return err; |
| } |
| x += inlen; |
| |
| if ((err = mp_read_unsigned_bin(num, (unsigned char *)in + x, y)) != CRYPT_OK) { |
| return err; |
| } |
| |
| /* see if it's negative */ |
| if (in[x] & 0x80) { |
| void *tmp; |
| if (mp_init(&tmp) != CRYPT_OK) { |
| return CRYPT_MEM; |
| } |
| |
| if (mp_2expt(tmp, mp_count_bits(num)) != CRYPT_OK || mp_sub(num, tmp, num) != CRYPT_OK) { |
| mp_clear(tmp); |
| return CRYPT_MEM; |
| } |
| mp_clear(tmp); |
| } |
| |
| return CRYPT_OK; |
| |
| } |
| |
| #endif |
| |
| /* ref: $Format:%D$ */ |
| /* git commit: $Format:%H$ */ |
| /* commit time: $Format:%ai$ */ |