pkgfs_open: follow symlinks

Caller is not interested in symlinks follow them.
Throw an error if too many links encountered.

Reviewed by:	stevek
Sponsored by:	Juniper Networks
--This line, and those below, will be ignored--
> Description of fields to fill in above:                     76 columns --|
> PR:                       If a GNATS PR is affected by the change.
> Differential Revision:    https://reviews.freebsd.org/D### (*full* phabric URL needed).
> Submitted by:             If someone else sent in the change.
> Reviewed by:              If someone else reviewed your modification.
> Approved by:              If you needed approval for this commit.
> Obtained from:            If the change is from a third party.
> MFC after:                N [day[s]|week[s]|month[s]].  Request a reminder email.
> MFH:                      Ports tree branch name.  Request approval for merge.
> Relnotes:                 Set to 'yes' for mention in release notes.
> Security:                 Vulnerability reference (one per line) or description.
> Sponsored by:             If the change was sponsored by an organization.
> Empty fields above will be automatically removed.

Change-Id: I4ef92ff256f503c620dc5bba79ed93b32cb2330d

1 files changed, 18 insertions, 1 deletions

diff --git a/stand/libsa/pkgfs.c b/stand/libsa/pkgfs.c
index 8018edd60d57..ffa16309ee6a 100644
--- a/stand/libsa/pkgfs.c
+++ b/stand/libsa/pkgfs.c
@@ -199,7 +199,7 @@ static int new_package(int, struct package **);
 static struct tarfile *scan_tarfile(struct package *, struct tarfile *);
 
 static int
-pkg_open(const char *fn, struct open_file *f)
+pkg_open_follow(const char *fn, struct open_file *f, int lnks)
 {
 	struct tarfile *tf;
 
@@ -242,6 +242,17 @@ pkg_open(const char *fn, struct open_file *f)
 		if (strcmp(fn, tf->tf_hdr.ut_name) == 0) {
 			f->f_fsdata = tf;
 			tf->tf_fp = 0;	/* Reset the file pointer. */
+			DBG(("%s: found %s type %c\n", __func__,
+			     fn, tf->tf_hdr.ut_typeflag[0]));
+			if (tf->tf_hdr.ut_typeflag[0] == '2') {
+			    /* we have a symlink
+			     * Note: ut_linkname is only 100 chars!
+			     */
+			    if (lnks++ >= 8)
+				return (EMLINK);
+			    return pkg_open_follow(tf->tf_hdr.ut_linkname,
+				f, lnks);
+			}
 			return (0);
 		}
 		tf = scan_tarfile(package, tf);
@@ -250,6 +261,12 @@ pkg_open(const char *fn, struct open_file *f)
 }
 
 static int
+pkg_open(const char *fn, struct open_file *f)
+{
+    return pkg_open_follow(fn, f, 0);
+}
+
+static int
 pkg_close(struct open_file *f)
 {
 	struct tarfile *tf;