From e2fe35c17fed62d4ab5038fa9bc489e967ff8416 Mon Sep 17 00:00:00 2001 From: Jan Engelhardt Date: Sat, 18 Jul 2009 15:22:30 +0200 Subject: netfilter: xtables: check for standard verdicts in policies This adds the second check that Rusty wanted to have a long time ago. :-) Base chain policies must have absolute verdicts that cease processing in the table, otherwise rule execution may continue in an unexpected spurious fashion (e.g. next chain that follows in memory). Signed-off-by: Jan Engelhardt --- net/ipv4/netfilter/arp_tables.c | 21 +++++++++++++++++++-- net/ipv4/netfilter/ip_tables.c | 21 +++++++++++++++++++-- net/ipv6/netfilter/ip6_tables.c | 21 +++++++++++++++++++-- 3 files changed, 57 insertions(+), 6 deletions(-) diff --git a/net/ipv4/netfilter/arp_tables.c b/net/ipv4/netfilter/arp_tables.c index 064082d..7bc11ff 100644 --- a/net/ipv4/netfilter/arp_tables.c +++ b/net/ipv4/netfilter/arp_tables.c @@ -533,6 +533,21 @@ out: return ret; } +static bool check_underflow(struct arpt_entry *e) +{ + const struct arpt_entry_target *t; + unsigned int verdict; + + if (!unconditional(&e->arp)) + return false; + t = arpt_get_target(e); + if (strcmp(t->u.user.name, XT_STANDARD_TARGET) != 0) + return false; + verdict = ((struct arpt_standard_target *)t)->verdict; + verdict = -verdict - 1; + return verdict == NF_DROP || verdict == NF_ACCEPT; +} + static inline int check_entry_size_and_hooks(struct arpt_entry *e, struct xt_table_info *newinfo, unsigned char *base, @@ -564,8 +579,10 @@ static inline int check_entry_size_and_hooks(struct arpt_entry *e, if ((unsigned char *)e - base == hook_entries[h]) newinfo->hook_entry[h] = hook_entries[h]; if ((unsigned char *)e - base == underflows[h]) { - if (!unconditional(&e->arp)) { - pr_err("Underflows must be unconditional\n"); + if (!check_underflow(e)) { + pr_err("Underflows must be unconditional and " + "use the STANDARD target with " + "ACCEPT/DROP\n"); return -EINVAL; } newinfo->underflow[h] = underflows[h]; diff --git a/net/ipv4/netfilter/ip_tables.c b/net/ipv4/netfilter/ip_tables.c index 6e546d5..0b43fd7 100644 --- a/net/ipv4/netfilter/ip_tables.c +++ b/net/ipv4/netfilter/ip_tables.c @@ -708,6 +708,21 @@ find_check_entry(struct ipt_entry *e, const char *name, unsigned int size, return ret; } +static bool check_underflow(struct ipt_entry *e) +{ + const struct ipt_entry_target *t; + unsigned int verdict; + + if (!unconditional(&e->ip)) + return false; + t = ipt_get_target(e); + if (strcmp(t->u.user.name, XT_STANDARD_TARGET) != 0) + return false; + verdict = ((struct ipt_standard_target *)t)->verdict; + verdict = -verdict - 1; + return verdict == NF_DROP || verdict == NF_ACCEPT; +} + static int check_entry_size_and_hooks(struct ipt_entry *e, struct xt_table_info *newinfo, @@ -740,8 +755,10 @@ check_entry_size_and_hooks(struct ipt_entry *e, if ((unsigned char *)e - base == hook_entries[h]) newinfo->hook_entry[h] = hook_entries[h]; if ((unsigned char *)e - base == underflows[h]) { - if (!unconditional(&e->ip)) { - pr_err("Underflows must be unconditional\n"); + if (!check_underflow(e)) { + pr_err("Underflows must be unconditional and " + "use the STANDARD target with " + "ACCEPT/DROP\n"); return -EINVAL; } newinfo->underflow[h] = underflows[h]; diff --git a/net/ipv6/netfilter/ip6_tables.c b/net/ipv6/netfilter/ip6_tables.c index b0599b9..a5d0c27 100644 --- a/net/ipv6/netfilter/ip6_tables.c +++ b/net/ipv6/netfilter/ip6_tables.c @@ -740,6 +740,21 @@ find_check_entry(struct ip6t_entry *e, const char *name, unsigned int size, return ret; } +static bool check_underflow(struct ip6t_entry *e) +{ + const struct ip6t_entry_target *t; + unsigned int verdict; + + if (!unconditional(&e->ipv6)) + return false; + t = ip6t_get_target(e); + if (strcmp(t->u.user.name, XT_STANDARD_TARGET) != 0) + return false; + verdict = ((struct ip6t_standard_target *)t)->verdict; + verdict = -verdict - 1; + return verdict == NF_DROP || verdict == NF_ACCEPT; +} + static int check_entry_size_and_hooks(struct ip6t_entry *e, struct xt_table_info *newinfo, @@ -772,8 +787,10 @@ check_entry_size_and_hooks(struct ip6t_entry *e, if ((unsigned char *)e - base == hook_entries[h]) newinfo->hook_entry[h] = hook_entries[h]; if ((unsigned char *)e - base == underflows[h]) { - if (!unconditional(&e->ipv6)) { - pr_err("Underflows must be unconditional\n"); + if (!check_underflow(e)) { + pr_err("Underflows must be unconditional and " + "use the STANDARD target with " + "ACCEPT/DROP\n"); return -EINVAL; } newinfo->underflow[h] = underflows[h]; -- cgit v1.1