Test --strip-components and fix it to actually work. Jaakko did a

good job writing this test; it exercises a lot of subtle cases.  The
trickiest one is that a hardlink to something that didn't get
extracted should not itself be extracted.  In some sense, this is not
the desired behavior (we'd rather restore the file), but it's the best
you can do in a single-pass restore of a tar archive.

The test here should be extended to exercise cpio and newc formats as
well, since their hardlink models are different, which will lead to
different handling of some of these edge cases.

Submitted by:	Jaakko Heinonen
MFC after:	30 days

3 files changed, 116 insertions, 16 deletions

diff --git a/usr.bin/tar/test/Makefile b/usr.bin/tar/test/Makefile
index fce819c..c05aaf9 100644
--- a/usr.bin/tar/test/Makefile
+++ b/usr.bin/tar/test/Makefile
@@ -18,6 +18,7 @@ TESTS=	\
 	test_option_q.c				\
 	test_patterns.c				\
 	test_stdio.c				\
+	test_strip_components.c			\
 	test_symlink_dir.c			\
 	test_version.c
 
diff --git a/usr.bin/tar/test/test_strip_components.c b/usr.bin/tar/test/test_strip_components.c
new file mode 100644
index 0000000..3150dfd
--- /dev/null
+++ b/usr.bin/tar/test/test_strip_components.c
@@ -0,0 +1,77 @@
+/*-
+ * Copyright (c) 2003-2007 Tim Kientzle
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR(S) ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR(S) BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+#include "test.h"
+__FBSDID("$FreeBSD$");
+
+static int
+touch(const char *fn)
+{
+	int fd = open(fn, O_RDWR | O_CREAT | 0644);
+	failure("Couldn't create file '%s', fd=%d, errno=%d (%s)\n",
+	    fn, fd, errno, strerror(errno));
+	if (!assert(fd > 0))
+		return (0); /* Failure. */
+	close(fd);
+	return (1); /* Success */
+}
+
+DEFINE_TEST(test_strip_components)
+{
+	struct stat st;
+
+	assertEqualInt(0, mkdir("d0", 0755));
+	assertEqualInt(0, chdir("d0"));
+	assertEqualInt(0, mkdir("d1", 0755));
+	assertEqualInt(0, mkdir("d1/d2", 0755));
+	assertEqualInt(0, mkdir("d1/d2/d3", 0755));
+	assertEqualInt(1, touch("d1/d2/f1"));
+	assertEqualInt(0, link("d1/d2/f1", "l1"));
+	assertEqualInt(0, link("d1/d2/f1", "d1/l2"));
+	assertEqualInt(0, symlink("d1/d2/f1", "s1"));
+	assertEqualInt(0, symlink("d2/f1", "d1/s2"));
+	assertEqualInt(0, chdir(".."));
+
+	assertEqualInt(0, systemf("%s -cf test.tar d0", testprog));
+
+	assertEqualInt(0, mkdir("target", 0755));
+	assertEqualInt(0, systemf("%s -x -C target --strip-components 2 "
+	    "-f test.tar", testprog));
+
+	failure("d0/ is too short and should not get restored");
+	assertEqualInt(-1, lstat("target/d0", &st));
+	failure("d0/d1/ is too short and should not get restored");
+	assertEqualInt(-1, lstat("target/d1", &st));
+	failure("d0/l1 is too short and should not get restored");
+	assertEqualInt(-1, lstat("target/l1", &st));
+	failure("d0/d1/l2 is a hardlink to file whose name was too short");
+	assertEqualInt(-1, lstat("target/l2", &st));
+	assertEqualInt(0, lstat("target/s2", &st));
+	failure("d0/d1/s2 is a symlink to something that won't be extracted");
+	assertEqualInt(-1, stat("target/s2", &st));
+	failure("d0/d1/d2 should be extracted");
+	assertEqualInt(0, lstat("target/d2", &st));
+	failure("d0/d1/d2/f1 is a hardlink to file whose name was too short");
+	assertEqualInt(-1, lstat("target/d2/f1", &st));
+}
diff --git a/usr.bin/tar/util.c b/usr.bin/tar/util.c
index 33281aa..638145a 100644
--- a/usr.bin/tar/util.c
+++ b/usr.bin/tar/util.c
@@ -51,6 +51,7 @@ __FBSDID("$FreeBSD$");
 
 static void	bsdtar_vwarnc(struct bsdtar *, int code,
 		    const char *fmt, va_list ap);
+static const char *strip_components(const char *path, int elements);
 
 /*
  * Print a string, taking care with any non-printable characters.
@@ -346,6 +347,31 @@ do_chdir(struct bsdtar *bsdtar)
 	bsdtar->pending_chdir = NULL;
 }
 
+const char *
+strip_components(const char *path, int elements)
+{
+	const char *p = path;
+
+	while (elements > 0) {
+		switch (*p++) {
+		case '/':
+			elements--;
+			path = p;
+			break;
+		case '\0':
+			/* Path is too short, skip it. */
+			return (NULL);
+		}
+	}
+
+	while (*path == '/')
+	       ++path;
+	if (*path == '\0')
+	       return (NULL);
+
+	return (path);
+}
+
 /*
  * Handle --strip-components and any future path-rewriting options.
  * Returns non-zero if the pathname should not be extracted.
@@ -402,24 +428,20 @@ edit_pathname(struct bsdtar *bsdtar, struct archive_entry *entry)
 #endif
 
 	/* Strip leading dir names as per --strip-components option. */
-	if ((r = bsdtar->strip_components) > 0) {
-		const char *p = name;
-
-		while (r > 0) {
-			switch (*p++) {
-			case '/':
-				r--;
-				name = p;
-				break;
-			case '\0':
-				/* Path is too short, skip it. */
+	if (bsdtar->strip_components > 0) {
+		const char *linkname = archive_entry_hardlink(entry);
+
+		name = strip_components(name, bsdtar->strip_components);
+		if (name == NULL)
+			return (1);
+
+		if (linkname != NULL) {
+			linkname = strip_components(linkname,
+			    bsdtar->strip_components);
+			if (linkname == NULL)
 				return (1);
-			}
+			archive_entry_copy_hardlink(entry, linkname);
 		}
-		while (*name == '/')
-			++name;
-		if (*name == '\0')
-			return (1);
 	}
 
 	/* Strip redundant leading '/' characters. */