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loader: verify the value from dhcp.interface-mtu and use snprintf to set mtu

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Since the uset can set dhcp.interface-mtu, we need to try to validate the
value. So we verify if the conversion to int is successful and we will not
allow to set value greater than max IPv4 packet size.

Also use snprintf for safety.

Reviewed by:	allanjude, bapt
Approved by:	allanjude (mentor)
Differential Revision:	https://reviews.freebsd.org/D8492
This commit is contained in:
tsoome 2017-03-20 22:20:17 +00:00
parent d412974c9f
commit 378f4212d7
3 changed files with 24 additions and 5 deletions
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25
lib/libstand/bootp.c
View File

@ -39,6 +39,7 @@
__FBSDID("$FreeBSD$");
#include <sys/types.h>
#include <sys/limits.h>
#include <sys/endian.h>
#include <netinet/in.h>
#include <netinet/in_systm.h>
@ -403,11 +404,29 @@ vend_rfc1048(cp, len)
strlcpy(hostname, val, sizeof(hostname));
}
if (tag == TAG_INTF_MTU) {
intf_mtu = 0;
if ((val = getenv("dhcp.interface-mtu")) != NULL) {
intf_mtu = (u_int)strtoul(val, NULL, 0);
} else {
intf_mtu = be16dec(cp);
unsigned long tmp;
char *end;
errno = 0;
/*
* Do not allow MTU to exceed max IPv4 packet
* size, max value of 16-bit word.
*/
tmp = strtoul(val, &end, 0);
if (errno != 0 ||
*val == '\0' || *end != '\0' ||
tmp > USHRT_MAX) {
printf("%s: bad value: \"%s\", "
"ignoring\n",
"dhcp.interface-mtu", val);
} else {
intf_mtu = (u_int)tmp;
}
}
if (intf_mtu <= 0)
intf_mtu = be16dec(cp);
}
#ifdef SUPPORT_DHCP
if (tag == TAG_DHCP_MSGTYPE) {

2
sys/boot/common/dev_net.c
View File

@ -175,7 +175,7 @@ net_open(struct open_file *f, ...)
}
if (intf_mtu != 0) {
char mtu[16];
sprintf(mtu, "%u", intf_mtu);
snprintf(mtu, sizeof(mtu), "%u", intf_mtu);
setenv("boot.netif.mtu", mtu, 1);
}

2
sys/boot/i386/libi386/pxe.c
View File

@ -342,7 +342,7 @@ pxe_open(struct open_file *f, ...)
}
if (intf_mtu != 0) {
char mtu[16];
sprintf(mtu, "%u", intf_mtu);
snprintf(sizeof(mtu), mtu, "%u", intf_mtu);
setenv("boot.netif.mtu", mtu, 1);
}
printf("pxe_open: server addr: %s\n", inet_ntoa(rootip));