Patch to musl to provide wtmp for Linux PAM

[Raphael Cohn <raphael.cohn@stormmq.com>]

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I've drafted a patch for musl which I'm using to get Linux-PAM to compile.

This patch:-
- defines _PATH_LASTLOG;
- uses macros in the utmpx struct for documentary value;
- adds an implementation of logwtmp
- alters _PATH_*TMP

It's probably not suitable for inclusion in musl mainline as it stands
(especially the last part) - but hopefully it'll be useful to others. It's
also quick and dirty, and so may be just plain wrong.

By the way, are there any plans to support writing to lastlog / wtmp / etc?
If not, I might create a private patch to redirect the writes to syslog. In
my view, this is where information like this belongs...

diff -N -u -r musl-0.9.14.orig/include/utmp.h musl-0.9.14/include/utmp.h
--- musl-0.9.14.orig/include/utmp.h    2013-09-23 22:01:11.000000000 +0100
+++ musl-0.9.14/include/utmp.h    2013-12-04 10:34:43.000000000 +0000
@@ -7,10 +7,6 @@

 #include <utmpx.h>

-#define ACCOUNTING 9
-#define UT_NAMESIZE 32
-#define UT_HOSTSIZE 256
-
 struct lastlog {
     time_t ll_time;
     char ll_line[UT_LINESIZE];
@@ -32,8 +28,11 @@

 void updwtmp(const char *, const struct utmp *);

-#define _PATH_UTMP "/dev/null/utmp"
-#define _PATH_WTMP "/dev/null/wtmp"
+void logwtmp(const char *, const char *, const char *);
+
+#define _PATH_UTMP "/var/run/utmp"
+#define _PATH_WTMP "/var/log/wtmp"
+#define _PATH_LASTLOG "/var/log/lastlog"

 #define UTMP_FILE _PATH_UTMP
 #define WTMP_FILE _PATH_WTMP
diff -N -u -r musl-0.9.14.orig/include/utmpx.h musl-0.9.14/include/utmpx.h
--- musl-0.9.14.orig/include/utmpx.h    2013-09-23 22:01:11.000000000 +0100
+++ musl-0.9.14/include/utmpx.h    2013-12-04 10:32:20.000000000 +0000
@@ -13,6 +13,8 @@
 #include <bits/alltypes.h>

 #define UT_LINESIZE 32
+#define UT_NAMESIZE 32
+#define UT_HOSTSIZE 256

 struct utmpx
 {
@@ -20,8 +22,8 @@
     pid_t ut_pid;
     char ut_line[UT_LINESIZE];
     char ut_id[4];
-    char ut_user[32];
-    char ut_host[256];
+    char ut_user[UT_NAMESIZE];
+    char ut_host[UT_HOSTSIZE];
     struct {
         short e_termination;
         short e_exit;
@@ -50,6 +52,7 @@
 #define LOGIN_PROCESS   6
 #define USER_PROCESS    7
 #define DEAD_PROCESS    8
+#define ACCOUNTING      9

 #ifdef __cplusplus
 }
diff -N -u -r musl-0.9.14.orig/src/legacy/utmp.c
musl-0.9.14/src/legacy/utmp.c
--- musl-0.9.14.orig/src/legacy/utmp.c    1970-01-01 01:00:00.000000000
+0100
+++ musl-0.9.14/src/legacy/utmp.c    2013-12-04 14:25:40.000000000 +0000
@@ -0,0 +1,20 @@
+#include <utmp.h>
+#include <string.h>
+#include <unistd.h>
+#include <sys/time.h>
+#include "libc.h"
+
+void logwtmp(const char * line, const char * name, const char * host)
+{
+    struct utmp u;
+    memset(&u, 0, sizeof(u));
+
+    u.ut_pid = getpid();
+    u.ut_type = name[0] ? USER_PROCESS : DEAD_PROCESS;
+    strncpy(u.ut_line, line, sizeof(u.ut_line));
+    strncpy(u.ut_name, name, sizeof(u.ut_name));
+    strncpy(u.ut_host, host, sizeof(u.ut_host));
+    gettimeofday(&(u.ut_tv), NULL);
+
+    updwtmp(_PATH_WTMP, &u);
+}

Raph

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