From 89de65dc184e7b7ed5bfededd647e190c3bf310a Mon Sep 17 00:00:00 2001 From: Pablo Neira Ayuso Date: Mon, 20 Aug 2012 16:11:00 +0200 Subject: conntrack: fix BPF code for IPv6 filtering in case of NFCT_FILTER_LOGIC_POSITIVE 4b6df76 conntrack: fix autogenerated BPF code for IPv6 filtering aimed to fix a bug the IPv6 BPF filtering. However, it didn't fix it for NFCT_FILTER_LOGIC_POSITIVE case since jump is still miscalculated. This chunk below shows the BPF code to filter IPv6 address 2:4:6:: {0x00020004, 0x00060000, 0x0, 0x0 } in case that NFCT_FILTER_LOGIC_POSITIVE is used, ie. if that address matches, accept the event. (0032) code= BPF_LD|BPF_W|BPF_IND jt=00 jf=00 k=00000004 (0033) code= BPF_ALU|BPF_AND|BPF_K jt=00 jf=00 k=ffffffff (0034) code= BPF_JMP|BPF_JEQ|BPF_K jt=00 jf=09 k=00020004 [ this above compares second 4 bytes with 00020004, if comparison fails it jumps to 003e ] (0035) code= BPF_LD|BPF_W|BPF_IND jt=00 jf=00 k=00000008 (0036) code= BPF_ALU|BPF_AND|BPF_K jt=00 jf=00 k=ffffffff (0037) code= BPF_JMP|BPF_JEQ|BPF_K jt=00 jf=06 k=00060000 [ this above compares second 4 bytes with 00060000, if comparison fails it jumps to 003e ] (0038) code= BPF_LD|BPF_W|BPF_IND jt=00 jf=00 k=0000000c (0039) code= BPF_ALU|BPF_AND|BPF_K jt=00 jf=00 k=ffffffff (003a) code= BPF_JMP|BPF_JEQ|BPF_K jt=00 jf=03 k=00000000 [ this above compares third 4 bytes with 00000000, if comparison fails it jumps to 003e ] (003b) code= BPF_LD|BPF_W|BPF_IND jt=00 jf=00 k=00000010 (003c) code= BPF_ALU|BPF_AND|BPF_K jt=00 jf=00 k=ffffffff (003d) code= BPF_JMP|BPF_JEQ|BPF_K jt=01 jf=00 k=00000000 [ this above compares last 4 bytes with 00000000, if comparison succeded it jumps to 003f, which means, accept event ] (003e) code= BPF_RET|BPF_K jt=00 jf=00 k=00000000 ---- final verdict ---- (003f) code= BPF_RET|BPF_K jt=00 jf=00 k=ffffffff Just for the record: This chunk below shows the BPF code to filter IPv6 address 2:4:6:: {0x00020004, 0x00060000, 0x0, 0x0 } in case that NFCT_FILTER_LOGIC_NEGATIVE is used, ie. if that address matches, drop the event. [...] (0032) code= BPF_LD|BPF_W|BPF_IND jt=00 jf=00 k=00000004 (0033) code= BPF_ALU|BPF_AND|BPF_K jt=00 jf=00 k=ffffffff (0034) code= BPF_JMP|BPF_JEQ|BPF_K jt=00 jf=09 k=00020004 [ this above compares first 4 bytes with 00020004, if comparison fails it jumps to 003e ] (0035) code= BPF_LD|BPF_W|BPF_IND jt=00 jf=00 k=00000008 (0036) code= BPF_ALU|BPF_AND|BPF_K jt=00 jf=00 k=ffffffff (0037) code= BPF_JMP|BPF_JEQ|BPF_K jt=00 jf=06 k=00060000 [ this above compares second 4 bytes with 00060000, if comparison fails it jumps to 003e ] (0038) code= BPF_LD|BPF_W|BPF_IND jt=00 jf=00 k=0000000c (0039) code= BPF_ALU|BPF_AND|BPF_K jt=00 jf=00 k=ffffffff (003a) code= BPF_JMP|BPF_JEQ|BPF_K jt=00 jf=03 k=00000000 [ this above compares third 4 bytes with 00000000, if comparison fails it jumps to 003e ] (003b) code= BPF_LD|BPF_W|BPF_IND jt=00 jf=00 k=00000010 (003c) code= BPF_ALU|BPF_AND|BPF_K jt=00 jf=00 k=ffffffff (003d) code= BPF_JMP|BPF_JEQ|BPF_K jt=01 jf=00 k=00000000 [ this above compares last 4 bytes with 00000000, if comparison succeded it jumps to 003e ] (003e) code= BPF_JMP|BPF_JA jt=00 jf=00 k=00000001 (003f) code= BPF_RET|BPF_K jt=00 jf=00 k=00000000 [ default action specified by 003e is to drop the event ] Tested-by: Eric Leblond Reported-by: Eric Leblond Signed-off-by: Pablo Neira Ayuso --- src/conntrack/bsf.c | 16 +++++++--------- 1 file changed, 7 insertions(+), 9 deletions(-) diff --git a/src/conntrack/bsf.c b/src/conntrack/bsf.c index c14531e..534202f 100644 --- a/src/conntrack/bsf.c +++ b/src/conntrack/bsf.c @@ -562,7 +562,7 @@ bsf_add_addr_ipv6_filter(const struct nfct_filter *f, unsigned int type) { unsigned int i, j, dir, attr; - unsigned int label_continue[2], jf; + unsigned int label_continue, jf; struct stack *s; struct jump jmp; @@ -592,23 +592,21 @@ bsf_add_addr_ipv6_filter(const struct nfct_filter *f, jf = 1; if (f->logic[attr] == NFCT_FILTER_LOGIC_POSITIVE) { - label_continue[0] = 1; - label_continue[1] = 2; + label_continue = 1; } else { - label_continue[0] = 2; - label_continue[1] = 1; + label_continue = 2; } j = 0; j += nfct_bsf_load_payload_offset(this, j); j += nfct_bsf_find_attr(this, CTA_TUPLE_ORIG, j); - j += nfct_bsf_cmp_k_stack(this, 0, label_continue[0] - j, j, s); + j += nfct_bsf_cmp_k_stack(this, 0, label_continue - j, j, s); /* no need to access attribute payload, we are using nest-based finder * j += nfct_bsf_add_attr_data_offset(this, j); */ j += nfct_bsf_find_attr_nest(this, CTA_TUPLE_IP, j); - j += nfct_bsf_cmp_k_stack(this, 0, label_continue[0] - j, j, s); + j += nfct_bsf_cmp_k_stack(this, 0, label_continue - j, j, s); j += nfct_bsf_find_attr_nest(this, type, j); - j += nfct_bsf_cmp_k_stack(this, 0, label_continue[0] - j, j, s); + j += nfct_bsf_cmp_k_stack(this, 0, label_continue - j, j, s); j += nfct_bsf_x_equal_a(this, j); for (i = 0; i < f->l3proto_elems_ipv6[dir]; i++) { @@ -624,7 +622,7 @@ bsf_add_addr_ipv6_filter(const struct nfct_filter *f, j); if (k < 3) { j += nfct_bsf_cmp_k_stack_jf(this, ip, - jf - j - label_continue[1], + jf - j - 1, j, s); } else { /* last word: jump if true */ -- cgit v1.2.3