iodine/src/base64.c

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/*
* Copyright (c) 2006-2007 Bjorn Andersson <flex@kryo.se>, Erik Ekman <yarrick@kryo.se>
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "encoding.h"
#include "common.h"
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#include "base64.h"
static const char cb64[] =
"abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ-0123456789.";
static unsigned char rev64[128];
static int reverse_init = 0;
#define REV64(x) rev64[(int) (x)]
#define MODE (cb64[62])
#define P62 (cb64[62])
#define P63 (cb64[63])
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static struct encoder base64_encoder =
{
"BASE64",
base64_encode,
base64_decode,
base64_handles_dots,
base64_handles_dots
};
struct encoder
*get_base64_encoder()
{
return &base64_encoder;
}
int
base64_handles_dots()
{
return 0;
}
static void
findesc(int *count, unsigned char *esc, char c1, char c2, char c3, char c4)
{
int min1 = 0;
int min2 = 0;
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int num1 = 0xFF; /* a very big number */
int num2 = 0xFE; /* a nearly as big number */
int i;
/* check if no more escapes needed */
if (count[62] == 0 && count[63] == 0) {
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esc[0] = MODE;
esc[1] = MODE;
return;
}
for (i = 0; i < 62; i++) {
if (i == c1 || i == c2 || i == c3 || i == c4) {
continue;
}
if (count[i] < num1) {
min2 = min1;
num2 = num1;
min1 = i;
num1 = count[i];
} else if (count[i] < num2) {
min2 = i;
num2 = count[i];
}
}
esc[0] = cb64[min1];
esc[1] = cb64[min2];
}
static void
escape_chars(char *buf, size_t buflen)
{
int counter[64];
int escapes;
int reset;
int i;
unsigned char temp[4096];
unsigned char *r;
unsigned char *w;
unsigned char *e;
unsigned char esc[2];
memset(counter, 0, sizeof(counter));
esc[0] = P62;
esc[1] = P63;
/* first, find the number of times each token is used */
r = (unsigned char *) buf;
w = temp;
while (*r) {
counter[REV64(*r)]++;
*w++ = *r++;
}
/* check if work needed */
if (counter[62] == 0 && counter[63] == 0)
return;
r = temp;
w = (unsigned char *) buf;
reset = 1;
escapes = 0;
/* check a block for esc chars */
while (*r) {
if (reset == 0 && escapes == 0 && (
r[0] == esc[0] || r[1] == esc[0] ||r[2] == esc[0] ||r[2] == esc[0] ||
r[0] == esc[1] || r[1] == esc[1] ||r[2] == esc[1] ||r[2] == esc[1])) {
/* last set of escape chars were unused.
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* if we reset last escape switch then maybe we dont have to switch now */
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/* change the latest escape switch to 999 (RESET) */
e[1] = MODE;
e[2] = MODE;
/* store default esc chars */
esc[0] = P62;
esc[1] = P63;
reset = 1;
}
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/* these two if blocks can not be combined because a block can contain both
* char 9 and/or . and the current escape chars. */
if (r[0] == esc[0] || r[1] == esc[0] ||r[2] == esc[0] ||r[2] == esc[0] ||
r[0] == esc[1] || r[1] == esc[1] ||r[2] == esc[1] ||r[2] == esc[1]) {
/* switch escape chars */
escapes = 0;
reset = 0;
/* find 2 suitable escape chars */
findesc(counter, esc, REV64(r[0]), REV64(r[1]), REV64(r[2]), REV64(r[3]));
/* store escape switch position */
e = w;
/* write new escape chars */
*w++ = MODE;
*w++ = esc[0];
*w++ = esc[1];
}
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/* update counter on remaining chars */
for (i = 0; i < 4; i++) {
if (r[i])
counter[REV64(r[i])]--;
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}
/* do the escaping */
for (i = 0; i < 4; i++) {
if (r[i] == P62) {
r[i] = esc[0];
escapes++;
} else if (r[i] == P63) {
r[i] = esc[1];
escapes++;
}
}
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/* copy back to buf */
*w++ = *r++;
*w++ = *r++;
*w++ = *r++;
*w++ = *r++;
}
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}
int
base64_encode(char *buf, size_t *buflen, const void *data, size_t size)
{
size_t newsize;
size_t maxsize;
unsigned char c;
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unsigned char *s;
unsigned char *p;
unsigned char *q;
int i;
memset(buf, 0, *buflen);
if (!reverse_init) {
for (i = 0; i < 64; i++) {
c = cb64[i];
rev64[(int) c] = i;
}
reverse_init = 1;
}
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/* how many chars can we encode within the buf */
maxsize = 3 * (*buflen / 4 - 1) - 1;
/* how big will the encoded data be */
newsize = 4 * (size / 3 + 1) + 1;
/* if the buffer is too small, eat some of the data */
if (*buflen < newsize) {
size = maxsize;
}
p = s = (unsigned char *) buf;
q = (unsigned char *)data;
for(i=0;i<size;i+=3) {
p[0] = cb64[((q[0] & 0xfc) >> 2)];
p[1] = cb64[(((q[0] & 0x03) << 4) | ((q[1] & 0xf0) >> 4))];
p[2] = (i+1 < size) ? cb64[((q[1] & 0x0f) << 2 ) | ((q[2] & 0xc0) >> 6)] : '\0';
p[3] = (i+2 < size) ? cb64[(q[2] & 0x3f)] : '\0';
q += 3;
p += 4;
}
*p = 0;
escape_chars(buf, *buflen);
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/* store number of bytes from data that was used */
*buflen = size;
return strlen(buf) - 1;
}
#define DECODE_ERROR 0xffffffff
static int
decode_token(const unsigned char *t, unsigned char *data, size_t len)
{
if (len < 2)
return 0;
data[0] = ((REV64(t[0]) & 0x3f) << 2) |
((REV64(t[1]) & 0x30) >> 4);
if (len < 3)
return 1;
data[1] = ((REV64(t[1]) & 0x0f) << 4) |
((REV64(t[2]) & 0x3c) >> 2);
if (len < 4)
return 2;
data[2] = ((REV64(t[2]) & 0x03) << 6) |
(REV64(t[3]) & 0x3f);
return 3;
}
int
base64_decode(void *buf, size_t *buflen, const char *str, size_t slen)
{
unsigned char *q;
size_t newsize;
size_t maxsize;
const char *p;
unsigned char c;
unsigned char block[4];
unsigned char prot62;
unsigned char prot63;
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int len;
int i;
if (!reverse_init) {
for (i = 0; i < 64; i++) {
c = cb64[i];
rev64[(int) c] = i;
}
reverse_init = 1;
}
/* chars needed to decode slen */
newsize = 3 * (slen / 4 + 1) + 1;
/* encoded chars that fit in buf */
maxsize = 4 * (*buflen / 3 + 1) + 1;
/* if the buffer is too small, eat some of the data */
if (*buflen < newsize) {
slen = maxsize;
}
prot62 = P62;
prot63 = P63;
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q = buf;
for (p = str; *p; p += 4) {
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/* handle escape instructions */
if (*p == MODE) {
p++;
if (p[0] == MODE && p[1] == MODE) {
/* reset escape chars */
prot62 = P62;
prot63 = P63;
p += 2;
} else {
prot62 = *p++;
prot63 = *p++;
}
}
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/* since the str is const, we unescape in another buf */
for (i = 0; i < 4; i++) {
block[i] = p[i];
if (prot62 == block[i]) {
block[i] = P62;
} else if (prot63 == block[i]) {
block[i] = P63;
}
}
len = decode_token(block, (unsigned char *) q, slen);
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q += len;
slen -= 4;
if (len < 3)
break;
}
*q = '\0';
return q - (unsigned char *) buf;
}