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make base64_decode relaxed mode less relaxed

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This commit is contained in:
Karel Miko 2018-03-25 15:46:49 +02:00
parent e299431be8
commit e7117ea9df
3 changed files with 31 additions and 20 deletions
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2
doc/crypt.tex
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@ -6550,6 +6550,8 @@ int base64_decode(const unsigned char *in,
\end{verbatim}
The function \textit{base64\_decode} works in a relaxed way which allows decoding some inputs that do not strictly follow the standard.
The relaxed mode ignores white-spaces (\textit{CR}, \textit{LF}, \textit{TAB}, \textit{space}), does not care about trailing \textit{=}
and also ignores the last input byte in case it is \textit{NUL}.
If you want to be strict during decoding you can use:
\index{base64\_strict\_decode()}
\begin{verbatim}

31
src/misc/base64/base64_decode.c
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@ -17,11 +17,16 @@
#if defined(LTC_BASE64) || defined (LTC_BASE64_URL)
/* 253 - ignored in "relaxed" mode: TAB(9), CR(13), LF(10), space(32)
* 254 - padding character '=' (allowed only at the end)
* 255 - invalid character (not allowed even in relaxed mode)
*/
#if defined(LTC_BASE64)
static const unsigned char map_base64[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, 255, 255, 253, 253, 255,
255, 253, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
255, 255, 255, 255, 255, 255, 255, 255, 253, 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, 254, 255, 255, 255, 0, 1, 2, 3, 4, 5, 6,
@ -45,9 +50,9 @@ static const unsigned char map_base64[256] = {
static const unsigned char map_base64url[] = {
#if defined(LTC_BASE64_URL)
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, 253, 253, 255,
255, 253, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
255, 255, 255, 255, 255, 255, 255, 255, 253, 255, 255, 255,
255, 255, 255, 255, 255, 255, 255, 255, 255, 62, 255, 255,
52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 255, 255,
255, 254, 255, 255, 255, 0, 1, 2, 3, 4, 5, 6,
@ -89,21 +94,25 @@ static int _base64_decode_internal(const unsigned char *in, unsigned long inlen
g = 0; /* '=' counter */
for (x = y = z = t = 0; x < inlen; x++) {
if (in[x] == 0 && x == (inlen - 1)) continue; /* allow the last byte to be NUL */
c = map[in[x]&0xFF];
if (c == 254) {
g++;
continue;
}
else if (is_strict && g > 0) {
/* we only allow '=' to be at the end */
return CRYPT_INVALID_PACKET;
}
if (c == 255) {
if (c == 253) {
if (is_strict)
return CRYPT_INVALID_PACKET;
else
continue;
}
if (c == 255) {
return CRYPT_INVALID_PACKET;
}
if (g > 0) {
/* we only allow '=' to be at the end */
return CRYPT_INVALID_PACKET;
}
t = (t<<6)|c;

18
tests/base64_test.c
View File

@ -50,14 +50,14 @@ int base64_test(void)
} url_cases[] = {
{"vuiSPKIl8PiR5O-rC4z9_xTQKZ0", 0},
{"vuiSPKIl8PiR5O-rC4z9_xTQKZ0=", 1},
{"vuiS*PKIl8P*iR5O-rC4*z9_xTQKZ0", 0},
{"vuiS*PKIl8P*iR5O-rC4*z9_xTQKZ0=", 0},
{"vuiS*PKIl8P*iR5O-rC4*z9_xTQKZ0==", 0},
{"vuiS*PKIl8P*iR5O-rC4*z9_xTQKZ0===", 0},
{"vuiS*PKIl8P*iR5O-rC4*z9_xTQKZ0====", 0},
{"vuiS*=PKIl8P*iR5O-rC4*z9_xTQKZ0=", 0},
{"vuiS*==PKIl8P*iR5O-rC4*z9_xTQKZ0=", 0},
{"vuiS*===PKIl8P*iR5O-rC4*z9_xTQKZ0=", 0},
{"vuiS PKIl8P\niR5O-rC4\tz9_xTQKZ0", 0},
{"vuiS PKIl8P\niR5O-rC4\tz9_xTQKZ0=", 0},
{"vuiS PKIl8P\niR5O-rC4\tz9_xTQKZ0==", 0},
{"vuiS PKIl8P\niR5O-rC4\tz9_xTQKZ0===", 0},
{"vuiS PKIl8P\niR5O-rC4\tz9_xTQKZ0====", 0},
{"vuiS\rPKIl8P\niR5O-rC4\tz9_xTQKZ0=", 0},
{"vuiS\rPKIl8P\niR5O-rC4\tz9_xTQKZ0= = = ", 0},
{"\nvuiS\rPKIl8P\niR5O-rC4\tz9_xTQKZ0=\n", 0},
};
for (x = 0; x < sizeof(url_cases)/sizeof(url_cases[0]); ++x) {
@ -105,7 +105,7 @@ int base64_test(void)
x--;
memmove(&out[11], &out[10], l1 - 10);
out[10] = '=';
out[10] = ' ';
l1++;
l2 = sizeof(tmp);
DO(base64_decode(out, l1, tmp, &l2));