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Fix following symlinks when processing the fixup list

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The previous fix in b41daecb5 was incomplete. Fixup entries are
given the original path without calling cleanup_pathname().
To make sure we don't follow a symlink, we must strip trailing
slashes from the path.

The fixup entries are always directories. Make sure we try to modify
only directories by providing O_DIRECTORY to open() (if supported)
and if it fails to check directory via lstat().
This commit is contained in:
Ondrej Dubaj 2021-08-30 08:45:44 +02:00
parent f16d49ae57
commit 09af57c726
2 changed files with 199 additions and 1 deletions
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193
libarchive-3.5.2-symlink-fix.patch Normal file
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@ -0,0 +1,193 @@
commit 8a1bd5c18e896f0411a991240ce0d772bb02c840
Author: Martin Matuska <martin@matuska.org>
Date: Fri Aug 27 10:56:28 2021 +0200
Fix following symlinks when processing the fixup list
The previous fix in b41daecb5 was incomplete. Fixup entries are
given the original path without calling cleanup_pathname().
To make sure we don't follow a symlink, we must strip trailing
slashes from the path.
The fixup entries are always directories. Make sure we try to modify
only directories by providing O_DIRECTORY to open() (if supported)
and if it fails to check directory via lstat().
Fixes #1566
diff --git a/libarchive/archive_write_disk_posix.c b/libarchive/archive_write_disk_posix.c
index fcd733af..aadc5871 100644
--- a/libarchive/archive_write_disk_posix.c
+++ b/libarchive/archive_write_disk_posix.c
@@ -2462,6 +2462,7 @@ _archive_write_disk_close(struct archive *_a)
struct archive_write_disk *a = (struct archive_write_disk *)_a;
struct fixup_entry *next, *p;
struct stat st;
+ char *c;
int fd, ret;
archive_check_magic(&a->archive, ARCHIVE_WRITE_DISK_MAGIC,
@@ -2475,24 +2476,49 @@ _archive_write_disk_close(struct archive *_a)
while (p != NULL) {
fd = -1;
a->pst = NULL; /* Mark stat cache as out-of-date. */
- if (p->fixup &
- (TODO_TIMES | TODO_MODE_BASE | TODO_ACLS | TODO_FFLAGS)) {
- fd = open(p->name,
- O_WRONLY | O_BINARY | O_NOFOLLOW | O_CLOEXEC);
+
+ /* We must strip trailing slashes from the path to avoid
+ dereferencing symbolic links to directories */
+ c = p->name;
+ while (*c != '\0')
+ c++;
+ while (c != p->name && *(c - 1) == '/') {
+ c--;
+ *c = '\0';
+ }
+
+ if (p->fixup == 0)
+ goto skip_fixup_entry;
+ else {
+ fd = open(p->name, O_BINARY | O_NOFOLLOW | O_RDONLY
+#if defined(O_DIRECTORY)
+ | O_DIRECTORY
+#endif
+ | O_CLOEXEC);
+ /*
+ ` * If we don't support O_DIRECTORY,
+ * or open() has failed, we must stat()
+ * to verify that we are opening a directory
+ */
+#if defined(O_DIRECTORY)
if (fd == -1) {
- /* If we cannot lstat, skip entry */
- if (lstat(p->name, &st) != 0)
+ if (lstat(p->name, &st) != 0 ||
+ !S_ISDIR(st.st_mode)) {
goto skip_fixup_entry;
- /*
- * If we deal with a symbolic link, mark
- * it in the fixup mode to ensure no
- * modifications are made to its target.
- */
- if (S_ISLNK(st.st_mode)) {
- p->mode &= ~S_IFMT;
- p->mode |= S_IFLNK;
}
}
+#else
+#if HAVE_FSTAT
+ if (fd > 0 && (
+ fstat(fd, &st) != 0 || !S_ISDIR(st.st_mode))) {
+ goto skip_fixup_entry;
+ } else
+#endif
+ if (lstat(p->name, &st) != 0 ||
+ !S_ISDIR(st.st_mode)) {
+ goto skip_fixup_entry;
+ }
+#endif
}
if (p->fixup & TODO_TIMES) {
set_times(a, fd, p->mode, p->name,
@@ -2504,14 +2530,13 @@ _archive_write_disk_close(struct archive *_a)
if (p->fixup & TODO_MODE_BASE) {
#ifdef HAVE_FCHMOD
if (fd >= 0)
- fchmod(fd, p->mode);
+ fchmod(fd, p->mode & 07777);
else
#endif
#ifdef HAVE_LCHMOD
- lchmod(p->name, p->mode);
+ lchmod(p->name, p->mode & 07777);
#else
- if (!S_ISLNK(p->mode))
- chmod(p->name, p->mode);
+ chmod(p->name, p->mode & 07777);
#endif
}
if (p->fixup & TODO_ACLS)
@@ -2664,7 +2689,6 @@ new_fixup(struct archive_write_disk *a, const char *pathname)
fe->next = a->fixup_list;
a->fixup_list = fe;
fe->fixup = 0;
- fe->mode = 0;
fe->name = strdup(pathname);
return (fe);
}
diff --git a/libarchive/test/test_write_disk_fixup.c b/libarchive/test/test_write_disk_fixup.c
index c399c984..b83b7307 100644
--- a/libarchive/test/test_write_disk_fixup.c
+++ b/libarchive/test/test_write_disk_fixup.c
@@ -47,26 +47,50 @@ DEFINE_TEST(test_write_disk_fixup)
/*
* Create a file
*/
- assertMakeFile("victim", 0600, "a");
+ assertMakeFile("file", 0600, "a");
+
+ /*
+ * Create a directory
+ */
+ assertMakeDir("dir", 0700);
/*
* Create a directory and a symlink with the same name
*/
- /* Directory: dir */
+ /* Directory: dir1 */
+ assert((ae = archive_entry_new()) != NULL);
+ archive_entry_copy_pathname(ae, "dir1/");
+ archive_entry_set_mode(ae, AE_IFDIR | 0555);
+ assertEqualIntA(ad, 0, archive_write_header(ad, ae));
+ assertEqualIntA(ad, 0, archive_write_finish_entry(ad));
+ archive_entry_free(ae);
+
+ /* Directory: dir2 */
assert((ae = archive_entry_new()) != NULL);
- archive_entry_copy_pathname(ae, "dir");
- archive_entry_set_mode(ae, AE_IFDIR | 0606);
+ archive_entry_copy_pathname(ae, "dir2/");
+ archive_entry_set_mode(ae, AE_IFDIR | 0555);
assertEqualIntA(ad, 0, archive_write_header(ad, ae));
assertEqualIntA(ad, 0, archive_write_finish_entry(ad));
archive_entry_free(ae);
- /* Symbolic Link: dir -> foo */
+ /* Symbolic Link: dir1 -> dir */
+ assert((ae = archive_entry_new()) != NULL);
+ archive_entry_copy_pathname(ae, "dir1");
+ archive_entry_set_mode(ae, AE_IFLNK | 0777);
+ archive_entry_set_size(ae, 0);
+ archive_entry_copy_symlink(ae, "dir");
+ assertEqualIntA(ad, 0, r = archive_write_header(ad, ae));
+ if (r >= ARCHIVE_WARN)
+ assertEqualIntA(ad, 0, archive_write_finish_entry(ad));
+ archive_entry_free(ae);
+
+ /* Symbolic Link: dir2 -> file */
assert((ae = archive_entry_new()) != NULL);
- archive_entry_copy_pathname(ae, "dir");
+ archive_entry_copy_pathname(ae, "dir2");
archive_entry_set_mode(ae, AE_IFLNK | 0777);
archive_entry_set_size(ae, 0);
- archive_entry_copy_symlink(ae, "victim");
+ archive_entry_copy_symlink(ae, "file");
assertEqualIntA(ad, 0, r = archive_write_header(ad, ae));
if (r >= ARCHIVE_WARN)
assertEqualIntA(ad, 0, archive_write_finish_entry(ad));
@@ -75,7 +99,9 @@ DEFINE_TEST(test_write_disk_fixup)
assertEqualInt(ARCHIVE_OK, archive_write_free(ad));
/* Test the entries on disk. */
- assertIsSymlink("dir", "victim", 0);
- assertFileMode("victim", 0600);
+ assertIsSymlink("dir1", "dir", 0);
+ assertIsSymlink("dir2", "file", 0);
+ assertFileMode("dir", 0700);
+ assertFileMode("file", 0600);
#endif
}

7
libarchive.spec
View File

@ -2,13 +2,15 @@
Name: libarchive
Version: 3.5.2
Release: 1%{?dist}
Release: 2%{?dist}
Summary: A library for handling streaming archive formats
License: BSD
URL: https://www.libarchive.org/
Source0: https://libarchive.org/downloads/%{name}-%{version}.tar.gz
Patch0: libarchive-3.5.2-symlink-fix.patch
BuildRequires: automake
BuildRequires: bison
BuildRequires: bzip2-devel
@ -211,6 +213,9 @@ run_testsuite
%changelog
* Mon Aug 30 2021 Ondrej Dubaj <odubaj@redhat.com> - 3.5.2-2
- Fixed symlink handling
* Mon Aug 23 2021 Ondrej Dubaj <odubaj@redhat.com> - 3.5.2-1
- Rebased to version 3.5.2