asn1: additional sanity checking during BER decoding (CVE-2008-1673)

- Don't trust a length which is greater than the working buffer.
  An invalid length could cause overflow when calculating buffer size
  for decoding oid.

- An oid length of zero is invalid and allows for an off-by-one error when
  decoding oid because the first subid actually encodes first 2 subids.

- A primitive encoding may not have an indefinite length.

Thanks to Wei Wang from McAfee for report.

Acked-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: Chris Wright <chrisw@sous-sol.org>
Signed-off-by: Adrian Bunk <bunk@kernel.org>

diff --git a/fs/cifs/asn1.c b/fs/cifs/asn1.c
index 086ae8f4a207a22f0d1bfe2863439ed20bd88f89..dcafda8315c3d78857b9213c312c2dd2f24857e5 100644 (file)
--- a/fs/cifs/asn1.c
+++ b/fs/cifs/asn1.c
@@ -183,6 +183,11 @@ asn1_length_decode(struct asn1_ctx *ctx, unsigned int *def, unsigned int *len)
                        }
                }
        }
+
+       /* don't trust len bigger than ctx buffer */
+       if (*len > ctx->end - ctx->pointer)
+               return 0;
+
        return 1;
 }
 
@@ -200,6 +205,10 @@ asn1_header_decode(struct asn1_ctx *ctx,
        if (!asn1_length_decode(ctx, &def, &len))
                return 0;
 
+       /* primitive shall be definite, indefinite shall be constructed */
+       if (*con == ASN1_PRI && !def)
+               return 0;
+
        if (def)
                *eoc = ctx->pointer + len;
        else
@@ -386,6 +395,11 @@ asn1_oid_decode(struct asn1_ctx *ctx,
        unsigned long *optr;
 
        size = eoc - ctx->pointer + 1;
+
+       /* first subid actually encodes first two subids */
+       if (size < 2 || size > ULONG_MAX/sizeof(unsigned long))
+               return 0;
+
        *oid = kmalloc(size * sizeof (unsigned long), GFP_ATOMIC);
        if (*oid == NULL) {
                return 0;

diff --git a/net/ipv4/netfilter/ip_nat_snmp_basic.c b/net/ipv4/netfilter/ip_nat_snmp_basic.c
index df57e7a117dbb4c46605e44dc349ca818e58171e..5a9c8dbdfcad40cbb855430fec7d58400d148d37 100644 (file)
--- a/net/ipv4/netfilter/ip_nat_snmp_basic.c
+++ b/net/ipv4/netfilter/ip_nat_snmp_basic.c
@@ -236,6 +236,11 @@ static unsigned char asn1_length_decode(struct asn1_ctx *ctx,
                        }
                }
        }
+
+       /* don't trust len bigger than ctx buffer */
+       if (*len > ctx->end - ctx->pointer)
+               return 0;
+
        return 1;
 }
 
@@ -253,6 +258,10 @@ static unsigned char asn1_header_decode(struct asn1_ctx *ctx,
        if (!asn1_length_decode(ctx, &def, &len))
                return 0;
                
+       /* primitive shall be definite, indefinite shall be constructed */
+       if (*con == ASN1_PRI && !def)
+               return 0;
+
        if (def)
                *eoc = ctx->pointer + len;
        else
@@ -437,6 +446,11 @@ static unsigned char asn1_oid_decode(struct asn1_ctx *ctx,
        unsigned long *optr;
        
        size = eoc - ctx->pointer + 1;
+
+       /* first subid actually encodes first two subids */
+       if (size < 2 || size > ULONG_MAX/sizeof(unsigned long))
+               return 0;
+
        *oid = kmalloc(size * sizeof(unsigned long), GFP_ATOMIC);
        if (*oid == NULL) {
                if (net_ratelimit())