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Don't treat the packet length as unsigned. 

The scanf family of functions are as annoyingly bad at handling unsigned
numbers as strtoul() is - both of them are perfectly willing to accept a
value beginning with a negative sign as an unsigned value.  When using
strtoul(), you can compensate for this by explicitly checking for a '-'
as the first character of the string, but you can't do that with
sscanf().

So revert to having pkt_len be signed, and scanning it with %d, but
check for a negative value and fail if we see a negative value.

Change-Id: I6450d468504e942df72342176a0e145e5ac3db5f
Reviewed-on: https://code.wireshark.org/review/15216
Reviewed-by: Guy Harris <guy@alum.mit.edu>
This commit is contained in:
Guy Harris 2016-05-01 16:02:40 -07:00
parent 2cb5985bf4
commit 29c78db2a8
1 changed files with 9 additions and 4 deletions
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13
wiretap/dbs-etherwatch.c
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@ -273,14 +273,13 @@ parse_dbs_etherwatch_packet(struct wtap_pkthdr *phdr, FILE_T fh, Buffer* buf,
guint8 *pd;
char line[DBS_ETHERWATCH_LINE_LENGTH];
int num_items_scanned;
int eth_hdr_len, csec;
guint pkt_len;
int eth_hdr_len, pkt_len, csec;
int length_pos, length_from, length;
struct tm tm;
char mon[4] = "xxx";
gchar *p;
static const gchar months[] = "JANFEBMARAPRMAYJUNJULAUGSEPOCTNOVDEC";
guint count, line_count;
int count, line_count;
/* Make sure we have enough room for a regular Ethernet packet */
ws_buffer_assure_space(buf, DBS_ETHERWATCH_MAX_ETHERNET_PACKET_LEN);
@ -351,7 +350,7 @@ parse_dbs_etherwatch_packet(struct wtap_pkthdr *phdr, FILE_T fh, Buffer* buf,
}
num_items_scanned = sscanf(line + LENGTH_POS,
"%9u byte buffer at %2d-%3s-%4d %2d:%2d:%2d.%9d",
"%9d byte buffer at %2d-%3s-%4d %2d:%2d:%2d.%9d",
&pkt_len,
&tm.tm_mday, mon,
&tm.tm_year, &tm.tm_hour, &tm.tm_min,
@ -363,6 +362,12 @@ parse_dbs_etherwatch_packet(struct wtap_pkthdr *phdr, FILE_T fh, Buffer* buf,
return FALSE;
}
if (pkt_len < 0) {
*err = WTAP_ERR_BAD_FILE;
*err_info = g_strdup("dbs_etherwatch: packet header has a negative packet length");
return FALSE;
}
/* Determine whether it is Ethernet II or IEEE 802 */
if(strncmp(&line[ETH_II_CHECK_POS], ETH_II_CHECK_STR,
strlen(ETH_II_CHECK_STR)) == 0) {