guix/gnu/packages/patches/libarchive-fix-symlink-check.patch

Make sure to check for symlinks even if the pathname is very long:

https://github.com/libarchive/libarchive/issues/744

Patch copied from upstream repository:

https://github.com/libarchive/libarchive/commit/1fa9c7bf90f0862036a99896b0501c381584451a

From 1fa9c7bf90f0862036a99896b0501c381584451a Mon Sep 17 00:00:00 2001
From: Tim Kientzle <kientzle@acm.org>
Date: Sun, 21 Aug 2016 17:11:45 -0700
Subject: [PATCH] Issue #744 (part of Issue #743): Enforce sandbox with very
 long pathnames

Because check_symlinks is handled separately from the deep-directory
support, very long pathnames cause problems.  Previously, the code
ignored most failures to lstat() a path component.  In particular,
this led to check_symlinks always passing for very long paths, which
in turn provides a way to evade the symlink checks in the sandboxing
code.

We now fail on unrecognized lstat() failures, which plugs this
hole at the cost of disabling deep directory support when the
user requests sandboxing.

TODO:  This probably cannot be completely fixed without
entirely reimplementing the deep directory support to
integrate the symlink checks.  I want to reimplement the
deep directory hanlding someday anyway; openat() and
related system calls now provide a much cleaner way to
handle deep directories than the chdir approach used by this
code.
---
 libarchive/archive_write_disk_posix.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/libarchive/archive_write_disk_posix.c b/libarchive/archive_write_disk_posix.c
index 39ee3b6..8f0421e 100644
--- a/libarchive/archive_write_disk_posix.c
+++ b/libarchive/archive_write_disk_posix.c
@@ -2401,8 +2401,18 @@ check_symlinks(struct archive_write_disk *a)
 		r = lstat(a->name, &st);
 		if (r != 0) {
 			/* We've hit a dir that doesn't exist; stop now. */
-			if (errno == ENOENT)
+			if (errno == ENOENT) {
 				break;
+			} else {
+				/* Note: This effectively disables deep directory
+				 * support when security checks are enabled.
+				 * Otherwise, very long pathnames that trigger
+				 * an error here could evade the sandbox.
+				 * TODO: We could do better, but it would probably
+				 * require merging the symlink checks with the
+				 * deep-directory editing. */
+				return (ARCHIVE_FAILED);
+			}
 		} else if (S_ISLNK(st.st_mode)) {
 			if (c == '\0') {
 				/*