| Message ID | 1454391454-22359-1-git-send-email-zhouzhouyi@gmail.com |
|---|---|
| State | Awaiting Upstream, archived |
| Delegated to: | David Miller |
| Headers | show |
Hello. On 2/2/2016 8:37 AM, Zhouyi Zhou wrote: > 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. > > In order to avoid this, I add a valid memory reference check in > get_h2x5_addr functions. > > 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 <yizhouzhou@ict.ac.cn> > > --- > net/netfilter/nf_conntrack_h323_main.c | 27 +++++++++++++++++++++++++++ > 1 file changed, 27 insertions(+) > > diff --git a/net/netfilter/nf_conntrack_h323_main.c b/net/netfilter/nf_conntrack_h323_main.c > index 9511af0..21665ec 100644 > --- a/net/netfilter/nf_conntrack_h323_main.c > +++ b/net/netfilter/nf_conntrack_h323_main.c > @@ -110,6 +110,25 @@ 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 bool h323_buffer_ref_valid(void *p, int len) > +{ > + > + if ((unsigned long)len > h323_buffer_valid_bytes) { > + return false; > + } {} not needed. > + > + if (p + len > (void *)h323_buffer + h323_buffer_valid_bytes) { > + return false; > + } Likewise. > + > + if (p < (void *)h323_buffer) { > + return false; > + } Likewise. [...] MBR, Sergei
diff --git a/net/netfilter/nf_conntrack_h323_main.c b/net/netfilter/nf_conntrack_h323_main.c index 9511af0..21665ec 100644 --- a/net/netfilter/nf_conntrack_h323_main.c +++ b/net/netfilter/nf_conntrack_h323_main.c @@ -110,6 +110,25 @@ 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 bool h323_buffer_ref_valid(void *p, int len) +{ + + if ((unsigned long)len > h323_buffer_valid_bytes) { + return false; + } + + if (p + len > (void *)h323_buffer + h323_buffer_valid_bytes) { + return false; + } + + if (p < (void *)h323_buffer) { + return false; + } + + return true; +} static struct nf_conntrack_helper nf_conntrack_helper_h245; static struct nf_conntrack_helper nf_conntrack_helper_q931[]; @@ -145,6 +164,7 @@ 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 +267,9 @@ 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 +692,9 @@ 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 +1274,7 @@ 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); }
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. In order to avoid this, I add a valid memory reference check in get_h2x5_addr functions. 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 <yizhouzhou@ict.ac.cn> --- net/netfilter/nf_conntrack_h323_main.c | 27 +++++++++++++++++++++++++++ 1 file changed, 27 insertions(+)