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journal: store the original timestamp as SYSLOG_TIMESTAMP=

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This is useful if someone wants to recreate the original syslog datagram. We
already include timestamp information as _SOURCE_REALTIME_TIMESTAMP=, and in
normal use that timestamp, converted back to the form used by syslog
(Mth dd HH:MM:SS) would usually give the value. But there are various
circumstances where this might not be true. Most obviously, if the datagram is
sent a bit later after being prepared, the time is rounded to the nearest
second, and it might be off. This is especially bad around New Year when the
syslog timestamp wraps around. Then the same timezone and locale need to be
used to recreate the original timestamp. In the end doing this reliably is
complicated, and it seems much easier to just unconditionally include the
original timestamp.

If the original timestamp cannot be located, we store the full log line.
This way, it should be always possible to recreate the original input.

Example:
MESSAGE=x
SYSLOG_TIMESTAMP=Sep 15 15:07:58
SYSLOG_RAW
^]^@^@^@^@^@^@^@<13>Sep 15 15:07:58 HOST: x^@y
_PID=3318
_SOURCE_REALTIME_TIMESTAMP=1530743976393553

Fixes #2398.
This commit is contained in:
Zbigniew Jędrzejewski-Szmek 2018-07-05 00:17:55 +02:00
parent 855a86a349
commit 7c30c3c44f
2 changed files with 50 additions and 36 deletions
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23
man/systemd.journal-fields.xml
View File

@ -103,13 +103,13 @@
<term><varname>SYSLOG_FACILITY=</varname></term>
<term><varname>SYSLOG_IDENTIFIER=</varname></term>
<term><varname>SYSLOG_PID=</varname></term>
<term><varname>SYSLOG_TIMESTAMP=</varname></term>
<listitem>
<para>Syslog compatibility fields containing the facility
(formatted as decimal string), the identifier string (i.e.
"tag"), and the client PID. (Note that the tag is usually
derived from glibc's
<varname>program_invocation_short_name</varname> variable,
see
<para>Syslog compatibility fields containing the facility (formatted as
decimal string), the identifier string (i.e. "tag"), the client PID, and
the timestamp as specified in the original datagram. (Note that the tag is
usually derived from glibc's
<varname>program_invocation_short_name</varname> variable, see
<citerefentry project='die-net'><refentrytitle>program_invocation_short_name</refentrytitle><manvolnum>3</manvolnum></citerefentry>.)</para>
</listitem>
</varlistentry>
@ -119,14 +119,17 @@
<listitem>
<para>The original contents of the syslog line as received in the syslog
datagram. This field is only included if the <varname>MESSAGE=</varname>
field was modified compared to the original payload. This happens when the
message contains leading or trailing whitespace (trailing and leading
field was modified compared to the original payload or the timestamp could
not be located properly and is not included in
<varname>SYSLOG_TIMESTAMP=</varname>. Message truncation occurs when when
the message contains leading or trailing whitespace (trailing and leading
whitespace is stripped), or it contains an embedded
<constant>NUL</constant> byte (the <constant>NUL</constant> byte and
anything after it is not included). Thus, the original syslog line is
either stored as <varname>SYSLOG_RAW=</varname> or it can be recreated
based on the stored priority, timestamp, hostname, and the message payload
stored in <varname>MESSAGE=</varname>.</para>
based on the stored priority and facility, timestamp, identifier, and the
message payload in <varname>MESSAGE=</varname>.
</para>
</listitem>
</varlistentry>
</variablelist>

63
src/journal/journald-syslog.c
View File

@ -225,7 +225,7 @@ size_t syslog_parse_identifier(const char **buf, char **identifier, char **pid)
return e;
}
static void syslog_skip_date(const char **buf) {
static int syslog_skip_timestamp(const char **buf) {
enum {
LETTER,
SPACE,
@ -245,24 +245,21 @@ static void syslog_skip_date(const char **buf) {
SPACE
};
const char *p;
const char *p, *t;
unsigned i;
assert(buf);
assert(*buf);
p = *buf;
for (i = 0; i < ELEMENTSOF(sequence); i++, p++) {
for (i = 0, p = *buf; i < ELEMENTSOF(sequence); i++, p++) {
if (!*p)
return;
return 0;
switch (sequence[i]) {
case SPACE:
if (*p != ' ')
return;
return 0;
break;
case SPACE_OR_NUMBER:
@ -272,26 +269,28 @@ static void syslog_skip_date(const char **buf) {
_fallthrough_;
case NUMBER:
if (*p < '0' || *p > '9')
return;
return 0;
break;
case LETTER:
if (!(*p >= 'A' && *p <= 'Z') &&
!(*p >= 'a' && *p <= 'z'))
return;
return 0;
break;
case COLON:
if (*p != ':')
return;
return 0;
break;
}
}
t = *buf;
*buf = p;
return p - t;
}
void server_process_syslog_message(
@ -303,14 +302,14 @@ void server_process_syslog_message(
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, *msg;
char *t, syslog_priority[sizeof("PRIORITY=") + DECIMAL_STR_MAX(int)],
syslog_facility[sizeof("SYSLOG_FACILITY=") + DECIMAL_STR_MAX(int)];
const char *msg, *syslog_ts, *a;
_cleanup_free_ char *identifier = NULL, *pid = NULL;
int priority = LOG_USER | LOG_INFO, r;
ClientContext *context = NULL;
struct iovec *iovec;
size_t n = 0, m, i, leading_ws;
size_t n = 0, m, i, leading_ws, syslog_ts_len;
bool store_raw;
assert(s);
@ -339,8 +338,6 @@ void server_process_syslog_message(
/* Nice! No need to strip anything on the end, let's optimize this a bit */
msg = buf + leading_ws;
else {
char *t;
msg = t = newa(char, i - leading_ws + 1);
memcpy(t, buf + leading_ws, i - leading_ws);
t[i - leading_ws] = 0;
@ -355,7 +352,12 @@ void server_process_syslog_message(
if (!client_context_test_priority(context, priority))
return;
syslog_skip_date(&msg);
syslog_ts = msg;
syslog_ts_len = syslog_skip_timestamp(&msg);
if (syslog_ts_len == 0)
/* We failed to parse the full timestamp, store the raw message too */
store_raw = true;
syslog_parse_identifier(&msg, &identifier, &pid);
if (s->forward_to_syslog)
@ -370,7 +372,7 @@ void server_process_syslog_message(
if (s->forward_to_wall)
server_forward_wall(s, priority, identifier, msg, ucred);
m = N_IOVEC_META_FIELDS + 7 + client_context_extra_fields_n_iovec(context);
m = N_IOVEC_META_FIELDS + 8 + client_context_extra_fields_n_iovec(context);
iovec = newa(struct iovec, m);
iovec[n++] = IOVEC_MAKE_STRING("_TRANSPORT=syslog");
@ -384,21 +386,30 @@ void server_process_syslog_message(
}
if (identifier) {
syslog_identifier = strjoina("SYSLOG_IDENTIFIER=", identifier);
iovec[n++] = IOVEC_MAKE_STRING(syslog_identifier);
a = strjoina("SYSLOG_IDENTIFIER=", identifier);
iovec[n++] = IOVEC_MAKE_STRING(a);
}
if (pid) {
syslog_pid = strjoina("SYSLOG_PID=", pid);
iovec[n++] = IOVEC_MAKE_STRING(syslog_pid);
a = strjoina("SYSLOG_PID=", pid);
iovec[n++] = IOVEC_MAKE_STRING(a);
}
message = strjoina("MESSAGE=", msg);
iovec[n++] = IOVEC_MAKE_STRING(message);
if (syslog_ts_len > 0) {
const size_t hlen = strlen("SYSLOG_TIMESTAMP=");
t = newa(char, hlen + raw_len);
memcpy(t, "SYSLOG_TIMESTAMP=", hlen);
memcpy(t + hlen, syslog_ts, syslog_ts_len);
iovec[n++] = IOVEC_MAKE(t, hlen + syslog_ts_len);
}
a = strjoina("MESSAGE=", msg);
iovec[n++] = IOVEC_MAKE_STRING(a);
if (store_raw) {
const size_t hlen = strlen("SYSLOG_RAW=");
char *t;
t = newa(char, hlen + raw_len);
memcpy(t, "SYSLOG_RAW=", hlen);