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conf: Safer parsing of MAC addresses

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In conf() we parse a MAC address in two places, for the --ns-mac-addr and
the -M options.  As well as duplicating code, the logic for this parsing
has several bugs:
  * The most serious is that if the given string is shorter than a MAC
    address should be, we'll access past the end of it.
  * We don't check the endptr supplied by strtol() which means we could
    ignore certain erroneous contents
  * We never check the separator characters between each octet
  * We ignore certain sorts of garbage that follow the MAC address

Correct all these bugs in a new parse_mac() helper.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
This commit is contained in:
David Gibson 2024-06-06 20:09:47 +10:00 committed by Stefano Brivio
parent bda80ef53f
commit c919bbbdd3
1 changed files with 36 additions and 17 deletions
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53
conf.c
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@ -1124,6 +1124,39 @@ static void conf_open_files(struct ctx *c)
c->pidfile_fd = pidfile_open(c->pidfile);
}
/**
* parse_mac - Parse a MAC address from a string
* @mac: Binary MAC address, initialised on success
* @str: String to parse
*
* Parses @str as an Ethernet MAC address stored in @mac on success. Exits on
* failure.
*/
static void parse_mac(unsigned char mac[ETH_ALEN], const char *str)
{
size_t i;
if (strlen(str) != (ETH_ALEN * 3 - 1))
goto fail;
for (i = 0; i < ETH_ALEN; i++) {
const char *octet = str + 3 * i;
unsigned long b;
char *end;
errno = 0;
b = strtoul(octet, &end, 16);
if (b > UCHAR_MAX || errno || end != octet + 2 ||
*end != ((i == ETH_ALEN - 1) ? '\0' : ':'))
goto fail;
mac[i] = b;
}
return;
fail:
die("Invalid MAC address: %s", str);
}
/**
* conf() - Process command-line arguments and set configuration
* @c: Execution context
@ -1200,9 +1233,9 @@ void conf(struct ctx *c, int argc, char **argv)
unsigned int ifi4 = 0, ifi6 = 0;
const char *logfile = NULL;
const char *optstring;
int name, ret, b, i;
size_t logsize = 0;
char *runas = NULL;
int name, ret;
uid_t uid;
gid_t gid;
@ -1243,14 +1276,7 @@ void conf(struct ctx *c, int argc, char **argv)
if (c->mode != MODE_PASTA)
die("--ns-mac-addr is for pasta mode only");
for (i = 0; i < ETH_ALEN; i++) {
errno = 0;
b = strtol(optarg + (intptr_t)i * 3, NULL, 16);
if (b < 0 || b > UCHAR_MAX || errno)
die("Invalid MAC address: %s", optarg);
c->mac_guest[i] = b;
}
parse_mac(c->mac_guest, optarg);
break;
case 5:
if (c->mode != MODE_PASTA)
@ -1510,14 +1536,7 @@ void conf(struct ctx *c, int argc, char **argv)
break;
case 'M':
for (i = 0; i < ETH_ALEN; i++) {
errno = 0;
b = strtol(optarg + (intptr_t)i * 3, NULL, 16);
if (b < 0 || b > UCHAR_MAX || errno)
die("Invalid MAC address: %s", optarg);
c->mac[i] = b;
}
parse_mac(c->mac, optarg);
break;
case 'g':
if (c->mode == MODE_PASTA)