From ddb2c43594f22843e9f3153da151deaba1a834c5 Mon Sep 17 00:00:00 2001 From: Chris Wright Date: Wed, 4 Jun 2008 09:16:33 -0700 Subject: asn1: additional sanity checking during BER decoding - 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. Cc: Steven French Cc: stable@kernel.org Acked-by: Patrick McHardy Signed-off-by: Chris Wright Signed-off-by: Linus Torvalds --- net/ipv4/netfilter/nf_nat_snmp_basic.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+) (limited to 'net/ipv4/netfilter/nf_nat_snmp_basic.c') diff --git a/net/ipv4/netfilter/nf_nat_snmp_basic.c b/net/ipv4/netfilter/nf_nat_snmp_basic.c index 5daefad3d193..7750c97fde7b 100644 --- a/net/ipv4/netfilter/nf_nat_snmp_basic.c +++ b/net/ipv4/netfilter/nf_nat_snmp_basic.c @@ -232,6 +232,11 @@ 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; } @@ -250,6 +255,10 @@ 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 @@ -434,6 +443,11 @@ 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()) -- cgit v1.2.3