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.Dd August 6, 1997
.Dt KRB5_OPENLOG 3
.Os HEIMDAL
.Sh NAME
.Nm krb5_initlog ,
.Nm krb5_openlog ,
.Nm krb5_closelog ,
.Nm krb5_addlog_dest ,
.Nm krb5_addlog_func ,
.Nm krb5_log ,
.Nm krb5_vlog ,
.Nm krb5_log_msg ,
.Nm krb5_vlog_msg
.Nd Heimdal logging functions
.Sh LIBRARY
Kerberos 5 Library (libkrb5, -lkrb5)
.Sh SYNOPSIS
.In krb5.h
.Ft "typedef void"
.Fn "\*(lp*krb5_log_log_func_t\*(rp" "const char *time" "const char *message" "void *data"
.Ft "typedef void"
.Fn "\*(lp*krb5_log_close_func_t\*(rp" "void *data"
.Ft krb5_error_code
.Fn krb5_addlog_dest "krb5_context context" "krb5_log_facility *facility" "const char *destination"
.Ft krb5_error_code
.Fn krb5_addlog_func "krb5_context context" "krb5_log_facility *facility" "int min" "int max" "krb5_log_log_func_t log" "krb5_log_close_func_t close" "void *data"
.Ft krb5_error_code
.Fn krb5_closelog "krb5_context context" "krb5_log_facility *facility"
.Ft krb5_error_code
.Fn krb5_initlog "krb5_context context" "const char *program" "krb5_log_facility **facility"
.Ft krb5_error_code
.Fn krb5_log "krb5_context context" "krb5_log_facility *facility" "int level" "const char *format" "..."
.Ft krb5_error_code
.Fn krb5_log_msg "krb5_context context" "krb5_log_facility *facility" "char **reply" "int level" "const char *format" "..."
.Ft krb5_error_code
.Fn krb5_openlog "krb5_context context" "const char *program" "krb5_log_facility **facility"
.Ft krb5_error_code
.Fn krb5_vlog "krb5_context context" "krb5_log_facility *facility" "int level" "const char *format" "va_list arglist"
.Ft krb5_error_code
.Fn krb5_vlog_msg "krb5_context context" "krb5_log_facility *facility" "char **reply" "int level" "const char *format" "va_list arglist"
.Sh DESCRIPTION
These functions logs messages to one or more destinations.
.Pp
The
.Fn krb5_openlog
function creates a logging
.Fa facility ,
that is used to log messages. A facility consists of one or more
destinations (which can be files or syslog or some other device). The
.Fa program
parameter should be the generic name of the program that is doing the
logging. This name is used to lookup which destinations to use. This
information is contained in the
.Li logging
section of the
.Pa krb5.conf
configuration file.  If no entry is found for
.Fa program ,
the entry for
.Li default
is used, or if that is missing too,
.Li SYSLOG
will be used as destination.
.Pp
To close a logging facility, use the
.Fn krb5_closelog
function.
.Pp
To log a message to a facility use one of the functions
.Fn krb5_log ,
.Fn krb5_log_msg ,
.Fn krb5_vlog ,
or
.Fn krb5_vlog_msg .
The functions ending in
.Li _msg
return in
.Fa reply
a pointer to the message that just got logged. This string is allocated,
and should be freed with
.Fn free .
The
.Fa format
is a standard
.Fn printf
style format string (but see the BUGS section).
.Pp
If you want better control of where things gets logged, you can instead of using
.Fn krb5_openlog
call
.Fn krb5_initlog ,
which just initializes a facility, but doesn't define any actual logging
destinations. You can then add destinations with the
.Fn krb5_addlog_dest
and
.Fn krb5_addlog_func
functions.  The first of these takes a string specifying a logging
destination, and adds this to the facility. If you want to do some
non-standard logging you can use the
.Fn krb5_addlog_func
function, which takes a function to use when logging.
The
.Fa log
function is called for each message with
.Fa time
being a string specifying the current time, and
.Fa message
the message to log.
.Fa close
is called when the facility is closed. You can pass application specific data in the
.Fa data
parameter. The
.Fa min
and
.Fa max
parameter are the same as in a destination (defined below). To specify a
max of infinity, pass -1.
.Pp
.Fn krb5_openlog
calls
.Fn krb5_initlog
and then calls
.Fn krb5_addlog_dest
for each destination found.
.Ss Destinations
The defined destinations (as specified in
.Pa krb5.conf )
follows:
.Bl -tag -width "xxx" -offset indent
.It Li STDERR
This logs to the program's stderr.
.It Li EFILE: Ns Pa /file
Log to the specified file if it exists, otherwise do nothing.
All writes will be appended to the end of the file and the file
will be re-opened for each new write.
Non-existence of the file is cached for 1 second which reduces
the potential performance impact significantly.
This is useful for defining a trace file which can be enabled
without restarting a server.
.It Li FILE: Ns Pa /file
Log to the specified file.
All writes will be appended to the end of the file and the file
will be re-opened for each new write.
.It Li FILE= Ns Pa /file
On the first write, this form will
.Xr truncate 2
the file and then append all subsequent messages whilst keeping the
file descriptor open.
This form is mainly for compatibility with MIT libkrb5.
.It Li DEVICE= Ns Pa /device
This logs to the specified device, at present this is the same as
.Li FILE:/device .
.It Li CONSOLE
Log to the console, this is the same as
.Li DEVICE=/dev/console .
.It Li SYSLOG Ns Op :priority Ns Op :facility
Send messages to the syslog system, using priority, and facility. To
get the name for one of these, you take the name of the macro passed
to
.Xr syslog 3 ,
and remove the leading
.Li LOG_
.No ( Li LOG_NOTICE
becomes
.Li NOTICE ) .
The default values (as well as the values used for unrecognised
values), are
.Li ERR ,
and
.Li AUTH ,
respectively.  See
.Xr syslog 3
for a list of priorities and facilities.
.El
.Pp
Each destination may optionally be prepended with a range of logging
levels, specified as
.Li min-max/ .
If the
.Fa level
parameter to
.Fn krb5_log
is within this range (inclusive) the message gets logged to this
destination, otherwise not. Either of the min and max valued may be
omitted, in this case min is assumed to be 0, and max is assumed to
be 3.
If you don't include a dash, both min and max get set to the
specified value.
.Pp
The paths specified are subject to token expansion.
For the purposes of logging, the most interesting token
expansion is
.ar %{strftime:<string>}
which calls
.Xr strftime 3
on
.Ar <string>
with the localised current time of day.
.Ss Levels
Each log message has a level as follows:
.Bl -tag -width "xxx" -offset indent
.It 0
Critical conditions.
This is a condition that should be corrected immediately, such as a
corrupted Kerberos database.
.It 1
Errors.
These are errors that occur in the normal processing of requests.
.It 2
Warning messages.
On the KDC, this includes malformed requests and requests that
are out of policy.
.It 3
Informational messages.
.It 4-6
Debugging messages with increasing obscurity as the level rises.
.It 7
Tracing messages.
These messages may be high volume and are likely to impact
performance significantly.
Notably, tracing messages may be emitted whilst locks are held.
.El
.Sh EXAMPLES
.Bd -literal -offset indent
[logging]
	kdc = 0/FILE:/var/log/kdc.log
	kdc = 1-/SYSLOG:INFO:USER
	default = STDERR
.Ed
.Pp
This will log all messages from the
.Nm kdc
program with level 0 to
.Pa /var/log/kdc.log ,
other messages will be logged to syslog with priority
.Li LOG_INFO ,
and facility
.Li LOG_USER .
.Bd -literal -offset indent
[logging]
	kdc = FILE:/var/log/kdc-%{strftime:%Y%m%d%H}
	kdc = 4-/EFILE:/tmp/kdc-trace
.Ed
.Pp
This will log all messages from the
.Nm kdc
program with level 0 to 3 (inclusively) to a file whose
name is generated using
.Xr strftime 3 .
As the file is
.Xr open 2 ed
each time a log message is written, this can be used to write
automatically rotating log files.
All of the KDC debugging messages will be written into
.Pa /tmp/kdc-trace
but only if it exists.
.Sh SEE ALSO
.Xr syslog 3 ,
.Xr krb5.conf 5
.Sh BUGS
These functions use
.Fn asprintf
to format the message. If your operating system does not have a working
.Fn asprintf ,
a replacement will be used. At present this replacement does not handle
some correct conversion specifications (like floating point numbers). Until
this is fixed, the use of these conversions should be avoided.
.Pp
If logging is done to the syslog facility, these functions might not be
thread-safe, depending on the implementation of
.Fn openlog ,
and
.Fn syslog .