1 files changed, 90 insertions, 0 deletions
diff --git a/lib/iolog/iolog_openat.c b/lib/iolog/iolog_openat.c
new file mode 100644
index 0000000..75146a5
--- /dev/null
+++ b/lib/iolog/iolog_openat.c
@@ -0,0 +1,90 @@
+/*
+ * SPDX-License-Identifier: ISC
+ *
+ * Copyright (c) 2009-2021 Todd C. Miller <Todd.Miller@sudo.ws>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+/*
+ * This is an open source non-commercial project. Dear PVS-Studio, please check it.
+ * PVS-Studio Static Code Analyzer for C, C++ and C#: http://www.viva64.com
+ */
+
+#include <config.h>
+
+#include <sys/stat.h>
+#include <stdio.h>
+#include <stdlib.h>
+#ifdef HAVE_STDBOOL_H
+# include <stdbool.h>
+#else
+# include <compat/stdbool.h>
+#endif
+#include <errno.h>
+#include <fcntl.h>
+#include <unistd.h>
+
+#include <sudo_compat.h>
+#include <sudo_debug.h>
+#include <sudo_fatal.h>
+#include <sudo_gettext.h>
+#include <sudo_iolog.h>
+#include <sudo_util.h>
+
+/*
+ * Wrapper for openat(2) that sets umask and retries as iolog_uid/iolog_gid
+ * if openat(2) returns EACCES.
+ */
+int
+iolog_openat(int dfd, const char *path, int flags)
+{
+    const mode_t iolog_filemode = iolog_get_file_mode();
+    const mode_t iolog_dirmode = iolog_get_dir_mode();
+    mode_t omask = S_IRWXG|S_IRWXO;
+    int fd;
+    debug_decl(iolog_openat, SUDO_DEBUG_UTIL);
+
+    if (ISSET(flags, O_CREAT)) {
+	/* umask must not be more restrictive than the file modes. */
+	omask = umask(ACCESSPERMS & ~(iolog_filemode|iolog_dirmode));
+    }
+    fd = openat(dfd, path, flags, iolog_filemode);
+    if (fd == -1 && errno == EACCES) {
+	/* Enable write bit if it is missing. */
+	struct stat sb;
+	if (fstatat(dfd, path, &sb, 0) == 0) {
+	    mode_t write_bits = iolog_filemode & (S_IWUSR|S_IWGRP|S_IWOTH);
+	    if ((sb.st_mode & write_bits) != write_bits) {
+		if (fchmodat(dfd, path, iolog_filemode, 0) == 0)
+		    fd = openat(dfd, path, flags, iolog_filemode);
+	    }
+	}
+    }
+    if (fd == -1 && errno == EACCES) {
+	/* Try again as the I/O log owner (for NFS). */
+	if (iolog_swapids(false)) {
+	    fd = openat(dfd, path, flags, iolog_filemode);
+	    if (!iolog_swapids(true)) {
+		/* iolog_swapids() warns on error. */
+		if (fd != -1) {
+		    close(fd);
+		    fd = -1;
+		}
+	    }
+	}
+    }
+    if (ISSET(flags, O_CREAT))
+	umask(omask);
+    debug_return_int(fd);
+}