Fix partially matching relative paths in xinstall.

Approved by:	so
Security:	FreeBSD-EN-19:09.xinstall

2 files changed, 37 insertions, 2 deletions

diff --git a/usr.bin/xinstall/tests/install_test.sh b/usr.bin/xinstall/tests/install_test.sh
index 4332f9b..92044f3 100755
--- a/usr.bin/xinstall/tests/install_test.sh
+++ b/usr.bin/xinstall/tests/install_test.sh
@@ -377,6 +377,29 @@ mkdir_simple_body() {
 	atf_check install -d dir1/dir2/dir3
 }
 
+atf_test_case symbolic_link_relative_absolute_common
+symbolic_link_relative_absolute_common_head() {
+	atf_set "descr" "Verify -l rs with absolute paths having common components"
+}
+symbolic_link_relative_absolute_common_body() {
+	filename=foo.so
+	src_path=lib
+	src_path_prefixed=$PWD/$src_path
+	dest_path=$PWD/libexec/
+	src_file=$src_path_prefixed/$filename
+	dest_file=$dest_path/$filename
+
+	atf_check mkdir $src_path_prefixed $dest_path
+	atf_check touch $src_file
+	atf_check install -l sr $src_file $dest_path
+
+	dest_path_relative=$(readlink $dest_file)
+	src_path_relative="../lib/$filename"
+	if [ "$src_path_relative" != "$dest_path_relative" ]; then
+		atf_fail "unexpected symlink contents ('$src_path_relative' != '$dest_path_relative')"
+	fi
+}
+
 atf_init_test_cases() {
 	atf_add_test_case copy_to_nonexistent
 	atf_add_test_case copy_to_nonexistent_safe
@@ -415,5 +438,6 @@ atf_init_test_cases() {
 	atf_add_test_case symbolic_link_relative_absolute_source_and_dest1
 	atf_add_test_case symbolic_link_relative_absolute_source_and_dest1_double_slash
 	atf_add_test_case symbolic_link_relative_absolute_source_and_dest2
+	atf_add_test_case symbolic_link_relative_absolute_common
 	atf_add_test_case mkdir_simple
 }
diff --git a/usr.bin/xinstall/xinstall.c b/usr.bin/xinstall/xinstall.c
index 16eba77..6688591 100644
--- a/usr.bin/xinstall/xinstall.c
+++ b/usr.bin/xinstall/xinstall.c
@@ -667,7 +667,7 @@ makelink(const char *from_name, const char *to_name,
 	}
 
 	if (dolink & LN_RELATIVE) {
-		char *to_name_copy, *cp, *d, *s;
+		char *to_name_copy, *cp, *d, *ld, *ls, *s;
 
 		if (*from_name != '/') {
 			/* this is already a relative link */
@@ -703,8 +703,19 @@ makelink(const char *from_name, const char *to_name,
 		free(to_name_copy);
 
 		/* Trim common path components. */
-		for (s = src, d = dst; *s == *d; s++, d++)
+		ls = ld = NULL;
+		for (s = src, d = dst; *s == *d; ls = s, ld = d, s++, d++)
 			continue;
+		/*
+		 * If we didn't end after a directory separator, then we've
+		 * falsely matched the last component.  For example, if one
+		 * invoked install -lrs /lib/foo.so /libexec/ then the source
+		 * would terminate just after the separator while the
+		 * destination would terminate in the middle of 'libexec',
+		 * leading to a full directory getting falsely eaten.
+		 */
+		if ((ls != NULL && *ls != '/') || (ld != NULL && *ld != '/'))
+			s--, d--;
 		while (*s != '/')
 			s--, d--;