diff options
Diffstat (limited to 'lib/base64.c')
| -rw-r--r-- | lib/base64.c | 184 |
1 files changed, 184 insertions, 0 deletions
diff --git a/lib/base64.c b/lib/base64.c new file mode 100644 index 000000000000..41961a444028 --- /dev/null +++ b/lib/base64.c @@ -0,0 +1,184 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * base64.c - Base64 with support for multiple variants + * + * Copyright (c) 2020 Hannes Reinecke, SUSE + * + * Based on the base64url routines from fs/crypto/fname.c + * (which are using the URL-safe Base64 encoding), + * modified to support multiple Base64 variants. + */ + +#include <linux/kernel.h> +#include <linux/types.h> +#include <linux/export.h> +#include <linux/string.h> +#include <linux/base64.h> + +static const char base64_tables[][65] = { + [BASE64_STD] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/", + [BASE64_URLSAFE] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_", + [BASE64_IMAP] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+,", +}; + +/* + * Initialize the base64 reverse mapping for a single character + * This macro maps a character to its corresponding base64 value, + * returning -1 if the character is invalid. + * char 'A'-'Z' maps to 0-25, 'a'-'z' maps to 26-51, '0'-'9' maps to 52-61, + * ch_62 maps to 62, ch_63 maps to 63, and other characters return -1 + */ +#define INIT_1(v, ch_62, ch_63) \ + [v] = (v) >= 'A' && (v) <= 'Z' ? (v) - 'A' \ + : (v) >= 'a' && (v) <= 'z' ? (v) - 'a' + 26 \ + : (v) >= '0' && (v) <= '9' ? (v) - '0' + 52 \ + : (v) == (ch_62) ? 62 : (v) == (ch_63) ? 63 : -1 + +/* + * Recursive macros to generate multiple Base64 reverse mapping table entries. + * Each macro generates a sequence of entries in the lookup table: + * INIT_2 generates 2 entries, INIT_4 generates 4, INIT_8 generates 8, and so on up to INIT_32. + */ +#define INIT_2(v, ...) INIT_1(v, __VA_ARGS__), INIT_1((v) + 1, __VA_ARGS__) +#define INIT_4(v, ...) INIT_2(v, __VA_ARGS__), INIT_2((v) + 2, __VA_ARGS__) +#define INIT_8(v, ...) INIT_4(v, __VA_ARGS__), INIT_4((v) + 4, __VA_ARGS__) +#define INIT_16(v, ...) INIT_8(v, __VA_ARGS__), INIT_8((v) + 8, __VA_ARGS__) +#define INIT_32(v, ...) INIT_16(v, __VA_ARGS__), INIT_16((v) + 16, __VA_ARGS__) + +#define BASE64_REV_INIT(ch_62, ch_63) { \ + [0 ... 0x1f] = -1, \ + INIT_32(0x20, ch_62, ch_63), \ + INIT_32(0x40, ch_62, ch_63), \ + INIT_32(0x60, ch_62, ch_63), \ + [0x80 ... 0xff] = -1 } + +static const s8 base64_rev_maps[][256] = { + [BASE64_STD] = BASE64_REV_INIT('+', '/'), + [BASE64_URLSAFE] = BASE64_REV_INIT('-', '_'), + [BASE64_IMAP] = BASE64_REV_INIT('+', ',') +}; + +#undef BASE64_REV_INIT +#undef INIT_32 +#undef INIT_16 +#undef INIT_8 +#undef INIT_4 +#undef INIT_2 +#undef INIT_1 +/** + * base64_encode() - Base64-encode some binary data + * @src: the binary data to encode + * @srclen: the length of @src in bytes + * @dst: (output) the Base64-encoded string. Not NUL-terminated. + * @padding: whether to append '=' padding characters + * @variant: which base64 variant to use + * + * Encodes data using the selected Base64 variant. + * + * Return: the length of the resulting Base64-encoded string in bytes. + */ +int base64_encode(const u8 *src, int srclen, char *dst, bool padding, enum base64_variant variant) +{ + u32 ac = 0; + char *cp = dst; + const char *base64_table = base64_tables[variant]; + + while (srclen >= 3) { + ac = src[0] << 16 | src[1] << 8 | src[2]; + *cp++ = base64_table[ac >> 18]; + *cp++ = base64_table[(ac >> 12) & 0x3f]; + *cp++ = base64_table[(ac >> 6) & 0x3f]; + *cp++ = base64_table[ac & 0x3f]; + + src += 3; + srclen -= 3; + } + + switch (srclen) { + case 2: + ac = src[0] << 16 | src[1] << 8; + *cp++ = base64_table[ac >> 18]; + *cp++ = base64_table[(ac >> 12) & 0x3f]; + *cp++ = base64_table[(ac >> 6) & 0x3f]; + if (padding) + *cp++ = '='; + break; + case 1: + ac = src[0] << 16; + *cp++ = base64_table[ac >> 18]; + *cp++ = base64_table[(ac >> 12) & 0x3f]; + if (padding) { + *cp++ = '='; + *cp++ = '='; + } + break; + } + return cp - dst; +} +EXPORT_SYMBOL_GPL(base64_encode); + +/** + * base64_decode() - Base64-decode a string + * @src: the string to decode. Doesn't need to be NUL-terminated. + * @srclen: the length of @src in bytes + * @dst: (output) the decoded binary data + * @padding: whether to append '=' padding characters + * @variant: which base64 variant to use + * + * Decodes a string using the selected Base64 variant. + * + * Return: the length of the resulting decoded binary data in bytes, + * or -1 if the string isn't a valid Base64 string. + */ +int base64_decode(const char *src, int srclen, u8 *dst, bool padding, enum base64_variant variant) +{ + u8 *bp = dst; + s8 input[4]; + s32 val; + const u8 *s = (const u8 *)src; + const s8 *base64_rev_tables = base64_rev_maps[variant]; + + while (srclen >= 4) { + input[0] = base64_rev_tables[s[0]]; + input[1] = base64_rev_tables[s[1]]; + input[2] = base64_rev_tables[s[2]]; + input[3] = base64_rev_tables[s[3]]; + + val = input[0] << 18 | input[1] << 12 | input[2] << 6 | input[3]; + + if (unlikely(val < 0)) { + if (!padding || srclen != 4 || s[3] != '=') + return -1; + padding = 0; + srclen = s[2] == '=' ? 2 : 3; + break; + } + + *bp++ = val >> 16; + *bp++ = val >> 8; + *bp++ = val; + + s += 4; + srclen -= 4; + } + + if (likely(!srclen)) + return bp - dst; + if (padding || srclen == 1) + return -1; + + val = (base64_rev_tables[s[0]] << 12) | (base64_rev_tables[s[1]] << 6); + *bp++ = val >> 10; + + if (srclen == 2) { + if (val & 0x800003ff) + return -1; + } else { + val |= base64_rev_tables[s[2]]; + if (val & 0x80000003) + return -1; + *bp++ = val >> 2; + } + return bp - dst; +} +EXPORT_SYMBOL_GPL(base64_decode); |