2 files changed, 94 insertions, 0 deletions

diff --git a/libbb/Kbuild b/libbb/Kbuild
index 4606d5aa7..1b11d5d39 100644
--- a/libbb/Kbuild
+++ b/libbb/Kbuild
@@ -120,6 +120,8 @@ lib-y += xgethostbyname.o
 lib-y += xreadlink.o
 lib-y += xrealloc_vector.o
 
+lib-$(CONFIG_FEATURE_UTMP) += utmp.o
+
 # A mix of optimizations (why build stuff we know won't be used)
 # and objects which may fail to build (SELinux on selinux-less system)
 lib-$(CONFIG_SELINUX) += selinux_common.o
diff --git a/libbb/utmp.c b/libbb/utmp.c
new file mode 100644
index 000000000..06b939b9d
--- /dev/null
+++ b/libbb/utmp.c
@@ -0,0 +1,92 @@
+/* vi: set sw=4 ts=4: */
+/*
+ * utmp/wtmp support routines.
+ *
+ * Copyright (C) 2010 Denys Vlasenko
+ *
+ * Licensed under GPL version 2, see file LICENSE in this tarball for details.
+ */
+#include "libbb.h"
+#include <utmp.h>
+
+static void touch(const char *filename)
+{
+        if (access(filename, R_OK | W_OK) == -1)
+                close(open(filename, O_WRONLY | O_CREAT, 0664));
+}
+
+/*
+ * Read "man utmp" to make sense out of it.
+ */
+void FAST_FUNC update_utmp(int new_type, const char *short_tty, const char *username, const char *opt_host)
+{
+        struct utmp utent;
+        struct utmp *ut;
+        pid_t pid;
+
+        touch(_PATH_UTMP);
+        utmpname(_PATH_UTMP);
+        setutent();
+
+        pid = getpid();
+        /* Did init/getty/telnetd/sshd/... create an entry for us?
+         * It should be (new_type-1), but we'd also reuse
+         * any other potentially stale xxx_PROCESS entry */
+        while ((ut = getutent()) != NULL) {
+                if (ut->ut_pid == pid
+                // && ut->ut_line[0]
+                 && ut->ut_id[0] /* must have nonzero id */
+                 && (  ut->ut_type == INIT_PROCESS
+                    || ut->ut_type == LOGIN_PROCESS
+                    || ut->ut_type == USER_PROCESS
+                    || ut->ut_type == DEAD_PROCESS
+                    )
+                ) {
+                        utent = *ut; /* struct copy */
+                        if (ut->ut_type >= new_type) {
+                                /* Stale record. Nuke hostname */
+                                memset(utent.ut_host, 0, sizeof(utent.ut_host));
+                        }
+                        /* NB: pututline (see later) searches for matching utent
+                         * using getutid(utent) - we must not change ut_id
+                         * if we want *exactly this* record to be overwritten!
+                         */
+                        break;
+                }
+        }
+        endutent();
+
+        if (!ut) {
+                /* Didn't find anything, create new one */
+                memset(&utent, 0, sizeof(utent));
+                utent.ut_pid = pid;
+                /* Invent our own ut_id. ut_id is only 4 chars wide.
+                 * Try to fit something remotely meaningful... */
+                if (short_tty[0] == 'p') {
+                        /* if "ptyXXX", map to "pXXX" */
+                        /* if "pts/XX", map to "p/XX" */
+                        utent.ut_id[0] = 'p';
+                        strncpy(utent.ut_id + 1, short_tty + 3, sizeof(utent.ut_id)-1);
+                } else {
+                        /* assuming it's "ttyXXXX", map to "XXXX" */
+                        strncpy(utent.ut_id, short_tty + 3, sizeof(utent.ut_id));
+                }
+        }
+
+        utent.ut_type = new_type;
+        safe_strncpy(utent.ut_line, short_tty, sizeof(utent.ut_line));
+        safe_strncpy(utent.ut_user, username, sizeof(utent.ut_user));
+        if (opt_host)
+                safe_strncpy(utent.ut_host, opt_host, sizeof(utent.ut_host));
+        utent.ut_tv.tv_sec = time(NULL);
+
+        /* Update, or append new one */
+        setutent();
+        pututline(&utent);
+        endutent();
+
+#if ENABLE_FEATURE_WTMP
+        touch(bb_path_wtmp_file);
+        updwtmp(bb_path_wtmp_file, &utent);
+#endif
+}