first commit

Signed-off-by: Sjoerd Simons <sjoerd.simons@collabora.co.uk>

meson.build

+project('libnss-unknown',
+        'c',
+        version: '0.0.1')
+
+sources = [ 'src/nss-unknown.c' ]
+shared_library('nss_unknown', sources, soversion: '2', install: true)

src/nss-unknown.c

+/* SPDX-License-Identifier: LGPL-2.1+ */
+
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <sys/types.h>
+
+
+#include <nss.h>
+#include <pwd.h>
+#include <stddef.h>
+
+#define UNKNOWN_USER_GECOS "Unknown user"
+#define UNKNOWN_USER_PASSWD "*"
+#define UNKNOWN_USER_DIR "/"
+#define UNKNOWN_USER_SHELL "/sbin/nologin"
+
+#define NOGROUP 65534
+
+#define UNKNOWN_FORMAT "uid-%d"
+
+static char * determine_homedir (uid_t uid, char *buffer, size_t buflen)
+{
+  char *home;
+
+  if (uid != getuid())
+    return UNKNOWN_USER_DIR;
+
+  home = getenv ("HOME");
+  if (home == NULL)
+    return UNKNOWN_USER_DIR;
+
+  strncpy (buffer, home, buflen);
+  return buffer;
+}
+
+enum nss_status _nss_unknown_getpwnam_r (const char *name,
+                                        struct passwd *pwd,
+                                        char *buffer,
+                                        size_t buflen,
+                                        int *errnop)
+{
+  uid_t uid = 0;
+  size_t n;
+
+  if (sscanf (name, UNKNOWN_FORMAT, &uid) != 1)
+    return NSS_STATUS_NOTFOUND;
+
+  strncpy (buffer, name, buflen);
+
+  pwd->pw_name = buffer;
+
+  n = strlen (name) + 1;
+  buffer += n;
+  buflen -= n;
+  pwd->pw_dir = determine_homedir (uid, buffer, buflen);
+
+  pwd->pw_uid = uid;
+  pwd->pw_gid = NOGROUP;
+  pwd->pw_gecos = UNKNOWN_USER_GECOS;
+  pwd->pw_passwd = UNKNOWN_USER_PASSWD;
+  pwd->pw_shell = UNKNOWN_USER_SHELL;
+
+  return NSS_STATUS_SUCCESS;
+}
+
+enum nss_status _nss_unknown_getpwuid_r (uid_t uid,
+                                         struct passwd *pwd,
+                                         char *buffer,
+                                         size_t buflen,
+                                         int *errnop)
+{
+  size_t n;
+
+  snprintf (buffer, buflen, UNKNOWN_FORMAT, uid);
+
+  pwd->pw_name = buffer;
+
+  n = strlen (buffer) + 1;
+  buffer += n;
+  buflen -= n;
+  pwd->pw_dir = determine_homedir (uid, buffer, buflen);
+
+  pwd->pw_uid = uid;
+  pwd->pw_gid = NOGROUP;
+  pwd->pw_gecos = UNKNOWN_USER_GECOS;
+  pwd->pw_passwd = UNKNOWN_USER_PASSWD;
+  pwd->pw_shell = UNKNOWN_USER_SHELL;
+
+	return NSS_STATUS_SUCCESS;
+}