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Authored by dereckson on May 14 2023, 12:39.
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F2217665: base64.c
May 14 2023, 12:39
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/* -------------------------------------------------------------
Base64 - RFC 1341
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Description: Base64 helper functions
Author: Jouni Malinen <j@w1.fi>
License: BSD-2-Clause
Source: This version has been extracted from FreeBSD
source code - src/contrib/wpa/src/utils/base64.c
Commit source: 0a6760a1de32bf5df91ef926eba25b3f74b4f84f
------------------------------------------------------------- */
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#ifndef BIT
#define BIT(x) (1U << (x))
#endif
/* -------------------------------------------------------------
Helper functions to actually do the encode/decode work
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
static const char base64_table[65] =
"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
#define BASE64_PAD BIT(0)
#define BASE64_LF BIT(1)
static char * base64_gen_encode(const unsigned char *src, size_t len,
size_t *out_len, const char *table, int add_pad)
{
char *out, *pos;
const unsigned char *end, *in;
size_t olen;
int line_len;
if (len >= SIZE_MAX / 4)
return NULL;
olen = len * 4 / 3 + 4; /* 3-byte blocks to 4-byte */
if (add_pad & BASE64_LF)
olen += olen / 72; /* line feeds */
olen++; /* nul termination */
if (olen < len)
return NULL; /* integer overflow */
out = malloc(olen);
if (out == NULL)
return NULL;
end = src + len;
in = src;
pos = out;
line_len = 0;
while (end - in >= 3) {
*pos++ = table[(in[0] >> 2) & 0x3f];
*pos++ = table[(((in[0] & 0x03) << 4) | (in[1] >> 4)) & 0x3f];
*pos++ = table[(((in[1] & 0x0f) << 2) | (in[2] >> 6)) & 0x3f];
*pos++ = table[in[2] & 0x3f];
in += 3;
line_len += 4;
if ((add_pad & BASE64_LF) && line_len >= 72) {
*pos++ = '\n';
line_len = 0;
}
}
if (end - in) {
*pos++ = table[(in[0] >> 2) & 0x3f];
if (end - in == 1) {
*pos++ = table[((in[0] & 0x03) << 4) & 0x3f];
if (add_pad & BASE64_PAD)
*pos++ = '=';
} else {
*pos++ = table[(((in[0] & 0x03) << 4) |
(in[1] >> 4)) & 0x3f];
*pos++ = table[((in[1] & 0x0f) << 2) & 0x3f];
}
if (add_pad & BASE64_PAD)
*pos++ = '=';
line_len += 4;
}
if ((add_pad & BASE64_LF) && line_len)
*pos++ = '\n';
*pos = '\0';
if (out_len)
*out_len = pos - out;
return out;
}
static unsigned char * base64_gen_decode(const char *src, size_t len,
size_t *out_len, const char *table)
{
unsigned char dtable[256], *out, *pos, block[4], tmp;
size_t i, count, olen;
int pad = 0;
size_t extra_pad;
memset(dtable, 0x80, 256);
for (i = 0; i < sizeof(base64_table) - 1; i++)
dtable[(unsigned char) table[i]] = (unsigned char) i;
dtable['='] = 0;
count = 0;
for (i = 0; i < len; i++) {
if (dtable[(unsigned char) src[i]] != 0x80)
count++;
}
if (count == 0)
return NULL;
extra_pad = (4 - count % 4) % 4;
olen = (count + extra_pad) / 4 * 3;
pos = out = malloc(olen);
if (out == NULL)
return NULL;
count = 0;
for (i = 0; i < len + extra_pad; i++) {
unsigned char val;
if (i >= len)
val = '=';
else
val = src[i];
tmp = dtable[val];
if (tmp == 0x80)
continue;
if (val == '=')
pad++;
block[count] = tmp;
count++;
if (count == 4) {
*pos++ = (block[0] << 2) | (block[1] >> 4);
*pos++ = (block[1] << 4) | (block[2] >> 2);
*pos++ = (block[2] << 6) | block[3];
count = 0;
if (pad) {
if (pad == 1)
pos--;
else if (pad == 2)
pos -= 2;
else {
/* Invalid padding */
free(out);
return NULL;
}
break;
}
}
}
*out_len = pos - out;
return out;
}
/* -------------------------------------------------------------
High-level functions to use as library
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
/**
* base64_encode - Base64 encode
* @src: Data to be encoded
* @len: Length of the data to be encoded
* @out_len: Pointer to output length variable, or %NULL if not used
* Returns: Allocated buffer of out_len bytes of encoded data,
* or %NULL on failure
*
* Caller is responsible for freeing the returned buffer. Returned buffer is
* nul terminated to make it easier to use as a C string. The nul terminator is
* not included in out_len.
*/
char * base64_encode(const void *src, size_t len, size_t *out_len)
{
return base64_gen_encode(src, len, out_len, base64_table,
BASE64_PAD | BASE64_LF);
}
/**
* base64_decode - Base64 decode
* @src: Data to be decoded
* @len: Length of the data to be decoded
* @out_len: Pointer to output length variable
* Returns: Allocated buffer of out_len bytes of decoded data,
* or %NULL on failure
*
* Caller is responsible for freeing the returned buffer.
*/
unsigned char * base64_decode(const char *src, size_t len, size_t *out_len)
{
return base64_gen_decode(src, len, out_len, base64_table);
}
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