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Make base64 decoding table-driven.

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This commit is contained in:
Todd C. Miller
2016-06-01 12:43:02 -06:00
parent fc517ba9f8
commit 7a35bab8c8
1 changed files with 45 additions and 30 deletions
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75
plugins/sudoers/base64.c
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@@ -1,5 +1,5 @@
/* /*
* Copyright (c) 2013-2015 Todd C. Miller <Todd.Miller@courtesan.com> * Copyright (c) 2013-2016 Todd C. Miller <Todd.Miller@courtesan.com>
* *
* Permission to use, copy, modify, and distribute this software for any * Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above * purpose with or without fee is hereby granted, provided that the above
@@ -30,44 +30,59 @@
#include "sudoers.h" #include "sudoers.h"
/*
* Derived from code with the following declaration:
* PUBLIC DOMAIN - Jon Mayo - November 13, 2003
*/
static const unsigned char base64dec_tab[256]= {
255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,
255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,
255,255,255,255,255,255,255,255,255,255,255, 62,255,255,255, 63,
52, 53, 54, 55, 56, 57, 58, 59, 60, 61,255,255,255, 0,255,255,
255, 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, 25,255,255,255,255,255,
255, 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, 51,255,255,255,255,255,
255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,
255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,
255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,
255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,
255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,
255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,
255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,
255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,
};
/* /*
* Decode a NUL-terminated string in base64 format and store the * Decode a NUL-terminated string in base64 format and store the
* result in dst. * result in dst.
*/ */
size_t size_t
base64_decode(const char *str, unsigned char *dst, size_t dsize) base64_decode(const char *in, unsigned char *out, size_t out_size)
{ {
static const char b64[] = unsigned char *out_end = out + out_size;
"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"; const unsigned char *out0 = out;
const unsigned char *dst0 = dst; unsigned int rem, v;
const unsigned char *dend = dst + dsize;
unsigned char ch[4];
char *pos;
int i;
debug_decl(base64_decode, SUDOERS_DEBUG_MATCH) debug_decl(base64_decode, SUDOERS_DEBUG_MATCH)
/* for (v = 0, rem = 0; *in != '\0' && *in != '='; in++) {
* Convert from base64 to binary. Each base64 char holds 6 bits of data unsigned char ch = base64dec_tab[(unsigned char)*in];
* so 4 base64 chars equals 3 chars of data. if (ch == 255)
* Padding (with the '=' char) may or may not be present.
*/
while (*str != '\0') {
for (i = 0; i < 4; i++) {
if (*str == '=' || *str == '\0')
break;
if ((pos = strchr(b64, *str++)) == NULL)
debug_return_size_t((size_t)-1); debug_return_size_t((size_t)-1);
ch[i] = (unsigned char)(pos - b64); v = (v << 6) | ch;
rem += 6;
if (rem >= 8) {
rem -= 8;
if (out >= out_end)
debug_return_size_t((size_t)-1);
*out++ = (v >> rem) & 0xff;
} }
if (i == 0 || i == 1 || dst == dend)
break;
*dst++ = (ch[0] << 2) | ((ch[1] & 0x30) >> 4);
if (i == 2 || dst == dend)
break;
*dst++ = ((ch[1] & 0x0f) << 4) | ((ch[2] & 0x3c) >> 2);
if (i == 3 || dst == dend)
break;
*dst++ = ((ch[2] & 0x03) << 6) | ch[3];
} }
debug_return_size_t((size_t)(dst - dst0)); if (rem >= 8) {
if (out >= out_end)
debug_return_size_t((size_t)-1);
*out++ = (v >> rem) & 0xff;
}
debug_return_size_t((size_t)(out - out0));
} }