From: Chris Wright Date: Wed, 4 Jun 2008 16:16:33 +0000 (-0700) Subject: asn1: additional sanity checking during BER decoding (CVE-2008-1673) X-Git-Url: http://git.osdn.net/view?a=commitdiff_plain;h=53d12affc55d827d895fba7b902fb03ec2098a29;hp=e5e375dae22e18119dcd45229550aff4f4a77bf6;p=linux-kernel-docs%2Flinux-2.4.36.git asn1: additional sanity checking during BER decoding (CVE-2008-1673) [backport of 2.6 commit ddb2c43594f22843e9f3153da151deaba1a834c5] - 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 [w@1wt.eu: backported to 2.4 : no cifs ; snmp in ip_nat_snmp_basic.c] Signed-off-by: Willy Tarreau --- diff --git a/net/ipv4/netfilter/ip_nat_snmp_basic.c b/net/ipv4/netfilter/ip_nat_snmp_basic.c index efc651c6..87d71d4a 100644 --- a/net/ipv4/netfilter/ip_nat_snmp_basic.c +++ b/net/ipv4/netfilter/ip_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; } @@ -248,7 +253,11 @@ 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 @@ -433,6 +442,11 @@ 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())