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Merge pull request #1351 from p12tic/fix-ssl-crash-closing-connections 

Fix ssl-related crashes when closing connections [SECURITY VULNERABILITY CVE-2021-42074]
This commit is contained in:
Povilas Kanapickas 2021-11-01 14:40:11 +02:00 committed by GitHub
parent caeebf6c36 f0efe043bb
commit 4486830fdb
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GPG Key ID: 4AEE18F83AFDEB23
4 changed files with 88 additions and 45 deletions
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4
doc/newsfragments/fix-crash-on-ssl-hello.bugfix Normal file
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@ -0,0 +1,4 @@
SECURITY ISSUE
Fixed a bug which caused Barrier to crash when disconnecting a TCP session just after sending Hello message.
This bug allowed an unauthenticated attacker to crash Barrier with only network access.

2
doc/newsfragments/ssl-corrupted-data.bugfix Normal file
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@ -0,0 +1,2 @@
Fixed a bug in SSL implementation that caused invalid data occasionally being sent to clients
under heavy load.

91
src/lib/net/SecureSocket.cpp
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@ -101,6 +101,8 @@ SecureSocket::close()
void SecureSocket::freeSSLResources()
{
std::lock_guard<std::mutex> ssl_lock{ssl_mutex_};
if (m_ssl->m_ssl != NULL) {
SSL_shutdown(m_ssl->m_ssl);
SSL_free(m_ssl->m_ssl);
@ -154,7 +156,7 @@ SecureSocket::secureAccept()
TCPSocket::EJobResult
SecureSocket::doRead()
{
static UInt8 buffer[4096];
UInt8 buffer[4096];
memset(buffer, 0, sizeof(buffer));
int bytesRead = 0;
int status = 0;
@ -213,11 +215,6 @@ SecureSocket::doRead()
TCPSocket::EJobResult
SecureSocket::doWrite()
{
static bool s_retry = false;
static int s_retrySize = 0;
static std::unique_ptr<char[]> s_staticBuffer;
static std::size_t s_staticBufferSize = 0;
// write data
int bufferSize = 0;
int bytesWrote = 0;
@ -226,16 +223,16 @@ SecureSocket::doWrite()
if (!isSecureReady())
return kRetry;
if (s_retry) {
bufferSize = s_retrySize;
if (do_write_retry_) {
bufferSize = do_write_retry_size_;
} else {
bufferSize = m_outputBuffer.getSize();
if (bufferSize > s_staticBufferSize) {
s_staticBuffer.reset(new char[bufferSize]);
s_staticBufferSize = bufferSize;
if (bufferSize > do_write_retry_buffer_size_) {
do_write_retry_buffer_.reset(new char[bufferSize]);
do_write_retry_buffer_size_ = bufferSize;
}
if (bufferSize > 0) {
memcpy(s_staticBuffer.get(), m_outputBuffer.peek(bufferSize), bufferSize);
std::memcpy(do_write_retry_buffer_.get(), m_outputBuffer.peek(bufferSize), bufferSize);
}
}
@ -243,14 +240,14 @@ SecureSocket::doWrite()
return kRetry;
}
status = secureWrite(s_staticBuffer.get(), bufferSize, bytesWrote);
status = secureWrite(do_write_retry_buffer_.get(), bufferSize, bytesWrote);
if (status > 0) {
s_retry = false;
do_write_retry_ = false;
} else if (status < 0) {
return kBreak;
} else if (status == 0) {
s_retry = true;
s_retrySize = bufferSize;
do_write_retry_ = true;
do_write_retry_size_ = bufferSize;
return kNew;
}
@ -265,16 +262,16 @@ SecureSocket::doWrite()
int
SecureSocket::secureRead(void* buffer, int size, int& read)
{
std::lock_guard<std::mutex> ssl_lock{ssl_mutex_};
if (m_ssl->m_ssl != NULL) {
LOG((CLOG_DEBUG2 "reading secure socket"));
read = SSL_read(m_ssl->m_ssl, buffer, size);
static int retry;
// Check result will cleanup the connection in the case of a fatal
checkResult(read, retry);
checkResult(read, secure_read_retry_);
if (retry) {
if (secure_read_retry_) {
return 0;
}
@ -291,17 +288,17 @@ SecureSocket::secureRead(void* buffer, int size, int& read)
int
SecureSocket::secureWrite(const void* buffer, int size, int& wrote)
{
std::lock_guard<std::mutex> ssl_lock{ssl_mutex_};
if (m_ssl->m_ssl != NULL) {
LOG((CLOG_DEBUG2 "writing secure socket:%p", this));
wrote = SSL_write(m_ssl->m_ssl, buffer, size);
static int retry;
// Check result will cleanup the connection in the case of a fatal
checkResult(wrote, retry);
checkResult(wrote, secure_write_retry_);
if (retry) {
if (secure_write_retry_) {
return 0;
}
@ -324,6 +321,8 @@ SecureSocket::isSecureReady()
void
SecureSocket::initSsl(bool server)
{
std::lock_guard<std::mutex> ssl_lock{ssl_mutex_};
m_ssl = new Ssl();
m_ssl->m_context = NULL;
m_ssl->m_ssl = NULL;
@ -333,6 +332,8 @@ SecureSocket::initSsl(bool server)
bool SecureSocket::load_certificates(const barrier::fs::path& path)
{
std::lock_guard<std::mutex> ssl_lock{ssl_mutex_};
if (path.empty()) {
showError("ssl certificate is not specified");
return false;
@ -374,6 +375,8 @@ static int cert_verify_ignore_callback(X509_STORE_CTX*, void*)
void
SecureSocket::initContext(bool server)
{
// ssl_mutex_ is assumed to be acquired
SSL_library_init();
const SSL_METHOD* method;
@ -419,6 +422,8 @@ SecureSocket::initContext(bool server)
void
SecureSocket::createSSL()
{
// ssl_mutex_ is assumed to be acquired
// I assume just one instance is needed
// get new SSL state with context
if (m_ssl->m_ssl == NULL) {
@ -430,6 +435,8 @@ SecureSocket::createSSL()
int
SecureSocket::secureAccept(int socket)
{
std::lock_guard<std::mutex> ssl_lock{ssl_mutex_};
createSSL();
// set connection socket to SSL state
@ -438,9 +445,7 @@ SecureSocket::secureAccept(int socket)
LOG((CLOG_DEBUG2 "accepting secure socket"));
int r = SSL_accept(m_ssl->m_ssl);
static int retry;
checkResult(r, retry);
checkResult(r, secure_accept_retry_);
if (isFatal()) {
// tell user and sleep so the socket isn't hammered.
@ -448,25 +453,25 @@ SecureSocket::secureAccept(int socket)
LOG((CLOG_INFO "client connection may not be secure"));
m_secureReady = false;
ARCH->sleep(1);
retry = 0;
secure_accept_retry_ = 0;
return -1; // Failed, error out
}
// If not fatal and no retry, state is good
if (retry == 0) {
if (secure_accept_retry_ == 0) {
if (security_level_ == ConnectionSecurityLevel::ENCRYPTED_AUTHENTICATED) {
if (verify_cert_fingerprint(
barrier::DataDirectories::trusted_clients_ssl_fingerprints_path())) {
LOG((CLOG_INFO "accepted secure socket"));
if (!ensure_peer_certificate()) {
retry = 0;
secure_accept_retry_ = 0;
disconnect();
return -1;// Cert fail, error
}
}
else {
LOG((CLOG_ERR "failed to verify server certificate fingerprint"));
retry = 0;
secure_accept_retry_ = 0;
disconnect();
return -1; // Fingerprint failed, error
}
@ -482,7 +487,7 @@ SecureSocket::secureAccept(int socket)
}
// If not fatal and retry is set, not ready, and return retry
if (retry > 0) {
if (secure_accept_retry_ > 0) {
LOG((CLOG_DEBUG2 "retry accepting secure socket"));
m_secureReady = false;
ARCH->sleep(s_retryDelay);
@ -497,12 +502,15 @@ SecureSocket::secureAccept(int socket)
int
SecureSocket::secureConnect(int socket)
{
// note that load_certificates acquires ssl_mutex_
if (!load_certificates(barrier::DataDirectories::ssl_certificate_path())) {
LOG((CLOG_ERR "could not load client certificates"));
// FIXME: this is fatal error, but we current don't disconnect because whole logic in this
// function needs to be cleaned up
}
std::lock_guard<std::mutex> ssl_lock{ssl_mutex_};
createSSL();
// attach the socket descriptor
@ -511,25 +519,23 @@ SecureSocket::secureConnect(int socket)
LOG((CLOG_DEBUG2 "connecting secure socket"));
int r = SSL_connect(m_ssl->m_ssl);
static int retry;
checkResult(r, retry);
checkResult(r, secure_connect_retry_);
if (isFatal()) {
LOG((CLOG_ERR "failed to connect secure socket"));
retry = 0;
secure_connect_retry_ = 0;
return -1;
}
// If we should retry, not ready and return 0
if (retry > 0) {
if (secure_connect_retry_ > 0) {
LOG((CLOG_DEBUG2 "retry connect secure socket"));
m_secureReady = false;
ARCH->sleep(s_retryDelay);
return 0;
}
retry = 0;
secure_connect_retry_ = 0;
// No error, set ready, process and return ok
m_secureReady = true;
if (verify_cert_fingerprint(barrier::DataDirectories::trusted_servers_ssl_fingerprints_path())) {
@ -555,6 +561,7 @@ SecureSocket::secureConnect(int socket)
bool
SecureSocket::ensure_peer_certificate()
{
// ssl_mutex_ is assumed to be acquired
X509* cert;
char* line;
@ -577,6 +584,8 @@ SecureSocket::ensure_peer_certificate()
void
SecureSocket::checkResult(int status, int& retry)
{
// ssl_mutex_ is assumed to be acquired
// ssl errors are a little quirky. the "want" errors are normal and
// should result in a retry.
@ -692,6 +701,8 @@ SecureSocket::disconnect()
bool SecureSocket::verify_cert_fingerprint(const barrier::fs::path& fingerprint_db_path)
{
// ssl_mutex_ is assumed to be acquired
// calculate received certificate fingerprint
barrier::FingerprintData fingerprint_sha1, fingerprint_sha256;
try {
@ -818,6 +829,8 @@ showCipherStackDesc(STACK_OF(SSL_CIPHER) * stack) {
void
SecureSocket::showSecureCipherInfo()
{
// ssl_mutex_ is assumed to be acquired
STACK_OF(SSL_CIPHER) * sStack = SSL_get_ciphers(m_ssl->m_ssl);
if (sStack == NULL) {
@ -860,6 +873,8 @@ SecureSocket::showSecureLibInfo()
void
SecureSocket::showSecureConnectInfo()
{
// ssl_mutex_ is assumed to be acquired
const SSL_CIPHER* cipher = SSL_get_current_cipher(m_ssl->m_ssl);
if (cipher != NULL) {

34
src/lib/net/SecureSocket.h
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@ -21,6 +21,7 @@
#include "net/TCPSocket.h"
#include "net/XSocket.h"
#include "io/filesystem.h"
#include <mutex>
class IEventQueue;
class SocketMultiplexer;
@ -61,31 +62,52 @@ public:
private:
// SSL
void initContext(bool server);
void createSSL();
void initContext(bool server); // may only be called with ssl_mutex_ acquired
void createSSL(); // may only be called with ssl_mutex_ acquired.
int secureAccept(int s);
int secureConnect(int s);
bool ensure_peer_certificate();
void checkResult(int n, int& retry);
bool ensure_peer_certificate(); // may only be called with ssl_mutex_ acquired
void checkResult(int n, int& retry); // may only be called with m_ssl_mutex_ acquired.
void showError(const std::string& reason);
std::string getError();
void disconnect();
// may only be called with ssl_mutex_ acquired
bool verify_cert_fingerprint(const barrier::fs::path& fingerprint_db_path);
MultiplexerJobStatus serviceConnect(ISocketMultiplexerJob*, bool, bool, bool);
MultiplexerJobStatus serviceAccept(ISocketMultiplexerJob*, bool, bool, bool);
void showSecureConnectInfo();
void showSecureConnectInfo(); // may only be called with ssl_mutex_ acquired
void showSecureLibInfo();
void showSecureCipherInfo();
void showSecureCipherInfo(); // may only be called with ssl_mutex_ acquired
void handleTCPConnected(const Event& event, void*);
void freeSSLResources();
private:
// all accesses to m_ssl must be protected by this mutex. The only function that is called
// from outside SocketMultiplexer thread is close(), so we mostly care about things accessed
// by it.
std::mutex ssl_mutex_;
Ssl* m_ssl;
bool m_secureReady;
bool m_fatal;
ConnectionSecurityLevel security_level_ = ConnectionSecurityLevel::ENCRYPTED;
int secure_accept_retry_ = 0; // used only in secureAccept()
int secure_connect_retry_ = 0; // used only in secureConnect()
int secure_read_retry_ = 0; // used only in secureRead()
int secure_write_retry_ = 0; // used only in secureWrite()
// The following are used only from doWrite()
// FIXME: using std::vector would simplify logic significantly.
bool do_write_retry_ = false;
int do_write_retry_size_ = 0;
std::unique_ptr<char[]> do_write_retry_buffer_;
std::size_t do_write_retry_buffer_size_ = 0;
};