From a84db18fc71d09e801df0ebca048d82e90b32c6a Mon Sep 17 00:00:00 2001 From: Denys Vlasenko Date: Tue, 20 Feb 2018 15:57:45 +0100 Subject: 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 --- archival/libarchive/data_extract_all.c | 28 ++++---------- archival/libarchive/unsafe_symlink_target.c | 59 +++++++++++++---------------- archival/tar.c | 2 + archival/unzip.c | 25 ++++++------ 4 files changed, 49 insertions(+), 65 deletions(-) (limited to 'archival') 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" -- cgit v1.2.3