From: mdw <mdw>
Date: Tue, 20 Apr 1999 00:19:03 +0000 (+0000)
Subject: Initial revision
X-Git-Tag: 1.0.0~10
X-Git-Url: https://git.distorted.org.uk/~mdw/shells/commitdiff_plain/ed36b0a2916c0fe31f7d0779ea758c358db85fc2

Initial revision
---

ed36b0a2916c0fe31f7d0779ea758c358db85fc2
diff --git a/.links b/.links
new file mode 100644
index 0000000..10f134c
--- /dev/null
+++ b/.links
@@ -0,0 +1,4 @@
+COPYING
+install-sh
+missing
+mkinstalldirs
diff --git a/Makefile.am b/Makefile.am
new file mode 100644
index 0000000..f416313
--- /dev/null
+++ b/Makefile.am
@@ -0,0 +1,14 @@
+AUTOMAKE_OPTIONS = foreign
+
+bin_PROGRAMS = banned chrootsh ushell
+man_MANS = banned.8 chrootsh.8 ushell.1
+
+INCLUDES = \
+	-DCHROOTSH_PATH=\"${bindir}/`echo chrootsh|sed '${transform}'`\"
+
+EXTRA_DIST = $(man_MANS)
+
+install-exec-hook:
+	chrootsh_prog="${bindir}/`echo chrootsh|sed '${transform}'`"; \
+	chown root $${chrootsh_prog}; \
+	chmod 4755 $${chrootsh_prog}
diff --git a/banned.8 b/banned.8
new file mode 100644
index 0000000..b8381bc
--- /dev/null
+++ b/banned.8
@@ -0,0 +1,36 @@
+.TH banned 8 "20 April 1999" "Local tools"
+.SH NAME
+banned \- tells a user that he's banned
+.SH SYNOPSIS
+.B banned
+.SH USAGE
+Set a user's shell to the
+.B banned
+program's path, and put a file
+.B .banned
+in his or her home directory (owned by
+.B root
+by preference).  When the user logs in, he or she will be told to go
+away, given the explanation from the
+.B .banned
+file, and logged out again.  An entry is also made in the system logs,
+using the
+.B LOG_AUTH
+facility.
+.PP
+Don't put
+.B banned
+in the
+.B /etc/shells
+file!
+.SH FILES
+.TP 5
+.B .banned
+An explanation given to a user to explain why he or she should go away.
+.SH BUGS
+None planned.
+.SEE ALSO
+.BR chrootsh (8),
+.BR ushell (1).
+.SH AUTHOR
+Mark Wooding (mdw@nsict.org)
diff --git a/banned.c b/banned.c
new file mode 100644
index 0000000..2fa3565
--- /dev/null
+++ b/banned.c
@@ -0,0 +1,120 @@
+/* -*-c-*-
+ *
+ * $Id: banned.c,v 1.1 1999/04/20 00:19:04 mdw Exp $
+ *
+ * Ban a user from logging in
+ *
+ * (c) 1999 Mark Wooding
+ */
+
+/*----- Licensing notice --------------------------------------------------* 
+ *
+ * This file is part of banned.
+ *
+ * banned 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 2 of the License, or
+ * (at your option) any later version.
+ * 
+ * banned 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 banned; if not, write to the Free Software Foundation,
+ * Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ */
+
+/*----- Revision history --------------------------------------------------* 
+ *
+ * $Log: banned.c,v $
+ * Revision 1.1  1999/04/20 00:19:04  mdw
+ * Initial revision
+ *
+ */
+
+/*----- Header files ------------------------------------------------------*/
+
+#include <errno.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/types.h>
+#include <pwd.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <syslog.h>
+
+/*----- Main code ---------------------------------------------------------*/
+
+static const char *quis = "banned";
+
+int main(int argc, char *argv[])
+{
+  struct passwd *pw;
+  int fd;
+  char buf[BUFSIZ];
+  int r;
+
+  /* --- Resolve the program name --- */
+
+  {
+    char *p, *q;
+    p = argv[0];
+    for (q = argv[0]; *q; q++) {
+      if (*q == '/')
+	p = q + 1;
+    }
+    quis = p;
+  }
+
+  /* --- Read the user's name --- */
+
+  pw = getpwuid(getuid());
+  if (!pw) {
+    fprintf(stderr, "%s: you don't exist.  Go away.\n", quis);
+    exit(EXIT_FAILURE);
+  }
+
+  /* --- Open the log file --- */
+
+  openlog(quis, 0, LOG_AUTH);
+  syslog(LOG_CRIT, "banned user `%s' attempted to log in", pw->pw_name);
+
+  /* --- Change directory to the user's home --- */
+
+  if (chdir(pw->pw_dir) < 0) {
+    fprintf(stderr, "%s: couldn't change directory: %s\n",
+	    quis, strerror(errno));
+    exit(EXIT_FAILURE);
+  }
+
+  /* --- Open the reason file --- */
+
+  if ((fd = open(".banned", O_RDONLY)) < 0) {
+    fprintf(stderr, "%s: couldn't open `.banned' file: %s\n",
+	    quis, strerror(errno));
+    exit(EXIT_FAILURE);
+  }
+
+  /* --- Dump the reason information out --- */
+
+  for (;;) {
+    r = read(fd, buf, sizeof(buf));
+    if (r == 0)
+      break;
+    else if (r < 0) {
+      fprintf(stderr, "%s: couldn't read: %s\n", quis, strerror(errno));
+      exit(EXIT_FAILURE);
+    }
+    write(STDOUT_FILENO, buf, r);
+  }
+
+  /* --- Done --- */
+
+  close(fd);
+  return (EXIT_FAILURE);
+}
+
+/*----- That's all, folks -------------------------------------------------*/
diff --git a/chrootsh.8 b/chrootsh.8
new file mode 100644
index 0000000..ce232f6
--- /dev/null
+++ b/chrootsh.8
@@ -0,0 +1,87 @@
+.TH chrootsh 8 "20 April 1999" "Local tools"
+.SH NAME
+chrootsh \- logs a user into a safe chrooted environment
+.SH SYNOPSIS
+.B chrootsh
+.SH USAGE
+Set a user's shell to the
+.B chrootsh
+program's path.
+.PP
+When run, 
+.B chrootsh
+ensures that the current user has his or her shell set to be
+.BR chrootsh .
+If not, an error is raised and the program exits.
+.PP
+Assuming things check out OK, the user's home directory is examined.  It
+should be of the form
+.IB gaoldir /./ homedir
+where
+.I gaoldir
+is the path to the chroot gaol in which the user is to be imprisoned,
+and
+.I homedir
+is the path from the root of the gaol to the user's actual home
+directory.  (This is for the benefit of users outside the gaol;
+.B chrootsh
+uses information from the gaol's
+.B /etc/passwd
+file to work this out.  You'd do yourself a favour to make sure the two
+are consistent.)
+.PP
+Once the new root directory is set,
+.B chrootsh
+drops all of its privileges, and re-reads the user's information
+(presumably from a local version of the
+.B /etc/passwd
+file) to find the appropriate shell and home directory.  It sets
+appropriate values in the environment, and invokes the user's shell.
+.SH EXAMPLE
+Suppose
+.B /home/gaol
+is a carefully set-up environment for users to run in, with a minimal
+set of tools installed.  To set up a user
+.B fred
+within the gaol, make a directory
+.B /home/gaol/home/fred
+for the user, setting the access permissions as required.  Then add a
+line like
+.PP
+.RS 5
+.nf
+.ft B
+fred:*:1042:1042:Fred:/home/gaol/./home/fred:/usr/bin/chrootsh
+.ft R
+.fi
+.RE
+.PP
+to the main password database (wherever that is).  Then, put a line
+.PP
+.RS 5
+.nf
+.ft B
+fred:*:1042:1042:Fred:/home/fred:/bin/sh
+.ft R
+.fi
+.RE
+.PP
+in the gaol's password file
+.BR /home/gaol/etc/passwd .
+Finally, set a sensible password for
+.B fred
+in the main password database, and everything ought to work.
+.SH BUGS
+The
+.B chrootsh
+program must be installed 
+.RB setuid- root .
+While the author has made a fair effort to avoid security holes, he
+might have missed something.  There's no substitute for thorough
+auditing.  If you find a security problem, please report it to the
+author as a serious bug.
+.SH SEE ALSO
+.BR banned (8),
+.BR ushell (1).
+.SH AUTHOR
+Mark Wooding (mdw@nsict.org)
diff --git a/chrootsh.c b/chrootsh.c
new file mode 100644
index 0000000..2dfa52b
--- /dev/null
+++ b/chrootsh.c
@@ -0,0 +1,197 @@
+/* -*-c-*-
+ *
+ * $Id: chrootsh.c,v 1.1 1999/04/20 00:19:04 mdw Exp $
+ *
+ * Chroot gaol shell
+ *
+ * (c) 1999 EBI
+ */
+
+/*----- Licensing notice --------------------------------------------------* 
+ *
+ * This file is part of Chroot shell.
+ *
+ * chrootsh 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 2 of the License, or
+ * (at your option) any later version.
+ * 
+ * chrootsh 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 chrootsh; if not, write to the Free Software Foundation,
+ * Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ */
+
+/*----- Revision history --------------------------------------------------* 
+ *
+ * $Log: chrootsh.c,v $
+ * Revision 1.1  1999/04/20 00:19:04  mdw
+ * Initial revision
+ *
+ */
+
+/*----- Header files ------------------------------------------------------*/
+
+#include <errno.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include <sys/types.h>
+#include <unistd.h>
+#include <pwd.h>
+
+extern char **environ;
+
+/*----- Main code ---------------------------------------------------------*/
+
+#ifndef CHROOTSH_PATH
+#  define CHROOTSH_PATH "/usr/bin/chrootsh"
+#endif
+
+static const char *quis = "chrootsh";
+
+static void *xmalloc(size_t sz)
+{
+  void *p = malloc(sz);
+  if (!p) {
+    fprintf(stderr, "%s: not enough memory\n", quis);
+    exit(EXIT_FAILURE);
+  }
+  return (p);
+}
+
+static char *xstrdup(const char *p)
+{
+  size_t sz = strlen(p) + 1;
+  char *q = xmalloc(sz);
+  memcpy(q, p, sz);
+  return (q);
+}
+
+int main(int argc, char *argv[])
+{
+  struct passwd *pw;
+  uid_t me = getuid();
+  char **env;
+  char **av;
+
+  /* --- Resolve the program name --- */
+
+  {
+    char *p, *q;
+    p = argv[0];
+    for (q = argv[0]; *q; q++) {
+      if (*q == '/')
+	p = q + 1;
+    }
+    quis = p;
+  }
+
+  /* --- Check the user is meant to be chrooted --- */
+
+  pw = getpwuid(me);
+  if (!pw) {
+    fprintf(stderr, "%s: you don't exist.  Go away.\n", quis);
+    exit(EXIT_FAILURE);
+  }
+  if (strcmp(pw->pw_shell, CHROOTSH_PATH) != 0) {
+    fprintf(stderr, "%s: you aren't a chrooted user\n", quis);
+    exit(EXIT_FAILURE);
+  }
+  endpwent();
+
+  /* --- Chroot the user --- */
+
+  {
+    char *p = xstrdup(pw->pw_dir);
+    char *q = strstr(p, "/./");
+    if (q)
+      *q = 0;
+    
+    if (chdir(p) || chroot(p)) {
+      fprintf(stderr, "%s: couldn't call chroot: %s", quis, strerror(errno));
+      exit(EXIT_FAILURE);
+    }
+    setuid(me);
+    free(p);
+  }
+
+  /* --- Read the new password block --- */
+
+  {
+    char *p = xstrdup(pw->pw_name);
+    pw = getpwnam(p);
+    free(p);
+    if (!pw) {
+      fprintf(stderr, "%s: you don't exist in the gaol\n", quis);
+      exit(EXIT_FAILURE);
+    }
+    endpwent();
+  }
+
+  /* --- Now fiddle with environment strings and suchlike --- */
+
+  {
+    size_t n;
+    for (n = 0; environ[n]; n++)
+      ;
+    env = xmalloc((n + 1) * sizeof(char *));
+
+    for (n = 0; environ[n]; n++) {
+      if (strncmp(environ[n], "HOME=", 5) == 0) {
+	char *p = xmalloc(6 + strlen(pw->pw_dir));
+	sprintf(p, "HOME=%s", pw->pw_dir);
+	env[n] = p;
+      } else if (strncmp(environ[n], "SHELL=", 6) == 0) {
+	char *p = xmalloc(7 + strlen(pw->pw_shell));
+	sprintf(p, "SHELL=%s", pw->pw_shell);
+	env[n] = p;
+      } else
+	env[n] = environ[n];
+    }
+    env[n] = 0;
+  }
+
+  /* --- Finally, sort the argument list --- */
+
+  {
+    char *p, *q;
+    int i;
+
+    av = xmalloc((argc + 1) * sizeof(char *));
+    p = pw->pw_shell;
+    for (q = p; *q; q++) {
+      if (*q == '/')
+	p = q + 1;
+    }
+    if (argv[0][0] == '-') {
+      q = xmalloc(2 + strlen(p));
+      *q = '-';
+      strcpy(q + 1, p);
+      av[0] = q;
+    } else
+      av[0] = p;
+
+    for (i = 1; i <= argc; i++)
+      av[i] = argv[i];
+  }
+
+  /* --- Change directory (again) --- */
+
+  if (chdir(pw->pw_dir))
+    fprintf(stderr, "No directory, logging in with HOME=/\n");
+
+  /* --- Run the real shell --- */
+
+  execve(pw->pw_shell, av, env);
+  fprintf(stderr, "%s: couldn't exec `%s': %s",
+	  quis, pw->pw_shell, strerror(errno));
+  return (EXIT_FAILURE);
+}
+  
+/*----- That's all, folks -------------------------------------------------*/
diff --git a/configure.in b/configure.in
new file mode 100644
index 0000000..cab3dcd
--- /dev/null
+++ b/configure.in
@@ -0,0 +1,5 @@
+AC_INIT(chrootsh.c)
+AM_INIT_AUTOMAKE(shells, 1.0.0)
+AC_PROG_CC
+mdw_GCC_FLAGS
+AC_OUTPUT(Makefile)
diff --git a/ushell.1 b/ushell.1
new file mode 100644
index 0000000..53a8314
--- /dev/null
+++ b/ushell.1
@@ -0,0 +1,37 @@
+.TH ushell 1 "20 April 1999" "Local tools"
+.SH NAME
+ushell \- display a user's shell
+.SH SYNOPSIS
+.B ushell
+.I user
+.SH USAGE
+Writes the named user's default shell to standard output.  This is
+useful in scripts sometimes.  In particular, it's handy in global
+.B xdm/Xstartup
+scripts for checking whether users have sensible shells:
+.sp 1
+.RS 5
+.nf
+.ft B
+SHELL=`ushell $USER`
+case $SHELL in
+  */banned)
+    xmessage -file $HOME/.banned
+    exit 1
+    ;;
+  *)
+    if ! grep -q "^$SHELL" /etc/shells; then
+      xmessage "You're not allowed to log in this way."
+      exit 1
+    fi
+    ;;
+esac
+.fi
+.ft R
+.SH BUGS
+None planned.
+.SH SEE ALSO
+.BR banned (8),
+.BR chrootsh (8).
+.SH AUTHOR
+Mark Wooding (mdw@nsict.org)
diff --git a/ushell.c b/ushell.c
new file mode 100644
index 0000000..14f017c
--- /dev/null
+++ b/ushell.c
@@ -0,0 +1,87 @@
+/* -*-c-*-
+ *
+ * $Id: ushell.c,v 1.1 1999/04/20 00:19:04 mdw Exp $
+ *
+ * Extract a user's shell
+ *
+ * (c) 1999 Mark Wooding
+ */
+
+/*----- Licensing notice --------------------------------------------------* 
+ *
+ * This file is part of ushell.
+ *
+ * ushell 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 2 of the License, or
+ * (at your option) any later version.
+ * 
+ * ushell 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 ushell; if not, write to the Free Software Foundation,
+ * Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ */
+
+/*----- Revision history --------------------------------------------------* 
+ *
+ * $Log: ushell.c,v $
+ * Revision 1.1  1999/04/20 00:19:04  mdw
+ * Initial revision
+ *
+ */
+
+/*----- Header files ------------------------------------------------------*/
+
+#include <errno.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <pwd.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+/*----- Main code ---------------------------------------------------------*/
+
+static const char *quis;
+
+int main(int argc, char *argv[])
+{
+  struct passwd *pw;
+
+  /* --- Resolve the program name --- */
+
+  {
+    char *p, *q;
+    p = argv[0];
+    for (q = argv[0]; *q; q++) {
+      if (*q == '/')
+	p = q + 1;
+    }
+    quis = p;
+  }
+
+  /* --- Get the argument name --- */
+
+  if (argc != 2) {
+    fprintf(stderr, "Usage: %s username\n", quis);
+    exit(EXIT_FAILURE);
+  }
+
+  /* --- Read the user information --- */
+
+  if ((pw = getpwnam(argv[1])) == 0) {
+    fprintf(stderr, "%s: user `%s' doesn't exist", quis, argv[1]);
+    exit(EXIT_FAILURE);
+  }
+
+  /* --- Done --- */
+
+  puts(pw->pw_shell);
+  return (0);
+}
+
+/*----- That's all, folks -------------------------------------------------*/