Fix: tar2sqfs: if --root-becomes is used, also retarget links

In addition to skipping non-prefixed files and stripping the prefix
off of entries we accept, the targets of links also have to be altered,
since they can be absolute paths with the root prefix attached.

This can affect symbolic links as well. Altough they are allowed to
point into nowhere, across filesystem boundaries, they may also be
absolute paths refering to existing locations in the filesystem, so
no distinction is made by default.

However, the later may be intended (e.g. only a subdirectory is packed
into SquashFS and then mounted at that location), so a command line
switch is added to disable symlink retargetting.

Signed-off-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at>

1 files changed, 21 insertions, 0 deletions

diff --git a/bin/tar2sqfs/process_tarball.c b/bin/tar2sqfs/process_tarball.c
index 7492f27..40a8157 100644
--- a/bin/tar2sqfs/process_tarball.c
+++ b/bin/tar2sqfs/process_tarball.c
@@ -203,6 +203,7 @@ int process_tarball(istream_t *input_file, sqfs_writer_t *sqfs)
 	sqfs_u64 offset, count;
 	sparse_map_t *m;
 	size_t rootlen;
+	char *target;
 	int ret;
 
 	rootlen = root_becomes == NULL ? 0 : strlen(root_becomes);
@@ -251,6 +252,26 @@ int process_tarball(istream_t *input_file, sqfs_writer_t *sqfs)
 				      stderr);
 				skip = true;
 			}
+
+			if (hdr.link_target != NULL &&
+			    (hdr.is_hard_link || !no_symlink_retarget)) {
+				target = strdup(hdr.link_target);
+				if (target == NULL) {
+					fprintf(stderr, "packing '%s': %s\n",
+						hdr.name, strerror(errno));
+					goto fail;
+				}
+
+				if (canonicalize_name(target) == 0 &&
+				    !strncmp(target, root_becomes, rootlen) &&
+				    target[rootlen] == '/') {
+					memmove(hdr.link_target,
+						target + rootlen,
+						strlen(target + rootlen) + 1);
+				}
+
+				free(target);
+			}
 		} else if (hdr.name[0] == '\0') {
 			is_root = true;
 		}