288 строки
6.9 KiB
C
288 строки
6.9 KiB
C
/*
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* base64.c - support for base64 alphabet system, described in RFC1521
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*
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* This file is part of the SSH Library
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*
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* Copyright (c) 2005-2005 by Aris Adamantiadis
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*
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* The SSH Library is free software; you can redistribute it and/or modify
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* it under the terms of the GNU Lesser General Public License as published by
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* the Free Software Foundation; either version 2.1 of the License, or (at your
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* option) any later version.
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*
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* The SSH Library is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
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* or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
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* License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public License
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* along with the SSH Library; see the file COPYING. If not, write to
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* the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
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* MA 02111-1307, USA.
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*/
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/* just the dirtiest part of code i ever made */
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#include <string.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include "libssh/priv.h"
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#include "libssh/buffer.h"
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static char alphabet[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
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"abcdefghijklmnopqrstuvwxyz"
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"0123456789+/";
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/* Transformations */
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#define SET_A(n, i) do { (n) |= ((i) & 63) <<18; } while (0)
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#define SET_B(n, i) do { (n) |= ((i) & 63) <<12; } while (0)
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#define SET_C(n, i) do { (n) |= ((i) & 63) << 6; } while (0)
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#define SET_D(n, i) do { (n) |= ((i) & 63); } while (0)
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#define GET_A(n) (((n) & 0xff0000) >> 16)
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#define GET_B(n) (((n) & 0xff00) >> 8)
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#define GET_C(n) ((n) & 0xff)
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static int _base64_to_bin(unsigned char dest[3], const char *source, int num);
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static int get_equals(char *string);
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/* First part: base64 to binary */
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/**
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* @internal
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*
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* @brief Translates a base64 string into a binary one.
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*
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* @returns A buffer containing the decoded string, NULL if something went
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* wrong (e.g. incorrect char).
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*/
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ssh_buffer base64_to_bin(const char *source) {
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ssh_buffer buffer = NULL;
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unsigned char block[3];
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char *base64;
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char *ptr;
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size_t len;
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int equals;
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base64 = strdup(source);
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if (base64 == NULL) {
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return NULL;
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}
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ptr = base64;
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/* Get the number of equals signs, which mirrors the padding */
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equals = get_equals(ptr);
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if (equals > 2) {
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SAFE_FREE(base64);
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return NULL;
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}
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buffer = ssh_buffer_new();
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if (buffer == NULL) {
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SAFE_FREE(base64);
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return NULL;
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}
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len = strlen(ptr);
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while (len > 4) {
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if (_base64_to_bin(block, ptr, 3) < 0) {
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goto error;
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}
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if (buffer_add_data(buffer, block, 3) < 0) {
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goto error;
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}
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len -= 4;
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ptr += 4;
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}
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/*
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* Depending on the number of bytes resting, there are 3 possibilities
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* from the RFC.
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*/
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switch (len) {
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/*
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* (1) The final quantum of encoding input is an integral multiple of
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* 24 bits. Here, the final unit of encoded output will be an integral
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* multiple of 4 characters with no "=" padding
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*/
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case 4:
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if (equals != 0) {
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goto error;
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}
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if (_base64_to_bin(block, ptr, 3) < 0) {
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goto error;
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}
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if (buffer_add_data(buffer, block, 3) < 0) {
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goto error;
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}
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SAFE_FREE(base64);
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return buffer;
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/*
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* (2) The final quantum of encoding input is exactly 8 bits; here, the
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* final unit of encoded output will be two characters followed by
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* two "=" padding characters.
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*/
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case 2:
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if (equals != 2){
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goto error;
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}
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if (_base64_to_bin(block, ptr, 1) < 0) {
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goto error;
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}
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if (buffer_add_data(buffer, block, 1) < 0) {
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goto error;
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}
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SAFE_FREE(base64);
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return buffer;
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/*
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* The final quantum of encoding input is exactly 16 bits. Here, the final
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* unit of encoded output will be three characters followed by one "="
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* padding character.
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*/
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case 3:
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if (equals != 1) {
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goto error;
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}
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if (_base64_to_bin(block, ptr, 2) < 0) {
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goto error;
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}
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if (buffer_add_data(buffer,block,2) < 0) {
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goto error;
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}
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SAFE_FREE(base64);
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return buffer;
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default:
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/* 4,3,2 are the only padding size allowed */
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goto error;
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}
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error:
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SAFE_FREE(base64);
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ssh_buffer_free(buffer);
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return NULL;
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}
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#define BLOCK(letter, n) do {ptr = strchr(alphabet, source[n]); \
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if(!ptr) return -1; \
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i = ptr - alphabet; \
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SET_##letter(*block, i); \
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} while(0)
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/* Returns 0 if ok, -1 if not (ie invalid char into the stuff) */
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static int to_block4(unsigned long *block, const char *source, int num) {
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char *ptr;
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unsigned int i;
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*block = 0;
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if (num < 1) {
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return 0;
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}
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BLOCK(A, 0); /* 6 bit */
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BLOCK(B,1); /* 12 bit */
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if (num < 2) {
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return 0;
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}
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BLOCK(C, 2); /* 18 bit */
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if (num < 3) {
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return 0;
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}
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BLOCK(D, 3); /* 24 bit */
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return 0;
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}
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/* num = numbers of final bytes to be decoded */
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static int _base64_to_bin(unsigned char dest[3], const char *source, int num) {
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unsigned long block;
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if (to_block4(&block, source, num) < 0) {
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return -1;
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}
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dest[0] = GET_A(block);
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dest[1] = GET_B(block);
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dest[2] = GET_C(block);
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return 0;
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}
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/* Count the number of "=" signs and replace them by zeroes */
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static int get_equals(char *string) {
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char *ptr = string;
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int num = 0;
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while ((ptr=strchr(ptr,'=')) != NULL) {
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num++;
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*ptr = '\0';
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ptr++;
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}
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return num;
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}
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/* thanks sysk for debugging my mess :) */
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#define BITS(n) ((1 << (n)) - 1)
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static void _bin_to_base64(unsigned char *dest, const unsigned char source[3],
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int len) {
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switch (len) {
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case 1:
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dest[0] = alphabet[(source[0] >> 2)];
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dest[1] = alphabet[((source[0] & BITS(2)) << 4)];
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dest[2] = '=';
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dest[3] = '=';
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break;
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case 2:
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dest[0] = alphabet[source[0] >> 2];
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dest[1] = alphabet[(source[1] >> 4) | ((source[0] & BITS(2)) << 4)];
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dest[2] = alphabet[(source[1] & BITS(4)) << 2];
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dest[3] = '=';
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break;
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case 3:
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dest[0] = alphabet[(source[0] >> 2)];
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dest[1] = alphabet[(source[1] >> 4) | ((source[0] & BITS(2)) << 4)];
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dest[2] = alphabet[ (source[2] >> 6) | (source[1] & BITS(4)) << 2];
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dest[3] = alphabet[source[2] & BITS(6)];
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break;
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}
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}
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/**
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* @internal
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*
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* @brief Converts binary data to a base64 string.
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*
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* @returns the converted string
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*/
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unsigned char *bin_to_base64(const unsigned char *source, int len) {
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unsigned char *base64;
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unsigned char *ptr;
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int flen = len + (3 - (len % 3)); /* round to upper 3 multiple */
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flen = (4 * flen) / 3 + 1;
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base64 = malloc(flen);
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if (base64 == NULL) {
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return NULL;
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}
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ptr = base64;
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while(len > 0){
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_bin_to_base64(ptr, source, len > 3 ? 3 : len);
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ptr += 4;
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source += 3;
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len -= 3;
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}
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ptr[0] = '\0';
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return base64;
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}
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/* vim: set ts=2 sw=2 et cindent: */
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