lib/net: Fix race conditions when closing SSL connections
This fixes the following security vulnerability: - CVE-2021-42074 SIGSEGV on quick open/close sequence while sending Hello message The issue has been reported by Matthias Gerstner <mgerstner@suse.de>.
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caeebf6c36
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@ -0,0 +1,4 @@
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SECURITY ISSUE
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Fixed a bug which caused Barrier to crash when disconnecting a TCP session just after sending Hello message.
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This bug allowed an unauthenticated attacker to crash Barrier with only network access.
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@ -101,6 +101,8 @@ SecureSocket::close()
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void SecureSocket::freeSSLResources()
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{
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std::lock_guard<std::mutex> ssl_lock{ssl_mutex_};
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if (m_ssl->m_ssl != NULL) {
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SSL_shutdown(m_ssl->m_ssl);
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SSL_free(m_ssl->m_ssl);
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@ -265,6 +267,8 @@ SecureSocket::doWrite()
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int
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SecureSocket::secureRead(void* buffer, int size, int& read)
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{
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std::lock_guard<std::mutex> ssl_lock{ssl_mutex_};
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if (m_ssl->m_ssl != NULL) {
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LOG((CLOG_DEBUG2 "reading secure socket"));
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read = SSL_read(m_ssl->m_ssl, buffer, size);
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@ -291,6 +295,8 @@ SecureSocket::secureRead(void* buffer, int size, int& read)
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int
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SecureSocket::secureWrite(const void* buffer, int size, int& wrote)
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{
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std::lock_guard<std::mutex> ssl_lock{ssl_mutex_};
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if (m_ssl->m_ssl != NULL) {
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LOG((CLOG_DEBUG2 "writing secure socket:%p", this));
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@ -324,6 +330,8 @@ SecureSocket::isSecureReady()
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void
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SecureSocket::initSsl(bool server)
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{
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std::lock_guard<std::mutex> ssl_lock{ssl_mutex_};
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m_ssl = new Ssl();
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m_ssl->m_context = NULL;
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m_ssl->m_ssl = NULL;
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@ -333,6 +341,8 @@ SecureSocket::initSsl(bool server)
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bool SecureSocket::load_certificates(const barrier::fs::path& path)
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{
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std::lock_guard<std::mutex> ssl_lock{ssl_mutex_};
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if (path.empty()) {
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showError("ssl certificate is not specified");
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return false;
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@ -374,6 +384,8 @@ static int cert_verify_ignore_callback(X509_STORE_CTX*, void*)
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void
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SecureSocket::initContext(bool server)
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{
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// ssl_mutex_ is assumed to be acquired
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SSL_library_init();
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const SSL_METHOD* method;
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@ -419,6 +431,8 @@ SecureSocket::initContext(bool server)
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void
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SecureSocket::createSSL()
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{
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// ssl_mutex_ is assumed to be acquired
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// I assume just one instance is needed
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// get new SSL state with context
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if (m_ssl->m_ssl == NULL) {
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@ -430,6 +444,8 @@ SecureSocket::createSSL()
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int
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SecureSocket::secureAccept(int socket)
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{
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std::lock_guard<std::mutex> ssl_lock{ssl_mutex_};
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createSSL();
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// set connection socket to SSL state
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@ -497,12 +513,15 @@ SecureSocket::secureAccept(int socket)
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int
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SecureSocket::secureConnect(int socket)
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{
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// note that load_certificates acquires ssl_mutex_
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if (!load_certificates(barrier::DataDirectories::ssl_certificate_path())) {
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LOG((CLOG_ERR "could not load client certificates"));
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// FIXME: this is fatal error, but we current don't disconnect because whole logic in this
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// function needs to be cleaned up
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}
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std::lock_guard<std::mutex> ssl_lock{ssl_mutex_};
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createSSL();
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// attach the socket descriptor
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@ -555,6 +574,7 @@ SecureSocket::secureConnect(int socket)
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bool
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SecureSocket::ensure_peer_certificate()
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{
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// ssl_mutex_ is assumed to be acquired
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X509* cert;
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char* line;
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@ -577,6 +597,8 @@ SecureSocket::ensure_peer_certificate()
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void
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SecureSocket::checkResult(int status, int& retry)
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{
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// ssl_mutex_ is assumed to be acquired
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// ssl errors are a little quirky. the "want" errors are normal and
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// should result in a retry.
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@ -692,6 +714,8 @@ SecureSocket::disconnect()
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bool SecureSocket::verify_cert_fingerprint(const barrier::fs::path& fingerprint_db_path)
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{
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// ssl_mutex_ is assumed to be acquired
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// calculate received certificate fingerprint
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barrier::FingerprintData fingerprint_sha1, fingerprint_sha256;
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try {
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@ -818,6 +842,8 @@ showCipherStackDesc(STACK_OF(SSL_CIPHER) * stack) {
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void
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SecureSocket::showSecureCipherInfo()
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{
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// ssl_mutex_ is assumed to be acquired
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STACK_OF(SSL_CIPHER) * sStack = SSL_get_ciphers(m_ssl->m_ssl);
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if (sStack == NULL) {
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@ -860,6 +886,8 @@ SecureSocket::showSecureLibInfo()
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void
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SecureSocket::showSecureConnectInfo()
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{
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// ssl_mutex_ is assumed to be acquired
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const SSL_CIPHER* cipher = SSL_get_current_cipher(m_ssl->m_ssl);
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if (cipher != NULL) {
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@ -21,6 +21,7 @@
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#include "net/TCPSocket.h"
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#include "net/XSocket.h"
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#include "io/filesystem.h"
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#include <mutex>
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class IEventQueue;
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class SocketMultiplexer;
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@ -61,29 +62,38 @@ public:
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private:
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// SSL
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void initContext(bool server);
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void createSSL();
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void initContext(bool server); // may only be called with ssl_mutex_ acquired
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void createSSL(); // may only be called with ssl_mutex_ acquired.
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int secureAccept(int s);
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int secureConnect(int s);
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bool ensure_peer_certificate();
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void checkResult(int n, int& retry);
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bool ensure_peer_certificate(); // may only be called with ssl_mutex_ acquired
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void checkResult(int n, int& retry); // may only be called with m_ssl_mutex_ acquired.
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void showError(const std::string& reason);
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std::string getError();
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void disconnect();
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// may only be called with ssl_mutex_ acquired
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bool verify_cert_fingerprint(const barrier::fs::path& fingerprint_db_path);
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MultiplexerJobStatus serviceConnect(ISocketMultiplexerJob*, bool, bool, bool);
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MultiplexerJobStatus serviceAccept(ISocketMultiplexerJob*, bool, bool, bool);
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void showSecureConnectInfo();
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void showSecureLibInfo();
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void showSecureCipherInfo();
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void showSecureConnectInfo(); // may only be called with ssl_mutex_ acquired
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void showSecureLibInfo();
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void showSecureCipherInfo(); // may only be called with ssl_mutex_ acquired
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void handleTCPConnected(const Event& event, void*);
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void freeSSLResources();
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private:
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// all accesses to m_ssl must be protected by this mutex. The only function that is called
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// from outside SocketMultiplexer thread is close(), so we mostly care about things accessed
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// by it.
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std::mutex ssl_mutex_;
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Ssl* m_ssl;
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bool m_secureReady;
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bool m_fatal;
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