gnu: openssh: Trust Guix store directory

* gnu/local.mk (dist_patch_DATA): Add the patch
* gnu/packages/patches/openssh-trust-guix-store-directory.patch: Patch it
* gnu/packages/ssh.scm (openssh[source]): Use it.

Signed-off-by: Ludovic Courtès <ludo@gnu.org>

gnu/local.mk

@@ -1568,6 +1568,7 @@ dist_patch_DATA =						\
   %D%/packages/patches/openjdk-15-xcursor-no-dynamic.patch	\
   %D%/packages/patches/openmpi-mtl-priorities.patch		\
   %D%/packages/patches/openssh-hurd.patch			\
+  %D%/packages/patches/openssh-trust-guix-store-directory.patch	\
   %D%/packages/patches/openresolv-restartcmd-guix.patch	\
   %D%/packages/patches/openrgb-unbundle-hueplusplus.patch	\
   %D%/packages/patches/opensles-add-license-file.patch			\

gnu/packages/patches/openssh-trust-guix-store-directory.patch

@@ -0,0 +1,40 @@
+From 0d85bbd42ddcd442864a9ba4719aca8b70d68048 Mon Sep 17 00:00:00 2001
+From: Alexey Abramov <levenson@mmer.org>
+Date: Fri, 22 Apr 2022 11:32:15 +0200
+Subject: [PATCH] Trust guix store directory
+
+To be able to execute binaries defined in OpenSSH configuration, we
+need to tell OpenSSH that we can trust Guix store objects. safe_path
+procedure takes a canonical path and for each component, walking
+upwards, checks ownership and permissions constrains which are: must
+be owned by root, not writable by group or others.
+---
+ misc.c | 5 +++++
+ 1 file changed, 5 insertions(+)
+
+diff --git a/misc.c b/misc.c
+index 0134d69..7131d5e 100644
+--- a/misc.c
++++ b/misc.c
+@@ -2146,6 +2146,7 @@ int
+ safe_path(const char *name, struct stat *stp, const char *pw_dir,
+     uid_t uid, char *err, size_t errlen)
+ {
++        static const char guix_store[] = @STORE_DIRECTORY@;
+ 	char buf[PATH_MAX], homedir[PATH_MAX];
+ 	char *cp;
+ 	int comparehome = 0;
+@@ -2178,6 +2179,10 @@ safe_path(const char *name, struct stat *stp, const char *pw_dir,
+ 		}
+ 		strlcpy(buf, cp, sizeof(buf));
+ 
++		/* If we are past the Guix store then we can stop */
++		if (strcmp(guix_store, buf) == 0)
++			break;
++
+ 		if (stat(buf, &st) == -1 ||
+ 		    (!platform_sys_dir_uid(st.st_uid) && st.st_uid != uid) ||
+ 		    (st.st_mode & 022) != 0) {
+-- 
+2.34.0
+

gnu/packages/ssh.scm

@@ -189,7 +189,8 @@ a server that supports the SSH-2 protocol.")
              (method url-fetch)
              (uri (string-append "mirror://openbsd/OpenSSH/portable/"
                                  "openssh-" version ".tar.gz"))
-             (patches (search-patches "openssh-hurd.patch"))
+             (patches (search-patches "openssh-hurd.patch"
+                                      "openssh-trust-guix-store-directory.patch"))
              (sha256
               (base32
                "1ry5prcax0134v6srkgznpl9ch5snkgq7yvjqvd8c5mbnxa7cjgx"))))
@@ -249,6 +250,11 @@ a server that supports the SSH-2 protocol.")
              (substitute* "Makefile"
                (("PRIVSEP_PATH=/var/empty")
                 (string-append "PRIVSEP_PATH=" out "/var/empty"))))))
+        (add-after 'configure 'set-store-location
+          (lambda* _
+            (substitute* "misc.c"
+              (("@STORE_DIRECTORY@")
+               (string-append "\"" (%store-directory) "\"")))))
         (add-before 'check 'patch-tests
          (lambda _
            (substitute* "regress/test-exec.sh"