Properly handle symlinks (hardlinks and .so only files were already ok):

Use the file name of the symlink but the inode number of the file pointed to,
such that we get multiple mlinks records but not multiple mpages records.
Also make sure they do not point outside the tree we are processing.

Issue found by kili@ in desktop-file-edit(1), thanks!

1 files changed, 75 insertions, 16 deletions

diff --git a/mandocdb.c b/mandocdb.c
index 206c7781..384f41f5 100644
--- a/mandocdb.c
+++ b/mandocdb.c
@@ -559,6 +559,7 @@ usage:
 static int
 treescan(void)
 {
+	char		 buf[PATH_MAX];
 	FTS		*f;
 	FTSENT		*ff;
 	struct mlink	*mlink;
@@ -570,11 +571,8 @@ treescan(void)
 	argv[0] = ".";
 	argv[1] = (char *)NULL;
 
-	/*
-	 * Walk through all components under the directory, using the
-	 * logical descent of files.
-	 */
-	f = fts_open((char * const *)argv, FTS_LOGICAL, NULL);
+	f = fts_open((char * const *)argv,
+	    FTS_PHYSICAL | FTS_NOCHDIR, NULL);
 	if (NULL == f) {
 		exitcode = (int)MANDOCLEVEL_SYSERR;
 		say("", "&fts_open");
@@ -586,11 +584,36 @@ treescan(void)
 
 	while (NULL != (ff = fts_read(f))) {
 		path = ff->fts_path + 2;
+		switch (ff->fts_info) {
+
+		/*
+		 * Symbolic links require various sanity checks,
+		 * then get handled just like regular files.
+		 */
+		case (FTS_SL):
+			if (NULL == realpath(path, buf)) {
+				if (warnings)
+					say(path, "&realpath");
+				continue;
+			}
+			if (strstr(buf, basedir) != buf) {
+				if (warnings) say("",
+				    "%s: outside base directory", buf);
+				continue;
+			}
+			/* Use logical inode to avoid mpages dupe. */
+			if (-1 == stat(path, ff->fts_statp)) {
+				if (warnings)
+					say(path, "&stat");
+				continue;
+			}
+			/* FALLTHROUGH */
+
 		/*
 		 * If we're a regular file, add an mlink by using the
 		 * stored directory data and handling the filename.
 		 */
-		if (FTS_F == ff->fts_info) {
+		case (FTS_F):
 			if (0 == strcmp(path, MANDOC_DB))
 				continue;
 			if ( ! use_all && ff->fts_level < 2) {
@@ -646,8 +669,13 @@ treescan(void)
 			mlink->gzip = gzip;
 			mlink_add(mlink, ff->fts_statp);
 			continue;
-		} else if (FTS_D != ff->fts_info &&
-				FTS_DP != ff->fts_info) {
+
+		case (FTS_D):
+			/* FALLTHROUGH */
+		case (FTS_DP):
+			break;
+
+		default:
 			if (warnings)
 				say(path, "Not a regular file");
 			continue;
@@ -736,6 +764,27 @@ filescan(const char *file)
 	if (0 == strncmp(file, "./", 2))
 		file += 2;
 
+	/*
+	 * We have to do lstat(2) before realpath(3) loses
+	 * the information whether this is a symbolic link.
+	 * We need to know that because for symbolic links,
+	 * we want to use the orginal file name, while for
+	 * regular files, we want to use the real path.
+	 */
+	if (-1 == lstat(file, &st)) {
+		exitcode = (int)MANDOCLEVEL_BADARG;
+		say(file, "&lstat");
+		return;
+	} else if (0 == ((S_IFREG | S_IFLNK) & st.st_mode)) {
+		exitcode = (int)MANDOCLEVEL_BADARG;
+		say(file, "Not a regular file");
+		return;
+	}
+
+	/*
+	 * We have to resolve the file name to the real path
+	 * in any case for the base directory check.
+	 */
 	if (NULL == realpath(file, buf)) {
 		exitcode = (int)MANDOCLEVEL_BADARG;
 		say(file, "&realpath");
@@ -752,14 +801,24 @@ filescan(const char *file)
 		return;
 	}
 
-	if (-1 == stat(buf, &st)) {
-		exitcode = (int)MANDOCLEVEL_BADARG;
-		say(file, "&stat");
-		return;
-	} else if ( ! (S_IFREG & st.st_mode)) {
-		exitcode = (int)MANDOCLEVEL_BADARG;
-		say(file, "Not a regular file");
-		return;
+	/*
+	 * Now we are sure the file is inside our tree.
+	 * If it is a symbolic link, ignore the real path
+	 * and use the original name.
+	 * This implies passing stuff like "cat1/../man1/foo.1"
+	 * on the command line won't work.  So don't do that.
+	 * Note the stat(2) can still fail if the link target
+	 * doesn't exist.
+	 */
+	if (S_IFLNK & st.st_mode) {
+		if (-1 == stat(buf, &st)) {
+			exitcode = (int)MANDOCLEVEL_BADARG;
+			say(file, "&stat");
+			return;
+		}
+		strlcpy(buf, file, sizeof(buf));
+		start = strstr(buf, basedir) == buf ?
+		    buf + strlen(basedir) + 1 : buf;
 	}
 
 	mlink = mandoc_calloc(1, sizeof(struct mlink));