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/* Copyright (C) 2007-2012 Open Information Security Foundation
*
* You can copy, redistribute or modify this Program under the terms of
* the GNU General Public License version 2 as published by the Free
* Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* version 2 along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
* 02110-1301, USA.
*/
/**
* \file
*
* \author David Abarbanel <david.abarbanel@baesystems.com>
*
*/
#include "util-base64.h"
/* Constants */
#define BASE64_TABLE_MAX 122
/* Base64 character to index conversion table */
/* Characters are mapped as "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/" */
static const int b64table[] = { -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, 62, -1, -1, -1, 63, 52, 53,
54, 55, 56, 57, 58, 59, 60, 61, -1, -1,
-1, -1, -1, -1, -1, 0, 1, 2, 3, 4,
5, 6, 7, 8, 9, 10, 11, 12, 13, 14,
15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
25, -1, -1, -1, -1, -1, -1, 26, 27, 28,
29, 30, 31, 32, 33, 34, 35, 36, 37, 38,
39, 40, 41, 42, 43, 44, 45, 46, 47, 48,
49, 50, 51 };
/**
* \brief Gets a base64-decoded value from an encoded character
*
* \param c The encoded character
*
* \return The decoded value (0 or above), or -1 if the parameter is invalid
*/
static inline int GetBase64Value(uint8_t c) {
int val = -1;
/* Pull from conversion table */
if (c <= BASE64_TABLE_MAX) {
val = b64table[(int) c];
}
return val;
}
/**
* \brief Decodes a 4-byte base64-encoded block into a 3-byte ascii-encoded block
*
* \param ascii the 3-byte ascii output block
* \param b64 the 4-byte base64 input block
*
* \return none
*/
static inline void DecodeBase64Block(uint8_t ascii[ASCII_BLOCK], uint8_t b64[B64_BLOCK]) {
ascii[0] = (uint8_t) (b64[0] << 2) | (b64[1] >> 4);
ascii[1] = (uint8_t) (b64[1] << 4) | (b64[2] >> 2);
ascii[2] = (uint8_t) (b64[2] << 6) | (b64[3]);
}
/**
* \brief Decodes a base64-encoded string buffer into an ascii-encoded byte buffer
*
* \param dest The destination byte buffer
* \param src The source string
* \param len The length of the source string
*
* \return Number of bytes decoded, or 0 if no data is decoded or it fails
*/
uint32_t DecodeBase64(uint8_t *dest, const uint8_t *src, uint32_t len) {
int val;
uint32_t padding = 0, numDecoded = 0, bbidx = 0, valid = 1, i;
uint8_t *dptr = dest;
uint8_t b64[B64_BLOCK] = { 0,0,0,0 };
/* Traverse through each alpha-numeric letter in the source array */
for(i = 0; i < len && src[i] != 0; i++) {
/* Get decimal representation */
val = GetBase64Value(src[i]);
if (val < 0) {
/* Invalid character found, so decoding fails */
if (src[i] != '=') {
valid = 0;
numDecoded = 0;
break;
}
padding++;
}
/* For each alpha-numeric letter in the source array, find the numeric
* value */
b64[bbidx++] = (val > 0 ? val : 0);
/* Decode every 4 base64 bytes into 3 ascii bytes */
if (bbidx == B64_BLOCK) {
/* For every 4 bytes, add 3 bytes but deduct the '=' padded blocks */
numDecoded += ASCII_BLOCK - (padding < B64_BLOCK ?
padding : ASCII_BLOCK);
/* Decode base-64 block into ascii block and move pointer */
DecodeBase64Block(dptr, b64);
dptr += ASCII_BLOCK;
/* Reset base-64 block and index */
bbidx = 0;
padding = 0;
}
}
/* Finish remaining b64 bytes by padding */
if (valid && bbidx > 0) {
/* Decode remaining */
numDecoded += ASCII_BLOCK - (B64_BLOCK - bbidx);
DecodeBase64Block(dptr, b64);
}
if (numDecoded == 0) {
SCLogDebug("base64 decoding failed");
}
return numDecoded;
}
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