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 | |