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authorGravatar Denys Vlasenko <vda.linux@googlemail.com>2018-02-20 15:57:45 +0100
committerGravatar Denys Vlasenko <vda.linux@googlemail.com>2018-02-20 16:06:53 +0100
commita84db18fc71d09e801df0ebca048d82e90b32c6a (patch)
tree1eda8cd659f78406f1b9f86d5e0b5757af20bad9
parent95121d98e6da12599246d8e25c3f300e422a06fb (diff)
downloadbusybox-a84db18fc71d09e801df0ebca048d82e90b32c6a.tar.gz
busybox-a84db18fc71d09e801df0ebca048d82e90b32c6a.tar.bz2
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@googlemail.com>
-rw-r--r--archival/libarchive/data_extract_all.c28
-rw-r--r--archival/libarchive/unsafe_symlink_target.c59
-rw-r--r--archival/tar.c2
-rw-r--r--archival/unzip.c25
-rw-r--r--include/bb_archive.h23
-rwxr-xr-xtestsuite/tar.tests10
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