Make more libc improvements

- Make memmem() faster
- Make readdir() thread safe
- Remove 64kb limit from mkdeps.com
- Add old crypt() function from Musl
- Improve new fix-third-party.py tool
- Improve libc/isystem/ headers and fix bugs

third_party/musl/crypt_r.c

@@ -0,0 +1,69 @@
+/*-*- mode:c;indent-tabs-mode:t;c-basic-offset:8;tab-width:8;coding:utf-8   -*-│
+│vi: set et ft=c ts=8 tw=8 fenc=utf-8                                       :vi│
+╚──────────────────────────────────────────────────────────────────────────────╝
+│                                                                              │
+│  Musl Libc                                                                   │
+│  Copyright © 2005-2014 Rich Felker, et al.                                   │
+│                                                                              │
+│  Permission is hereby granted, free of charge, to any person obtaining       │
+│  a copy of this software and associated documentation files (the             │
+│  "Software"), to deal in the Software without restriction, including         │
+│  without limitation the rights to use, copy, modify, merge, publish,         │
+│  distribute, sublicense, and/or sell copies of the Software, and to          │
+│  permit persons to whom the Software is furnished to do so, subject to       │
+│  the following conditions:                                                   │
+│                                                                              │
+│  The above copyright notice and this permission notice shall be              │
+│  included in all copies or substantial portions of the Software.             │
+│                                                                              │
+│  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,             │
+│  EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF          │
+│  MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.      │
+│  IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY        │
+│  CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,        │
+│  TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE           │
+│  SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.                      │
+│                                                                              │
+╚─────────────────────────────────────────────────────────────────────────────*/
+#include "third_party/musl/crypt.h"
+#include "third_party/musl/crypt.internal.h"
+
+asm(".ident\t\"\\n\\n\
+Musl libc (MIT License)\\n\
+Copyright 2005-2014 Rich Felker, et. al.\"");
+asm(".include \"libc/disclaimer.inc\"");
+// clang-format off
+
+/**
+ * Encrypts password the old fashioned way.
+ *
+ * The method of encryption depends on the first three chars of salt:
+ *
+ * - `$1$` is MD5
+ * - `$2$` is Blowfish
+ * - `$5$` is SHA-256
+ * - `$6$` is SHA-512
+ * - Otherwise DES
+ *
+ * @return static memory with encrypted password
+ * @see third_party/argon2/
+ */
+char *crypt_r(const char *key, const char *salt, struct crypt_data *data)
+{
+	/* Per the crypt_r API, the caller has provided a pointer to
+	 * struct crypt_data; however, this implementation does not
+	 * use the structure to store any internal state, and treats
+	 * it purely as a char buffer for storing the result. */
+	char *output = (char *)data;
+	if (salt[0] == '$' && salt[1] && salt[2]) {
+		if (salt[1] == '1' && salt[2] == '$')
+			return __crypt_md5(key, salt, output);
+		if (salt[1] == '2' && salt[3] == '$')
+			return __crypt_blowfish(key, salt, output);
+		if (salt[1] == '5' && salt[2] == '$')
+			return __crypt_sha256(key, salt, output);
+		if (salt[1] == '6' && salt[2] == '$')
+			return __crypt_sha512(key, salt, output);
+	}
+	return __crypt_des(key, salt, output);
+}