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/*
* Code based on busybox-1.23.2
*
* Copyright 2003, Glenn McGrath
* Copyright 2006, Rob Landley <rob@landley.net>
* Copyright 2010, Denys Vlasenko
*
* Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
*/
#include <common.h>
#include <base64.h>
/* Conversion table. for base 64 */
static const char uuenc_tbl_base64[65 + 1] = {
'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H',
'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P',
'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X',
'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f',
'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n',
'o', 'p', 'q', 'r', 's', 't', 'u', 'v',
'w', 'x', 'y', 'z', '0', '1', '2', '3',
'4', '5', '6', '7', '8', '9', '+', '/',
'=' /* termination character */,
'\0' /* needed for uudecode.c only */
};
static char base64_trchr(char ch, bool url)
{
if (!url)
return ch;
switch (ch) {
case '+':
return '-';
case '/':
return '_';
case '-':
return '+';
case '_':
return '/';
default:
return ch;
}
}
/*
* Encode bytes at S of length LENGTH to uuencode or base64 format and place it
* to STORE. STORE will be 0-terminated, and must point to a writable
* buffer of at least 1+BASE64_LENGTH(length) bytes.
* where BASE64_LENGTH(len) = (4 * ((LENGTH + 2) / 3))
*/
void uuencode(char *p, const char *src, int length)
{
const unsigned char *s = src;
const char *tbl = uuenc_tbl_base64;
/* Transform the 3x8 bits to 4x6 bits */
while (length > 0) {
unsigned s1, s2;
/* Are s[1], s[2] valid or should be assumed 0? */
s1 = s2 = 0;
length -= 3; /* can be >=0, -1, -2 */
if (length >= -1) {
s1 = s[1];
if (length >= 0)
s2 = s[2];
}
*p++ = tbl[s[0] >> 2];
*p++ = tbl[((s[0] & 3) << 4) + (s1 >> 4)];
*p++ = tbl[((s1 & 0xf) << 2) + (s2 >> 6)];
*p++ = tbl[s2 & 0x3f];
s += 3;
}
/* Zero-terminate */
*p = '\0';
/* If length is -2 or -1, pad last char or two */
while (length) {
*--p = tbl[64];
length++;
}
}
EXPORT_SYMBOL(uuencode);
/*
* Decode base64 encoded string. Stops on '\0'.
*
*/
static int __decode_base64(char *p_dst, int dst_len, const char *src, bool url)
{
const char *src_tail;
char *dst = p_dst;
int length = 0;
bool end_reached = false;
while (dst_len > 0 && !end_reached) {
unsigned char six_bit[4];
int count = 0;
/* Fetch up to four 6-bit values */
src_tail = src;
while (count < 4) {
const char *table_ptr;
int ch;
/*
* Get next _valid_ character.
* uuenc_tbl_base64[] contains this string:
* 0 1 2 3 4 5 6
* 01234567890123456789012345678901234567890123456789012345678901234
* "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/="
*/
do {
ch = *src;
if (ch == '\0') {
/*
* Example:
* If we decode "QUJD <NUL>", we want
* to return ptr to NUL, not to ' ',
* because we did fully decode
* the string (to "ABC").
*/
if (count == 0) {
src_tail = src;
} else if (url) {
end_reached = true;
goto out;
}
goto ret;
}
src++;
table_ptr = strchr(uuenc_tbl_base64, base64_trchr(ch, url));
} while (!table_ptr && !url);
if (!table_ptr) {
end_reached = true;
goto out;
}
/* Convert encoded character to decimal */
ch = table_ptr - uuenc_tbl_base64;
/* ch is 64 if char was '=', otherwise 0..63 */
if (ch == 64)
break;
six_bit[count] = ch;
count++;
}
out:
/*
* Transform 6-bit values to 8-bit ones.
* count can be < 4 when we decode the tail:
* "eQ==" -> "y", not "y NUL NUL".
* Note that (count > 1) is always true,
* "x===" encoding is not valid:
* even a single zero byte encodes as "AA==".
* However, with current logic we come here with count == 1
* when we decode "==" tail.
*/
if (count > 1)
*dst++ = six_bit[0] << 2 | six_bit[1] >> 4;
if (count > 2)
*dst++ = six_bit[1] << 4 | six_bit[2] >> 2;
if (count > 3)
*dst++ = six_bit[2] << 6 | six_bit[3];
/*
* Note that if we decode "AA==" and ate first '=',
* we just decoded one char (count == 2) and now we'll
* do the loop once more to decode second '='.
*/
dst_len -= count-1;
/* last character was "=" */
if (count != 0)
length += count - 1;
}
ret:
p_dst = dst;
return length;
}
/*
* Decode base64 encoded string. Stops on '\0'.
*
*/
int decode_base64(char *p_dst, int dst_len, const char *src)
{
return __decode_base64(p_dst, dst_len, src, false);
}
EXPORT_SYMBOL(decode_base64);
/*
* Decode base64url encoded string. Stops on '\0'.
*
*/
int decode_base64url(char *p_dst, int dst_len, const char *src)
{
return __decode_base64(p_dst, dst_len, src, true);
}
EXPORT_SYMBOL(decode_base64url);
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