!nshlib: Require explicit fixed login password at build time

fsutils/passwd/CMakeLists.txt

@@ -23,7 +23,14 @@
 if(CONFIG_FSUTILS_PASSWD)
   set(CSRCS)
 
-  list(APPEND CSRCS passwd_verify.c passwd_find.c passwd_encrypt.c)
+  list(
+    APPEND
+    CSRCS
+    passwd_verify.c
+    passwd_find.c
+    passwd_encrypt.c
+    passwd_base64.c
+    passwd_pbkdf2.c)
 
   if(NOT CONFIG_FSUTILS_PASSWD_READONLY)
     list(

fsutils/passwd/Kconfig

@@ -6,8 +6,15 @@
 config FSUTILS_PASSWD
 	bool "Password file support"
 	default n
+	select CRYPTO
+	select ALLOW_BSD_COMPONENTS
+	select CRYPTO_CRYPTODEV
 	---help---
-		Enables support for /etc/passwd file access routines
+		Enables support for /etc/passwd file access routines.
+
+		NOTE: Password hashes use PBKDF2-HMAC-SHA256 (modular crypt format).
+		Existing TEA-encrypted /etc/passwd entries are NOT compatible and
+		must be regenerated.
 
 if FSUTILS_PASSWD
 
@@ -23,20 +30,14 @@ config FSUTILS_PASSWD_IOBUFFER_SIZE
 	int "Allocated I/O buffer size"
 	default 512
 
-config FSUTILS_PASSWD_KEY1
-	hex "Encryption key value 1"
-	default 0x12345678
-
-config FSUTILS_PASSWD_KEY2
-	hex "Encryption key value 2"
-	default 0x9abcdef0
-
-config FSUTILS_PASSWD_KEY3
-	hex "Encryption key value 3"
-	default 0x12345678
-
-config FSUTILS_PASSWD_KEY4
-	hex "Encryption key value 4"
-	default 0x9abcdef0
+	config FSUTILS_PASSWD_PBKDF2_ITERATIONS
+	int "Default PBKDF2 iteration count for new passwords"
+	default 10000
+	range 1000 200000
+	---help---
+		Number of PBKDF2-HMAC-SHA256 iterations applied when setting a new
+		password.  Higher values slow brute-force attacks but also increase
+		login latency on low-MHz MCUs.  The iteration count is stored in each
+		hash string, so changing this option only affects newly-set passwords.
 
 endif # FSUTILS_PASSWD

fsutils/passwd/Makefile

@@ -25,7 +25,8 @@ include $(APPDIR)/Make.defs
 # Password file access library
 
 ifeq ($(CONFIG_FSUTILS_PASSWD),y)
-CSRCS += passwd_verify.c passwd_find.c passwd_encrypt.c
+CSRCS += passwd_verify.c passwd_find.c passwd_encrypt.c passwd_base64.c
+CSRCS += passwd_pbkdf2.c
 ifneq ($(CONFIG_FSUTILS_PASSWD_READONLY),y)
 CSRCS += passwd_adduser.c passwd_deluser.c passwd_update.c passwd_append.c
 CSRCS += passwd_delete.c passwd_lock.c

fsutils/passwd/passwd.h

@@ -36,17 +36,18 @@
  * Pre-processor Definitions
  ****************************************************************************/
 
-#define MAX_ENCRYPTED 48         /* Maximum size of a password (encrypted, ASCII) */
-#define MAX_USERNAME  48         /* Maximum size of a username */
-#define MAX_RECORD    (MAX_USERNAME + MAX_ENCRYPTED + 1)
+/* MCF format: $pbkdf2-sha256$<iter>$<salt>$<hash> */
 
-/* The TEA incryption algorithm generates 8 bytes of encrypted data per
- * 8 bytes of unencrypted data.  The encrypted presentation is base64 which
- * is 8-bits of ASCII for each 6 bits of data.  That is a 3-to-4 expansion
- * ratio.  MAX_ENCRYPTED must be a multiple of 8 bytes.
- */
+#define PASSWD_MCF_PREFIX           "$pbkdf2-sha256$"
+#define PASSWD_SALT_BYTES           16
+#define PASSWD_HASH_BYTES           32
 
-#define MAX_PASSWORD  (3 * MAX_ENCRYPTED / 4)
+/* 15 + 6 + 1 + 22 + 1 + 43 = 88 bytes for default parameters */
+
+#define MAX_ENCRYPTED               96
+#define MAX_USERNAME                48
+#define MAX_RECORD                  (MAX_USERNAME + MAX_ENCRYPTED + 1)
+#define MAX_PASSWORD                256
 
 /****************************************************************************
  * Public Types
@@ -55,7 +56,7 @@
 struct passwd_s
 {
   off_t offset;                      /* File offset (start of record) */
-  char encrypted[MAX_ENCRYPTED + 1]; /* Encrtyped password in file */
+  char encrypted[MAX_ENCRYPTED + 1]; /* Password hash in file */
 };
 
 /****************************************************************************
@@ -94,10 +95,11 @@ void passwd_unlock(FAR sem_t *sem);
  * Name: passwd_encrypt
  *
  * Description:
- *   Encrypt a password.  Currently uses the Tiny Encryption Algorithm.
+ *   Hash a password with PBKDF2-HMAC-SHA256 and encode the result in modular
+ *   crypt format for storage in /etc/passwd.
  *
  * Input Parameters:
- *   password -- The password string to be encrypted
+ *   password -- The password string to be hashed
  *
  * Returned Value:
  *   Zero (OK) is returned on success; a negated errno value is returned on

fsutils/passwd/passwd_base64.c

@@ -0,0 +1,187 @@
+/****************************************************************************
+ * apps/fsutils/passwd/passwd_base64.c
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.  The
+ * ASF licenses this file to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance with the
+ * License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
+ * License for the specific language governing permissions and limitations
+ * under the License.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+
+#include <errno.h>
+#include <stdint.h>
+
+#include "passwd_base64.h"
+
+/****************************************************************************
+ * Pre-processor Definitions
+ ****************************************************************************/
+
+/* RFC 4648 section 5 base64url alphabet (no padding). */
+
+static const char g_base64url[] =
+  "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_";
+
+/****************************************************************************
+ * Private Functions
+ ****************************************************************************/
+
+static int passwd_base64url_val(char c)
+{
+  if (c >= 'A' && c <= 'Z')
+    {
+      return c - 'A';
+    }
+
+  if (c >= 'a' && c <= 'z')
+    {
+      return c - 'a' + 26;
+    }
+
+  if (c >= '0' && c <= '9')
+    {
+      return c - '0' + 52;
+    }
+
+  if (c == '-')
+    {
+      return 62;
+    }
+
+  if (c == '_')
+    {
+      return 63;
+    }
+
+  return -1;
+}
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: passwd_base64url_encode
+ *
+ * Description:
+ *   Encode binary data as unpadded base64url (RFC 4648 section 5).
+ *
+ ****************************************************************************/
+
+int passwd_base64url_encode(FAR const uint8_t *in, size_t inlen,
+                            FAR char *out, size_t outlen)
+{
+  uint32_t acc = 0;
+  size_t i;
+  size_t o = 0;
+  int bits = 0;
+
+  for (i = 0; i < inlen; i++)
+    {
+      acc = (acc << 8) | in[i];
+      bits += 8;
+
+      while (bits >= 6)
+        {
+          if (o + 1 >= outlen)
+            {
+              return -E2BIG;
+            }
+
+          bits -= 6;
+          out[o++] = g_base64url[(acc >> bits) & 0x3f];
+        }
+    }
+
+  if (bits > 0)
+    {
+      if (o + 1 >= outlen)
+        {
+          return -E2BIG;
+        }
+
+      out[o++] = g_base64url[(acc << (6 - bits)) & 0x3f];
+    }
+
+  if (o >= outlen)
+    {
+      return -E2BIG;
+    }
+
+  out[o] = '\0';
+  return OK;
+}
+
+/****************************************************************************
+ * Name: passwd_base64url_decode
+ *
+ * Description:
+ *   Decode unpadded base64url (RFC 4648 section 5).
+ *
+ ****************************************************************************/
+
+int passwd_base64url_decode(FAR const char *in,
+                            FAR uint8_t *out, size_t outmax,
+                            FAR size_t *outlen)
+{
+  uint32_t acc = 0;
+  size_t o = 0;
+  int bits = 0;
+  int v;
+
+  *outlen = 0;
+
+  while (*in != '\0')
+    {
+      if (*in == '$' || *in == ':')
+        {
+          break;
+        }
+
+      v = passwd_base64url_val(*in++);
+      if (v < 0)
+        {
+          return -EINVAL;
+        }
+
+      acc = (acc << 6) | (uint32_t)v;
+      bits += 6;
+
+      if (bits >= 8)
+        {
+          bits -= 8;
+          if (o >= outmax)
+            {
+              return -E2BIG;
+            }
+
+          out[o++] = (uint8_t)((acc >> bits) & 0xff);
+        }
+    }
+
+  if (bits >= 6)
+    {
+      return -EINVAL;
+    }
+
+  *outlen = o;
+  return OK;
+}

fsutils/passwd/passwd_base64.h

@@ -0,0 +1,45 @@
+/****************************************************************************
+ * apps/fsutils/passwd/passwd_base64.h
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.  The
+ * ASF licenses this file to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance with the
+ * License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
+ * License for the specific language governing permissions and limitations
+ * under the License.
+ *
+ ****************************************************************************/
+
+#ifndef __APPS_FSUTILS_PASSWD_PASSWD_BASE64_H
+#define __APPS_FSUTILS_PASSWD_PASSWD_BASE64_H
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+
+#include <sys/types.h>
+#include <stdint.h>
+
+/****************************************************************************
+ * Public Function Prototypes
+ ****************************************************************************/
+
+int passwd_base64url_encode(FAR const uint8_t *in, size_t inlen,
+                            FAR char *out, size_t outlen);
+int passwd_base64url_decode(FAR const char *in,
+                            FAR uint8_t *out, size_t outmax,
+                            FAR size_t *outlen);
+
+#endif /* __APPS_FSUTILS_PASSWD_PASSWD_BASE64_H */