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asc2log: do not read beyond the end of line when parsing hex data

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The data parsing loops in the CANFD/CANXL evaluation functions jumped
three characters forward after each hex byte without checking the
separator. When a line ended directly after a hex byte (e.g. last line
without newline or a line split by fgets()) the pointer skipped the
string termination and continued parsing stale content from previous
lines - or in the worst case read beyond the input buffer.

Factor out the four identical loops into get_hex_data() which requires
a whitespace separator behind each hex byte.

Assisted-by: Claude:claude-opus-5-5
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
This commit is contained in:
Oliver Hartkopp
2026-10-14 11:15:54 +02:00
parent cbbad5eede
commit fa647cc3e2
1 changed files with 51 additions and 68 deletions
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asc2log.c
+51 -68
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@@ -42,6 +42,7 @@
*
*/
#include <ctype.h>
#include <libgen.h>
#include <locale.h>
#include <stdio.h>
@@ -114,6 +115,42 @@ static void get_can_id(canid_t *can_id, char *idstring, int base)
*can_id |= strtoul(idstring, NULL, base);
}
/*
* Read 'len' ASCII hex bytes separated by single whitespace characters.
* Returns a pointer to the content behind the data or NULL on error.
*/
static char *get_hex_data(char *ptr, unsigned char *data, int len)
{
unsigned char ctmp;
int i;
for (i = 0; i < len; i++) {
ctmp = asc2nibble(ptr[0]);
if (ctmp > 0x0F)
return NULL;
data[i] = (ctmp << 4);
ctmp = asc2nibble(ptr[1]);
if (ctmp > 0x0F)
return NULL;
data[i] |= ctmp;
/*
* The hex byte has to be followed by a separator (space/tab)
* or an EOL char ('\n', '\r'). This also ensures that we do
* not skip the string termination with ptr += 3 below.
*/
if (!isspace((unsigned char)ptr[2]))
return NULL;
ptr += 3; /* start of next ASCII hex byte */
}
return ptr;
}
static void calc_tv(struct timeval *tv, struct timeval *read_tv,
struct timeval *date_tv, char timestamps, int dplace)
{
@@ -261,13 +298,12 @@ static void eval_canfd(char* buf, struct timeval *date_tvp, char timestamps,
static struct timeval tv; /* current frame timestamp */
static struct timeval read_tv; /* frame timestamp from ASC file */
struct canfd_frame cf = { 0 };
unsigned char brs, esi, ctmp;
unsigned char brs, esi;
unsigned int flags;
int dlc, dlen = 0;
char idstr[21];
char dir[5]; /* 'Rx'/'Tx'/'TxRq' plus terminating zero */
char *ptr;
int i;
int n = 0; /* sscanf consumed characters */
unsigned long long sec, usec;
@@ -328,21 +364,9 @@ static void eval_canfd(char* buf, struct timeval *date_tvp, char timestamps,
cf.len = dlen;
for (i = 0; i < dlen; i++) {
ctmp = asc2nibble(ptr[0]);
if (ctmp > 0x0F)
return;
cf.data[i] = (ctmp << 4);
ctmp = asc2nibble(ptr[1]);
if (ctmp > 0x0F)
return;
cf.data[i] |= ctmp;
ptr += 3; /* start of next ASCII hex byte */
}
ptr = get_hex_data(ptr, cf.data, dlen);
if (!ptr)
return;
/* skip MessageDuration and MessageLength to get Flags value */
if (sscanf(ptr, " %*x %*x %x ", &flags) != 1)
@@ -387,13 +411,11 @@ static void eval_canxl_cc(char* buf, struct timeval *date_tvp, char timestamps,
static struct timeval tv; /* current frame timestamp */
static struct timeval read_tv; /* frame timestamp from ASC file */
struct can_frame cf = { 0 };
unsigned char ctmp;
unsigned int flags;
int dlc, dlen = 0;
char idstr[21];
char dir[5]; /* 'Rx'/'Tx'/'TxRq' plus terminating zero */
char *ptr;
int i;
int n = 0; /* sscanf consumed characters */
unsigned long long sec, usec;
@@ -452,21 +474,9 @@ static void eval_canxl_cc(char* buf, struct timeval *date_tvp, char timestamps,
cf.len = dlen;
for (i = 0; i < dlen; i++) {
ctmp = asc2nibble(ptr[0]);
if (ctmp > 0x0F)
return;
cf.data[i] = (ctmp << 4);
ctmp = asc2nibble(ptr[1]);
if (ctmp > 0x0F)
return;
cf.data[i] |= ctmp;
ptr += 3; /* start of next ASCII hex byte */
}
ptr = get_hex_data(ptr, cf.data, dlen);
if (!ptr)
return;
/* skip FCRC to get Flags value */
if (sscanf(ptr, "%*x %x ", &flags) != 1)
@@ -498,13 +508,11 @@ static void eval_canxl_fd(char* buf, struct timeval *date_tvp, char timestamps,
static struct timeval tv; /* current frame timestamp */
static struct timeval read_tv; /* frame timestamp from ASC file */
struct canfd_frame cf = { 0 };
unsigned char ctmp;
unsigned int flags;
int dlc, dlen = 0;
char idstr[21];
char dir[5]; /* 'Rx'/'Tx'/'TxRq' plus terminating zero */
char *ptr;
int i;
int n = 0; /* sscanf consumed characters */
unsigned long long sec, usec;
@@ -563,21 +571,9 @@ static void eval_canxl_fd(char* buf, struct timeval *date_tvp, char timestamps,
cf.len = dlen;
for (i = 0; i < dlen; i++) {
ctmp = asc2nibble(ptr[0]);
if (ctmp > 0x0F)
return;
cf.data[i] = (ctmp << 4);
ctmp = asc2nibble(ptr[1]);
if (ctmp > 0x0F)
return;
cf.data[i] |= ctmp;
ptr += 3; /* start of next ASCII hex byte */
}
ptr = get_hex_data(ptr, cf.data, dlen);
if (!ptr)
return;
/* skip stuff field and FCRC to get Flags value */
if (sscanf(ptr, "%*s %*s %x ", &flags) != 1)
@@ -605,13 +601,12 @@ static void eval_canxl_xl(char* buf, struct timeval *date_tvp, char timestamps,
static struct timeval tv; /* current frame timestamp */
static struct timeval read_tv; /* frame timestamp from ASC file */
struct canxl_frame cf = { 0 };
unsigned char sdt, vcid, secbit, ctmp;
unsigned char sdt, vcid, secbit;
unsigned int af, flags;
int dlc, dlen = 0;
char idstr[21];
char dir[5]; /* 'Rx'/'Tx'/'TxRq' plus terminating zero */
char *ptr;
int i;
int n = 0; /* sscanf consumed characters */
unsigned long long sec, usec;
@@ -689,21 +684,9 @@ static void eval_canxl_xl(char* buf, struct timeval *date_tvp, char timestamps,
cf.len = dlen;
for (i = 0; i < dlen; i++) {
ctmp = asc2nibble(ptr[0]);
if (ctmp > 0x0F)
return;
cf.data[i] = (ctmp << 4);
ctmp = asc2nibble(ptr[1]);
if (ctmp > 0x0F)
return;
cf.data[i] |= ctmp;
ptr += 3; /* start of next ASCII hex byte */
}
ptr = get_hex_data(ptr, cf.data, dlen);
if (!ptr)
return;
/* skip FCRC to get Flags value */
if (sscanf(ptr, "%*x %x ", &flags) != 1)