Make our mktemp(3) callback-driven and split into multiple files.

Previously, calling any of the mktemp(3) family would pull in
lstat(2), open(2) and mkdir(2).  Now, only the necessary system
calls will be reachable from the binary.  OK deraadt@ guenther@

1 files changed, 83 insertions, 0 deletions

diff --git a/src/lib/libc/stdlib/__mktemp4.c b/src/lib/libc/stdlib/__mktemp4.c
new file mode 100644
index 0000000000..4b4500018b
--- /dev/null
+++ b/src/lib/libc/stdlib/__mktemp4.c
@@ -0,0 +1,83 @@
+/*      $OpenBSD: __mktemp4.c,v 1.1 2024/01/19 19:45:02 millert Exp $ */
+/*
+ * Copyright (c) 1996-1998, 2008 Theo de Raadt
+ * Copyright (c) 1997, 2008-2009, 2024 Todd C. Miller
+ *
+ * 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.
+ */
+
+#include <errno.h>
+#include <limits.h>
+#include <stdlib.h>
+#include <string.h>
+
+#define TEMPCHARS       "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789"
+#define NUM_CHARS       (sizeof(TEMPCHARS) - 1)
+#define MIN_X           6
+
+#ifndef nitems
+#define nitems(_a)      (sizeof((_a)) / sizeof((_a)[0]))
+#endif
+
+/*
+ * Internal driver for the mktemp(3) family of functions.
+ * The supplied callback does the actual work of testing or
+ * creating the file/directory.
+ */
+int
+__mktemp4(char *path, int slen, int flags, int (*cb)(const char *, int))
+{
+        char *start, *cp, *ep;
+        const char tempchars[] = TEMPCHARS;
+        unsigned int tries;
+        size_t len;
+        int ret;
+
+        len = strlen(path);
+        if (len < MIN_X || slen < 0 || (size_t)slen > len - MIN_X) {
+                errno = EINVAL;
+                return -1;
+        }
+        ep = path + len - slen;
+
+        for (start = ep; start > path && start[-1] == 'X'; start--)
+                ;
+        if (ep - start < MIN_X) {
+                errno = EINVAL;
+                return -1;
+        }
+
+        tries = INT_MAX;
+        do {
+                cp = start;
+                do {
+                        unsigned short rbuf[16];
+                        unsigned int i;
+
+                        /*
+                         * Avoid lots of arc4random() calls by using
+                         * a buffer sized for up to 16 Xs at a time.
+                         */
+                        arc4random_buf(rbuf, sizeof(rbuf));
+                        for (i = 0; i < nitems(rbuf) && cp != ep; i++)
+                                *cp++ = tempchars[rbuf[i] % NUM_CHARS];
+                } while (cp != ep);
+
+                ret = cb(path, flags);
+                if (ret != -1 || errno != EEXIST)
+                        return ret;
+        } while (--tries);
+
+        errno = EEXIST;
+        return -1;
+}