1 /*
2 * Copyright (C) 2020 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except
6 * in compliance with the License. You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17 #include "adb/tls/adb_ca_list.h"
18
19 #include <iomanip>
20 #include <sstream>
21 #include <vector>
22
23 #include <android-base/logging.h>
24 #include <android-base/strings.h>
25 #include <openssl/ssl.h>
26
27 namespace adb {
28 namespace tls {
29
30 namespace {
31
32 // CA issuer identifier to distinguished embedded keys. Also has version
33 // information appended to the end of the string (e.g. "AdbKey-0").
34 static constexpr int kAdbKeyIdentifierNid = NID_organizationName;
35 static constexpr char kAdbKeyIdentifierV0[] = "AdbKey-0";
36
37 // Where we store the actual data
38 static constexpr int kAdbKeyValueNid = NID_commonName;
39
40 // TODO: Remove this once X509_NAME_add_entry_by_NID is fixed to use const unsigned char*
41 // https://boringssl-review.googlesource.com/c/boringssl/+/39764
X509_NAME_add_entry_by_NID_const(X509_NAME * name,int nid,int type,const unsigned char * bytes,int len,int loc,int set)42 int X509_NAME_add_entry_by_NID_const(X509_NAME* name, int nid, int type, const unsigned char* bytes,
43 int len, int loc, int set) {
44 return X509_NAME_add_entry_by_NID(name, nid, type, const_cast<unsigned char*>(bytes), len, loc,
45 set);
46 }
47
IsHexDigit(char c)48 bool IsHexDigit(char c) {
49 return (c >= '0' && c <= '9') || (c >= 'A' && c <= 'F') || (c >= 'a' && c <= 'f');
50 }
51
52 // Wrapper around X509_NAME_get_text_by_NID that first calculates the size
53 // of the string. Returns empty string on failure.
GetX509NameTextByNid(X509_NAME * name,int nid)54 std::optional<std::string> GetX509NameTextByNid(X509_NAME* name, int nid) {
55 // |len| is the len of the text excluding the final null
56 int len = X509_NAME_get_text_by_NID(name, nid, nullptr, -1);
57 if (len <= 0) {
58 return std::nullopt;
59 }
60
61 // Include the space for the final null byte
62 std::vector<char> buf(len + 1, '\0');
63 CHECK(X509_NAME_get_text_by_NID(name, nid, buf.data(), buf.size()));
64 return std::make_optional(std::string(buf.data()));
65 }
66
67 } // namespace
68
69 // Takes an encoded public key and generates a X509_NAME that can be used in
70 // TlsConnection::SetClientCAList(), to allow the client to figure out which of
71 // its keys it should try to use in the TLS handshake.
CreateCAIssuerFromEncodedKey(std::string_view key)72 bssl::UniquePtr<X509_NAME> CreateCAIssuerFromEncodedKey(std::string_view key) {
73 // "O=AdbKey-0;CN=<key>;"
74 CHECK(!key.empty());
75
76 std::string identifier = kAdbKeyIdentifierV0;
77 bssl::UniquePtr<X509_NAME> name(X509_NAME_new());
78 CHECK(X509_NAME_add_entry_by_NID_const(name.get(), kAdbKeyIdentifierNid, MBSTRING_ASC,
79 reinterpret_cast<const uint8_t*>(identifier.data()),
80 identifier.size(), -1, 0));
81
82 CHECK(X509_NAME_add_entry_by_NID_const(name.get(), kAdbKeyValueNid, MBSTRING_ASC,
83 reinterpret_cast<const uint8_t*>(key.data()), key.size(),
84 -1, 0));
85 return name;
86 }
87
88 // Parses a CA issuer and returns the encoded key, if any.
ParseEncodedKeyFromCAIssuer(X509_NAME * issuer)89 std::optional<std::string> ParseEncodedKeyFromCAIssuer(X509_NAME* issuer) {
90 CHECK(issuer);
91
92 auto buf = GetX509NameTextByNid(issuer, kAdbKeyIdentifierNid);
93 if (!buf) {
94 return std::nullopt;
95 }
96
97 // Check for supported versions
98 if (*buf == kAdbKeyIdentifierV0) {
99 return GetX509NameTextByNid(issuer, kAdbKeyValueNid);
100 }
101 return std::nullopt;
102 }
103
SHA256BitsToHexString(std::string_view sha256)104 std::string SHA256BitsToHexString(std::string_view sha256) {
105 CHECK_EQ(sha256.size(), static_cast<size_t>(SHA256_DIGEST_LENGTH));
106 std::stringstream ss;
107 auto* u8 = reinterpret_cast<const uint8_t*>(sha256.data());
108 ss << std::uppercase << std::setfill('0') << std::hex;
109 // Convert to hex-string representation
110 for (size_t i = 0; i < SHA256_DIGEST_LENGTH; ++i) {
111 // Need to cast to something bigger than one byte, or
112 // stringstream will interpret it as a char value.
113 ss << std::setw(2) << static_cast<uint16_t>(u8[i]);
114 }
115 return ss.str();
116 }
117
SHA256HexStringToBits(std::string_view sha256_str)118 std::optional<std::string> SHA256HexStringToBits(std::string_view sha256_str) {
119 if (sha256_str.size() != SHA256_DIGEST_LENGTH * 2) {
120 return std::nullopt;
121 }
122
123 std::string result;
124 for (size_t i = 0; i < SHA256_DIGEST_LENGTH; ++i) {
125 auto bytestr = std::string(sha256_str.substr(i * 2, 2));
126 if (!IsHexDigit(bytestr[0]) || !IsHexDigit(bytestr[1])) {
127 LOG(ERROR) << "SHA256 string has invalid non-hex chars";
128 return std::nullopt;
129 }
130 result += static_cast<char>(std::stol(bytestr, nullptr, 16));
131 }
132 return result;
133 }
134
135 } // namespace tls
136 } // namespace adb
137