Skip to content

Commit

Permalink
config script: add b64_decode function
Browse files Browse the repository at this point in the history
  • Loading branch information
@KGuillemot @frikilax
KGuillemot authored and frikilax committed Oct 15, 2024
1 parent fea3bea commit cb0f5b5
Show file tree
Hide file tree
Showing 2 changed files with 173 additions and 0 deletions.
137 changes: 137 additions & 0 deletions grammar/rainerscript.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -2913,6 +2913,142 @@ doFuncCall(struct cnffunc *__restrict__ const func, struct svar *__restrict__ co
}
}

/* Base64 function to predict decoded length (for allocation) from Apache */
static int
base64_decode_len(const char *str)
{
int len;

len = strlen(str);
while (len && str[len - 1] == '=') {
len--;
}

return len * 3 / 4;
}

/* The following code comes from
* https://en.wikibooks.org/wiki/Algorithm_Implementation/Miscellaneous/Base64#C_2 */
static const unsigned char base64_table[] = {
66,66,66,66,66,66,66,66,66,66,64,66,66,66,66,66,66,66,66,66,66,66,66,66,66,
66,66,66,66,66,66,66,66,66,66,66,66,66,66,66,66,66,66,62,66,66,66,63,52,53,
54,55,56,57,58,59,60,61,66,66,66,65,66,66,66, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9,
10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,66,66,66,66,66,66,26,27,28,
29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,66,66,
66,66,66,66,66,66,66,66,66,66,66,66,66,66,66,66,66,66,66,66,66,66,66,66,66,
66,66,66,66,66,66,66,66,66,66,66,66,66,66,66,66,66,66,66,66,66,66,66,66,66,
66,66,66,66,66,66,66,66,66,66,66,66,66,66,66,66,66,66,66,66,66,66,66,66,66,
66,66,66,66,66,66,66,66,66,66,66,66,66,66,66,66,66,66,66,66,66,66,66,66,66,
66,66,66,66,66,66,66,66,66,66,66,66,66,66,66,66,66,66,66,66,66,66,66,66,66,
66,66,66,66,66,66
};

/* From https://en.wikibooks.org/wiki/Algorithm_Implementation/Miscellaneous/Base64#C_2
* This code is public domain.
* This solution has been optimized using pointer math and a look-up table.
* This algorithm handles multiple encoding formats: with and without line breaks,
* with and without whitespace,
* and with and without padding characters.
* */
static int base64_decode (char *in, size_t inLen, unsigned char *out, size_t *outLen) {
char *end = in + inLen;
char iter = 0;
uint32_t buf = 0;
size_t len = 0;

while (in < end) {
unsigned char c = base64_table[(unsigned char)*in++];

switch (c) {
case 64: continue; /* skip whitespace */
case 66: return 1; /* invalid input, return error */
case 65: /* = char, pad character, end of data */
in = end;
continue;
default:
buf = buf << 6 | c;
iter++; // increment the number of iteration
/* If the buffer is full, split it into bytes */
if (iter == 4) {
if ((len += 3) > *outLen) return 1; /* buffer overflow */
*(out++) = (buf >> 16) & 255;
*(out++) = (buf >> 8) & 255;
*(out++) = buf & 255;
buf = 0; iter = 0;
}
}
}

if (iter == 3) {
if ((len += 2) > *outLen) return 1; /* buffer overflow */
*(out++) = (buf >> 10) & 255;
*(out++) = (buf >> 2) & 255;
}
else if (iter == 2) {
if (++len > *outLen) return 1; /* buffer overflow */
*(out++) = (buf >> 4) & 255;
}

*outLen = len; /* modify to reflect the actual output size */
return 0;
}

static void ATTR_NONNULL()
doFunct_Base64Dec(struct cnffunc *__restrict__ const func,
struct svar *__restrict__ const ret,
void *__restrict__ const usrptr,
wti_t *__restrict__ const pWti)
{
struct svar srcVal;
int bMustFree;
char *cstr = NULL;
unsigned char *res = NULL;
size_t len = 0;
ret->d.estr = NULL;

if(func->expr[0]->nodetype == 'S') {
/* if we already have a string, we do not need to
* do one more recursive call.
*/
cstr = (char*)es_str2cstr(((struct cnfstringval*) func->expr[0])->estr, NULL);
bMustFree = 1;
} else {
// Otherwise, retrieve the value from the specified value name
cnfexprEval(func->expr[0], &srcVal, usrptr, pWti);
cstr = (char*)var2CString(&srcVal, &bMustFree);
varFreeMembers(&srcVal);
}
DBGPRINTF("rainerscript: (base64_dec) String to decode = '%s' \n", cstr);
len = base64_decode_len((const char*)cstr);
if( len == 0 ) {
if( strlen(cstr) != 0 ) {
DBGPRINTF("base64_enc: Failed to determine decoded payload length of '%s' \n", cstr);
}
goto finalize_it;
}
DBGPRINTF("rainerscript: (base64_dec) Predicted decoded data length : '%lu' \n", (long unsigned int)len);
res = malloc(len+1);
if( base64_decode(cstr, strlen(cstr), res, &len) ) {
DBGPRINTF("rainerscript: (base64_dec) Failed to decode base64 data '%s'", cstr);
goto finalize_it;
}
res[len] = '\0';
// Beware, decoded data (for instance \x01\x02) will be ''
DBGPRINTF("rainerscript: (base64_enc) Decoded data = '%.*s' \n", (int)len, res);
ret->d.estr = es_newStrFromCStr((char*)res, len);

finalize_it:
ret->datatype = 'S';
if( ret->d.estr == NULL ) {
ret->d.estr = es_newStr(0);
}
if( res != NULL ) {
free(res);
}
if( bMustFree ) {
free(cstr);
}
}

/* Perform the special "exists()" function to check presence of a variable.
*/
Expand Down Expand Up @@ -3727,6 +3863,7 @@ static struct scriptFunct functions[] = {
{"get_property", 2, 2, doFunc_get_property, NULL, NULL},
{"script_error", 0, 0, doFunct_ScriptError, NULL, NULL},
{"previous_action_suspended", 0, 0, doFunct_PreviousActionSuspended, NULL, NULL},
{"b64_decode", 1, 1, doFunct_Base64Dec, NULL, NULL},
{NULL, 0, 0, NULL, NULL, NULL} //last element to check end of array
};

Expand Down
36 changes: 36 additions & 0 deletions tests/rscript_b64_decode.sh
View file
Original file line number Diff line number Diff line change
@@ -0,0 +1,36 @@
#!/bin/bash
# test for b64_decode function in rainerscript
# added 2024-06-11 by KGuillemot
# This file is part of the rsyslog project, released under ASL 2.0
. ${srcdir:=.}/diag.sh init
generate_conf
add_conf '
module(load="../plugins/imtcp/.libs/imtcp")
input(type="imtcp" port="0" listenPortFileName="'$RSYSLOG_DYNNAME'.tcpflood_port")
set $!str!var1 = b64_decode(""); # Empty string
set $!str!var2 = b64_decode("AAAAA"); # Invalid base64
set $!str!var3 = b64_decode("dGVzdA=="); # "test" base64
set $!str!var4 = b64_decode("dGVzdA"); # "test" base64 - without padding
set $!str!var5 = b64_decode("AQI"); # \x01\x02 base64 (binary)
set $!str!var6 = b64_decode("AQI="); # \x01\x02 base64 (binary) - with padding
set $!str!var7 = b64_decode("dGVzdA==dGVzdA=="); # Early ended payload
set $!str!var8 = b64_decode("YWJjZAplZmdoCg=="); # \n in encoded data
set $!str!var9 = b64_decode("YWJjZA1lZmdoCg=="); # \r in encoded data
template(name="outfmt" type="string" string="%!str%\n")
local4.* action(type="omfile" file=`echo $RSYSLOG_OUT_LOG` template="outfmt")
'
startup
tcpflood -m1 -y
shutdown_when_empty
wait_shutdown
# var1 is not present (empty)
# var2 is empty (invalid base64)
if ! cmp $RSYSLOG_OUT_LOG '{ "var2": "", "var3": "test", "var4": "test", "var5": "\u0001\u0002", "var6": "\u0001\u0002", "var7": "test", "var8": "abcd\nefgh\n", "var9": "abcd\refgh\n" }' ; then
echo "invalid function output detected, $RSYSLOG_OUT_LOG is:"
cat $RSYSLOG_OUT_LOG
error_exit 1
fi;
exit_test

0 comments on commit cb0f5b5

Please sign in to comment.