Bug#514015: Patch to run tar within a chroot

[Matt Kraai]

Hi,

The attached patch makes cdebootstrap chroot to the target directory
before running tar, which should prevent it from following symlinks
out of the target directory.  I've verified that it works on i386.
I've tried to ensure that it will work on other architectures, but I
haven't tested it on any.

It requires that ldd be available, which may be a problem for
debian-installer.

-- 
Matt                                            http://ftbfs.org/kraai

diff -rux config.guess -x config.sub cdebootstrap-0.5.5/include/packages.h cdebootstrap-0.5.5.1/include/packages.h
--- cdebootstrap-0.5.5/include/packages.h	2005-01-22 04:03:24.000000000 -0800
+++ cdebootstrap-0.5.5.1/include/packages.h	2009-12-05 23:00:28.000000000 -0800
@@ -28,6 +28,6 @@
 #include <debian-installer.h>
 
 const char *package_get_local_filename (di_package *package);
-int package_extract (di_package *package);
+int package_extract (di_package *package, const char *loader);
 
 #endif
diff -rux config.guess -x config.sub cdebootstrap-0.5.5/src/install.c cdebootstrap-0.5.5.1/src/install.c
--- cdebootstrap-0.5.5/src/install.c	2008-03-23 13:55:27.000000000 -0700
+++ cdebootstrap-0.5.5.1/src/install.c	2009-12-05 23:01:07.000000000 -0800
@@ -25,6 +25,7 @@
 #include <config.h>
 
 #include <errno.h>
+#include <libgen.h>
 #include <limits.h>
 #include <stdlib.h>
 #include <string.h>
@@ -256,13 +257,56 @@
 
 int install_extract (di_slist *install)
 {
+  char buf[4096];
+  char line[4096];
+  char loader[4096];
+  FILE *pi;
+  int ret;
   struct di_slist_node *node;
 
+  snprintf (buf, sizeof buf, "cp /bin/tar %s/var/cache/bootstrap", target_root);
+  ret = execute (buf);
+  if (ret)
+    return ret;
+
+  pi = popen ("ldd /bin/tar", "r");
+  if (!pi)
+    return 1;
+
+  while (fgets (line, sizeof line, pi))
+  {
+    char *end;
+    char *library;
+
+    library = strchr (line, '/');
+    if (!library)
+      continue;
+
+    end = strchr (library, ' ');
+    if (end)
+      *end = '\0';
+
+    snprintf (buf, sizeof buf, "cp %s %s/var/cache/bootstrap", library, target_root);
+    ret = execute (buf);
+    if (ret)
+    {
+      fclose (pi);
+      return ret;
+    }
+
+    if (!strstr (line, " => "))
+      strcpy (loader, basename (library));
+  }
+
+  ret = fclose (pi);
+  if (ret)
+    return ret;
+
   for (node = install->head; node; node = node->next)
   {
     di_package *p = node->data;
     log_message (LOG_MESSAGE_INFO_INSTALL_PACKAGE_EXTRACT, p->package);
-    package_extract (p);
+    package_extract (p, loader);
   }
 
   return 0;
diff -rux config.guess -x config.sub cdebootstrap-0.5.5/src/packages.c cdebootstrap-0.5.5.1/src/packages.c
--- cdebootstrap-0.5.5/src/packages.c	2008-02-23 13:46:32.000000000 -0800
+++ cdebootstrap-0.5.5.1/src/packages.c	2009-12-05 23:10:05.000000000 -0800
@@ -159,13 +159,13 @@
   return ret;
 }
 
-int package_extract (di_package *package)
+int package_extract (di_package *package, const char *loader)
 {
   char buf_file[PATH_MAX];
   char buf[PATH_MAX];
 
   build_target_deb (buf_file, PATH_MAX, package_get_local_filename (package));
-  snprintf (buf, PATH_MAX, "tar -xz -C %s -f -", target_root);
+  snprintf (buf, PATH_MAX, "gzip -d | chroot %s /var/cache/bootstrap/%s --library-path /var/cache/bootstrap /var/cache/bootstrap/tar -x -f -", target_root, loader);
   return package_extract_self (buf_file, buf);
 }