1 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
4
5 #include "net/quic/crypto/crypto_secret_boxer.h"
6
7 #include "base/logging.h"
8 #include "base/memory/scoped_ptr.h"
9 #include "net/quic/crypto/crypto_protocol.h"
10 #include "net/quic/crypto/quic_decrypter.h"
11 #include "net/quic/crypto/quic_encrypter.h"
12 #include "net/quic/crypto/quic_random.h"
13
14 using base::StringPiece;
15 using std::string;
16
17 namespace net {
18
19 // Defined kKeySize for GetKeySize() and SetKey().
20 static const size_t kKeySize = 16;
21
22 // kBoxNonceSize contains the number of bytes of nonce that we use in each box.
23 // TODO(rtenneti): Add support for kBoxNonceSize to be 16 bytes.
24 //
25 // From agl@:
26 // 96-bit nonces are on the edge. An attacker who can collect 2^41
27 // source-address tokens has a 1% chance of finding a duplicate.
28 //
29 // The "average" DDoS is now 32.4M PPS. That's 2^25 source-address tokens
30 // per second. So one day of that DDoS botnot would reach the 1% mark.
31 //
32 // It's not terrible, but it's not a "forget about it" margin.
33 static const size_t kBoxNonceSize = 12;
34
35 // static
GetKeySize()36 size_t CryptoSecretBoxer::GetKeySize() { return kKeySize; }
37
SetKey(StringPiece key)38 void CryptoSecretBoxer::SetKey(StringPiece key) {
39 DCHECK_EQ(kKeySize, key.size());
40 key_ = key.as_string();
41 }
42
Box(QuicRandom * rand,StringPiece plaintext) const43 string CryptoSecretBoxer::Box(QuicRandom* rand, StringPiece plaintext) const {
44 scoped_ptr<QuicEncrypter> encrypter(QuicEncrypter::Create(kAESG));
45 if (!encrypter->SetKey(key_)) {
46 DLOG(DFATAL) << "CryptoSecretBoxer's encrypter->SetKey failed.";
47 return string();
48 }
49 size_t ciphertext_size = encrypter->GetCiphertextSize(plaintext.length());
50
51 string ret;
52 const size_t len = kBoxNonceSize + ciphertext_size;
53 ret.resize(len);
54 char* data = &ret[0];
55
56 // Generate nonce.
57 rand->RandBytes(data, kBoxNonceSize);
58 memcpy(data + kBoxNonceSize, plaintext.data(), plaintext.size());
59
60 if (!encrypter->Encrypt(StringPiece(data, kBoxNonceSize), StringPiece(),
61 plaintext, reinterpret_cast<unsigned char*>(
62 data + kBoxNonceSize))) {
63 DLOG(DFATAL) << "CryptoSecretBoxer's Encrypt failed.";
64 return string();
65 }
66
67 return ret;
68 }
69
Unbox(StringPiece ciphertext,string * out_storage,StringPiece * out) const70 bool CryptoSecretBoxer::Unbox(StringPiece ciphertext,
71 string* out_storage,
72 StringPiece* out) const {
73 if (ciphertext.size() < kBoxNonceSize) {
74 return false;
75 }
76
77 char nonce[kBoxNonceSize];
78 memcpy(nonce, ciphertext.data(), kBoxNonceSize);
79 ciphertext.remove_prefix(kBoxNonceSize);
80
81 size_t len = ciphertext.size();
82 out_storage->resize(len);
83 char* data = const_cast<char*>(out_storage->data());
84
85 scoped_ptr<QuicDecrypter> decrypter(QuicDecrypter::Create(kAESG));
86 if (!decrypter->SetKey(key_)) {
87 DLOG(DFATAL) << "CryptoSecretBoxer's decrypter->SetKey failed.";
88 return false;
89 }
90 if (!decrypter->Decrypt(StringPiece(nonce, kBoxNonceSize), StringPiece(),
91 ciphertext, reinterpret_cast<unsigned char*>(data),
92 &len)) {
93 return false;
94 }
95
96 out->set(data, len);
97 return true;
98 }
99
100 } // namespace net
101