From 6ab007dbb1958371abff2eaaad2b26da89b3c74e Mon Sep 17 00:00:00 2001
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From: Yi Zhao <yi.zhao@windriver.com>
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Date: Fri, 24 Apr 2020 09:43:44 +0800
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Subject: [PATCH] telnetd/utility.c: fix CVE-2020-10188
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Upstream-Status: Backport
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[Fedora: https://src.fedoraproject.org/rpms/telnet/raw/master/f/telnet-0.17-overflow-exploit.patch]
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CVE: CVE-2020-10188
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Signed-off-by: Yi Zhao <yi.zhao@windriver.com>
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---
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telnetd/utility.c | 32 +++++++++++++++++++++-----------
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1 file changed, 21 insertions(+), 11 deletions(-)
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diff --git a/telnetd/utility.c b/telnetd/utility.c
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index 75314cb..b9a46a6 100644
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--- a/telnetd/utility.c
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+++ b/telnetd/utility.c
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@@ -169,31 +169,38 @@ void ptyflush(void)
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*/
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static
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char *
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-nextitem(char *current)
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+nextitem(char *current, const char *endp)
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{
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+ if (current >= endp) {
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+ return NULL;
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+ }
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if ((*current&0xff) != IAC) {
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return current+1;
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}
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+ if (current+1 >= endp) {
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+ return NULL;
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+ }
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switch (*(current+1)&0xff) {
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case DO:
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case DONT:
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case WILL:
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case WONT:
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- return current+3;
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+ return current+3 <= endp ? current+3 : NULL;
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case SB: /* loop forever looking for the SE */
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{
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register char *look = current+2;
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- for (;;) {
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+ while (look < endp) {
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if ((*look++&0xff) == IAC) {
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- if ((*look++&0xff) == SE) {
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+ if (look < endp && (*look++&0xff) == SE) {
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return look;
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}
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}
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}
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+ return NULL;
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}
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default:
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- return current+2;
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+ return current+2 <= endp ? current+2 : NULL;
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}
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} /* end of nextitem */
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@@ -219,7 +226,7 @@ void netclear(void)
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register char *thisitem, *next;
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char *good;
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#define wewant(p) ((nfrontp > p) && ((*p&0xff) == IAC) && \
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- ((*(p+1)&0xff) != EC) && ((*(p+1)&0xff) != EL))
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+ (nfrontp > p+1 && (((*(p+1)&0xff) != EC) && ((*(p+1)&0xff) != EL))))
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#if defined(ENCRYPT)
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thisitem = nclearto > netobuf ? nclearto : netobuf;
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@@ -227,7 +234,7 @@ void netclear(void)
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thisitem = netobuf;
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#endif
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- while ((next = nextitem(thisitem)) <= nbackp) {
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+ while ((next = nextitem(thisitem, nbackp)) != NULL && next <= nbackp) {
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thisitem = next;
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}
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@@ -239,20 +246,23 @@ void netclear(void)
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good = netobuf; /* where the good bytes go */
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#endif
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- while (nfrontp > thisitem) {
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+ while (thisitem != NULL && nfrontp > thisitem) {
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if (wewant(thisitem)) {
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int length;
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next = thisitem;
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do {
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- next = nextitem(next);
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- } while (wewant(next) && (nfrontp > next));
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+ next = nextitem(next, nfrontp);
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+ } while (next != NULL && wewant(next) && (nfrontp > next));
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+ if (next == NULL) {
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+ next = nfrontp;
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+ }
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length = next-thisitem;
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bcopy(thisitem, good, length);
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good += length;
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thisitem = next;
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} else {
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- thisitem = nextitem(thisitem);
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+ thisitem = nextitem(thisitem, nfrontp);
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}
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}
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--
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2.7.4
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