tar: add support for --strip-components=N

function                                             old     new   delta
data_extract_all                                     882     995    +113
tar_longopts                                         290     309     +19
tar_main                                             938     942      +4
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 3/0 up/down: 136/0)             Total: 136 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

2 files changed, 77 insertions, 32 deletions

diff --git a/archival/libarchive/data_extract_all.c b/archival/libarchive/data_extract_all.c
index 45776dcbe..bd51d2ad3 100644
--- a/archival/libarchive/data_extract_all.c
+++ b/archival/libarchive/data_extract_all.c
@@ -8,9 +8,17 @@
 
 void FAST_FUNC data_extract_all(archive_handle_t *archive_handle)
 {
+
         file_header_t *file_header = archive_handle->file_header;
         int dst_fd;
         int res;
+#if ENABLE_FEATURE_TAR_LONG_OPTIONS
+        char *dst_name;
+        char *dst_link;
+#else
+# define dst_name (file_header->name)
+# define dst_link (file_header->link_target)
+#endif
 
 #if ENABLE_FEATURE_TAR_SELINUX
         char *sctx = archive_handle->tar__sctx[PAX_NEXT_FILE];
@@ -23,11 +31,47 @@ void FAST_FUNC data_extract_all(archive_handle_t *archive_handle)
         }
 #endif
 
+#if ENABLE_FEATURE_TAR_LONG_OPTIONS
+        dst_name = file_header->name;
+        dst_link = file_header->link_target;
+        if (archive_handle->tar__strip_components) {
+                unsigned n = archive_handle->tar__strip_components;
+                do {
+                        dst_name = strchr(dst_name, '/');
+                        if (!dst_name || dst_name[1] == '\0') {
+                                data_skip(archive_handle);
+                                return;
+                        }
+                        dst_name++;
+                        /*
+                         * Link target is shortened only for hardlinks:
+                         * softlinks restored unchanged.
+                         */
+                        if (S_ISREG(file_header->mode)
+                         && file_header->size == 0
+                         && dst_link
+                        ) {
+// GNU tar 1.26 does not check that we reached end of link name:
+// if "dir/hardlink" is hardlinked to "file",
+// tar xvf a.tar --strip-components=1 says:
+//  tar: hardlink: Cannot hard link to '': No such file or directory
+// and continues processing. We silently skip such entries.
+                                dst_link = strchr(dst_link, '/');
+                                if (!dst_link || dst_link[1] == '\0') {
+                                        data_skip(archive_handle);
+                                        return;
+                                }
+                                dst_link++;
+                        }
+                } while (--n != 0);
+        }
+#endif
+
         if (archive_handle->ah_flags & ARCHIVE_CREATE_LEADING_DIRS) {
-                char *slash = strrchr(file_header->name, '/');
+                char *slash = strrchr(dst_name, '/');
                 if (slash) {
                         *slash = '\0';
-                        bb_make_directory(file_header->name, -1, FILEUTILS_RECUR);
+                        bb_make_directory(dst_name, -1, FILEUTILS_RECUR);
                         *slash = '/';
                 }
         }
@@ -38,8 +82,8 @@ void FAST_FUNC data_extract_all(archive_handle_t *archive_handle)
                         /* Is it hardlink?
                          * We encode hard links as regular files of size 0 with a symlink */
                         if (S_ISREG(file_header->mode)
-                         && file_header->link_target
                          && file_header->size == 0
+                         && dst_link
                         ) {
                                 /* Ugly special case:
                                  * tar cf t.tar hardlink1 hardlink2 hardlink1
@@ -48,22 +92,22 @@ void FAST_FUNC data_extract_all(archive_handle_t *archive_handle)
                                  * hardlink2 -> hardlink1
                                  * hardlink1 -> hardlink1 <== !!!
                                  */
-                                if (strcmp(file_header->link_target, file_header->name) == 0)
+                                if (strcmp(dst_link, dst_name) == 0)
                                         goto ret;
                         }
                         /* Proceed with deleting */
-                        if (unlink(file_header->name) == -1
+                        if (unlink(dst_name) == -1
                          && errno != ENOENT
                         ) {
                                 bb_perror_msg_and_die("can't remove old file %s",
-                                                file_header->name);
+                                                dst_name);
                         }
                 }
         }
         else if (archive_handle->ah_flags & ARCHIVE_EXTRACT_NEWER) {
                 /* Remove the existing entry if its older than the extracted entry */
                 struct stat existing_sb;
-                if (lstat(file_header->name, &existing_sb) == -1) {
+                if (lstat(dst_name, &existing_sb) == -1) {
                         if (errno != ENOENT) {
                                 bb_perror_msg_and_die("can't stat old file");
                         }
@@ -73,30 +117,30 @@ void FAST_FUNC data_extract_all(archive_handle_t *archive_handle)
                          && !S_ISDIR(file_header->mode)
                         ) {
                                 bb_error_msg("%s not created: newer or "
-                                        "same age file exists", file_header->name);
+                                        "same age file exists", dst_name);
                         }
                         data_skip(archive_handle);
                         goto ret;
                 }
-                else if ((unlink(file_header->name) == -1) && (errno != EISDIR)) {
+                else if ((unlink(dst_name) == -1) && (errno != EISDIR)) {
                         bb_perror_msg_and_die("can't remove old file %s",
-                                        file_header->name);
+                                        dst_name);
                 }
         }
 
         /* Handle hard links separately
          * We encode hard links as regular files of size 0 with a symlink */
         if (S_ISREG(file_header->mode)
-         && file_header->link_target
          && file_header->size == 0
+         && dst_link
         ) {
-                /* hard link */
-                res = link(file_header->link_target, file_header->name);
-                if ((res == -1) && !(archive_handle->ah_flags & ARCHIVE_EXTRACT_QUIET)) {
+                /* Hard link */
+                res = link(dst_link, dst_name);
+                if (res != 0 && !(archive_handle->ah_flags & ARCHIVE_EXTRACT_QUIET)) {
                         bb_perror_msg("can't create %slink "
                                         "from %s to %s", "hard",
-                                        file_header->name,
-                                        file_header->link_target);
+                                        dst_name,
+                                        dst_link);
                 }
                 /* Hardlinks have no separate mode/ownership, skip chown/chmod */
                 goto ret;
@@ -106,17 +150,17 @@ void FAST_FUNC data_extract_all(archive_handle_t *archive_handle)
         switch (file_header->mode & S_IFMT) {
         case S_IFREG: {
                 /* Regular file */
-                char *dst_name;
+                char *dst_nameN;
                 int flags = O_WRONLY | O_CREAT | O_EXCL;
                 if (archive_handle->ah_flags & ARCHIVE_O_TRUNC)
                         flags = O_WRONLY | O_CREAT | O_TRUNC;
-                dst_name = file_header->name;
+                dst_nameN = dst_name;
 #ifdef ARCHIVE_REPLACE_VIA_RENAME
                 if (archive_handle->ah_flags & ARCHIVE_REPLACE_VIA_RENAME)
                         /* rpm-style temp file name */
-                        dst_name = xasprintf("%s;%x", dst_name, (int)getpid());
+                        dst_nameN = xasprintf("%s;%x", dst_name, (int)getpid());
 #endif
-                dst_fd = xopen3(dst_name,
+                dst_fd = xopen3(dst_nameN,
                         flags,
                         file_header->mode
                         );
@@ -124,32 +168,32 @@ void FAST_FUNC data_extract_all(archive_handle_t *archive_handle)
                 close(dst_fd);
 #ifdef ARCHIVE_REPLACE_VIA_RENAME
                 if (archive_handle->ah_flags & ARCHIVE_REPLACE_VIA_RENAME) {
-                        xrename(dst_name, file_header->name);
-                        free(dst_name);
+                        xrename(dst_nameN, dst_name);
+                        free(dst_nameN);
                 }
 #endif
                 break;
         }
         case S_IFDIR:
-                res = mkdir(file_header->name, file_header->mode);
+                res = mkdir(dst_name, file_header->mode);
                 if ((res == -1)
                  && (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", file_header->name);
+                        bb_perror_msg("can't make dir %s", dst_name);
                 }
                 break;
         case S_IFLNK:
                 /* Symlink */
 //TODO: what if file_header->link_target == NULL (say, corrupted tarball?)
-                res = symlink(file_header->link_target, file_header->name);
-                if ((res == -1)
+                res = symlink(file_header->link_target, dst_name);
+                if (res != 0
                  && !(archive_handle->ah_flags & ARCHIVE_EXTRACT_QUIET)
                 ) {
                         bb_perror_msg("can't create %slink "
                                 "from %s to %s", "sym",
-                                file_header->name,
+                                dst_name,
                                 file_header->link_target);
                 }
                 break;
@@ -157,11 +201,11 @@ void FAST_FUNC data_extract_all(archive_handle_t *archive_handle)
         case S_IFBLK:
         case S_IFCHR:
         case S_IFIFO:
-                res = mknod(file_header->name, file_header->mode, file_header->device);
+                res = mknod(dst_name, file_header->mode, file_header->device);
                 if ((res == -1)
                  && !(archive_handle->ah_flags & ARCHIVE_EXTRACT_QUIET)
                 ) {
-                        bb_perror_msg("can't create node %s", file_header->name);
+                        bb_perror_msg("can't create node %s", dst_name);
                 }
                 break;
         default:
@@ -186,20 +230,20 @@ void FAST_FUNC data_extract_all(archive_handle_t *archive_handle)
                         }
 #endif
                         /* GNU tar 1.15.1 uses chown, not lchown */
-                        chown(file_header->name, uid, gid);
+                        chown(dst_name, uid, gid);
                 }
                 /* uclibc has no lchmod, glibc is even stranger -
                  * it has lchmod which seems to do nothing!
                  * so we use chmod... */
                 if (!(archive_handle->ah_flags & ARCHIVE_DONT_RESTORE_PERM)) {
-                        chmod(file_header->name, file_header->mode);
+                        chmod(dst_name, file_header->mode);
                 }
                 if (archive_handle->ah_flags & ARCHIVE_RESTORE_DATE) {
                         struct timeval t[2];
 
                         t[1].tv_sec = t[0].tv_sec = file_header->mtime;
                         t[1].tv_usec = t[0].tv_usec = 0;
-                        utimes(file_header->name, t);
+                        utimes(dst_name, t);
                 }
         }
 
diff --git a/archival/libarchive/get_header_tar.c b/archival/libarchive/get_header_tar.c
index fb68673b9..ac2be726f 100644
--- a/archival/libarchive/get_header_tar.c
+++ b/archival/libarchive/get_header_tar.c
@@ -418,6 +418,7 @@ char FAST_FUNC get_header_tar(archive_handle_t *archive_handle)
 
         /* Everything up to and including last ".." component is stripped */
         overlapping_strcpy(file_header->name, strip_unsafe_prefix(file_header->name));
+//TODO: do the same for file_header->link_target?
 
         /* Strip trailing '/' in directories */
         /* Must be done after mode is set as '/' is used to check if it's a directory */