upstream: SFTP protocol extension to allow the server to expand

~-prefixed paths, in particular ~user ones. Allows scp in sftp mode to accept
these paths, like scp in rcp mode does.

prompted by and much discussion deraadt@
ok markus@

OpenBSD-Commit-ID: 7d794def9e4de348e1e777f6030fc9bafdfff392

1 files changed, 35 insertions, 14 deletions

diff --git a/misc.c b/misc.c
index adfe9033..b8d1040d 100644
--- a/misc.c
+++ b/misc.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: misc.c,v 1.168 2021/07/12 06:22:57 dtucker Exp $ */
+/* $OpenBSD: misc.c,v 1.169 2021/08/09 23:47:44 djm Exp $ */
 /*
  * Copyright (c) 2000 Markus Friedl.  All rights reserved.
  * Copyright (c) 2005-2020 Damien Miller.  All rights reserved.
@@ -1115,29 +1115,37 @@ freeargs(arglist *args)
  * Expands tildes in the file name.  Returns data allocated by xmalloc.
  * Warning: this calls getpw*.
  */
-char *
-tilde_expand_filename(const char *filename, uid_t uid)
+int
+tilde_expand(const char *filename, uid_t uid, char **retp)
 {
 	const char *path, *sep;
 	char user[128], *ret;
 	struct passwd *pw;
 	u_int len, slash;
 
-	if (*filename != '~')
-		return (xstrdup(filename));
+	if (*filename != '~') {
+		*retp = xstrdup(filename);
+		return 0;
+	}
 	filename++;
 
 	path = strchr(filename, '/');
 	if (path != NULL && path > filename) {		/* ~user/path */
 		slash = path - filename;
-		if (slash > sizeof(user) - 1)
-			fatal("tilde_expand_filename: ~username too long");
+		if (slash > sizeof(user) - 1) {
+			error_f("~username too long");
+			return -1;
+		}
 		memcpy(user, filename, slash);
 		user[slash] = '\0';
-		if ((pw = getpwnam(user)) == NULL)
-			fatal("tilde_expand_filename: No such user %s", user);
-	} else if ((pw = getpwuid(uid)) == NULL)	/* ~/path */
-		fatal("tilde_expand_filename: No such uid %ld", (long)uid);
+		if ((pw = getpwnam(user)) == NULL) {
+			error_f("No such user %s", user);
+			return -1;
+		}
+	} else if ((pw = getpwuid(uid)) == NULL) {	/* ~/path */
+		error_f("No such uid %ld", (long)uid);
+		return -1;
+	}
 
 	/* Make sure directory has a trailing '/' */
 	len = strlen(pw->pw_dir);
@@ -1150,10 +1158,23 @@ tilde_expand_filename(const char *filename, uid_t uid)
 	if (path != NULL)
 		filename = path + 1;
 
-	if (xasprintf(&ret, "%s%s%s", pw->pw_dir, sep, filename) >= PATH_MAX)
-		fatal("tilde_expand_filename: Path too long");
+	if (xasprintf(&ret, "%s%s%s", pw->pw_dir, sep, filename) >= PATH_MAX) {
+		error_f("Path too long");
+		return -1;
+	}
+
+	*retp = ret;
+	return 0;
+}
 
-	return (ret);
+char *
+tilde_expand_filename(const char *filename, uid_t uid)
+{
+	char *ret;
+
+	if (tilde_expand(filename, uid, &ret) != 0)
+		cleanup_exit(255);
+	return ret;
 }
 
 /*