Add a buffer reader/writer for NTLM.

net/ntlm/ntlm_buffer_reader.h

Index: net/ntlm/ntlm_buffer_reader.h
diff --git a/net/ntlm/ntlm_buffer_reader.h b/net/ntlm/ntlm_buffer_reader.h
new file mode 100644
index 0000000000000000000000000000000000000000..e3f701320038d48c1381bdd57dc5c4a27140b555
--- /dev/null
+++ b/net/ntlm/ntlm_buffer_reader.h
@@ -0,0 +1,192 @@
+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef NET_BASE_NTLM_BUFFER_READER_H_
+#define NET_BASE_NTLM_BUFFER_READER_H_
+
+#include <stddef.h>
+#include <stdint.h>
+
+#include <string>
+
+#include "base/strings/string_piece.h"
+#include "net/base/net_export.h"
+#include "net/ntlm/ntlm_constants.h"
+
+namespace net {
+namespace ntlm {
+
+// Supports various bounds-checked low level buffer operations required by an
+// NTLM implementation.
+//
+// The class supports sequential read of a provided buffer. All reads perform

[Ryan Sleevi, 2017/07/10 15:07:56]

s/supports sequential/supports the sequential/

Alternatively
s/sequential read/sequential reading/

[zentaro, 2017/07/11 14:00:29]

Done.

+// bounds checking to ensure enough space is remaining in the buffer.
+//
+// Read* methods read from the buffer at the current cursor position and
+// perform any necessary type conversion and provide the data in out params.
+// After a successful read the cursor position is advanced past the read
+// field.
+//
+// Failed Read*s or Match*s leave the cursor in an undefined position and the
+// buffer MUST be discarded with no further operations performed.
+//
+// Read*Payload methods first reads a security buffer (see
+// |ReadSecurityBuffer|), then reads the requested payload from the offset
+// and length stated in the security buffer.
+//
+// If the length and offset in the security buffer would cause a read outside
+// the message buffer the payload will not be read and the function will
+// return false.
+//
+// Based on [MS-NLMP]: NT LAN Manager (NTLM) Authentication Protocol
+// Specification version 28.0 [1]. Additional NTLM reference [2].
+//
+// [1] https://msdn.microsoft.com/en-us/library/cc236621.aspx
+// [2] http://davenport.sourceforge.net/ntlm.html
+class NET_EXPORT_PRIVATE NtlmBufferReader {
+ public:
+  explicit NtlmBufferReader(base::StringPiece buffer);
+
+  // This class does not take ownership of |ptr| so the caller must ensure

[Ryan Sleevi, 2017/07/10 15:07:56]

s/|ptr| so/|ptr|, so/

[zentaro, 2017/07/11 14:00:29]

Done.

+  // that the buffer outlives the |NtlmBufferReader|.
+  NtlmBufferReader(const uint8_t* ptr, size_t len);
+  ~NtlmBufferReader();
+
+  size_t GetLength() const { return buffer_.length(); }
+  size_t GetCursor() const { return cursor_; }
+  bool IsEndOfBuffer() const { return cursor_ >= GetLength(); }
+
+  // Returns true if there are |len| more bytes between the current cursor
+  // position and the end of the buffer.
+  bool CanRead(size_t len) const;
+
+  // Returns true if there are |len| more bytes between |offset| and the end
+  // of the buffer. The cursor position is not used or modified.
+  bool CanReadFrom(size_t offset, size_t len) const;
+
+  // Returns true if it would be possible to read the payload described by the
+  // security buffer.
+  bool CanReadFrom(SecurityBuffer sec_buf) const {
+    return CanReadFrom(sec_buf.offset, sec_buf.length);
+  }
+
+  // Reads a 16 bit value (little endian) as a uint16_t. If there are not 16
+  // more bits available it returns false.

[Ryan Sleevi, 2017/07/10 15:07:56]

s/available it/available, it/

[zentaro, 2017/07/11 14:00:29]

Done.

+  bool ReadUInt16(uint16_t* value) WARN_UNUSED_RESULT;
+
+  // Reads a 32 bit value (little endian) as a uint32_t. If there are not 32
+  // more bits available it returns false.

[Ryan Sleevi, 2017/07/10 15:07:56]

s/available it/available, it/

[zentaro, 2017/07/11 14:00:29]

Done.

+  bool ReadUInt32(uint32_t* value) WARN_UNUSED_RESULT;
+
+  // Reads a 64 bit value (little endian) as a uint64_t. If there are not 64
+  // more bits available it returns false.

[Ryan Sleevi, 2017/07/10 15:07:56]

s/available it/available, it/

[zentaro, 2017/07/11 14:00:29]

Done.

+  bool ReadUInt64(uint64_t* value) WARN_UNUSED_RESULT;
+
+  // Calls |ReadUInt32| and returns it cast as |NegotiateFlags|. No
+  // validation of the value takes place.
+  bool ReadFlags(NegotiateFlags* flags) WARN_UNUSED_RESULT;
+
+  // Reads |len| bytes and copies them into |buffer|.
+  bool ReadBytes(uint8_t* buffer, size_t len) WARN_UNUSED_RESULT;
+
+  // Reads |sec_buf.length| bytes from offset |sec_buf.offset| and copies them
+  // into |buffer|. If the security buffer specifies a payload outside the
+  // buffer then the call fails.

[Ryan Sleevi, 2017/07/10 15:07:56]

s/buffer then/buffer, then/

[zentaro, 2017/07/11 14:00:29]

Done.

+  bool ReadBytesFrom(const SecurityBuffer& sec_buf,

[asanka, 2017/07/11 15:19:16]

Should note that this method doesn't affect the cursor.

[zentaro, 2017/07/11 20:19:53]

Done.

+                     uint8_t* buffer) WARN_UNUSED_RESULT;
+
+  // A security buffer is an 8 byte structure that defines the offset and
+  // length of a payload (string, struct or byte array) that appears after the
+  // fixed part of the message.
+  //
+  // The structure is (little endian fields):
+  //     uint16 - |length| Length of payload
+  //     uint16 - Allocation (this is always ignored and not returned)
+  //     uint32 - |offset| Offset from start of message
+  bool ReadSecurityBuffer(SecurityBuffer* sec_buf) WARN_UNUSED_RESULT;
+
+  // There are 3 message types Negotiate (sent by client), Challenge (sent by
+  // server), and Authenticate (sent by client).
+  //
+  // This reads the message type from the header and will return false if the
+  // value is invalid.
+  bool ReadMessageType(MessageType* message_type) WARN_UNUSED_RESULT;
+
+  // Skips over a security buffer field without reading the fields. This is
+  // the equivalent of advancing the cursor 8 bytes. Returns false if there
+  // are less than 8 bytes left in the buffer.
+  bool SkipSecurityBuffer() WARN_UNUSED_RESULT;
+
+  // Skips over the security buffer without returning the values, but fails if
+  // the values would cause a read outside the buffer if the payload was
+  // actually read.
+  bool SkipSecurityBufferWithValidation() WARN_UNUSED_RESULT;
+
+  // Skips over |count| bytes in the buffer. Returns false if there is not

[Ryan Sleevi, 2017/07/10 15:07:56]

s/is not/are not/ (subject/verb agreement with plural bytes)

[zentaro, 2017/07/11 14:00:29]

Done.

+  // |count| bytes left in the buffer.
+  bool SkipBytes(size_t count) WARN_UNUSED_RESULT;
+
+  // Reads and returns true if the next 8 bytes matches the signature in an
+  // NTLM message "NTLMSSP\0". The cursor advances if the the signature
+  // is matched.
+  bool MatchSignature() WARN_UNUSED_RESULT;
+
+  // Performs |ReadMessageType| and returns true if the value is
+  // |message_type|. If the read fails or the message type does not match,
+  // the buffer is invalid and MUST be discarded.
+  bool MatchMessageType(MessageType message_type) WARN_UNUSED_RESULT;
+
+  // Performs |MatchSignature| then |MatchMessageType|.
+  bool MatchMessageHeader(MessageType message_type) WARN_UNUSED_RESULT;
+
+  // Performs |ReadBytes(count)| and returns true if the contents is all
+  // zero.
+  bool MatchZeros(size_t count) WARN_UNUSED_RESULT;
+
+  // Reads the security buffer and returns true if the length is 0 and
+  // the offset is within the message. On failure the buffer is invalid

[Ryan Sleevi, 2017/07/10 15:07:56]

s/failure the/failure, the/

[zentaro, 2017/07/11 14:00:29]

Done.

+  // and MUST be discarded.
+  bool MatchEmptySecurityBuffer() WARN_UNUSED_RESULT;
+
+ private:
+  // Reads |sizeof(T)| bytes of an integer type from a little-endian buffer.
+  template <typename T>
+  bool ReadUInt(T* value);
+
+  // Sets the cursor position. This is used when reading payloads to move the
+  // cursor to the start of the payload indicated by the security buffer.

[Ryan Sleevi, 2017/07/10 15:07:56]

comment nit: You're describing how this is used (an implementation detail),
rather than how to use it (a documentation detail)

That said, I'm not sure how to reword this better, so I'm happy to leave as-is,
unless asanka@ has suggestions.

[zentaro, 2017/07/11 14:00:29]

Acknowledged.

[asanka, 2017/07/11 15:19:16]

I'd be okay with leaving out the "this is used when ..." part which will quickly
become incorrect if we add a call site. The caveat about the caller being
responsible for bounds checking is good but strictly speaking isn't enough. I'd
note that the caller should only set the cursor to a known field boundary as
returned by a previous call to GetCursor().

BTW, is this called at all?

[zentaro, 2017/07/11 20:19:53]

Removed the "this is used" because we removed all cursor rollback and moved to
using ReadFrom. So it was wrong anyway.

It is currently called in one place AdvanceCursor.

+  // The caller should use |GetLength|, |CanRead|, or |CanReadFrom| to verify
+  // the bounds before calling this method.
+  void SetCursor(size_t cursor);
+
+  // Advances the cursor by |count| bytes. The caller should use |GetLength|,
+  // |CanRead|, or |CanReadFrom| to verify the bounds before calling this
+  // method.
+  void AdvanceCursor(size_t count) { SetCursor(GetCursor() + count); }
+
+  // Returns a constant pointer to the start of the buffer.
+  const uint8_t* GetBufferPtr() const {
+    return reinterpret_cast<const uint8_t*>(buffer_.data());
+  }
+
+  // Returns a pointer to the underlying buffer at the current cursor
+  // position.
+  const uint8_t* GetBufferAtCursor() const { return GetBufferPtr() + cursor_; }
+
+  // Returns the byte at the current cursor position.
+  uint8_t GetByteAtCursor() const {
+    DCHECK(!IsEndOfBuffer());
+    return *(GetBufferAtCursor());
+  }
+
+  const base::StringPiece buffer_;
+  size_t cursor_;
+
+  DISALLOW_COPY_AND_ASSIGN(NtlmBufferReader);
+};
+
+}  // namespace ntlm
+}  // namespace net
+
+#endif  // NET_BASE_NTLM_BUFFER_READER_H_