1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * base64.c - Base64 with support for multiple variants 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 support multiple Base64 variants. 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_tables[][65] = { 19 [BASE64_STD] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/", 20 [BASE64_URLSAFE] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_", 21 [BASE64_IMAP] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+,", 22 }; 23 24 /** 25 * base64_encode() - Base64-encode some binary data 26 * @src: the binary data to encode 27 * @srclen: the length of @src in bytes 28 * @dst: (output) the Base64-encoded string. Not NUL-terminated. 29 * @padding: whether to append '=' padding characters 30 * @variant: which base64 variant to use 31 * 32 * Encodes data using the selected Base64 variant. 33 * 34 * Return: the length of the resulting Base64-encoded string in bytes. 35 */ 36 int base64_encode(const u8 *src, int srclen, char *dst, bool padding, enum base64_variant variant) 37 { 38 u32 ac = 0; 39 int bits = 0; 40 int i; 41 char *cp = dst; 42 const char *base64_table = base64_tables[variant]; 43 44 for (i = 0; i < srclen; i++) { 45 ac = (ac << 8) | src[i]; 46 bits += 8; 47 do { 48 bits -= 6; 49 *cp++ = base64_table[(ac >> bits) & 0x3f]; 50 } while (bits >= 6); 51 } 52 if (bits) { 53 *cp++ = base64_table[(ac << (6 - bits)) & 0x3f]; 54 bits -= 6; 55 } 56 if (padding) { 57 while (bits < 0) { 58 *cp++ = '='; 59 bits += 2; 60 } 61 } 62 return cp - dst; 63 } 64 EXPORT_SYMBOL_GPL(base64_encode); 65 66 /** 67 * base64_decode() - Base64-decode a string 68 * @src: the string to decode. Doesn't need to be NUL-terminated. 69 * @srclen: the length of @src in bytes 70 * @dst: (output) the decoded binary data 71 * @padding: whether to append '=' padding characters 72 * @variant: which base64 variant to use 73 * 74 * Decodes a string using the selected Base64 variant. 75 * 76 * This implementation hasn't been optimized for performance. 77 * 78 * Return: the length of the resulting decoded binary data in bytes, 79 * or -1 if the string isn't a valid Base64 string. 80 */ 81 int base64_decode(const char *src, int srclen, u8 *dst, bool padding, enum base64_variant variant) 82 { 83 u32 ac = 0; 84 int bits = 0; 85 int i; 86 u8 *bp = dst; 87 const char *base64_table = base64_tables[variant]; 88 89 for (i = 0; i < srclen; i++) { 90 const char *p = strchr(base64_table, src[i]); 91 if (padding) { 92 if (src[i] == '=') { 93 ac = (ac << 6); 94 bits += 6; 95 if (bits >= 8) 96 bits -= 8; 97 continue; 98 } 99 } 100 if (p == NULL || src[i] == 0) 101 return -1; 102 ac = (ac << 6) | (p - base64_table); 103 bits += 6; 104 if (bits >= 8) { 105 bits -= 8; 106 *bp++ = (u8)(ac >> bits); 107 } 108 } 109 if (ac & ((1 << bits) - 1)) 110 return -1; 111 return bp - dst; 112 } 113 EXPORT_SYMBOL_GPL(base64_decode); 114