crp@ccivax.UUCP (Chuck Privitera) (03/28/85)
Index: /usr/src/lib/libc/gen/syslog.c 4.2BSD +FIX
Description:
The syslog subroutine in the C library does not handle
printf format specifications correctly. The syslog subroutine
that sendmail uses (/usr/src/usr.lib/sendmail/lib/syslog.c)
does. Messages handed to syslog that contain printf format
specifications will not be printed in the system log(s).
Repeat-By:
Try this simple test program:
#include <syslog.h>
main()
{
int i;
/*
* None of the following will be added to
* the system log(s).
*/
for(i = 1; i < 10; i++)
syslog(i, "Test message %d", i);
syslog(LOG_INFO, "But this will be added");
}
Fix:
The problem is that syslog looks for format specifications
so it can handle %m which means interpolate the system error
message for the current value of errno. It handles %m allright,
but %AnythingElse fails because after copying in the format
specification it adds a '\0' to terminate the line and then
increments the pointer PAST the null terminator. Thus you
have a null byte in your message. This would be fine if
the syslog daemon didn't throw out messages that don't
have a newline at the end of them. The fix is simple,
you can either simply delete the addition of the null
terminator, or don't increment the pointer after adding
the null terminator. The addition of the null terminator
is just a remnant of an older version of syslog that handled
the % special case with a switch and upon falling out of
the switch did ptr += strlen(ptr). It no longer gets to
that line for printf format specifications. Here is a
visual aid for the two character fix:
diff old new
73c73
< *b++ = '%', *b++ = c, *b++ = '\0';
---
> *b++ = '%', *b++ = c, *b = '\0';