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