1 // Copyright 2015 Google Inc. All rights reserved.
2 //
3 // Licensed under the Apache License, Version 2.0 (the "License");
4 // you may not use this file except in compliance with the License.
5 // You may obtain a copy of the License at
6 //
7 // http://www.apache.org/licenses/LICENSE-2.0
8 //
9 // Unless required by applicable law or agreed to in writing, software
10 // distributed under the License is distributed on an "AS IS" BASIS,
11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12 // See the License for the specific language governing permissions and
13 // limitations under the License.
14
15 #include "openssl_hash_impl.h"
16
17 #include <stdlib.h>
18 #include <string>
19
20 #include <openssl/evp.h> // EVP_sha256
21 #include <openssl/hmac.h> // HMAC
22 #include <openssl/md5.h> // MD5
23 #include <openssl/sha.h> // SHA256_DIGEST_LENGTH
24
25 namespace rappor {
26
27 // of type HmacFunc in rappor_deps.h
HmacSha256(const std::string & key,const std::string & value,std::vector<uint8_t> * output)28 bool HmacSha256(const std::string& key, const std::string& value,
29 std::vector<uint8_t>* output) {
30 output->resize(SHA256_DIGEST_LENGTH, 0);
31
32 // Returns a pointer on success, or NULL on failure.
33 unsigned char* result = HMAC(
34 EVP_sha256(), key.c_str(), key.size(),
35 // std::string has 'char', OpenSSL wants unsigned char.
36 reinterpret_cast<const unsigned char*>(value.c_str()),
37 value.size(),
38 output->data(),
39 NULL);
40
41 return (result != NULL);
42 }
43
44 // Of type HmacFunc in rappor_deps.h
45 //
46 // The length of the passed-in output vector determines how many
47 // bytes are returned.
48 //
49 // No reseed operation, but recommended reseed_interval <= 2^48 updates.
50 // Since we're seeding for each value and typically don't need
51 // so many bytes, we should be OK.
HmacDrbg(const std::string & key,const std::string & value,std::vector<uint8_t> * output)52 bool HmacDrbg(const std::string& key, const std::string& value,
53 std::vector<uint8_t>* output) {
54 const unsigned char k_array[] = {
55 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
56 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
57 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
58 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
59 };
60 std::string v;
61 std::vector<uint8_t> temp_output;
62 int num_bytes = output->size();
63 if (num_bytes == 0) {
64 // By default return 32 bytes for Uint32 applications.
65 num_bytes = 32;
66 }
67
68 v.append(32u, 0x01);
69 temp_output.resize(32, 0);
70
71 std::string temp_str(v);
72 temp_str.append(std::string("\0", 1));
73 // provided_data is key|value.
74 temp_str.append(key);
75 temp_str.append(value);
76
77 output->resize(0);
78
79 // Instantiate.
80 if (!HmacSha256(std::string(k_array, k_array + 32), temp_str, &temp_output)) {
81 return false;
82 }
83 std::string k(temp_output.begin(), temp_output.end());
84 if (!HmacSha256(k, v, &temp_output)) {
85 return false;
86 }
87 v = std::string(temp_output.begin(), temp_output.end());
88 if (!HmacSha256(k, v + std::string("\1", 1) + key + value, &temp_output)) {
89 return false;
90 }
91 k = std::string(temp_output.begin(), temp_output.end());
92 if (!HmacSha256(k, v, &temp_output)) {
93 return false;
94 }
95 v = std::string(temp_output.begin(), temp_output.end());
96
97 while (output->size() < num_bytes) {
98 // Generate.
99 if (!HmacSha256(k, v, &temp_output)) {
100 return false;
101 }
102 v = std::string(temp_output.begin(), temp_output.end());
103 output->insert(output->end(), temp_output.begin(), temp_output.end());
104 }
105 output->resize(num_bytes);
106 return true;
107 }
108
109 // of type HashFunc in rappor_deps.h
Md5(const std::string & value,std::vector<uint8_t> * output)110 bool Md5(const std::string& value, std::vector<uint8_t>* output) {
111 output->resize(MD5_DIGEST_LENGTH, 0);
112
113 // std::string has 'char', OpenSSL wants unsigned char.
114 MD5(reinterpret_cast<const unsigned char*>(value.c_str()),
115 value.size(), output->data());
116 return true; // OpenSSL MD5 doesn't return an error code
117 }
118
119 } // namespace rappor
120