ischroot utility by Aurelien Jarno. closes: #627205.

5 files changed, 246 insertions, 4 deletions

diff --git a/Makefile.am b/Makefile.am
index 789d641..2ad3d26 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -2,9 +2,10 @@ AUTOMAKE_OPTIONS = foreign
 
 SUBDIRS = po4a
 
-bin_PROGRAMS = run-parts tempfile
+bin_PROGRAMS = run-parts tempfile ischroot
 run_parts_SOURCES = run-parts.c
 tempfile_SOURCES = tempfile.c
+ischroot_SOURCES = ischroot.c
 
 bin_SCRIPTS = which savelog
 
@@ -12,4 +13,5 @@ sbin_SCRIPTS = installkernel add-shell remove-shell
 
 man_MANS = run-parts.8 \
 	   installkernel.8 savelog.8 \
-	   tempfile.1 which.1 add-shell.8 remove-shell.8
+	   tempfile.1 which.1 add-shell.8 \
+	   remove-shell.8 ischroot.1
diff --git a/debian/rules b/debian/rules
index dd44f41..e1d4e49 100755
--- a/debian/rules
+++ b/debian/rules
@@ -64,7 +64,8 @@ binary-arch:	checkroot build
 ifeq (,$(findstring nostrip,$(DEB_BUILD_OPTIONS)))
 	strip --remove-section=.comment --remove-section=.note \
 		debian/tmp/bin/run-parts \
-	   	debian/tmp/bin/tempfile
+	   	debian/tmp/bin/tempfile \
+	   	debian/tmp/usr/bin/ischroot
 endif
 
 ifneq ($(DEB_HOST_ARCH_OS),hurd)
@@ -91,7 +92,9 @@ endif
 
 	cd debian/tmp && find * -type f ! -regex '^DEBIAN/.*' -print0 | xargs -r0 md5sum > DEBIAN/md5sums
 
-	dpkg-shlibdeps debian/tmp/bin/run-parts debian/tmp/bin/tempfile
+	dpkg-shlibdeps debian/tmp/bin/run-parts \
+			debian/tmp/bin/tempfile \
+			debian/tmp/usr/bin/ischroot
 	dpkg-gencontrol -isp
 	dpkg --build debian/tmp ..
 
diff --git a/ischroot.1 b/ischroot.1
new file mode 100644
index 0000000..7a84c09
--- /dev/null
+++ b/ischroot.1
@@ -0,0 +1,37 @@
+.\" -*- nroff -*-
+.TH ISCHROOT 1 "17 May 2011" "Debian"
+.SH NAME
+ischroot \- detect if running in a chroot
+.SH SYNOPSIS
+.B ischroot
+[\-\-default\-false] [\-\-default\-true] [\-\-help] [\-\-version]
+.SH DESCRIPTION
+.PP
+.B ischroot
+detects if it is currently running in a chroot. The exit status is:
+.TP
+0
+if currently running in a chroot
+.TP
+1
+if currently not running in a chroot
+.TP
+2
+if the detection is not possible (On GNU/Linux in happens if the script
+is not run as root).
+.SH OPTIONS
+.TP
+.B "-f, --default-false "
+Exit with status 1 if the detection is not possible.
+.TP
+.B "-t, --default-true "
+Exit with status 0 if the detection is not possible.
+.TP
+.B "--help"
+Print a usage message on standard output and exit successfully.
+.TP
+.B "--version"
+Print version information on standard output and exit successfully.
+.SH BUGS
+On GNU/Linux, chroot detection is not possible as root. This works correctly
+on GNU/Hurd and GNU/kFreeBSD.
diff --git a/ischroot.c b/ischroot.c
new file mode 100644
index 0000000..f280602
--- /dev/null
+++ b/ischroot.c
@@ -0,0 +1,196 @@
+/* ischroot: detect if running in a chroot
+ *
+ * Debian ischroot program
+ * Copyright (C) 2011 Aurelien Jarno <aurel32@debian.org>
+ *
+ * This is free software; see the GNU General Public License version 2
+ * or later for copying conditions.  There is NO warranty.
+ */
+
+#include <stdio.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <unistd.h>
+#ifdef HAVE_GETOPT_H
+#include <getopt.h>
+#endif /* HAVE_GETOPT_H */
+
+void version()
+{
+  fprintf(stderr, "Debian ischroot, version " PACKAGE_VERSION
+          "Copyright (C) 2011 Aurelien Jarno\n"
+          "This is free software; see the GNU General Public License version 2\n"
+          "or later for copying conditions.  There is NO warranty.\n");
+  exit(0);
+}
+
+void usage()
+{
+  fprintf(stderr, "Usage: ischroot [OPTION]\n"
+          "  -f, --default-false return false if detection fails\n"
+          "  -t, --default-true  return true if detection fails\n"
+          "  -V, --version       output version information and exit.\n"
+          "  -h, --help          display this help and exit.\n");
+  exit(0);
+}
+
+#if defined (__linux__)
+
+/* On Linux we can detect chroots by checking if the 
+ * devicenumber/inode pair of / are the same as that of 
+ * /sbin/init's. This may fail if not running as root or if
+ * /proc is not mounted, in which case 2 is returned.
+ */
+
+static int ischroot()
+{
+  struct stat st1, st2;
+
+  if (stat("/", &st1) || stat("/proc/1/root", &st2))
+    return 2;
+  else if ((st1.st_dev == st2.st_dev) && (st1.st_ino == st2.st_ino))
+    return 1;
+  else
+    return 0;
+}
+
+#elif defined (__FreeBSD_kernel__) || defined (__FreeBSD__)
+
+#include <sys/sysctl.h>
+#include <sys/user.h>
+
+/* On FreeBSD we can detect chroot by looking for a specific
+ * file descriptor pointing to the location of the chroot. There
+ * is not need to be root, so it is unlikely to fail in normal 
+ * cases, but return 2 if a memory failure or the like happens. */
+
+static int ischroot()
+{
+  int mib[4];
+  size_t kf_len = 0;
+  char *kf_buf, *kf_bufp;
+
+  mib[0] = CTL_KERN;
+  mib[1] = KERN_PROC;
+  mib[2] = KERN_PROC_FILEDESC;
+  mib[3] = getpid ();
+
+  if (sysctl (mib, 4, NULL, &kf_len, NULL, 0) != 0)
+    return 2;
+
+  kf_buf = kf_bufp = malloc (kf_len);
+  if (kf_buf == NULL)
+    return 2;
+
+  if (sysctl (mib, 4, kf_buf, &kf_len, NULL, 0) != 0)
+  {
+    free(kf_buf);
+    return 2;
+  }
+
+  while (kf_bufp < kf_buf + kf_len)
+  {   
+    struct kinfo_file *kf = (struct kinfo_file *) (uintptr_t) kf_bufp;
+
+    if (kf->kf_fd == KF_FD_TYPE_JAIL)
+    {
+      free(kf_buf);
+      return 0;
+    }
+    kf_bufp += kf->kf_structsize;
+  }   
+
+  free(kf_buf);
+  return 1;
+}
+
+#elif defined (__GNU__)
+
+/* On Hurd we can detect chroot by looking at the device number
+ * containing /. The device number of the first mounted filesystem
+ * equals 3, and due to bug http://savannah.gnu.org/bugs/?23213
+ * chroots have to be created on a different filesystem. Return 2
+ * if it is not possible to probe this device. */
+
+static int ischroot()
+{
+  struct stat st;
+
+  if (stat("/", &st))
+    return 2;
+  else if (st.st_dev == 3)
+    return 1;
+  else
+    return 0;
+}
+
+#else
+
+static int ischroot()
+{
+  return 2;
+}
+
+#warning unknown system, chroot detection will always fail
+
+#endif
+
+/* Process options */
+int main(int argc, char *argv[])
+{
+  int default_false = 0;
+  int default_true = 0;
+  int exit_status;
+
+  for (;;) {
+    int c;
+    int option_index = 0;
+
+    static struct option long_options[] = {
+      {"default-false", 0, 0, 'f'},
+      {"default-true", 0, 0, 't'},
+      {"help", 0, 0, 'h'},
+      {"version", 0, 0, 'V'},
+      {0, 0, 0, 0}
+    };
+    c = getopt_long(argc, argv, "fthV", long_options, &option_index);
+    if (c == EOF)
+      break;
+    switch (c) {
+    case 'f':
+      default_false = 1;
+      break;
+    case 't':
+      default_true = 1;
+      break;
+    case 'h':
+      usage();
+      break;
+    case 'V':
+      version();
+      break;
+    default:
+      fprintf(stderr, "Try `ischroot --help' for more information.\n");
+      exit(1);
+    }
+  }
+
+  if (default_false && default_true) {
+    fprintf(stderr, "Can't default to both true and false!\n");
+    fprintf(stderr, "Try `ischroot --help' for more information.\n");
+    exit(1);
+  }
+
+  exit_status = ischroot();
+
+  if (exit_status == 2) {
+    if (default_true)
+      exit_status = 0;
+    if (default_false)
+      exit_status = 1;
+  }
+
+  return exit_status;
+}
diff --git a/po4a/po4a.conf b/po4a/po4a.conf
index e6d0626..97d8437 100644
--- a/po4a/po4a.conf
+++ b/po4a/po4a.conf
@@ -11,6 +11,10 @@
 	   		      sl:sl/installkernel.8 add_sl:sl/translator_slovene.add \
 	   		      de:de/installkernel.8 add_de:de/translator_german.add \
 	   		      es:es/installkernel.8
+[type:man] ../ischroot.1 fr:fr/ischroot.1 add_fr:fr/ischroot.1.fr.add \
+	   	      sl:sl/ischroot.1 add_sl:sl/translator_slovene.add \
+	   	      de:de/ischroot.1 add_de:de/translator_german.add \
+	   	      es:es/ischroot.1
 # There is no mdoc module in po4a. This one is still translated manually
 [type:man] ../remove-shell.8 fr:fr/remove-shell.8 add_fr:fr/translator_french.add \
 	   		     sl:sl/remove-shell.8 add_sl:sl/translator_slovene.add \