telnet/telnet-0.17-overflow-exploit.patch

93 lines
2.4 KiB
Diff
Raw Normal View History

diff -up netkit-telnet-0.17/telnetd/utility.c.orig netkit-telnet-0.17/telnetd/utility.c
--- netkit-telnet-0.17/telnetd/utility.c.orig 2020-03-25 11:53:56.772624325 +0100
+++ netkit-telnet-0.17/telnetd/utility.c 2020-03-25 11:54:01.966601415 +0100
@@ -221,31 +221,38 @@ void ptyflush(void)
*/
static
char *
-nextitem(char *current)
+nextitem(char *current, const char *endp)
{
+ if (current >= endp) {
+ return NULL;
+ }
if ((*current&0xff) != IAC) {
return current+1;
}
+ if (current+1 >= endp) {
+ return NULL;
+ }
switch (*(current+1)&0xff) {
case DO:
case DONT:
case WILL:
case WONT:
- return current+3;
+ return current+3 <= endp ? current+3 : NULL;
case SB: /* loop forever looking for the SE */
{
register char *look = current+2;
- for (;;) {
+ while (look < endp) {
if ((*look++&0xff) == IAC) {
- if ((*look++&0xff) == SE) {
+ if (look < endp && (*look++&0xff) == SE) {
return look;
}
}
}
+ return NULL;
}
default:
- return current+2;
+ return current+2 <= endp ? current+2 : NULL;
}
} /* end of nextitem */
@@ -271,7 +278,7 @@ void netclear(void)
register char *thisitem, *next;
char *good;
#define wewant(p) ((nfrontp > p) && ((*p&0xff) == IAC) && \
- ((*(p+1)&0xff) != EC) && ((*(p+1)&0xff) != EL))
+ (nfrontp > p+1 && (((*(p+1)&0xff) != EC) && ((*(p+1)&0xff) != EL))))
#if defined(ENCRYPT)
thisitem = nclearto > netobuf ? nclearto : netobuf;
@@ -279,7 +286,7 @@ void netclear(void)
thisitem = netobuf;
#endif
- while ((next = nextitem(thisitem)) <= nbackp) {
+ while ((next = nextitem(thisitem, nbackp)) != NULL && next <= nbackp) {
thisitem = next;
}
@@ -291,20 +298,23 @@ void netclear(void)
good = netobuf; /* where the good bytes go */
#endif
- while (nfrontp > thisitem) {
+ while (thisitem != NULL && nfrontp > thisitem) {
if (wewant(thisitem)) {
int length;
next = thisitem;
do {
- next = nextitem(next);
- } while (wewant(next) && (nfrontp > next));
+ next = nextitem(next, nfrontp);
+ } while (next != NULL && wewant(next) && (nfrontp > next));
+ if (next == NULL) {
+ next = nfrontp;
+ }
length = next-thisitem;
bcopy(thisitem, good, length);
good += length;
thisitem = next;
} else {
- thisitem = nextitem(thisitem);
+ thisitem = nextitem(thisitem, nfrontp);
}
}