1 files changed, 106 insertions, 0 deletions
diff --git a/src/lib/safe-mkstemp.c b/src/lib/safe-mkstemp.c
new file mode 100644
index 0000000..27b401e
--- /dev/null
+++ b/src/lib/safe-mkstemp.c
@@ -0,0 +1,106 @@
+/* Copyright (c) 2007-2018 Dovecot authors, see the included COPYING file */
+
+#include "lib.h"
+#include "str.h"
+#include "hex-binary.h"
+#include "randgen.h"
+#include "hostpid.h"
+#include "eacces-error.h"
+#include "safe-mkstemp.h"
+
+#include <unistd.h>
+#include <fcntl.h>
+#include <sys/stat.h>
+
+static int ATTR_NULL(5)
+safe_mkstemp_full(string_t *prefix, mode_t mode, uid_t uid, gid_t gid,
+		  const char *gid_origin)
+{
+	size_t prefix_len;
+	struct stat st;
+	unsigned char randbuf[8];
+	mode_t old_umask;
+	int fd;
+
+	prefix_len = str_len(prefix);
+	for (;;) {
+		do {
+			random_fill(randbuf, sizeof(randbuf));
+			str_truncate(prefix, prefix_len);
+			str_append(prefix,
+				   binary_to_hex(randbuf, sizeof(randbuf)));
+		} while (lstat(str_c(prefix), &st) == 0);
+
+		if (errno != ENOENT) {
+			i_error("stat(%s) failed: %m", str_c(prefix));
+			str_truncate(prefix, prefix_len);
+			return -1;
+		}
+
+		old_umask = umask(0666 ^ mode);
+		fd = open(str_c(prefix), O_RDWR | O_EXCL | O_CREAT, 0666);
+		umask(old_umask);
+		if (fd != -1)
+			break;
+
+		if (errno != EEXIST) {
+			if (errno != ENOENT && errno != EACCES)
+				i_error("open(%s) failed: %m", str_c(prefix));
+			str_truncate(prefix, prefix_len);
+			return -1;
+		}
+	}
+	if (uid == (uid_t)-1 && gid == (gid_t)-1)
+		return fd;
+
+	if (fchown(fd, uid, gid) < 0) {
+		if (errno == EPERM) {
+			i_error("%s", eperm_error_get_chgrp("fchown",
+					str_c(prefix), gid, gid_origin));
+		} else {
+			i_error("fchown(%s, %ld, %ld) failed: %m",
+				str_c(prefix),
+				uid == (uid_t)-1 ? -1L : (long)uid,
+				gid == (gid_t)-1 ? -1L : (long)gid);
+		}
+		i_close_fd(&fd);
+		i_unlink(str_c(prefix));
+		str_truncate(prefix, prefix_len);
+		return -1;
+	}
+	return fd;
+}
+
+int safe_mkstemp(string_t *prefix, mode_t mode, uid_t uid, gid_t gid)
+{
+	return safe_mkstemp_full(prefix, mode, uid, gid, NULL);
+}
+
+int safe_mkstemp_group(string_t *prefix, mode_t mode,
+		       gid_t gid, const char *gid_origin)
+{
+	return safe_mkstemp_full(prefix, mode, (uid_t)-1, gid, gid_origin);
+}
+
+int safe_mkstemp_hostpid(string_t *prefix, mode_t mode, uid_t uid, gid_t gid)
+{
+	size_t orig_prefix_len = str_len(prefix);
+	int fd;
+
+	str_printfa(prefix, "%s.%s.", my_hostname, my_pid);
+	if ((fd = safe_mkstemp(prefix, mode, uid, gid)) == -1)
+		str_truncate(prefix, orig_prefix_len);
+	return fd;
+}
+
+int safe_mkstemp_hostpid_group(string_t *prefix, mode_t mode,
+			       gid_t gid, const char *gid_origin)
+{
+	size_t orig_prefix_len = str_len(prefix);
+	int fd;
+
+	str_printfa(prefix, "%s.%s.", my_hostname, my_pid);
+	if ((fd = safe_mkstemp_group(prefix, mode, gid, gid_origin)) == -1)
+		str_truncate(prefix, orig_prefix_len);
+	return fd;
+}