From ce76a6f4392d1f1ca37fe9514daa69a99db2fcb7 Mon Sep 17 00:00:00 2001 From: Chris Wright Date: Mon, 14 Jul 2008 21:09:23 +0300 Subject: [PATCH] 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 Signed-off-by: Chris Wright Signed-off-by: Adrian Bunk --- fs/cifs/asn1.c | 14 ++++++++++++++ net/ipv4/netfilter/ip_nat_snmp_basic.c | 14 ++++++++++++++ 2 files changed, 28 insertions(+) diff --git a/fs/cifs/asn1.c b/fs/cifs/asn1.c index 086ae8f4a207..dcafda8315c3 100644 --- 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 df57e7a117db..5a9c8dbdfcad 100644 --- 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()) -- 2.39.5