Because pledge(2) does not allow us to pass directory file descriptors

around, we can't use file descriptors for the working directory because
we will be unable to pass it to a privileged process to tell it where to
read or write files or spawn children. So move tmux back to using
strings for the current working directory. We try to check it exists
with access() when it is set but ultimately fall back to ~ if it fails
at time of use (or / if that fails too).

1 files changed, 18 insertions, 19 deletions

diff --git a/usr.bin/tmux/cmd-save-buffer.c b/usr.bin/tmux/cmd-save-buffer.c
index 4dc46a65285..b85a16bdb63 100644
--- a/usr.bin/tmux/cmd-save-buffer.c
+++ b/usr.bin/tmux/cmd-save-buffer.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: cmd-save-buffer.c,v 1.30 2015/08/29 09:36:46 nicm Exp $ */
+/* $OpenBSD: cmd-save-buffer.c,v 1.31 2015/10/31 08:13:58 nicm Exp $ */
 
 /*
  * Copyright (c) 2009 Tiago Cunha <me@tiagocunha.org>
@@ -57,10 +57,10 @@ cmd_save_buffer_exec(struct cmd *self, struct cmd_q *cmdq)
 	struct client		*c = cmdq->client;
 	struct session          *s;
 	struct paste_buffer	*pb;
-	const char		*path, *bufname, *bufdata, *start, *end;
-	char			*msg;
+	const char		*path, *bufname, *bufdata, *start, *end, *cwd;
+	const char		*flags;
+	char			*msg, *file, resolved[PATH_MAX];
 	size_t			 size, used, msglen, bufsize;
-	int			 cwd, fd;
 	FILE			*f;
 
 	if (!args_has(args, 'b')) {
@@ -97,26 +97,25 @@ cmd_save_buffer_exec(struct cmd *self, struct cmd_q *cmdq)
 	else if ((s = cmd_find_current(cmdq)) != NULL)
 		cwd = s->cwd;
 	else
-		cwd = AT_FDCWD;
+		cwd = ".";
 
-	f = NULL;
-	if (args_has(self->args, 'a')) {
-		fd = openat(cwd, path, O_CREAT|O_RDWR|O_APPEND, 0600);
-		if (fd != -1)
-			f = fdopen(fd, "ab");
-	} else {
-		fd = openat(cwd, path, O_CREAT|O_RDWR|O_TRUNC, 0600);
-		if (fd != -1)
-			f = fdopen(fd, "wb");
-	}
+	flags = "wb";
+	if (args_has(self->args, 'a'))
+		flags = "ab";
+
+	xasprintf(&file, "%s/%s", cwd, path);
+	if (realpath(file, resolved) == NULL)
+		f = NULL;
+	else
+		f = fopen(resolved, flags);
+	free(file);
 	if (f == NULL) {
-		if (fd != -1)
-			close(fd);
-		cmdq_error(cmdq, "%s: %s", path, strerror(errno));
+		cmdq_error(cmdq, "%s: %s", resolved, strerror(errno));
 		return (CMD_RETURN_ERROR);
 	}
+
 	if (fwrite(bufdata, 1, bufsize, f) != bufsize) {
-		cmdq_error(cmdq, "%s: fwrite error", path);
+		cmdq_error(cmdq, "%s: write error", resolved);
 		fclose(f);
 		return (CMD_RETURN_ERROR);
 	}