Merge bitcoin/bitcoin#17127: util: Set safe permissions for data directory and wallets/ subdir

c9ba4f9ecb test: Add test for file system permissions (Hennadii Stepanov)
581f16ef34 Apply default umask in `SetupEnvironment()` (Hennadii Stepanov)
8a6219e543 Remove `-sysperms` option (Hennadii Stepanov)

Pull request description:

  On master (1e7564eca8) docs say:
  ```
  $ ./src/bitcoind -help | grep -A 3 sysperms
    -sysperms
         Create new files with system default permissions, instead of umask 077
         (only effective with disabled wallet functionality)

  ```

  Basing on that, one could expect that running `bitcoind` first time will create data directory and `wallets/` subdirectory with safe 0700 permissions.

  But that is not the case:
  ```
  $ stat .bitcoin | grep id
  Access: (0775/drwxrwxr-x)  Uid: ( 1000/ hebasto)   Gid: ( 1000/ hebasto)
  $ stat .bitcoin/wallets | grep id
  Access: (0775/drwxrwxr-x)  Uid: ( 1000/ hebasto)   Gid: ( 1000/ hebasto)
  ```

  Both directories, in fact, are created with system default permissions.

  With this PR:
  ```
  $ stat .bitcoin/wallets | grep id
  Access: (0700/drwx------)  Uid: ( 1000/ hebasto)   Gid: ( 1000/ hebasto)
  $ stat .bitcoin/wallets | grep id
  Access: (0700/drwx------)  Uid: ( 1000/ hebasto)   Gid: ( 1000/ hebasto)
  ```

  ---

  This PR:
  - is alternative to bitcoin/bitcoin#13389
  - fixes bitcoin/bitcoin#15902
  - fixes bitcoin/bitcoin#22595
  - closes bitcoin/bitcoin#13371
  - reverts bitcoin/bitcoin#4286

  Changes in behavior: removed `-sysperms` command-line argument / configure option. The related discussions are here:
  - https://github.com/bitcoin/bitcoin/pull/13389#issuecomment-395306690
  - https://github.com/bitcoin/bitcoin/pull/13389#issuecomment-539906114
  - https://github.com/bitcoin/bitcoin/pull/13389#discussion_r279160472

  If users rely on non-default access permissions, they could use `chmod`.

ACKs for top commit:
  john-moffett:
    ACK c9ba4f9ecb
  willcl-ark:
    ACK c9ba4f9ecb

Tree-SHA512: 96c745339e6bd0e4d7bf65daf9a721e2e1945b2b0ab74ca0f66576d0dc358b5de8eb8cdb89fe2160f3b19c39d2798bb8b291784316085dc73a27102d3415bd57

doc/init.md

@@ -70,7 +70,7 @@ NOTE: When using the systemd .service file, the creation of the aforementioned
 directories and the setting of their permissions is automatically handled by
 systemd. Directories are given a permission of 710, giving the bitcoin group
 access to files under it _if_ the files themselves give permission to the
-bitcoin group to do so (e.g. when `-sysperms` is specified). This does not allow
+bitcoin group to do so. This does not allow
 for the listing of files under the directory.
 
 NOTE: It is not currently possible to override `datadir` in

src/i2p.cpp

@@ -336,7 +336,7 @@ void Session::GenerateAndSavePrivateKey(const Sock& sock)
 {
     DestGenerate(sock);
 
-    // umask is set to 077 in init.cpp, which is ok (unless -sysperms is given)
+    // umask is set to 0077 in util/system.cpp, which is ok.
     if (!WriteBinaryFile(m_private_key_file,
                          std::string(m_private_key.begin(), m_private_key.end()))) {
         throw std::runtime_error(

src/init.cpp

@@ -458,11 +458,6 @@ void SetupServerArgs(ArgsManager& argsman)
 #if HAVE_SYSTEM
     argsman.AddArg("-startupnotify=<cmd>", "Execute command on startup.", ArgsManager::ALLOW_ANY, OptionsCategory::OPTIONS);
     argsman.AddArg("-shutdownnotify=<cmd>", "Execute command immediately before beginning shutdown. The need for shutdown may be urgent, so be careful not to delay it long (if the command doesn't require interaction with the server, consider having it fork into the background).", ArgsManager::ALLOW_ANY, OptionsCategory::OPTIONS);
-#endif
-#ifndef WIN32
-    argsman.AddArg("-sysperms", "Create new files with system default permissions, instead of umask 077 (only effective with disabled wallet functionality)", ArgsManager::ALLOW_ANY, OptionsCategory::OPTIONS);
-#else
-    hidden_args.emplace_back("-sysperms");
 #endif
     argsman.AddArg("-txindex", strprintf("Maintain a full transaction index, used by the getrawtransaction rpc call (default: %u)", DEFAULT_TXINDEX), ArgsManager::ALLOW_ANY, OptionsCategory::OPTIONS);
     argsman.AddArg("-blockfilterindex=<type>",
@@ -821,10 +816,6 @@ bool AppInitBasicSetup(const ArgsManager& args)
     }
 
 #ifndef WIN32
-    if (!args.GetBoolArg("-sysperms", false)) {
-        umask(077);
-    }
-
     // Clean shutdown on SIGTERM
     registerSignalHandler(SIGTERM, HandleSIGTERM);
     registerSignalHandler(SIGINT, HandleSIGTERM);

src/rpc/request.cpp

@@ -86,7 +86,7 @@ bool GenerateAuthCookie(std::string *cookie_out)
     std::string cookie = COOKIEAUTH_USER + ":" + HexStr(rand_pwd);
 
     /** the umask determines what permissions are used to create this file -
-     * these are set to 077 in init.cpp unless overridden with -sysperms.
+     * these are set to 0077 in util/system.cpp.
      */
     std::ofstream file;
     fs::path filepath_tmp = GetAuthCookieFile(true);

src/util/system.cpp

@@ -1360,6 +1360,11 @@ void SetupEnvironment()
     SetConsoleCP(CP_UTF8);
     SetConsoleOutputCP(CP_UTF8);
 #endif
+
+#ifndef WIN32
+    constexpr mode_t private_umask = 0077;
+    umask(private_umask);
+#endif
 }
 
 bool SetupNetworking()

src/wallet/init.cpp

@@ -122,9 +122,6 @@ bool WalletInit::ParameterInteraction() const
         return InitError(Untranslated("-zapwallettxes has been removed. If you are attempting to remove a stuck transaction from your wallet, please use abandontransaction instead."));
     }
 
-    if (gArgs.GetBoolArg("-sysperms", false))
-        return InitError(Untranslated("-sysperms is not allowed in combination with enabled wallet functionality"));
-
     return true;
 }
 

test/functional/feature_posix_fs_permissions.py

@@ -0,0 +1,43 @@
+#!/usr/bin/env python3
+# Copyright (c) 2022 The Bitcoin Core developers
+# Distributed under the MIT software license, see the accompanying
+# file COPYING or http://www.opensource.org/licenses/mit-license.php.
+"""Test file system permissions for POSIX platforms.
+"""
+
+import os
+import stat
+
+from test_framework.test_framework import BitcoinTestFramework
+
+
+class PosixFsPermissionsTest(BitcoinTestFramework):
+    def set_test_params(self):
+        self.setup_clean_chain = True
+        self.num_nodes = 1
+
+    def skip_test_if_missing_module(self):
+        self.skip_if_platform_not_posix()
+
+    def check_directory_permissions(self, dir):
+        mode = os.lstat(dir).st_mode
+        self.log.info(f"{stat.filemode(mode)} {dir}")
+        assert mode == (stat.S_IFDIR | stat.S_IRUSR | stat.S_IWUSR | stat.S_IXUSR)
+
+    def check_file_permissions(self, file):
+        mode = os.lstat(file).st_mode
+        self.log.info(f"{stat.filemode(mode)} {file}")
+        assert mode == (stat.S_IFREG | stat.S_IRUSR | stat.S_IWUSR)
+
+    def run_test(self):
+        self.stop_node(0)
+        datadir = os.path.join(self.nodes[0].datadir, self.chain)
+        self.check_directory_permissions(datadir)
+        walletsdir = os.path.join(datadir, "wallets")
+        self.check_directory_permissions(walletsdir)
+        debuglog = os.path.join(datadir, "debug.log")
+        self.check_file_permissions(debuglog)
+
+
+if __name__ == '__main__':
+    PosixFsPermissionsTest().main()

test/functional/test_framework/test_framework.py

@@ -880,6 +880,11 @@ class BitcoinTestFramework(metaclass=BitcoinTestMetaClass):
         if platform.system() != "Linux":
             raise SkipTest("not on a Linux system")
 
+    def skip_if_platform_not_posix(self):
+        """Skip the running test if we are not on a POSIX platform"""
+        if os.name != 'posix':
+            raise SkipTest("not on a POSIX system")
+
     def skip_if_no_bitcoind_zmq(self):
         """Skip the running test if bitcoind has not been compiled with zmq support."""
         if not self.is_zmq_compiled():

test/functional/test_runner.py

@@ -211,6 +211,7 @@ BASE_SCRIPTS = [
     'p2p_addrv2_relay.py',
     'p2p_compactblocks_hb.py',
     'p2p_disconnect_ban.py',
+    'feature_posix_fs_permissions.py',
     'rpc_decodescript.py',
     'rpc_blockchain.py',
     'rpc_deprecated.py',