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Systemd/src/journal/journald-syslog.c
Christian Seiler ccf23ad5fa journal: Fix syslog forwarding without CAP_SYS_ADMIN 
In case CAP_SYS_ADMIN is missing (like in containers), one cannot fake pid in
struct ucred (uid/gid are fine if CAP_SETUID/CAP_SETGID are present).

Ensure that journald will try again to forward the messages to syslog without
faking the SCM_CREDENTIALS pid (which isn't guaranteed to succeed anyway, since
it also does the same thing if the process has already exited).

With this patch, journald will no longer silently discard messages
that are supposed to be sent to syslog in these situations.

https://bugs.debian.org/775067
2015-01-21 12:36:58 +01:00

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/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
/***
This file is part of systemd.
Copyright 2011 Lennart Poettering
systemd is free software; you can redistribute it and/or modify it
under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 2.1 of the License, or
(at your option) any later version.
systemd is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with systemd; If not, see <http://www.gnu.org/licenses/>.
***/
#include <unistd.h>
#include <stddef.h>
#include <sys/epoll.h>
#include "systemd/sd-messages.h"
#include "socket-util.h"
#include "selinux-util.h"
#include "journald-server.h"
#include "journald-syslog.h"
#include "journald-kmsg.h"
#include "journald-console.h"
#include "journald-wall.h"
/* Warn once every 30s if we missed syslog message */
#define WARN_FORWARD_SYSLOG_MISSED_USEC (30 * USEC_PER_SEC)
static void forward_syslog_iovec(Server *s, const struct iovec *iovec, unsigned n_iovec, const struct ucred *ucred, const struct timeval *tv) {
static const union sockaddr_union sa = {
.un.sun_family = AF_UNIX,
.un.sun_path = "/run/systemd/journal/syslog",
};
struct msghdr msghdr = {
.msg_iov = (struct iovec *) iovec,
.msg_iovlen = n_iovec,
.msg_name = (struct sockaddr*) &sa.sa,
.msg_namelen = offsetof(union sockaddr_union, un.sun_path)
+ strlen("/run/systemd/journal/syslog"),
};
struct cmsghdr *cmsg;
union {
struct cmsghdr cmsghdr;
uint8_t buf[CMSG_SPACE(sizeof(struct ucred))];
} control;
assert(s);
assert(iovec);
assert(n_iovec > 0);
if (ucred) {
zero(control);
msghdr.msg_control = &control;
msghdr.msg_controllen = sizeof(control);
cmsg = CMSG_FIRSTHDR(&msghdr);
cmsg->cmsg_level = SOL_SOCKET;
cmsg->cmsg_type = SCM_CREDENTIALS;
cmsg->cmsg_len = CMSG_LEN(sizeof(struct ucred));
memcpy(CMSG_DATA(cmsg), ucred, sizeof(struct ucred));
msghdr.msg_controllen = cmsg->cmsg_len;
}
/* Forward the syslog message we received via /dev/log to
* /run/systemd/syslog. Unfortunately we currently can't set
* the SO_TIMESTAMP auxiliary data, and hence we don't. */
if (sendmsg(s->syslog_fd, &msghdr, MSG_NOSIGNAL) >= 0)
return;
/* The socket is full? I guess the syslog implementation is
* too slow, and we shouldn't wait for that... */
if (errno == EAGAIN) {
s->n_forward_syslog_missed++;
return;
}
if (ucred && (errno == ESRCH || errno == EPERM)) {
struct ucred u;
/* Hmm, presumably the sender process vanished
* by now, or we don't have CAP_SYS_AMDIN, so
* let's fix it as good as we can, and retry */
u = *ucred;
u.pid = getpid();
memcpy(CMSG_DATA(cmsg), &u, sizeof(struct ucred));
if (sendmsg(s->syslog_fd, &msghdr, MSG_NOSIGNAL) >= 0)
return;
if (errno == EAGAIN) {
s->n_forward_syslog_missed++;
return;
}
}
if (errno != ENOENT)
log_debug_errno(errno, "Failed to forward syslog message: %m");
}
static void forward_syslog_raw(Server *s, int priority, const char *buffer, const struct ucred *ucred, const struct timeval *tv) {
struct iovec iovec;
assert(s);
assert(buffer);
if (LOG_PRI(priority) > s->max_level_syslog)
return;
IOVEC_SET_STRING(iovec, buffer);
forward_syslog_iovec(s, &iovec, 1, ucred, tv);
}
void server_forward_syslog(Server *s, int priority, const char *identifier, const char *message, const struct ucred *ucred, const struct timeval *tv) {
struct iovec iovec[5];
char header_priority[6], header_time[64], header_pid[16];
int n = 0;
time_t t;
struct tm *tm;
char *ident_buf = NULL;
assert(s);
assert(priority >= 0);
assert(priority <= 999);
assert(message);
if (LOG_PRI(priority) > s->max_level_syslog)
return;
/* First: priority field */
snprintf(header_priority, sizeof(header_priority), "<%i>", priority);
char_array_0(header_priority);
IOVEC_SET_STRING(iovec[n++], header_priority);
/* Second: timestamp */
t = tv ? tv->tv_sec : ((time_t) (now(CLOCK_REALTIME) / USEC_PER_SEC));
tm = localtime(&t);
if (!tm)
return;
if (strftime(header_time, sizeof(header_time), "%h %e %T ", tm) <= 0)
return;
IOVEC_SET_STRING(iovec[n++], header_time);
/* Third: identifier and PID */
if (ucred) {
if (!identifier) {
get_process_comm(ucred->pid, &ident_buf);
identifier = ident_buf;
}
snprintf(header_pid, sizeof(header_pid), "["PID_FMT"]: ", ucred->pid);
char_array_0(header_pid);
if (identifier)
IOVEC_SET_STRING(iovec[n++], identifier);
IOVEC_SET_STRING(iovec[n++], header_pid);
} else if (identifier) {
IOVEC_SET_STRING(iovec[n++], identifier);
IOVEC_SET_STRING(iovec[n++], ": ");
}
/* Fourth: message */
IOVEC_SET_STRING(iovec[n++], message);
forward_syslog_iovec(s, iovec, n, ucred, tv);
free(ident_buf);
}
int syslog_fixup_facility(int priority) {
if ((priority & LOG_FACMASK) == 0)
return (priority & LOG_PRIMASK) | LOG_USER;
return priority;
}
size_t syslog_parse_identifier(const char **buf, char **identifier, char **pid) {
const char *p;
char *t;
size_t l, e;
assert(buf);
assert(identifier);
assert(pid);
p = *buf;
p += strspn(p, WHITESPACE);
l = strcspn(p, WHITESPACE);
if (l <= 0 ||
p[l-1] != ':')
return 0;
e = l;
l--;
if (p[l-1] == ']') {
size_t k = l-1;
for (;;) {
if (p[k] == '[') {
t = strndup(p+k+1, l-k-2);
if (t)
*pid = t;
l = k;
break;
}
if (k == 0)
break;
k--;
}
}
t = strndup(p, l);
if (t)
*identifier = t;
e += strspn(p + e, WHITESPACE);
*buf = p + e;
return e;
}
void syslog_parse_priority(const char **p, int *priority, bool with_facility) {
int a = 0, b = 0, c = 0;
int k;
assert(p);
assert(*p);
assert(priority);
if ((*p)[0] != '<')
return;
if (!strchr(*p, '>'))
return;
if ((*p)[2] == '>') {
c = undecchar((*p)[1]);
k = 3;
} else if ((*p)[3] == '>') {
b = undecchar((*p)[1]);
c = undecchar((*p)[2]);
k = 4;
} else if ((*p)[4] == '>') {
a = undecchar((*p)[1]);
b = undecchar((*p)[2]);
c = undecchar((*p)[3]);
k = 5;
} else
return;
if (a < 0 || b < 0 || c < 0 ||
(!with_facility && (a || b || c > 7)))
return;
if (with_facility)
*priority = a*100 + b*10 + c;
else
*priority = (*priority & LOG_FACMASK) | c;
*p += k;
}
static void syslog_skip_date(char **buf) {
enum {
LETTER,
SPACE,
NUMBER,
SPACE_OR_NUMBER,
COLON
} sequence[] = {
LETTER, LETTER, LETTER,
SPACE,
SPACE_OR_NUMBER, NUMBER,
SPACE,
SPACE_OR_NUMBER, NUMBER,
COLON,
SPACE_OR_NUMBER, NUMBER,
COLON,
SPACE_OR_NUMBER, NUMBER,
SPACE
};
char *p;
unsigned i;
assert(buf);
assert(*buf);
p = *buf;
for (i = 0; i < ELEMENTSOF(sequence); i++, p++) {
if (!*p)
return;
switch (sequence[i]) {
case SPACE:
if (*p != ' ')
return;
break;
case SPACE_OR_NUMBER:
if (*p == ' ')
break;
/* fall through */
case NUMBER:
if (*p < '0' || *p > '9')
return;
break;
case LETTER:
if (!(*p >= 'A' && *p <= 'Z') &&
!(*p >= 'a' && *p <= 'z'))
return;
break;
case COLON:
if (*p != ':')
return;
break;
}
}
*buf = p;
}
void server_process_syslog_message(
Server *s,
const char *buf,
const struct ucred *ucred,
const struct timeval *tv,
const char *label,
size_t label_len) {
char syslog_priority[sizeof("PRIORITY=") + DECIMAL_STR_MAX(int)],
syslog_facility[sizeof("SYSLOG_FACILITY") + DECIMAL_STR_MAX(int)];
const char *message = NULL, *syslog_identifier = NULL, *syslog_pid = NULL;
struct iovec iovec[N_IOVEC_META_FIELDS + 6];
unsigned n = 0;
int priority = LOG_USER | LOG_INFO;
_cleanup_free_ char *identifier = NULL, *pid = NULL;
const char *orig;
assert(s);
assert(buf);
orig = buf;
syslog_parse_priority(&buf, &priority, true);
if (s->forward_to_syslog)
forward_syslog_raw(s, priority, orig, ucred, tv);
syslog_skip_date((char**) &buf);
syslog_parse_identifier(&buf, &identifier, &pid);
if (s->forward_to_kmsg)
server_forward_kmsg(s, priority, identifier, buf, ucred);
if (s->forward_to_console)
server_forward_console(s, priority, identifier, buf, ucred);
if (s->forward_to_wall)
server_forward_wall(s, priority, identifier, buf, ucred);
IOVEC_SET_STRING(iovec[n++], "_TRANSPORT=syslog");
sprintf(syslog_priority, "PRIORITY=%i", priority & LOG_PRIMASK);
IOVEC_SET_STRING(iovec[n++], syslog_priority);
if (priority & LOG_FACMASK) {
sprintf(syslog_facility, "SYSLOG_FACILITY=%i", LOG_FAC(priority));
IOVEC_SET_STRING(iovec[n++], syslog_facility);
}
if (identifier) {
syslog_identifier = strappenda("SYSLOG_IDENTIFIER=", identifier);
if (syslog_identifier)
IOVEC_SET_STRING(iovec[n++], syslog_identifier);
}
if (pid) {
syslog_pid = strappenda("SYSLOG_PID=", pid);
if (syslog_pid)
IOVEC_SET_STRING(iovec[n++], syslog_pid);
}
message = strappenda("MESSAGE=", buf);
if (message)
IOVEC_SET_STRING(iovec[n++], message);
server_dispatch_message(s, iovec, n, ELEMENTSOF(iovec), ucred, tv, label, label_len, NULL, priority, 0);
}
int server_open_syslog_socket(Server *s) {
static const int one = 1;
int r;
assert(s);
if (s->syslog_fd < 0) {
static const union sockaddr_union sa = {
.un.sun_family = AF_UNIX,
.un.sun_path = "/run/systemd/journal/dev-log",
};
s->syslog_fd = socket(AF_UNIX, SOCK_DGRAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0);
if (s->syslog_fd < 0)
return log_error_errno(errno, "socket() failed: %m");
unlink(sa.un.sun_path);
r = bind(s->syslog_fd, &sa.sa, offsetof(union sockaddr_union, un.sun_path) + strlen(sa.un.sun_path));
if (r < 0)
return log_error_errno(errno, "bind(%s) failed: %m", sa.un.sun_path);
chmod(sa.un.sun_path, 0666);
} else
fd_nonblock(s->syslog_fd, 1);
r = setsockopt(s->syslog_fd, SOL_SOCKET, SO_PASSCRED, &one, sizeof(one));
if (r < 0)
return log_error_errno(errno, "SO_PASSCRED failed: %m");
#ifdef HAVE_SELINUX
if (mac_selinux_use()) {
r = setsockopt(s->syslog_fd, SOL_SOCKET, SO_PASSSEC, &one, sizeof(one));
if (r < 0)
log_warning_errno(errno, "SO_PASSSEC failed: %m");
}
#endif
r = setsockopt(s->syslog_fd, SOL_SOCKET, SO_TIMESTAMP, &one, sizeof(one));
if (r < 0)
return log_error_errno(errno, "SO_TIMESTAMP failed: %m");
r = sd_event_add_io(s->event, &s->syslog_event_source, s->syslog_fd, EPOLLIN, server_process_datagram, s);
if (r < 0)
return log_error_errno(r, "Failed to add syslog server fd to event loop: %m");
return 0;
}
void server_maybe_warn_forward_syslog_missed(Server *s) {
usec_t n;
assert(s);
if (s->n_forward_syslog_missed <= 0)
return;
n = now(CLOCK_MONOTONIC);
if (s->last_warn_forward_syslog_missed + WARN_FORWARD_SYSLOG_MISSED_USEC > n)
return;
server_driver_message(s, SD_MESSAGE_FORWARD_SYSLOG_MISSED, "Forwarding to syslog missed %u messages.", s->n_forward_syslog_missed);
s->n_forward_syslog_missed = 0;
s->last_warn_forward_syslog_missed = n;
}
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