commit 07ffb49749c310b82e44278ae05e081d6f4a82bf
Author: Hans Petter Jansson <hpj@cl.no>
Date:   Fri Sep 27 01:57:16 2019 +0200

    ssh-keygen: Preserve known_hosts permissions on rewrite
    
    Transfer the permissions of the old known_hosts file instead of
    just going with what mkstemp() gives us. This is useful in corner
    cases where known_hosts is shared between users.

diff --git a/ssh-keygen.c b/ssh-keygen.c
index 03a7fe5..ca8a309 100644
--- a/ssh-keygen.c
+++ b/ssh-keygen.c
@@ -1338,6 +1338,11 @@ do_known_hosts(struct passwd *pw, const char *name)
 		if (inplace)
 			unlink(tmp);
 	} else if (inplace) {
+		struct stat st;
+
+		/* Get metadata for existing file */
+		r = stat(identity_file, &st);
+
 		/* Backup existing file */
 		if (unlink(old) == -1 && errno != ENOENT)
 			fatal("unlink %.100s: %s", old, strerror(errno));
@@ -1352,6 +1357,12 @@ do_known_hosts(struct passwd *pw, const char *name)
 			unlink(old);
 			exit(1);
 		}
+		/* Preserve permissions; non-critical */
+		if (r != -1)
+			r = chown(identity_file, st.st_uid, st.st_gid);
+		if (r != -1)
+			chmod(identity_file,
+			      st.st_mode & (S_IRWXU | S_IRWXG | S_IRWXO));
 
 		printf("%s updated.\n", identity_file);
 		printf("Original contents retained as %s\n", old);