linux kernel 2.6.38.8 ipv4 arp_tables infoleak to userspace

2011-06-27 / 2011-06-28
Risk: Low
Local: Yes
Remote: No
CWE: CWE-200


CVSS Base Score: 2.1/10
Impact Subscore: 2.9/10
Exploitability Subscore: 3.9/10
Exploit range: Local
Attack complexity: Low
Authentication: No required
Confidentiality impact: Partial
Integrity impact: None
Availability impact: None

Structures ipt_replace, compat_ipt_replace, and xt_get_revision are copied from userspace. Fields of these structs that are zero-terminated strings are not checked. When they are used as argument to a format string containing "%s" in request_module(), some sensitive information is leaked to userspace via argument of spawned modprobe process. The first bug was introduced before the git epoch; the second is introduced by 6b7d31fc (v2.6.15-rc1); the third is introduced by 6b7d31fc (v2.6.15-rc1). To trigger the bug one should have CAP_NET_ADMIN. Signed-off-by: Vasiliy Kulikov <segoon@openwall.com> --- Compile tested. net/ipv4/netfilter/arp_tables.c | 3 +++ 1 files changed, 3 insertions(+), 0 deletions(-) diff --git a/net/ipv4/netfilter/arp_tables.c b/net/ipv4/netfilter/arp_tables.c index e95054c..4b5d457 100644 --- a/net/ipv4/netfilter/arp_tables.c +++ b/net/ipv4/netfilter/arp_tables.c @@ -1066,6 +1066,7 @@ static int do_replace(struct net *net, const void __user *user, /* overflow check */ if (tmp.num_counters >= INT_MAX / sizeof(struct xt_counters)) return -ENOMEM; + tmp.name[sizeof(tmp.name)-1] = 0; newinfo = xt_alloc_table_info(tmp.size); if (!newinfo) @@ -1488,6 +1489,7 @@ static int compat_do_replace(struct net *net, void __user *user, return -ENOMEM; if (tmp.num_counters >= INT_MAX / sizeof(struct xt_counters)) return -ENOMEM; + tmp.name[sizeof(tmp.name)-1] = 0; newinfo = xt_alloc_table_info(tmp.size); if (!newinfo) @@ -1740,6 +1742,7 @@ static int do_arpt_get_ctl(struct sock *sk, int cmd, void __user *user, int *len ret = -EFAULT; break; } + rev.name[sizeof(rev.name)-1] = 0; try_then_request_module(xt_find_revision(NFPROTO_ARP, rev.name, rev.revision, 1, &ret), -- 1.7.0.4 --

References:

https://bugzilla.redhat.com/show_bug.cgi?id=689321
http://www.openwall.com/lists/oss-security/2011/03/21/4
http://www.openwall.com/lists/oss-security/2011/03/21/1
http://www.openwall.com/lists/oss-security/2011/03/18/15
http://marc.info/?l=netfilter-devel&m=129978081009955&w=2
http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=42eab94fff18cb1091d3501cd284d6bd6cc9c143
http://www.kernel.org/pub/linux/kernel/v2.6/ChangeLog-2.6.39


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