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d3a64d8365
tcpdump/print-resp.c
Guy Harris d3a64d8365 Do better checking of RESP packets. 
Don't call strtol() on the contents of a packet; there is *no* guarantee
that it won't run past the end of the buffer, as the buffer isn't a
null-terminated string.  Instead, have our own routine to parse ASCII
numbers (based on the FreeBSD strtol()), which uses ND_TCHECK() and
checks against the on-the-wire length to ensure it doesn't go past the
end of the packet or the end of the captured data.  Have it check for
other errors as well, such as checking for negative lengths that aren't
-1.

Clean up other aspects of the packet parsing.  Have them check the
on-the-wire length as well as the captured length.

Update the results of the resp_3 test.
2017-01-18 09:16:41 +01:00

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/*
* Copyright (c) 2015 The TCPDUMP project
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*
* Initial contribution by Andrew Darqui (andrew.darqui@gmail.com).
*/
/* \summary: REdis Serialization Protocol (RESP) printer */
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#include <netdissect-stdinc.h>
#include "netdissect.h"
#include <limits.h>
#include <string.h>
#include <stdlib.h>
#include <errno.h>
#include "extract.h"
static const char tstr[] = " [|RESP]";
/*
* For information regarding RESP, see: http://redis.io/topics/protocol
*/
#define RESP_SIMPLE_STRING '+'
#define RESP_ERROR '-'
#define RESP_INTEGER ':'
#define RESP_BULK_STRING '$'
#define RESP_ARRAY '*'
#define resp_print_empty(ndo) ND_PRINT((ndo, " empty"))
#define resp_print_null(ndo) ND_PRINT((ndo, " null"))
#define resp_print_length_too_large(ndo) ND_PRINT((ndo, " length too large"))
#define resp_print_length_negative(ndo) ND_PRINT((ndo, " length negative and not -1"))
#define resp_print_invalid(ndo) ND_PRINT((ndo, " invalid"))
void resp_print(netdissect_options *, const u_char *, u_int);
static int resp_parse(netdissect_options *, register const u_char *, int);
static int resp_print_string_error_integer(netdissect_options *, register const u_char *, int);
static int resp_print_simple_string(netdissect_options *, register const u_char *, int);
static int resp_print_integer(netdissect_options *, register const u_char *, int);
static int resp_print_error(netdissect_options *, register const u_char *, int);
static int resp_print_bulk_string(netdissect_options *, register const u_char *, int);
static int resp_print_bulk_array(netdissect_options *, register const u_char *, int);
static int resp_print_inline(netdissect_options *, register const u_char *, int);
static int resp_get_length(netdissect_options *, register const u_char *, int, const u_char **);
#define LCHECK2(_tot_len, _len) \
{ \
if (_tot_len < _len) \
goto trunc; \
}
#define LCHECK(_tot_len) LCHECK2(_tot_len, 1)
/*
* FIND_CRLF:
* Attempts to move our 'ptr' forward until a \r\n is found,
* while also making sure we don't exceed the buffer '_len'
* or go past the end of the captured data.
* If we exceed or go past the end of the captured data,
* jump to trunc.
*/
#define FIND_CRLF(_ptr, _len) \
for (;;) { \
LCHECK2(_len, 2); \
ND_TCHECK2(*_ptr, 2); \
if (*_ptr == '\r' && *(_ptr+1) == '\n') \
break; \
_ptr++; \
_len--; \
}
/*
* CONSUME_CRLF
* Consume a CRLF that we've just found.
*/
#define CONSUME_CRLF(_ptr, _len) \
_ptr += 2; \
_len -= 2;
/*
* FIND_CR_OR_LF
* Attempts to move our '_ptr' forward until a \r or \n is found,
* while also making sure we don't exceed the buffer '_len'
* or go past the end of the captured data.
* If we exceed or go past the end of the captured data,
* jump to trunc.
*/
#define FIND_CR_OR_LF(_ptr, _len) \
for (;;) { \
LCHECK(_len); \
ND_TCHECK(*_ptr); \
if (*_ptr == '\r' || *_ptr == '\n') \
break; \
_ptr++; \
_len--; \
}
/*
* CONSUME_CR_OR_LF
* Consume all consecutive \r and \n bytes.
* If we exceed '_len' or go past the end of the captured data,
* jump to trunc.
*/
#define CONSUME_CR_OR_LF(_ptr, _len) \
{ \
int _found_cr_or_lf = 0; \
for (;;) { \
/* \
* Have we hit the end of data? \
*/ \
if (_len == 0 || !ND_TTEST(*_ptr)) { \
/* \
* Yes. Have we seen a \r \
* or \n? \
*/ \
if (_found_cr_or_lf) { \
/* \
* Yes. Just stop. \
*/ \
break; \
} \
/* \
* No. We ran out of packet. \
*/ \
goto trunc; \
} \
if (*_ptr != '\r' && *_ptr != '\n') \
break; \
_found_cr_or_lf = 1; \
_ptr++; \
_len--; \
} \
}
/*
* SKIP_OPCODE
* Skip over the opcode character.
* The opcode has already been fetched, so we know it's there, and don't
* need to do any checks.
*/
#define SKIP_OPCODE(_ptr, _tot_len) \
_ptr++; \
_tot_len--;
/*
* GET_LENGTH
* Get a bulk string or array length.
*/
#define GET_LENGTH(_ndo, _tot_len, _ptr, _len) \
{ \
const u_char *_endp; \
_len = resp_get_length(_ndo, _ptr, _tot_len, &_endp); \
_tot_len -= (_endp - _ptr); \
_ptr = _endp; \
}
/*
* TEST_RET_LEN
* If ret_len is < 0, jump to the trunc tag which returns (-1)
* and 'bubbles up' to printing tstr. Otherwise, return ret_len.
*/
#define TEST_RET_LEN(rl) \
if (rl < 0) { goto trunc; } else { return rl; }
/*
* TEST_RET_LEN_NORETURN
* If ret_len is < 0, jump to the trunc tag which returns (-1)
* and 'bubbles up' to printing tstr. Otherwise, continue onward.
*/
#define TEST_RET_LEN_NORETURN(rl) \
if (rl < 0) { goto trunc; }
/*
* RESP_PRINT_SEGMENT
* Prints a segment in the form of: ' "<stuff>"\n"
* Assumes the data has already been verified as present.
*/
#define RESP_PRINT_SEGMENT(_ndo, _bp, _len) \
ND_PRINT((_ndo, " \"")); \
if (fn_printn(_ndo, _bp, _len, _ndo->ndo_snapend)) \
goto trunc; \
fn_print_char(_ndo, '"');
void
resp_print(netdissect_options *ndo, const u_char *bp, u_int length)
{
int ret_len = 0, length_cur = length;
if(!bp || length <= 0)
return;
ND_PRINT((ndo, ": RESP"));
while (length_cur > 0) {
/*
* This block supports redis pipelining.
* For example, multiple operations can be pipelined within the same string:
* "*2\r\n\$4\r\nINCR\r\n\$1\r\nz\r\n*2\r\n\$4\r\nINCR\r\n\$1\r\nz\r\n*2\r\n\$4\r\nINCR\r\n\$1\r\nz\r\n"
* or
* "PING\r\nPING\r\nPING\r\n"
* In order to handle this case, we must try and parse 'bp' until
* 'length' bytes have been processed or we reach a trunc condition.
*/
ret_len = resp_parse(ndo, bp, length_cur);
TEST_RET_LEN_NORETURN(ret_len);
bp += ret_len;
length_cur -= ret_len;
}
return;
trunc:
ND_PRINT((ndo, "%s", tstr));
}
static int
resp_parse(netdissect_options *ndo, register const u_char *bp, int length)
{
u_char op;
int ret_len;
LCHECK2(length, 1);
ND_TCHECK(*bp);
op = *bp;
/* bp now points to the op, so these routines must skip it */
switch(op) {
case RESP_SIMPLE_STRING: ret_len = resp_print_simple_string(ndo, bp, length); break;
case RESP_INTEGER: ret_len = resp_print_integer(ndo, bp, length); break;
case RESP_ERROR: ret_len = resp_print_error(ndo, bp, length); break;
case RESP_BULK_STRING: ret_len = resp_print_bulk_string(ndo, bp, length); break;
case RESP_ARRAY: ret_len = resp_print_bulk_array(ndo, bp, length); break;
default: ret_len = resp_print_inline(ndo, bp, length); break;
}
/*
* This gives up with a "truncated" indicator for all errors,
* including invalid packet errors; that's what we want, as
* we have to give up on further parsing in that case.
*/
TEST_RET_LEN(ret_len);
trunc:
return (-1);
}
static int
resp_print_simple_string(netdissect_options *ndo, register const u_char *bp, int length) {
return resp_print_string_error_integer(ndo, bp, length);
}
static int
resp_print_integer(netdissect_options *ndo, register const u_char *bp, int length) {
return resp_print_string_error_integer(ndo, bp, length);
}
static int
resp_print_error(netdissect_options *ndo, register const u_char *bp, int length) {
return resp_print_string_error_integer(ndo, bp, length);
}
static int
resp_print_string_error_integer(netdissect_options *ndo, register const u_char *bp, int length) {
int length_cur = length, len, ret_len;
const u_char *bp_ptr;
/* bp points to the op; skip it */
SKIP_OPCODE(bp, length_cur);
bp_ptr = bp;
/*
* bp now prints past the (+-;) opcode, so it's pointing to the first
* character of the string (which could be numeric).
* +OK\r\n
* -ERR ...\r\n
* :02912309\r\n
*
* Find the \r\n with FIND_CRLF().
*/
FIND_CRLF(bp_ptr, length_cur);
/*
* bp_ptr points to the \r\n, so bp_ptr - bp is the length of text
* preceding the \r\n. That includes the opcode, so don't print
* that.
*/
len = (bp_ptr - bp);
RESP_PRINT_SEGMENT(ndo, bp, len);
ret_len = 1 /*<opcode>*/ + len /*<string>*/ + 2 /*<CRLF>*/;
TEST_RET_LEN(ret_len);
trunc:
return (-1);
}
static int
resp_print_bulk_string(netdissect_options *ndo, register const u_char *bp, int length) {
int length_cur = length, string_len;
/* bp points to the op; skip it */
SKIP_OPCODE(bp, length_cur);
/* <length>\r\n */
GET_LENGTH(ndo, length_cur, bp, string_len);
if (string_len >= 0) {
/* Byte string of length string_len, starting at bp */
if (string_len == 0)
resp_print_empty(ndo);
else {
LCHECK2(length_cur, string_len);
ND_TCHECK2(*bp, string_len);
RESP_PRINT_SEGMENT(ndo, bp, string_len);
bp += string_len;
length_cur -= string_len;
}
/*
* Find the \r\n at the end of the string and skip past it.
* XXX - report an error if the \r\n isn't immediately after
* the item?
*/
FIND_CRLF(bp, length_cur);
CONSUME_CRLF(bp, length_cur);
} else {
/* null, truncated, or invalid for some reason */
switch(string_len) {
case (-1): resp_print_null(ndo); break;
case (-2): goto trunc;
case (-3): resp_print_length_too_large(ndo); break;
case (-4): resp_print_length_negative(ndo); break;
default: resp_print_invalid(ndo); break;
}
}
return (length - length_cur);
trunc:
return (-1);
}
static int
resp_print_bulk_array(netdissect_options *ndo, register const u_char *bp, int length) {
u_int length_cur = length;
int array_len, i, ret_len;
/* bp points to the op; skip it */
SKIP_OPCODE(bp, length_cur);
/* <array_length>\r\n */
GET_LENGTH(ndo, length_cur, bp, array_len);
if (array_len > 0) {
/* non empty array */
for (i = 0; i < array_len; i++) {
ret_len = resp_parse(ndo, bp, length_cur);
TEST_RET_LEN_NORETURN(ret_len);
bp += ret_len;
length_cur -= ret_len;
}
} else {
/* empty, null, truncated, or invalid */
switch(array_len) {
case 0: resp_print_empty(ndo); break;
case (-1): resp_print_null(ndo); break;
case (-2): goto trunc;
case (-3): resp_print_length_too_large(ndo); break;
case (-4): resp_print_length_negative(ndo); break;
default: resp_print_invalid(ndo); break;
}
}
return (length - length_cur);
trunc:
return (-1);
}
static int
resp_print_inline(netdissect_options *ndo, register const u_char *bp, int length) {
int length_cur = length;
int len;
const u_char *bp_ptr;
/*
* Inline commands are simply 'strings' followed by \r or \n or both.
* Redis will do its best to split/parse these strings.
* This feature of redis is implemented to support the ability of
* command parsing from telnet/nc sessions etc.
*
* <string><\r||\n||\r\n...>
*/
/*
* Skip forward past any leading \r, \n, or \r\n.
*/
CONSUME_CR_OR_LF(bp, length_cur);
bp_ptr = bp;
/*
* Scan forward looking for \r or \n.
*/
FIND_CR_OR_LF(bp_ptr, length_cur);
/*
* Found it; bp_ptr points to the \r or \n, so bp_ptr - bp is the
* Length of the line text that preceeds it. Print it.
*/
len = (bp_ptr - bp);
RESP_PRINT_SEGMENT(ndo, bp, len);
/*
* Skip forward past the \r, \n, or \r\n.
*/
CONSUME_CR_OR_LF(bp_ptr, length_cur);
/*
* Return the number of bytes we processed.
*/
return (length - length_cur);
trunc:
return (-1);
}
static int
resp_get_length(netdissect_options *ndo, register const u_char *bp, int len, const u_char **endp)
{
int result;
u_char c;
int saw_digit;
int neg;
int too_large;
if (len == 0)
goto trunc;
ND_TCHECK(*bp);
too_large = 0;
neg = 0;
if (*bp == '-') {
neg = 1;
bp++;
len--;
}
result = 0;
saw_digit = 0;
for (;;) {
if (len == 0)
goto trunc;
ND_TCHECK(*bp);
c = *bp;
if (!(c >= '0' && c <= '9')) {
if (!saw_digit)
goto invalid;
break;
}
c -= '0';
if (result > (INT_MAX / 10)) {
/* This will overflow an int when we multiply it by 10. */
too_large = 1;
} else {
result *= 10;
if (result == INT_MAX && c > (INT_MAX % 10)) {
/* This will overflow an int when we add c */
too_large = 1;
} else
result += c;
}
bp++;
len--;
saw_digit = 1;
}
if (!saw_digit)
goto invalid;
/*
* OK, the next thing should be \r\n.
*/
if (len == 0)
goto trunc;
ND_TCHECK(*bp);
if (*bp != '\r')
goto invalid;
bp++;
len--;
if (len == 0)
goto trunc;
ND_TCHECK(*bp);
if (*bp != '\n')
goto invalid;
bp++;
len--;
*endp = bp;
if (neg) {
/* -1 means "null", anything else is invalid */
if (too_large || result != 1)
return (-4);
result = -1;
}
return (too_large ? -3 : result);
trunc:
return (-2);
invalid:
return (-5);
}
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