[PATCH V4] netfilter: h323: avoid potential attack
From: Zhouyi Zhou <hidden>
Date: 2016-02-02 03:13:55
Also in:
lkml, netfilter-devel
Subsystem:
netfilter, networking [general], the rest · Maintainers:
Pablo Neira Ayuso, Florian Westphal, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds
I think hackers chould build a malicious h323 packet to overflow the pointer p which will panic during the memcpy(addr, p, len) For example, he may fabricate a very large taddr->ipAddress.ip. As suggested by Eric, this module is protected by a lock (nf_h323_lock) so adding a variable h323_buffer_valid_bytes that would contain the number of valid bytes would not require to change prototypes of get_h2x5_addr. Signed-off-by: Zhouyi Zhou <redacted> --- net/netfilter/nf_conntrack_h323_main.c | 31 +++++++++++++++++++++++++++++++ 1 file changed, 31 insertions(+)
diff --git a/net/netfilter/nf_conntrack_h323_main.c b/net/netfilter/nf_conntrack_h323_main.c
index 9511af0..fba9d71 100644
--- a/net/netfilter/nf_conntrack_h323_main.c
+++ b/net/netfilter/nf_conntrack_h323_main.c@@ -110,6 +110,29 @@ int (*nat_q931_hook) (struct sk_buff *skb, static DEFINE_SPINLOCK(nf_h323_lock); static char *h323_buffer; +static int h323_buffer_valid_bytes; + +static int h323_buffer_ref_valid(void *p, int len) +{ + int err = 0; + + if ((unsigned long)len > h323_buffer_valid_bytes) { + err = -1; + goto out; + } + + if (p + len > (void *)h323_buffer + h323_buffer_valid_bytes) { + err = -1; + goto out; + } + + if (p < (void *)h323_buffer) { + err = -1; + goto out; + } +out: + return err; +} static struct nf_conntrack_helper nf_conntrack_helper_h245; static struct nf_conntrack_helper nf_conntrack_helper_q931[];
@@ -145,6 +168,7 @@ static int get_tpkt_data(struct sk_buff *skb, unsigned int protoff, if (*data == NULL) { /* first TPKT */ /* Get first TPKT pointer */ + h323_buffer_valid_bytes = tcpdatalen; tpkt = skb_header_pointer(skb, tcpdataoff, tcpdatalen, h323_buffer); BUG_ON(tpkt == NULL);
@@ -247,6 +271,9 @@ static int get_h245_addr(struct nf_conn *ct, const unsigned char *data, return 0; } + if (h323_buffer_ref_valid((void *)p, len + sizeof(__be16))) + return 0; + memcpy(addr, p, len); memset((void *)addr + len, 0, sizeof(*addr) - len); memcpy(port, p + len, sizeof(__be16));
@@ -669,6 +696,9 @@ int get_h225_addr(struct nf_conn *ct, unsigned char *data, return 0; } + if (h323_buffer_ref_valid((void *)p, len + sizeof(__be16))) + return 0; + memcpy(addr, p, len); memset((void *)addr + len, 0, sizeof(*addr) - len); memcpy(port, p + len, sizeof(__be16));
@@ -1248,6 +1278,7 @@ static unsigned char *get_udp_data(struct sk_buff *skb, unsigned int protoff, if (dataoff >= skb->len) return NULL; *datalen = skb->len - dataoff; + h323_buffer_valid_bytes = *datalen; return skb_header_pointer(skb, dataoff, *datalen, h323_buffer); }
--
1.9.1