1 /* -*- mode: c; c-basic-offset: 4; indent-tabs-mode: nil -*- */
2 /* util/support/hex.c - hex encoding/decoding implementation */
3 /*
4 * Copyright (C) 2018 by the Massachusetts Institute of Technology.
5 * All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 *
11 * * Redistributions of source code must retain the above copyright
12 * notice, this list of conditions and the following disclaimer.
13 *
14 * * Redistributions in binary form must reproduce the above copyright
15 * notice, this list of conditions and the following disclaimer in
16 * the documentation and/or other materials provided with the
17 * distribution.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
20 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
21 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
22 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
23 * COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
24 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
25 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
26 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
28 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
29 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
30 * OF THE POSSIBILITY OF SUCH DAMAGE.
31 */
32
33 #include <k5-platform.h>
34 #include <k5-hex.h>
35 #include <ctype.h>
36
37 static inline char
hex_digit(uint8_t bval,int uppercase)38 hex_digit(uint8_t bval, int uppercase)
39 {
40 assert(bval <= 0xF);
41 if (bval < 10)
42 return '0' + bval;
43 else if (uppercase)
44 return 'A' + (bval - 10);
45 else
46 return 'a' + (bval - 10);
47 }
48
49 int
k5_hex_encode(const void * bytes,size_t len,int uppercase,char ** hex_out)50 k5_hex_encode(const void *bytes, size_t len, int uppercase, char **hex_out)
51 {
52 size_t i;
53 const uint8_t *p = bytes;
54 char *hex;
55
56 *hex_out = NULL;
57
58 hex = malloc(len * 2 + 1);
59 if (hex == NULL)
60 return ENOMEM;
61
62 for (i = 0; i < len; i++) {
63 hex[i * 2] = hex_digit(p[i] >> 4, uppercase);
64 hex[i * 2 + 1] = hex_digit(p[i] & 0xF, uppercase);
65 }
66 hex[len * 2] = '\0';
67
68 *hex_out = hex;
69 return 0;
70 }
71
72 /* Decode a hex digit. Return 0-15 on success, -1 on invalid input. */
73 static inline int
decode_hexchar(unsigned char c)74 decode_hexchar(unsigned char c)
75 {
76 if (isdigit(c))
77 return c - '0';
78 if (c >= 'A' && c <= 'F')
79 return c - 'A' + 10;
80 if (c >= 'a' && c <= 'f')
81 return c - 'a' + 10;
82 return -1;
83 }
84
85 int
k5_hex_decode(const char * hex,uint8_t ** bytes_out,size_t * len_out)86 k5_hex_decode(const char *hex, uint8_t **bytes_out, size_t *len_out)
87 {
88 size_t hexlen, i;
89 int h1, h2;
90 uint8_t *bytes;
91
92 *bytes_out = NULL;
93 *len_out = 0;
94
95 hexlen = strlen(hex);
96 if (hexlen % 2 != 0)
97 return EINVAL;
98 bytes = malloc(hexlen / 2 + 1);
99 if (bytes == NULL)
100 return ENOMEM;
101
102 for (i = 0; i < hexlen / 2; i++) {
103 h1 = decode_hexchar(hex[i * 2]);
104 h2 = decode_hexchar(hex[i * 2 + 1]);
105 if (h1 == -1 || h2 == -1) {
106 free(bytes);
107 return EINVAL;
108 }
109 bytes[i] = h1 * 16 + h2;
110 }
111 bytes[i] = 0;
112
113 *bytes_out = bytes;
114 *len_out = hexlen / 2;
115 return 0;
116 }
117