Bruno Rocha | 7f9aea2 | 2011-09-12 14:31:24 -0700 | [diff] [blame] | 1 | // Copyright (c) 2011 The Chromium OS 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 | #ifndef CHROMEOS_PLATFORM_UPDATE_ENGINE_CERTIFICATE_CHECKER_H_ |
| 6 | #define CHROMEOS_PLATFORM_UPDATE_ENGINE_CERTIFICATE_CHECKER_H_ |
| 7 | |
| 8 | #include <string> |
| 9 | |
| 10 | #include <base/basictypes.h> |
| 11 | #include <curl/curl.h> |
| 12 | #include <gtest/gtest_prod.h> // for FRIEND_TEST |
| 13 | #include <openssl/ssl.h> |
| 14 | |
| 15 | class MetricsLibraryInterface; |
| 16 | namespace chromeos_update_engine { class PrefsInterface; } |
| 17 | |
| 18 | namespace chromeos_update_engine { |
| 19 | |
| 20 | // Wrapper for openssl operations with the certificates. |
| 21 | class OpenSSLWrapper { |
| 22 | public: |
| 23 | OpenSSLWrapper() {} |
| 24 | virtual ~OpenSSLWrapper() {} |
| 25 | |
| 26 | // Takes an openssl X509_STORE_CTX, extracts the corresponding certificate |
| 27 | // from it and calculates its fingerprint (SHA256 digest). Returns true on |
| 28 | // success and false otherwise. |
| 29 | // |
| 30 | // |x509_ctx| is the pointer to the openssl object that holds the certificate. |
| 31 | // |out_depth| is the depth of the current certificate, in the certificate |
| 32 | // chain. |
| 33 | // |out_digest_length| is the length of the generated digest. |
| 34 | // |out_digest| is the byte array where the digest itself will be written. |
| 35 | // It should be big enough to hold a SHA1 digest (e.g. EVP_MAX_MD_SIZE). |
| 36 | virtual bool GetCertificateDigest(X509_STORE_CTX* x509_ctx, |
| 37 | int* out_depth, |
| 38 | unsigned int* out_digest_length, |
| 39 | unsigned char* out_digest) const; |
| 40 | |
| 41 | private: |
| 42 | DISALLOW_COPY_AND_ASSIGN(OpenSSLWrapper); |
| 43 | }; |
| 44 | |
| 45 | // Responsible for checking whether update server certificates change, and |
| 46 | // reporting to UMA when this happens. Since all state information is persisted, |
| 47 | // and openssl forces us to use a static callback with no data pointer, this |
| 48 | // class is entirely static. |
| 49 | class CertificateChecker { |
| 50 | public: |
| 51 | // These values are used to generate the keys of files persisted via prefs. |
| 52 | // This means that changing these will cause loss of information on metrics |
| 53 | // reporting, during the transition. |
| 54 | enum ServerToCheck { |
| 55 | kUpdate = 0, |
| 56 | kDownload = 1, |
| 57 | kNone = 2 // This needs to be the last element. Changing its value is ok. |
| 58 | }; |
| 59 | |
| 60 | CertificateChecker() {} |
| 61 | virtual ~CertificateChecker() {} |
| 62 | |
| 63 | // This callback is called by libcurl just before the initialization of an |
| 64 | // SSL connection after having processed all other SSL related options. Used |
| 65 | // to check if server certificates change. |ptr| is expected to be a |
| 66 | // pointer to a ServerToCheck. |
| 67 | static CURLcode ProcessSSLContext(CURL* curl_handle, SSL_CTX* ssl_ctx, |
| 68 | void* ptr); |
| 69 | |
| 70 | // Flushes to UMA any certificate-related report that was persisted. |
| 71 | static void FlushReport(); |
| 72 | |
| 73 | // Setters. |
| 74 | static void set_metrics_lib(MetricsLibraryInterface* metrics_lib) { |
| 75 | metrics_lib_ = metrics_lib; |
| 76 | } |
| 77 | |
| 78 | static void set_prefs(PrefsInterface* prefs) { |
| 79 | prefs_ = prefs; |
| 80 | } |
| 81 | |
| 82 | static void set_openssl_wrapper(OpenSSLWrapper* openssl_wrapper) { |
| 83 | openssl_wrapper_ = openssl_wrapper; |
| 84 | } |
| 85 | |
| 86 | private: |
| 87 | FRIEND_TEST(CertificateCheckerTest, NewCertificate); |
| 88 | FRIEND_TEST(CertificateCheckerTest, SameCertificate); |
| 89 | FRIEND_TEST(CertificateCheckerTest, ChangedCertificate); |
| 90 | FRIEND_TEST(CertificateCheckerTest, FailedCertificate); |
| 91 | FRIEND_TEST(CertificateCheckerTest, FlushReport); |
| 92 | FRIEND_TEST(CertificateCheckerTest, FlushNothingToReport); |
| 93 | |
| 94 | // These callbacks are called by openssl after initial SSL verification. They |
| 95 | // are used to perform any additional security verification on the connection, |
| 96 | // but we use them here to get hold of the server certificate, in order to |
| 97 | // determine if it has changed since the last connection. Since openssl forces |
| 98 | // us to do this statically, we define two different callbacks for the two |
| 99 | // different official update servers, and only assign the correspondent one. |
| 100 | // The assigned callback is then called once per each certificate on the |
| 101 | // server and returns 1 for success and 0 for failure. |
| 102 | static int VerifySSLCallbackUpdateCheck(int preverify_ok, |
| 103 | X509_STORE_CTX* x509_ctx); |
| 104 | static int VerifySSLCallbackDownload(int preverify_ok, |
| 105 | X509_STORE_CTX* x509_ctx); |
| 106 | |
| 107 | // Checks if server certificate for |server_to_check|, stored in |x509_ctx|, |
| 108 | // has changed since last connection to that same server. This is called by |
| 109 | // one of the two callbacks defined above. If certificate fails to check or |
| 110 | // changes, a report is generated and persisted, to be later sent by |
| 111 | // FlushReport. Returns true on success and false otherwise. |
| 112 | static bool CheckCertificateChange(ServerToCheck server_to_check, |
| 113 | int preverify_ok, |
| 114 | X509_STORE_CTX* x509_ctx); |
| 115 | |
| 116 | // Metrics library used to report to UMA. |
| 117 | static MetricsLibraryInterface* metrics_lib_; |
| 118 | |
| 119 | // Prefs used to store certificates and UMA reports. |
| 120 | static PrefsInterface* prefs_; |
| 121 | |
| 122 | // The wrapper for openssl operations. |
| 123 | static OpenSSLWrapper* openssl_wrapper_; |
| 124 | |
| 125 | DISALLOW_COPY_AND_ASSIGN(CertificateChecker); |
| 126 | }; |
| 127 | |
| 128 | } // namespace chromeos_update_engine |
| 129 | |
| 130 | #endif // CHROMEOS_PLATFORM_UPDATE_ENGINE_CERTIFICATE_CHECKER_H_ |