1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * base64.c - RFC4648-compliant base64 encoding
4 *
5 * Copyright (c) 2020 Hannes Reinecke, SUSE
6 *
7 * Based on the base64url routines from fs/crypto/fname.c
8 * (which are using the URL-safe base64 encoding),
9 * modified to use the standard coding table from RFC4648 section 4.
10 */
11
12 #include <linux/kernel.h>
13 #include <linux/types.h>
14 #include <linux/export.h>
15 #include <linux/string.h>
16 #include <linux/base64.h>
17
18 static const char base64_table[65] =
19 "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
20
21 /**
22 * base64_encode() - base64-encode some binary data
23 * @src: the binary data to encode
24 * @srclen: the length of @src in bytes
25 * @dst: (output) the base64-encoded string. Not NUL-terminated.
26 *
27 * Encodes data using base64 encoding, i.e. the "Base 64 Encoding" specified
28 * by RFC 4648, including the '='-padding.
29 *
30 * Return: the length of the resulting base64-encoded string in bytes.
31 */
32 int base64_encode(const u8 *src, int srclen, char *dst)
33 {
34 u32 ac = 0;
35 int bits = 0;
36 int i;
37 char *cp = dst;
38
39 for (i = 0; i < srclen; i++) {
40 ac = (ac << 8) | src[i];
41 bits += 8;
42 do {
43 bits -= 6;
44 *cp++ = base64_table[(ac >> bits) & 0x3f];
45 } while (bits >= 6);
46 }
47 if (bits) {
48 *cp++ = base64_table[(ac << (6 - bits)) & 0x3f];
49 bits -= 6;
50 }
51 while (bits < 0) {
52 *cp++ = '=';
53 bits += 2;
54 }
55 return cp - dst;
56 }
57 EXPORT_SYMBOL_GPL(base64_encode);
58
59 /**
60 * base64_decode() - base64-decode a string
61 * @src: the string to decode. Doesn't need to be NUL-terminated.
62 * @srclen: the length of @src in bytes
63 * @dst: (output) the decoded binary data
64 *
65 * Decodes a string using base64 encoding, i.e. the "Base 64 Encoding"
66 * specified by RFC 4648, including the '='-padding.
67 *
68 * This implementation hasn't been optimized for performance.
69 *
70 * Return: the length of the resulting decoded binary data in bytes,
71 * or -1 if the string isn't a valid base64 string.
72 */
73 int base64_decode(const char *src, int srclen, u8 *dst)
74 {
75 u32 ac = 0;
76 int bits = 0;
77 int i;
78 u8 *bp = dst;
79
80 for (i = 0; i < srclen; i++) {
81 const char *p = strchr(base64_table, src[i]);
82
83 if (src[i] == '=') {
84 ac = (ac << 6);
85 bits += 6;
86 if (bits >= 8)
87 bits -= 8;
88 continue;
89 }
90 if (p == NULL || src[i] == 0)
91 return -1;
92 ac = (ac << 6) | (p - base64_table);
93 bits += 6;
94 if (bits >= 8) {
95 bits -= 8;
96 *bp++ = (u8)(ac >> bits);
97 }
98 }
99 if (ac & ((1 << bits) - 1))
100 return -1;
101 return bp - dst;
102 }
103 EXPORT_SYMBOL_GPL(base64_decode);
104
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