[Buildroot] [PATCH] package/busybox: Unbreak the `tar` implementation
Jan Kundrát
jan.kundrat at cesnet.cz
Wed Mar 14 16:58:40 UTC 2018
The `tar` implementation in Busybox 1.28.0 and 1.28.1 won't extract a
rootfs with some symlinks that appear to look "dangerous". This
completely (and silently!) breaks on-target updates via RAUC for me, for
example.
In the meanwhile, upstream already reverted the commit in question
(in their commit a84db18fc71d09e801df0ebca048d82e90b32c6a), so this
patch simply applies that revert in Buildroot. The fix has not made it
to a release, yet.
Signed-off-by: Jan Kundrát <jan.kundrat at cesnet.cz>
Bug: https://bugs.busybox.net/show_bug.cgi?id=8411
Bug: https://github.com/rauc/rauc/issues/249
---
...ostpone-creation-of-symlinks-with-suspici.patch | 358 +++++++++++++++++++++
1 file changed, 358 insertions(+)
create mode 100644 package/busybox/0003-tar-unzip-postpone-creation-of-symlinks-with-suspici.patch
diff --git a/package/busybox/0003-tar-unzip-postpone-creation-of-symlinks-with-suspici.patch b/package/busybox/0003-tar-unzip-postpone-creation-of-symlinks-with-suspici.patch
new file mode 100644
index 0000000000..f6f1359654
--- /dev/null
+++ b/package/busybox/0003-tar-unzip-postpone-creation-of-symlinks-with-suspici.patch
@@ -0,0 +1,358 @@
+From a84db18fc71d09e801df0ebca048d82e90b32c6a Mon Sep 17 00:00:00 2001
+From: Denys Vlasenko <vda.linux at googlemail.com>
+Date: Tue, 20 Feb 2018 15:57:45 +0100
+Subject: [PATCH] tar,unzip: postpone creation of symlinks with "suspicious"
+ targets
+
+This mostly reverts commit bc9bbeb2b81001e8731cd2ae501c8fccc8d87cc7
+"libarchive: do not extract unsafe symlinks unless $EXTRACT_UNSAFE_SYMLINKS=1"
+
+Users report that it is somewhat too restrictive. See
+https://bugs.busybox.net/show_bug.cgi?id=8411
+
+In particular, this interferes with unpacking of busybox-based
+filesystems with links like "sbin/applet" -> "../bin/busybox".
+
+The change is made smaller by deleting ARCHIVE_EXTRACT_QUIET flag -
+it is unused since 2010, and removing conditionals on it
+allows commonalizing some error message codes.
+
+function old new delta
+create_or_remember_symlink - 94 +94
+create_symlinks_from_list - 64 +64
+tar_main 1002 1006 +4
+unzip_main 2732 2724 -8
+data_extract_all 984 891 -93
+unsafe_symlink_target 147 - -147
+------------------------------------------------------------------------------
+(add/remove: 2/1 grow/shrink: 1/2 up/down: 162/-248) Total: -86 bytes
+
+Signed-off-by: Denys Vlasenko <vda.linux at googlemail.com>
+---
+ archival/libarchive/data_extract_all.c | 28 ++++----------
+ archival/libarchive/unsafe_symlink_target.c | 59 +++++++++++++----------------
+ archival/tar.c | 2 +
+ archival/unzip.c | 25 ++++++------
+ include/bb_archive.h | 23 ++++++-----
+ testsuite/tar.tests | 10 ++---
+ 6 files changed, 68 insertions(+), 79 deletions(-)
+
+diff --git a/archival/libarchive/data_extract_all.c b/archival/libarchive/data_extract_all.c
+index d3a6df5e8..8fa69ffaf 100644
+--- a/archival/libarchive/data_extract_all.c
++++ b/archival/libarchive/data_extract_all.c
+@@ -107,9 +107,7 @@ void FAST_FUNC data_extract_all(archive_handle_t *archive_handle)
+ }
+ }
+ else if (existing_sb.st_mtime >= file_header->mtime) {
+- if (!(archive_handle->ah_flags & ARCHIVE_EXTRACT_QUIET)
+- && !S_ISDIR(file_header->mode)
+- ) {
++ if (!S_ISDIR(file_header->mode)) {
+ bb_error_msg("%s not created: newer or "
+ "same age file exists", dst_name);
+ }
+@@ -125,7 +123,7 @@ void FAST_FUNC data_extract_all(archive_handle_t *archive_handle)
+ /* Handle hard links separately */
+ if (hard_link) {
+ res = link(hard_link, dst_name);
+- if (res != 0 && !(archive_handle->ah_flags & ARCHIVE_EXTRACT_QUIET)) {
++ if (res != 0) {
+ /* shared message */
+ bb_perror_msg("can't create %slink '%s' to '%s'",
+ "hard", dst_name, hard_link
+@@ -165,10 +163,9 @@ void FAST_FUNC data_extract_all(archive_handle_t *archive_handle)
+ }
+ case S_IFDIR:
+ res = mkdir(dst_name, file_header->mode);
+- if ((res == -1)
++ if ((res != 0)
+ && (errno != EISDIR) /* btw, Linux doesn't return this */
+ && (errno != EEXIST)
+- && !(archive_handle->ah_flags & ARCHIVE_EXTRACT_QUIET)
+ ) {
+ bb_perror_msg("can't make dir %s", dst_name);
+ }
+@@ -198,27 +195,16 @@ void FAST_FUNC data_extract_all(archive_handle_t *archive_handle)
+ *
+ * Untarring bug.tar would otherwise place evil.py in '/tmp'.
+ */
+- if (!unsafe_symlink_target(file_header->link_target)) {
+- res = symlink(file_header->link_target, dst_name);
+- if (res != 0
+- && !(archive_handle->ah_flags & ARCHIVE_EXTRACT_QUIET)
+- ) {
+- /* shared message */
+- bb_perror_msg("can't create %slink '%s' to '%s'",
+- "sym",
+- dst_name, file_header->link_target
+- );
+- }
+- }
++ create_or_remember_symlink(&archive_handle->symlink_placeholders,
++ file_header->link_target,
++ dst_name);
+ break;
+ case S_IFSOCK:
+ case S_IFBLK:
+ case S_IFCHR:
+ case S_IFIFO:
+ res = mknod(dst_name, file_header->mode, file_header->device);
+- if ((res == -1)
+- && !(archive_handle->ah_flags & ARCHIVE_EXTRACT_QUIET)
+- ) {
++ if (res != 0) {
+ bb_perror_msg("can't create node %s", dst_name);
+ }
+ break;
+diff --git a/archival/libarchive/unsafe_symlink_target.c b/archival/libarchive/unsafe_symlink_target.c
+index 441ba8b24..8dcafeaa1 100644
+--- a/archival/libarchive/unsafe_symlink_target.c
++++ b/archival/libarchive/unsafe_symlink_target.c
+@@ -5,44 +5,37 @@
+ #include "libbb.h"
+ #include "bb_archive.h"
+
+-int FAST_FUNC unsafe_symlink_target(const char *target)
++void FAST_FUNC create_or_remember_symlink(llist_t **symlink_placeholders,
++ const char *target,
++ const char *linkname)
+ {
+- const char *dot;
+-
+- if (target[0] == '/') {
+- const char *var;
+- unsafe:
+- var = getenv("EXTRACT_UNSAFE_SYMLINKS");
+- if (var) {
+- if (LONE_CHAR(var, '1'))
+- return 0; /* pretend it's safe */
+- return 1; /* "UNSAFE!" */
+- }
+- bb_error_msg("skipping unsafe symlink to '%s' in archive,"
+- " set %s=1 to extract",
+- target,
+- "EXTRACT_UNSAFE_SYMLINKS"
++ if (target[0] == '/' || strstr(target, "..")) {
++ llist_add_to(symlink_placeholders,
++ xasprintf("%s%c%s", linkname, '\0', target)
++ );
++ return;
++ }
++ if (symlink(target, linkname) != 0) {
++ /* shared message */
++ bb_perror_msg_and_die("can't create %slink '%s' to '%s'",
++ "sym", linkname, target
+ );
+- /* Prevent further messages */
+- setenv("EXTRACT_UNSAFE_SYMLINKS", "0", 0);
+- return 1; /* "UNSAFE!" */
+ }
++}
+
+- dot = target;
+- for (;;) {
+- dot = strchr(dot, '.');
+- if (!dot)
+- return 0; /* safe target */
++void FAST_FUNC create_symlinks_from_list(llist_t *list)
++{
++ while (list) {
++ char *target;
+
+- /* Is it a path component starting with ".."? */
+- if ((dot[1] == '.')
+- && (dot == target || dot[-1] == '/')
+- /* Is it exactly ".."? */
+- && (dot[2] == '/' || dot[2] == '\0')
+- ) {
+- goto unsafe;
++ target = list->data + strlen(list->data) + 1;
++ if (symlink(target, list->data)) {
++ /* shared message */
++ bb_error_msg_and_die("can't create %slink '%s' to '%s'",
++ "sym",
++ list->data, target
++ );
+ }
+- /* NB: it can even be trailing ".", should only add 1 */
+- dot += 1;
++ list = list->link;
+ }
+ }
+diff --git a/archival/tar.c b/archival/tar.c
+index 9ed3821d5..415ebde0d 100644
+--- a/archival/tar.c
++++ b/archival/tar.c
+@@ -1244,6 +1244,8 @@ int tar_main(int argc UNUSED_PARAM, char **argv)
+ while (get_header_tar(tar_handle) == EXIT_SUCCESS)
+ bb_got_signal = EXIT_SUCCESS; /* saw at least one header, good */
+
++ create_symlinks_from_list(tar_handle->symlink_placeholders);
++
+ /* Check that every file that should have been extracted was */
+ while (tar_handle->accept) {
+ if (!find_list_entry(tar_handle->reject, tar_handle->accept->data)
+diff --git a/archival/unzip.c b/archival/unzip.c
+index da4b2a544..0d00d8dc9 100644
+--- a/archival/unzip.c
++++ b/archival/unzip.c
+@@ -345,7 +345,9 @@ static void unzip_create_leading_dirs(const char *fn)
+ }
+
+ #if ENABLE_FEATURE_UNZIP_CDF
+-static void unzip_extract_symlink(zip_header_t *zip, const char *dst_fn)
++static void unzip_extract_symlink(llist_t **symlink_placeholders,
++ zip_header_t *zip,
++ const char *dst_fn)
+ {
+ char *target;
+
+@@ -370,15 +372,9 @@ static void unzip_extract_symlink(zip_header_t *zip, const char *dst_fn)
+ target[xstate.mem_output_size] = '\0';
+ #endif
+ }
+- if (!unsafe_symlink_target(target)) {
+-//TODO: libbb candidate
+- if (symlink(target, dst_fn)) {
+- /* shared message */
+- bb_perror_msg_and_die("can't create %slink '%s' to '%s'",
+- "sym", dst_fn, target
+- );
+- }
+- }
++ create_or_remember_symlink(symlink_placeholders,
++ target,
++ dst_fn);
+ free(target);
+ }
+ #endif
+@@ -490,6 +486,9 @@ int unzip_main(int argc, char **argv)
+ llist_t *zaccept = NULL;
+ llist_t *zreject = NULL;
+ char *base_dir = NULL;
++#if ENABLE_FEATURE_UNZIP_CDF
++ llist_t *symlink_placeholders = NULL;
++#endif
+ int i;
+ char key_buf[80]; /* must match size used by my_fgets80 */
+
+@@ -954,7 +953,7 @@ int unzip_main(int argc, char **argv)
+ #if ENABLE_FEATURE_UNZIP_CDF
+ if (S_ISLNK(file_mode)) {
+ if (dst_fd != STDOUT_FILENO) /* not -p? */
+- unzip_extract_symlink(&zip, dst_fn);
++ unzip_extract_symlink(&symlink_placeholders, &zip, dst_fn);
+ } else
+ #endif
+ {
+@@ -990,6 +989,10 @@ int unzip_main(int argc, char **argv)
+ total_entries++;
+ }
+
++#if ENABLE_FEATURE_UNZIP_CDF
++ create_symlinks_from_list(symlink_placeholders);
++#endif
++
+ if ((opts & OPT_l) && quiet <= 1) {
+ if (!verbose) {
+ // " Length Date Time Name\n"
+diff --git a/include/bb_archive.h b/include/bb_archive.h
+index 8ed20d70e..a5c61e95b 100644
+--- a/include/bb_archive.h
++++ b/include/bb_archive.h
+@@ -64,6 +64,9 @@ typedef struct archive_handle_t {
+ /* Currently processed file's header */
+ file_header_t *file_header;
+
++ /* List of symlink placeholders */
++ llist_t *symlink_placeholders;
++
+ /* Process the header component, e.g. tar -t */
+ void FAST_FUNC (*action_header)(const file_header_t *);
+
+@@ -119,15 +122,14 @@ typedef struct archive_handle_t {
+ #define ARCHIVE_RESTORE_DATE (1 << 0)
+ #define ARCHIVE_CREATE_LEADING_DIRS (1 << 1)
+ #define ARCHIVE_UNLINK_OLD (1 << 2)
+-#define ARCHIVE_EXTRACT_QUIET (1 << 3)
+-#define ARCHIVE_EXTRACT_NEWER (1 << 4)
+-#define ARCHIVE_DONT_RESTORE_OWNER (1 << 5)
+-#define ARCHIVE_DONT_RESTORE_PERM (1 << 6)
+-#define ARCHIVE_NUMERIC_OWNER (1 << 7)
+-#define ARCHIVE_O_TRUNC (1 << 8)
+-#define ARCHIVE_REMEMBER_NAMES (1 << 9)
++#define ARCHIVE_EXTRACT_NEWER (1 << 3)
++#define ARCHIVE_DONT_RESTORE_OWNER (1 << 4)
++#define ARCHIVE_DONT_RESTORE_PERM (1 << 5)
++#define ARCHIVE_NUMERIC_OWNER (1 << 6)
++#define ARCHIVE_O_TRUNC (1 << 7)
++#define ARCHIVE_REMEMBER_NAMES (1 << 8)
+ #if ENABLE_RPM
+-#define ARCHIVE_REPLACE_VIA_RENAME (1 << 10)
++#define ARCHIVE_REPLACE_VIA_RENAME (1 << 9)
+ #endif
+
+
+@@ -197,7 +199,10 @@ void seek_by_jump(int fd, off_t amount) FAST_FUNC;
+ void seek_by_read(int fd, off_t amount) FAST_FUNC;
+
+ const char *strip_unsafe_prefix(const char *str) FAST_FUNC;
+-int unsafe_symlink_target(const char *target) FAST_FUNC;
++void create_or_remember_symlink(llist_t **symlink_placeholders,
++ const char *target,
++ const char *linkname) FAST_FUNC;
++void create_symlinks_from_list(llist_t *list) FAST_FUNC;
+
+ void data_align(archive_handle_t *archive_handle, unsigned boundary) FAST_FUNC;
+ const llist_t *find_list_entry(const llist_t *list, const char *filename) FAST_FUNC;
+diff --git a/testsuite/tar.tests b/testsuite/tar.tests
+index b7cd74ca5..1675b07b1 100755
+--- a/testsuite/tar.tests
++++ b/testsuite/tar.tests
+@@ -279,7 +279,7 @@ optional UUDECODE FEATURE_TAR_AUTODETECT FEATURE_SEAMLESS_BZ2
+ testing "tar does not extract into symlinks" "\
+ >>/tmp/passwd && uudecode -o input && tar xf input 2>&1 && rm passwd; cat /tmp/passwd; echo \$?
+ " "\
+-tar: skipping unsafe symlink to '/tmp/passwd' in archive, set EXTRACT_UNSAFE_SYMLINKS=1 to extract
++tar: can't create symlink 'passwd' to '/tmp/passwd'
+ 0
+ " \
+ "" "\
+@@ -299,7 +299,7 @@ optional UUDECODE FEATURE_TAR_AUTODETECT FEATURE_SEAMLESS_BZ2
+ testing "tar -k does not extract into symlinks" "\
+ >>/tmp/passwd && uudecode -o input && tar xf input -k 2>&1 && rm passwd; cat /tmp/passwd; echo \$?
+ " "\
+-tar: skipping unsafe symlink to '/tmp/passwd' in archive, set EXTRACT_UNSAFE_SYMLINKS=1 to extract
++tar: can't create symlink 'passwd' to '/tmp/passwd'
+ 0
+ " \
+ "" "\
+@@ -324,11 +324,11 @@ rm -rf etc usr
+ ' "\
+ etc/ssl/certs/3b2716e5.0
+ etc/ssl/certs/EBG_Elektronik_Sertifika_Hizmet_Sağlayıcısı.pem
+-tar: skipping unsafe symlink to '/usr/share/ca-certificates/mozilla/EBG_Elektronik_Sertifika_Hizmet_Sağlayıcısı.crt' in archive, set EXTRACT_UNSAFE_SYMLINKS=1 to extract
+ etc/ssl/certs/f80cc7f6.0
+ usr/share/ca-certificates/mozilla/EBG_Elektronik_Sertifika_Hizmet_Sağlayıcısı.crt
+ 0
+ etc/ssl/certs/3b2716e5.0 -> EBG_Elektronik_Sertifika_Hizmet_Sağlayıcısı.pem
++etc/ssl/certs/EBG_Elektronik_Sertifika_Hizmet_Sağlayıcısı.pem -> /usr/share/ca-certificates/mozilla/EBG_Elektronik_Sertifika_Hizmet_Sağlayıcısı.crt
+ etc/ssl/certs/f80cc7f6.0 -> EBG_Elektronik_Sertifika_Hizmet_Sağlayıcısı.pem
+ " \
+ "" ""
+@@ -346,9 +346,9 @@ ls symlink/bb_test_evilfile
+ ' "\
+ anything.txt
+ symlink
+-tar: skipping unsafe symlink to '/tmp' in archive, set EXTRACT_UNSAFE_SYMLINKS=1 to extract
+ symlink/bb_test_evilfile
+-0
++tar: can't create symlink 'symlink' to '/tmp'
++1
+ ls: /tmp/bb_test_evilfile: No such file or directory
+ ls: bb_test_evilfile: No such file or directory
+ symlink/bb_test_evilfile
+--
+2.16.2
+
--
2.16.2
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