1 // SPDX-License-Identifier: BSD-2-Clause
2 /* LibTomCrypt, modular cryptographic library -- Tom St Denis
3 *
4 * LibTomCrypt is a library that provides various cryptographic
5 * algorithms in a highly modular and flexible manner.
6 *
7 * The library is free for all purposes without any express
8 * guarantee it works.
9 */
10
11 #include "tomcrypt_private.h"
12
13 /**
14 @file base16_decode.c
15 Base16/Hex decode a string.
16 Based on https://stackoverflow.com/a/23898449
17 Adapted for libtomcrypt by Steffen Jaeckel
18 */
19
20 #ifdef LTC_BASE16
21
22 /**
23 Base16 decode a string
24 @param in The Base16 string to decode
25 @param inlen The length of the Base16 data
26 @param out [out] The destination of the binary decoded data
27 @param outlen [in/out] The max size and resulting size of the decoded data
28 @return CRYPT_OK if successful
29 */
base16_decode(const char * in,unsigned long inlen,unsigned char * out,unsigned long * outlen)30 int base16_decode(const char *in, unsigned long inlen,
31 unsigned char *out, unsigned long *outlen)
32 {
33 unsigned long pos, out_len;
34 unsigned char idx0, idx1;
35 char in0, in1;
36
37 const unsigned char hashmap[] = {
38 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, /* 01234567 */
39 0x08, 0x09, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, /* 89:;<=>? */
40 0xff, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f, 0xff, /* @ABCDEFG */
41 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, /* HIJKLMNO */
42 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, /* PQRSTUVW */
43 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, /* XYZ[\]^_ */
44 0xff, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f, 0xff, /* `abcdefg */
45 };
46
47 LTC_ARGCHK(in != NULL);
48 LTC_ARGCHK(out != NULL);
49 LTC_ARGCHK(outlen != NULL);
50
51 if ((inlen % 2) == 1) return CRYPT_INVALID_PACKET;
52 out_len = *outlen * 2;
53 for (pos = 0; ((pos + 1 < out_len) && (pos + 1 < inlen)); pos += 2) {
54 in0 = in[pos + 0];
55 in1 = in[pos + 1];
56
57 if ((in0 < '0') || (in0 > 'g')) return CRYPT_INVALID_PACKET;
58 if ((in1 < '0') || (in1 > 'g')) return CRYPT_INVALID_PACKET;
59
60 idx0 = (unsigned char) (in0 & 0x1F) ^ 0x10;
61 idx1 = (unsigned char) (in1 & 0x1F) ^ 0x10;
62
63 if (hashmap[idx0] == 0xff) return CRYPT_INVALID_PACKET;
64 if (hashmap[idx1] == 0xff) return CRYPT_INVALID_PACKET;
65
66 out[pos / 2] = (unsigned char) (hashmap[idx0] << 4) | hashmap[idx1];
67 }
68 *outlen = pos / 2;
69 return CRYPT_OK;
70 }
71
72 #endif
73
74 /* ref: $Format:%D$ */
75 /* git commit: $Format:%H$ */
76 /* commit time: $Format:%ai$ */
77