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diff --git a/security/sandbox/linux/broker/SandboxBroker.h b/security/sandbox/linux/broker/SandboxBroker.h
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+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_SandboxBroker_h
+#define mozilla_SandboxBroker_h
+
+#include "mozilla/SandboxBrokerCommon.h"
+
+#include "base/platform_thread.h"
+#include "mozilla/Attributes.h"
+#include "mozilla/UniquePtr.h"
+#include "nsTHashMap.h"
+#include "nsHashKeys.h"
+#include "nsString.h"
+
+namespace mozilla {
+
+namespace ipc {
+class FileDescriptor;
+}
+
+// This class implements a broker for filesystem operations requested
+// by a sandboxed child process -- opening files and accessing their
+// metadata.  (This is necessary in order to restrict access by path;
+// seccomp-bpf can filter only on argument register values, not
+// parameters passed in memory like pathnames.)
+//
+// The broker currently runs on a thread in the parent process (with
+// effective uid changed on B2G), which is for memory efficiency
+// (compared to forking a process) and simplicity (compared to having
+// a separate executable and serializing/deserializing the policy).
+//
+// See also ../SandboxBrokerClient.h for the corresponding client.
+
+class SandboxBroker final : private SandboxBrokerCommon,
+                            public PlatformThread::Delegate {
+ public:
+  enum Perms {
+    MAY_ACCESS = 1 << 0,
+    MAY_READ = 1 << 1,
+    MAY_WRITE = 1 << 2,
+    MAY_CREATE = 1 << 3,
+    // This flag is for testing policy changes -- when the client is
+    // used with the seccomp-bpf integration, an access to this file
+    // will invoke a crash dump with the context of the syscall.
+    // (This overrides all other flags.)
+    CRASH_INSTEAD = 1 << 4,
+    // Applies to everything below this path, including subdirs created
+    // at runtime
+    RECURSIVE = 1 << 5,
+    // Allow Unix-domain socket connections to a path
+    MAY_CONNECT = 1 << 6,
+    // This flag is for adding a deny rule, so that we can e.g., allow read
+    // access to ~/.config/ but still deny access to ~/.config/mozilla/.
+    // It will bypass other checks.
+    FORCE_DENY = 1 << 7,
+  };
+  // Bitwise operations on enum values return ints, so just use int in
+  // the hash table type (and below) to avoid cluttering code with casts.
+  typedef nsTHashMap<nsCStringHashKey, int> PathPermissionMap;
+
+  class Policy {
+    PathPermissionMap mMap;
+
+   public:
+    Policy();
+    Policy(const Policy& aOther);
+    ~Policy();
+
+    // Add permissions from AddDir/AddDynamic rules to any rules that
+    // exist for their descendents, and remove any descendent rules
+    // made redundant by this process.
+    //
+    // Call this after adding rules and before using the policy to
+    // prevent the descendent rules from shadowing the ancestor rules
+    // and removing permissions that we expect the file to have.
+    void FixRecursivePermissions();
+
+    enum AddCondition {
+      AddIfExistsNow,
+      AddAlways,
+    };
+    // Typically, files that don't exist at policy creation time don't
+    // need to be whitelisted, but this allows adding entries for
+    // them if they'll exist later.  See also the overload below.
+    void AddPath(int aPerms, const char* aPath, AddCondition aCond);
+    // This adds all regular files (not directories) in the tree
+    // rooted at the given path.
+    void AddTree(int aPerms, const char* aPath);
+    // A directory, and all files and directories under it, even those
+    // added after creation (the dir itself must exist).
+    void AddDir(int aPerms, const char* aPath);
+    // A directory, and all files and directories under it, even those
+    // added after creation (the dir itself may not exist).
+    void AddFutureDir(int aPerms, const char* aPath);
+    // All files in a directory with a given prefix; useful for devices.
+    void AddFilePrefix(int aPerms, const char* aDir, const char* aPrefix);
+    // Everything starting with the given path, even those files/dirs
+    // added after creation. The file or directory may or may not exist.
+    void AddPrefix(int aPerms, const char* aPath);
+    // Adds a file or dir (end with /) if it exists, and a prefix otherwhise.
+    void AddDynamic(int aPerms, const char* aPath);
+    // Adds permissions on all ancestors of a path.  (This doesn't
+    // include the root directory, but if the path is given with a
+    // trailing slash it includes the path without the slash.)
+    void AddAncestors(const char* aPath, int aPerms = MAY_ACCESS);
+    // Default: add file if it exists when creating policy or if we're
+    // conferring permission to create it (log files, etc.).
+    void AddPath(int aPerms, const char* aPath) {
+      AddPath(aPerms, aPath,
+              (aPerms & MAY_CREATE) ? AddAlways : AddIfExistsNow);
+    }
+    int Lookup(const nsACString& aPath) const;
+    int Lookup(const char* aPath) const {
+      return Lookup(nsDependentCString(aPath));
+    }
+
+    bool IsEmpty() const { return mMap.Count() == 0; }
+
+   private:
+    // ValidatePath checks |path| and returns true if these conditions are met
+    // * Greater than 0 length
+    // * Is an absolute path
+    // * No trailing slash
+    // * No /../ path traversal
+    bool ValidatePath(const char* path) const;
+    void AddPrefixInternal(int aPerms, const nsACString& aPath);
+    void AddDirInternal(int aPerms, const char* aPath);
+  };
+
+  // Constructing a broker involves creating a socketpair and a
+  // background thread to handle requests, so it can fail.  If this
+  // returns nullptr, do not use the value of aClientFdOut.
+  static UniquePtr<SandboxBroker> Create(UniquePtr<const Policy> aPolicy,
+                                         int aChildPid,
+                                         ipc::FileDescriptor& aClientFdOut);
+  virtual ~SandboxBroker();
+
+ private:
+  PlatformThreadHandle mThread;
+  int mFileDesc;
+  const int mChildPid;
+  const UniquePtr<const Policy> mPolicy;
+  nsCString mTempPath;
+  nsCString mContentTempPath;
+
+  typedef nsTHashMap<nsCStringHashKey, nsCString> PathMap;
+  PathMap mSymlinkMap;
+
+  SandboxBroker(UniquePtr<const Policy> aPolicy, int aChildPid, int& aClientFd);
+  void ThreadMain(void) override;
+  void AuditPermissive(int aOp, int aFlags, int aPerms, const char* aPath);
+  void AuditDenial(int aOp, int aFlags, int aPerms, const char* aPath);
+  // Remap relative paths to absolute paths.
+  size_t ConvertRelativePath(char* aPath, size_t aBufSize, size_t aPathLen);
+  size_t RealPath(char* aPath, size_t aBufSize, size_t aPathLen);
+  // Remap references to /tmp and friends to the content process tempdir
+  size_t RemapTempDirs(char* aPath, size_t aBufSize, size_t aPathLen);
+  nsCString ReverseSymlinks(const nsACString& aPath);
+  // Retrieves permissions for the path the original symlink sits in.
+  int SymlinkPermissions(const char* aPath, const size_t aPathLen);
+  // In SandboxBrokerRealPath.cpp
+  char* SymlinkPath(const Policy* aPolicy, const char* __restrict aPath,
+                    char* __restrict aResolved, int* aPermission);
+
+  // Holding a UniquePtr should disallow copying, but to make that explicit:
+  SandboxBroker(const SandboxBroker&) = delete;
+  void operator=(const SandboxBroker&) = delete;
+};
+
+}  // namespace mozilla
+
+#endif  // mozilla_SandboxBroker_h