add crypt auth module

Signed-off-by: Mattias Andrée <maandree@operamail.com>

1 files changed, 122 insertions, 0 deletions

diff --git a/src/auth/crypt.c b/src/auth/crypt.c
new file mode 100644
index 0000000..27238e2
--- /dev/null
+++ b/src/auth/crypt.c
@@ -0,0 +1,122 @@
+/**
+ * cerberus – Minimal login program
+ * 
+ * Copyright © 2013  Mattias Andrée (maandree@member.fsf.org)
+ * 
+ * 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 License, 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, see <http://www.gnu.org/licenses/>.
+ */
+#ifndef NO_SHADOW
+# ifndef HAVE_SHADOW
+#  define HAVE_SHADOW
+# endif
+#endif
+
+#define _XOPEN_SOURCE
+#include <unistd.h>
+#include <stdio.h>
+#include <sys/types.h>
+#include <pwd.h>
+#include <string.h>
+#ifdef HAVE_SHADOW
+#include <shadow.h>
+#endif
+
+#include "../config.h"
+
+#include "crypt.h"
+
+
+#if !defined(__USE_SVID) && !defined(__USE_MISC) && !defined(__USE_XOPEN_EXTENDED) 
+#define endpwent()  /* do nothing */
+#endif
+
+
+/**
+ * Function that can be used to read a passphrase from the terminal
+ */
+static char* (*passphrase_reader)(void) = NULL;
+
+/**
+ * The username of the user to log in to
+ */
+static char* login_username;
+
+
+
+/**
+ * Initialise crypt authentication module
+ * 
+ * @param  remote    The remote computer, {@code NULL} for local login
+ * @param  username  The username of the user to log in to
+ * @param  reader    Function that can be used to read a passphrase from the terminal
+ */
+void initialise_crypt(char* remote, char* username, char* (*reader)(void))
+{
+  (void) remote;
+  
+  login_username = username;
+  passphrase_reader = reader;
+}
+
+
+/**
+ * Perform token authentication
+ * 
+ * @return  Whether the user got automatically authenticated
+ */
+char authenticate_crypt(void)
+{
+#ifdef HAVE_SHADOW
+  struct spwd* shadow_entry = NULL;
+#endif
+  struct passwd* passwd_entry = NULL;
+  char* crypted;
+  char* entered;
+  
+#ifdef HAVE_SHADOW
+  shadow_entry = getspnam(login_username);
+  endspent();
+  
+  if (shadow_entry)
+    crypted = shadow_entry->sp_pwdp;
+  else
+    {
+#endif
+      passwd_entry = getpwnam(login_username);
+      if (passwd_entry)
+	crypted = passwd_entry->pw_passwd;
+      else
+	{
+	  perror("getpwnam");
+	  endpwent();
+	  sleep(ERROR_SLEEP);
+	  _exit(1);
+	}
+      endpwent();
+#ifdef HAVE_SHADOW
+    }
+#endif
+  
+  if (!(crypted && *crypted)) /* empty means that no passphrase is required (not even Enter) */
+    return 1;
+  
+  entered = crypt(passphrase_reader(), crypted /* salt argument stops parsing when encrypted begins */);
+  if (entered && !strcmp(entered, crypted))
+    return 0;
+  
+  printf("Incorrect passphrase\n");
+  sleep(FAILURE_SLEEP);
+  _exit(1);
+}
+