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Fix uid resolution failing after some time with root

Browse Source 
Since the indroduction of netlink-based UID resolution in a626e11, UID
resolution will break after some time due to netlink sequence number
mismatches.
This fix recovers from off-by-one sequence number mismathes and
falls-back to slower UID resolution if some other netlink error occurs
This commit is contained in:
emanuele-f 2022-05-28 18:47:09 +02:00
parent 7433dcf9de
commit dbfaab6164
2 changed files with 32 additions and 10 deletions
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29
app/src/main/jni/pcapd/nl_utils.c
View File

@ -29,6 +29,7 @@
#include <net/if.h>
#include "nl_utils.h"
#include "common/uid_resolver.h"
#include "common/utils.h"
int nl_route_socket(uint32_t groups) {
struct sockaddr_nl snl;
@ -165,6 +166,7 @@ static int diag_uid_lookup(int nlsock, int family, int ipproto,
u_char buf[512];
static int seq = 0;
ssize_t rv;
uint8_t do_retry = 1;
struct nlmsghdr *nmsg = (struct nlmsghdr*) buf;
struct inet_diag_req_v2 *req = (struct inet_diag_req_v2*) (nmsg + 1);
@ -208,17 +210,28 @@ static int diag_uid_lookup(int nlsock, int family, int ipproto,
iov.iov_base = buf;
iov.iov_len = sizeof(buf);
retry:
// Recv reply
if((rv = recvmsg(nlsock, &msg, 0)) <= 0)
return -3;
// NOTE: nmsg points to buf
if(nmsg->nlmsg_len < (int)sizeof(*nmsg) || nmsg->nlmsg_len > rv ||
nmsg->nlmsg_seq != seq) {
if(nmsg->nlmsg_len < (int)sizeof(*nmsg) || nmsg->nlmsg_len > rv) {
errno = EINVAL;
return -4;
}
if(nmsg->nlmsg_seq != seq) {
if(do_retry && (nmsg->nlmsg_seq == (seq - 1))) {
do_retry = 0;
goto retry; // this issue is recoverable, retry once
}
log_e("out of sequence: %d/%d", nmsg->nlmsg_seq, seq);
errno = EINVAL;
return -5;
}
if(nmsg->nlmsg_type == NLMSG_ERROR) {
const struct nlmsgerr *err = NLMSG_DATA(nmsg);
@ -229,7 +242,7 @@ static int diag_uid_lookup(int nlsock, int family, int ipproto,
} else
errno = EINVAL;
return -5;
return -6;
}
if(nmsg->nlmsg_type == NLMSG_DONE)
@ -237,7 +250,7 @@ static int diag_uid_lookup(int nlsock, int family, int ipproto,
if(nmsg->nlmsg_len < NLMSG_LENGTH(sizeof(struct inet_diag_msg))) {
errno = EINVAL;
return -6;
return -7;
}
struct inet_diag_msg *diag_msg = (struct inet_diag_msg*) NLMSG_DATA(nmsg);
@ -280,13 +293,13 @@ int nl_get_uid(int nlsock, const zdtun_5tuple_t *tuple) {
const pd_sockaddr_t *remote = (ipproto == IPPROTO_UDP) ? &src : &dst;
uid = diag_uid_lookup(nlsock, family, ipproto, local, remote, NLM_F_REQUEST);
if(uid >= 0)
if((uid >= 0) || (uid != UID_UNKNOWN))
return uid;
// Search for IPv4-mapped IPv6 addresses
if(family == AF_INET) {
uid = diag_uid_lookup(nlsock, AF_INET6, ipproto, local, remote, NLM_F_REQUEST);
if(uid >= 0)
if((uid >= 0) || (uid != UID_UNKNOWN))
return uid;
}
@ -296,13 +309,13 @@ int nl_get_uid(int nlsock, const zdtun_5tuple_t *tuple) {
pd_sockaddr_t wildcard = {0};
uid = diag_uid_lookup(nlsock, family, ipproto, &src, &wildcard, NLM_F_REQUEST | NLM_F_DUMP);
if(uid >= 0)
if((uid >= 0) || (uid != UID_UNKNOWN))
return uid;
// Search for IPv4-mapped IPv6 addresses
if(family == AF_INET) {
uid = diag_uid_lookup(nlsock, AF_INET6, ipproto, &src, &wildcard, NLM_F_REQUEST | NLM_F_DUMP);
if(uid >= 0)
if((uid >= 0) || (uid != UID_UNKNOWN))
return uid;
}
}

13
app/src/main/jni/pcapd/pcapd.c
View File

@ -752,10 +752,19 @@ static int read_pkt(pcapd_runtime_t *rt, pcapd_iface_t *iface, time_t now) {
uid = uid_lru_find(rt->lru, &zpkt.tuple);
if(uid == -2) {
if((rt->nldiag_sock > 0) && (zpkt.tuple.ipproto != IPPROTO_ICMP))
if((rt->nldiag_sock > 0) && (zpkt.tuple.ipproto != IPPROTO_ICMP)) {
// retrieve via netlink
uid = nl_get_uid(rt->nldiag_sock, &zpkt.tuple);
else
if((uid < 0) && (uid != UID_UNKNOWN)) {
log_e("nl_get_uid failed with error %d [%d]: %s", uid, errno, strerror(errno));
close(rt->nldiag_sock);
rt->nldiag_sock = -1;
// fallback to slow method
uid = get_uid(rt->resolver, &zpkt.tuple);
}
} else
// slow method
uid = get_uid(rt->resolver, &zpkt.tuple);