// 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);