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conntrack: fix ftp ipv4 address substitution.
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When replacing the ipv4 address in repl_ftp_v4_addr(), the remaining size
was incorrectly calculated which could lead to the wrong replacement
adjustment.

This goes unnoticed most of the time, unless you choose carefully your
initial and replacement addresses.

Example fail address combination with 10.1.1.200 DNAT'd to 10.1.100.1.

Fix this by doing something similar to V6 and also splicing out common
code for better coverage and maintainability.

A test is updated to exercise different initial and replacement addresses
and another test is added.

Fixes: bd5e81a ("Userspace Datapath: Add ALG infra and FTP.")
Reported-by: David Marchand <david.marchand@redhat.com>
Reviewed-by: David Marchand <david.marchand@redhat.com>
Signed-off-by: Darrell Ball <dlu998@gmail.com>
Signed-off-by: Ben Pfaff <blp@ovn.org>
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@darball1 @blp
darball1 authored and blp committed Feb 4, 2019
1 parent fabb9e3 commit 48ff966
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Showing 2 changed files with 123 additions and 69 deletions.
118 changes: 56 additions & 62 deletions lib/conntrack.c
View file
Expand Up @@ -136,15 +136,16 @@ expectation_lookup(struct hmap *alg_expectations, const struct conn_key *key,
static int
repl_ftp_v4_addr(struct dp_packet *pkt, ovs_be32 v4_addr_rep,
char *ftp_data_v4_start,
size_t addr_offset_from_ftp_data_start);
size_t addr_offset_from_ftp_data_start, size_t addr_size);

static enum ftp_ctl_pkt
process_ftp_ctl_v4(struct conntrack *ct,
struct dp_packet *pkt,
const struct conn *conn_for_expectation,
ovs_be32 *v4_addr_rep,
char **ftp_data_v4_start,
size_t *addr_offset_from_ftp_data_start);
size_t *addr_offset_from_ftp_data_start,
size_t *addr_size);

static enum ftp_ctl_pkt
detect_ftp_ctl_type(const struct conn_lookup_ctx *ctx,
Expand Down Expand Up @@ -2771,13 +2772,6 @@ expectation_create(struct conntrack *ct, ovs_be16 dst_port,
ct_rwlock_unlock(&ct->resources_lock);
}

static uint8_t
get_v4_byte_be(ovs_be32 v4_addr, uint8_t index)
{
uint8_t *byte_ptr = (OVS_FORCE uint8_t *) &v4_addr;
return byte_ptr[index];
}

static void
replace_substring(char *substr, uint8_t substr_size,
uint8_t total_size, char *rep_str,
Expand All @@ -2788,51 +2782,56 @@ replace_substring(char *substr, uint8_t substr_size,
memcpy(substr, rep_str, rep_str_size);
}

static void
repl_bytes(char *str, char c1, char c2)
{
while (*str) {
if (*str == c1) {
*str = c2;
}
str++;
}
}

static void
modify_packet(struct dp_packet *pkt, char *pkt_str, size_t size,
char *repl_str, size_t repl_size,
uint32_t orig_used_size)
{
replace_substring(pkt_str, size,
(const char *) dp_packet_tail(pkt) - pkt_str,
repl_str, repl_size);
dp_packet_set_size(pkt, orig_used_size + (int) repl_size - (int) size);
}

/* Replace IPV4 address in FTP message with NATed address. */
static int
repl_ftp_v4_addr(struct dp_packet *pkt, ovs_be32 v4_addr_rep,
char *ftp_data_start,
size_t addr_offset_from_ftp_data_start)
size_t addr_offset_from_ftp_data_start,
size_t addr_size OVS_UNUSED)
{
enum { MAX_FTP_V4_NAT_DELTA = 8 };

/* Do conservative check for pathological MTU usage. */
uint32_t orig_used_size = dp_packet_size(pkt);
uint16_t allocated_size = dp_packet_get_allocated(pkt);
if (orig_used_size + MAX_FTP_V4_NAT_DELTA > allocated_size) {
if (orig_used_size + MAX_FTP_V4_NAT_DELTA >
dp_packet_get_allocated(pkt)) {

static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(5, 5);
VLOG_WARN_RL(&rl, "Unsupported effective MTU %u used with FTP",
allocated_size);
VLOG_WARN_RL(&rl, "Unsupported effective MTU %u used with FTP V4",
dp_packet_get_allocated(pkt));
return 0;
}

size_t remain_size = tcp_payload_length(pkt) -
addr_offset_from_ftp_data_start;
int overall_delta = 0;
char *byte_str = ftp_data_start + addr_offset_from_ftp_data_start;

/* Replace the existing IPv4 address by the new one. */
for (uint8_t i = 0; i < 4; i++) {
/* Find the end of the string for this octet. */
char *next_delim = memchr(byte_str, ',', 4);
ovs_assert(next_delim);
int substr_size = next_delim - byte_str;
remain_size -= substr_size;

/* Compose the new string for this octet, and replace it. */
char rep_str[4];
uint8_t rep_byte = get_v4_byte_be(v4_addr_rep, i);
int replace_size = sprintf(rep_str, "%d", rep_byte);
replace_substring(byte_str, substr_size, remain_size,
rep_str, replace_size);
overall_delta += replace_size - substr_size;

/* Advance past the octet and the following comma. */
byte_str += replace_size + 1;
}

dp_packet_set_size(pkt, orig_used_size + overall_delta);
return overall_delta;
char v4_addr_str[INET_ADDRSTRLEN] = {0};
ovs_assert(inet_ntop(AF_INET, &v4_addr_rep, v4_addr_str,
sizeof v4_addr_str));
repl_bytes(v4_addr_str, '.', ',');
modify_packet(pkt, ftp_data_start + addr_offset_from_ftp_data_start,
addr_size, v4_addr_str, strlen(v4_addr_str),
orig_used_size);
return (int) strlen(v4_addr_str) - (int) addr_size;
}

static char *
Expand Down Expand Up @@ -2901,7 +2900,8 @@ process_ftp_ctl_v4(struct conntrack *ct,
const struct conn *conn_for_expectation,
ovs_be32 *v4_addr_rep,
char **ftp_data_v4_start,
size_t *addr_offset_from_ftp_data_start)
size_t *addr_offset_from_ftp_data_start,
size_t *addr_size)
{
struct tcp_header *th = dp_packet_l4(pkt);
size_t tcp_hdr_len = TCP_OFFSET(th->tcp_ctl) * 4;
Expand Down Expand Up @@ -2957,6 +2957,7 @@ process_ftp_ctl_v4(struct conntrack *ct,
return CT_FTP_CTL_INVALID;
}

*addr_size = ftp - ip_addr_start - 1;
char *save_ftp = ftp;
ftp = terminate_number_str(ftp, MAX_FTP_PORT_DGTS);
if (!ftp) {
Expand Down Expand Up @@ -3149,31 +3150,22 @@ repl_ftp_v6_addr(struct dp_packet *pkt, struct ct_addr v6_addr_rep,

/* Do conservative check for pathological MTU usage. */
uint32_t orig_used_size = dp_packet_size(pkt);
uint16_t allocated_size = dp_packet_get_allocated(pkt);
if (orig_used_size + MAX_FTP_V6_NAT_DELTA > allocated_size) {
if (orig_used_size + MAX_FTP_V6_NAT_DELTA >
dp_packet_get_allocated(pkt)) {

static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(5, 5);
VLOG_WARN_RL(&rl, "Unsupported effective MTU %u used with FTP",
allocated_size);
VLOG_WARN_RL(&rl, "Unsupported effective MTU %u used with FTP V6",
dp_packet_get_allocated(pkt));
return 0;
}

char v6_addr_str[IPV6_SCAN_LEN] = {0};
ovs_assert(inet_ntop(AF_INET6, &v6_addr_rep.ipv6_aligned, v6_addr_str,
IPV6_SCAN_LEN - 1));

size_t replace_addr_size = strlen(v6_addr_str);

size_t remain_size = tcp_payload_length(pkt) -
addr_offset_from_ftp_data_start;

char *pkt_addr_str = ftp_data_start + addr_offset_from_ftp_data_start;
replace_substring(pkt_addr_str, addr_size, remain_size,
v6_addr_str, replace_addr_size);

int overall_delta = (int) replace_addr_size - (int) addr_size;

dp_packet_set_size(pkt, orig_used_size + overall_delta);
return overall_delta;
modify_packet(pkt, ftp_data_start + addr_offset_from_ftp_data_start,
addr_size, v6_addr_str, strlen(v6_addr_str),
orig_used_size);
return (int) strlen(v6_addr_str) - (int) addr_size;
}

/* Increment/decrement a TCP sequence number. */
Expand Down Expand Up @@ -3213,7 +3205,8 @@ handle_ftp_ctl(struct conntrack *ct, const struct conn_lookup_ctx *ctx,
} else {
rc = process_ftp_ctl_v4(ct, pkt, ec,
&v4_addr_rep, &ftp_data_start,
&addr_offset_from_ftp_data_start);
&addr_offset_from_ftp_data_start,
&addr_size);
}
if (rc == CT_FTP_CTL_INVALID) {
static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(5, 5);
Expand All @@ -3240,7 +3233,8 @@ handle_ftp_ctl(struct conntrack *ct, const struct conn_lookup_ctx *ctx,
if (nat) {
seq_skew = repl_ftp_v4_addr(pkt, v4_addr_rep,
ftp_data_start,
addr_offset_from_ftp_data_start);
addr_offset_from_ftp_data_start,
addr_size);
}
if (seq_skew) {
ip_len = ntohs(l3_hdr->ip_tot_len) + seq_skew;
Expand Down
74 changes: 67 additions & 7 deletions tests/system-traffic.at
View file
Expand Up @@ -4652,6 +4652,66 @@ tcp,orig=(src=10.1.1.1,dst=10.1.1.2,sport=<cleared>,dport=<cleared>),reply=(src=
OVS_TRAFFIC_VSWITCHD_STOP
AT_CLEANUP

AT_SETUP([conntrack - IPv4 FTP Passive with DNAT 2])
AT_SKIP_IF([test $HAVE_FTP = no])
CHECK_CONNTRACK()
CHECK_CONNTRACK_NAT()
CHECK_CONNTRACK_ALG()

OVS_TRAFFIC_VSWITCHD_START()

ADD_NAMESPACES(at_ns0, at_ns1)

ADD_VETH(p0, at_ns0, br0, "10.1.1.1/16")
NS_CHECK_EXEC([at_ns0], [ip link set dev p0 address e6:66:c1:11:11:11])
NS_CHECK_EXEC([at_ns0], [arp -s 10.1.1.200 e6:66:c1:22:22:22])
NS_CHECK_EXEC([at_ns0], [arp -s 10.1.100.1 e6:66:c1:22:22:22])

ADD_VETH(p1, at_ns1, br0, "10.1.100.1/16")
NS_CHECK_EXEC([at_ns1], [ip link set dev p1 address e6:66:c1:22:22:22])
NS_CHECK_EXEC([at_ns1], [arp -s 10.1.1.1 e6:66:c1:11:11:11])

dnl Allow any traffic from ns0->ns1.
AT_DATA([flows.txt], [dnl
dnl track all IPv4 traffic and NAT any established traffic.
table=0 priority=10 ip, action=ct(nat,table=1)
table=0 priority=0 action=drop
dnl
dnl Table 1
dnl
dnl Allow new FTP control connections.
table=1 in_port=1 ct_state=+new tcp nw_src=10.1.1.1 tp_dst=21 action=ct(alg=ftp,commit,nat(dst=10.1.100.1)),2
dnl Allow related TCP connections from port 1.
table=1 in_port=1 ct_state=+new+rel tcp nw_src=10.1.1.1 action=ct(commit,nat),2
dnl Allow established TCP connections both ways, post-NAT match.
table=1 in_port=1 ct_state=+est tcp nw_dst=10.1.100.1 action=2
table=1 in_port=2 ct_state=+est tcp nw_dst=10.1.1.1 action=1

dnl Allow ICMP both ways.
table=1 priority=100 in_port=1 icmp, action=2
table=1 priority=100 in_port=2 icmp, action=1
table=1 priority=0, action=drop
])

AT_CHECK([ovs-ofctl --bundle add-flows br0 flows.txt])

dnl Check that the stacks working to avoid races.
OVS_WAIT_UNTIL([ip netns exec at_ns0 ping -c 1 10.1.100.1 >/dev/null])

OVS_START_L7([at_ns1], [ftp])

dnl FTP requests from p0->p1 should work fine.
NS_CHECK_EXEC([at_ns0], [wget ftp://10.1.1.200 -t 3 -T 1 --retry-connrefused -v -o wget0.log])

dnl Discards CLOSE_WAIT and CLOSING
AT_CHECK([ovs-appctl dpctl/dump-conntrack | FORMAT_CT(10.1.1.200)], [0], [dnl
tcp,orig=(src=10.1.1.1,dst=10.1.1.200,sport=<cleared>,dport=<cleared>),reply=(src=10.1.100.1,dst=10.1.1.1,sport=<cleared>,dport=<cleared>),protoinfo=(state=<cleared>)
tcp,orig=(src=10.1.1.1,dst=10.1.1.200,sport=<cleared>,dport=<cleared>),reply=(src=10.1.100.1,dst=10.1.1.1,sport=<cleared>,dport=<cleared>),protoinfo=(state=<cleared>),helper=ftp
])

OVS_TRAFFIC_VSWITCHD_STOP
AT_CLEANUP

AT_SETUP([conntrack - IPv4 FTP Active with DNAT])
AT_SKIP_IF([test $HAVE_FTP = no])
CHECK_CONNTRACK()
Expand Down Expand Up @@ -4722,12 +4782,12 @@ OVS_TRAFFIC_VSWITCHD_START()

ADD_NAMESPACES(at_ns0, at_ns1)

ADD_VETH(p0, at_ns0, br0, "10.1.1.1/24")
ADD_VETH(p0, at_ns0, br0, "10.1.1.1/16")
NS_CHECK_EXEC([at_ns0], [ip link set dev p0 address e6:66:c1:11:11:11])
NS_CHECK_EXEC([at_ns0], [arp -s 10.1.1.2 e6:66:c1:22:22:22])
NS_CHECK_EXEC([at_ns0], [arp -s 10.1.1.240 e6:66:c1:22:22:22])
NS_CHECK_EXEC([at_ns0], [arp -s 10.1.120.240 e6:66:c1:22:22:22])

ADD_VETH(p1, at_ns1, br0, "10.1.1.2/24")
ADD_VETH(p1, at_ns1, br0, "10.1.1.2/16")
NS_CHECK_EXEC([at_ns1], [ip link set dev p1 address e6:66:c1:22:22:22])
NS_CHECK_EXEC([at_ns1], [arp -s 10.1.1.1 e6:66:c1:11:11:11])

Expand Down Expand Up @@ -4761,12 +4821,12 @@ OVS_WAIT_UNTIL([ip netns exec at_ns0 ping -c 1 10.1.1.2 >/dev/null])
OVS_START_L7([at_ns1], [ftp])

dnl FTP requests from p0->p1 should work fine.
NS_CHECK_EXEC([at_ns0], [wget ftp://10.1.1.240 --no-passive-ftp -t 3 -T 1 --retry-connrefused -v -o wget0.log])
NS_CHECK_EXEC([at_ns0], [wget ftp://10.1.120.240 --no-passive-ftp -t 3 -T 1 --retry-connrefused -v -o wget0.log])

dnl Discards CLOSE_WAIT and CLOSING
AT_CHECK([ovs-appctl dpctl/dump-conntrack | FORMAT_CT(10.1.1.2)], [0], [dnl
tcp,orig=(src=10.1.1.1,dst=10.1.1.240,sport=<cleared>,dport=<cleared>),reply=(src=10.1.1.2,dst=10.1.1.1,sport=<cleared>,dport=<cleared>),protoinfo=(state=<cleared>),helper=ftp
tcp,orig=(src=10.1.1.2,dst=10.1.1.1,sport=<cleared>,dport=<cleared>),reply=(src=10.1.1.1,dst=10.1.1.240,sport=<cleared>,dport=<cleared>),protoinfo=(state=<cleared>)
AT_CHECK([ovs-appctl dpctl/dump-conntrack | FORMAT_CT(10.1.120.240)], [0], [dnl
tcp,orig=(src=10.1.1.1,dst=10.1.120.240,sport=<cleared>,dport=<cleared>),reply=(src=10.1.1.2,dst=10.1.1.1,sport=<cleared>,dport=<cleared>),protoinfo=(state=<cleared>),helper=ftp
tcp,orig=(src=10.1.1.2,dst=10.1.1.1,sport=<cleared>,dport=<cleared>),reply=(src=10.1.1.1,dst=10.1.120.240,sport=<cleared>,dport=<cleared>),protoinfo=(state=<cleared>)
])

OVS_TRAFFIC_VSWITCHD_STOP
Expand Down

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