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package/tcpdump: fix CVE-2020-8037

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The ppp decapsulator in tcpdump 4.9.3 can be convinced to allocate a
large amount of memory.

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
(cherry picked from commit e3a663f570)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
This commit is contained in:
Fabrice Fontaine 2020-11-13 21:21:15 +01:00 committed by Peter Korsgaard
parent 64aa92911a
commit 20d3a17f64
2 changed files with 70 additions and 0 deletions
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67
package/tcpdump/0001-PPP-When-un-escaping-don-t-allocate-a-too-large-buffer.patch Normal file
View File

@ -0,0 +1,67 @@
From 32027e199368dad9508965aae8cd8de5b6ab5231 Mon Sep 17 00:00:00 2001
From: Guy Harris <guy@alum.mit.edu>
Date: Sat, 18 Apr 2020 14:04:59 -0700
Subject: [PATCH] PPP: When un-escaping, don't allocate a too-large buffer.
The buffer should be big enough to hold the captured data, but it
doesn't need to be big enough to hold the entire on-the-network packet,
if we haven't captured all of it.
(backported from commit e4add0b010ed6f2180dcb05a13026242ed935334)
[Retrieved from:
https://github.com/the-tcpdump-group/tcpdump/commit/32027e199368dad9508965aae8cd8de5b6ab5231]
Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
---
print-ppp.c | 18 ++++++++++++++----
1 file changed, 14 insertions(+), 4 deletions(-)
diff --git a/print-ppp.c b/print-ppp.c
index 891761728..33fb03412 100644
--- a/print-ppp.c
+++ b/print-ppp.c
@@ -1367,19 +1367,29 @@ print_bacp_config_options(netdissect_options *ndo,
return 0;
}
+/*
+ * Un-escape RFC 1662 PPP in HDLC-like framing, with octet escapes.
+ * The length argument is the on-the-wire length, not the captured
+ * length; we can only un-escape the captured part.
+ */
static void
ppp_hdlc(netdissect_options *ndo,
const u_char *p, int length)
{
+ u_int caplen = ndo->ndo_snapend - p;
u_char *b, *t, c;
const u_char *s;
- int i, proto;
+ u_int i;
+ int proto;
const void *se;
+ if (caplen == 0)
+ return;
+
if (length <= 0)
return;
- b = (u_char *)malloc(length);
+ b = (u_char *)malloc(caplen);
if (b == NULL)
return;
@@ -1388,10 +1398,10 @@ ppp_hdlc(netdissect_options *ndo,
* Do this so that we dont overwrite the original packet
* contents.
*/
- for (s = p, t = b, i = length; i > 0 && ND_TTEST(*s); i--) {
+ for (s = p, t = b, i = caplen; i != 0; i--) {
c = *s++;
if (c == 0x7d) {
- if (i <= 1 || !ND_TTEST(*s))
+ if (i <= 1)
break;
i--;
c = *s++ ^ 0x20;

3
package/tcpdump/tcpdump.mk
View File

@ -18,6 +18,9 @@ TCPDUMP_CONF_OPTS = \
$(if $(BR2_PACKAGE_TCPDUMP_SMB),--enable-smb,--disable-smb)
TCPDUMP_DEPENDENCIES = libpcap
# 0001-PPP-When-un-escaping-don-t-allocate-a-too-large-buffer.patch
TCPDUMP_IGNORE_CVES += CVE-2020-8037
ifeq ($(BR2_STATIC_LIBS),y)
TCPDUMP_CONF_OPTS += LIBS="`$(STAGING_DIR)/usr/bin/pcap-config --static --additional-libs`"
endif