daemon: emulate fgetpwent() if we don't have it

We use fgetpwent directly on /etc/passwd in order to ensure we only get
a list of local users (and not ones from the network directory service).
Unfortunately, this function is not commonly found on non-GNU systems.

Provide our own implementation of fgetpwent if the operating system does
not provide it.

https://bugs.freedesktop.org/show_bug.cgi?id=41747

4 files changed, 118 insertions, 0 deletions

diff --git a/configure.ac b/configure.ac
index 39c5b92..ee9dbcb 100644
--- a/configure.ac
+++ b/configure.ac
@@ -187,6 +187,8 @@ AC_SUBST(WARN_CFLAGS)
 
 AC_CHECK_HEADERS([shadow.h utmpx.h])
 
+AC_CHECK_FUNCS([fgetpwent])
+
 dnl ---------------------------------------------------------------------------
 dnl - gtk-doc Documentation
 dnl ---------------------------------------------------------------------------
diff --git a/src/Makefile.am b/src/Makefile.am
index 6940f2d..30e5c8a 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -47,6 +47,10 @@ accounts_daemon_LDADD = 	\
 	libaccounts-generated.la	\
 	$(POLKIT_LIBS)
 
+EXTRA_DIST = \
+	fgetpwent.c	\
+	$(NULL)
+
 CLEANFILES = \
 	$(BUILT_SOURCES) \
 	*.gcda \
diff --git a/src/daemon.c b/src/daemon.c
index cb36f01..233f374 100644
--- a/src/daemon.c
+++ b/src/daemon.c
@@ -162,6 +162,10 @@ user_previous_login_free (UserPreviousLogin *previous_login)
         g_free (previous_login);
 }
 
+#ifndef HAVE_FGETPWENT
+#include "fgetpwent.c"
+#endif
+
 static struct passwd *
 entry_generator_wtmp (GHashTable *users,
                       gpointer   *state)
diff --git a/src/fgetpwent.c b/src/fgetpwent.c
new file mode 100644
index 0000000..3a2d77c
--- /dev/null
+++ b/src/fgetpwent.c
@@ -0,0 +1,108 @@
+/*
+ * Copyright (C) 2013 Canonical Limited
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3 of the licence, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+ *
+ * Authors: Ryan Lortie <desrt@desrt.ca>
+ */
+
+static gchar *
+fgetpwent_getline (FILE *fp)
+{
+  static GString str;
+
+  /* We could be "more clever" here and avoid the strlen() but this is a
+   * clear case of dumb is better.
+   */
+  str.len = 0;
+  while (!str.len || str.str[str.len - 1] != '\n')
+    {
+      if (str.allocated_len < str.len + 32)
+        {
+          str.allocated_len = str.len + 32;
+          str.str = g_realloc (str.str, str.allocated_len);
+        }
+
+      if (fgets (str.str + str.len, str.allocated_len - str.len, fp) == NULL)
+        return NULL;
+
+      str.len = strlen (str.str + str.len) + str.len;
+    }
+
+  /* chomp the '\n' */
+  str.str[str.len - 1] = '\0';
+
+  return str.str;
+}
+
+static struct passwd *
+fgetpwent (FILE *fp)
+{
+  static struct passwd pw;
+  guint64 intval;
+  gchar *line;
+
+  /* In case of failure, we ignore the line and start again */
+again:
+  line = fgetpwent_getline (fp);
+  if (!line)
+    return NULL;
+
+  while (g_ascii_isspace (*line))
+    line++;
+
+  /* comments, empty lines */
+  if (line[0] == '#' || line[0] == '\0')
+    goto again;
+
+  /* username */
+  pw.pw_name = line;
+  if (!(line = strchr (line, ':')))
+    goto again;
+  *line++ = '\0';
+
+  /* password */
+  pw.pw_passwd = line;
+  if (!(line = strchr (line, ':')))
+    goto again;
+  *line++ = '\0';
+
+  /* uid */
+  pw.pw_uid = intval = g_ascii_strtoull (line, &line, 10);
+  if (pw.pw_uid != intval || *line++ != ':')
+    goto again;
+
+  /* gid */
+  pw.pw_gid = intval = g_ascii_strtoull (line, &line, 10);
+  if (pw.pw_gid != intval || *line++ != ':')
+    goto again;
+
+  /* gecos */
+  pw.pw_gecos = line;
+  if (!(line = strchr (line, ':')))
+    goto again;
+  *line++ = '\0';
+
+  /* home directory */
+  pw.pw_dir = line;
+  if (!(line = strchr (line, ':')))
+    goto again;
+  *line++ = '\0';
+
+  /* shell */
+  pw.pw_shell = line;
+
+  return &pw;
+}