Index: src/OFTLSStream.h
==================================================================
--- src/OFTLSStream.h
+++ src/OFTLSStream.h
@@ -32,11 +32,11 @@
 typedef enum {
 	/** @brief An unknown error. */
 	OFTLSStreamErrorCodeUnknown,
 	/** @brief Initialization of the TLS context failed. */
 	OFTLSStreamErrorCodeInitializationFailed,
-	/** @brief Verification of the certificate failed. */
+	/** @brief Failed to verify certificate. */
 	OFTLSStreamErrorCodeCertificateVerificationFailed,
 	/** @brief The certificate has an untrusted or unknown issuer. */
 	OFTLSStreamErrorCodeCertificateIssuerUntrusted,
 	/** @brief The certificate is for a different name. */
 	OFTLSStreamErrorCodeCertificateNameMismatch,

Index: src/OFTLSStream.m
==================================================================
--- src/OFTLSStream.m
+++ src/OFTLSStream.m
@@ -52,11 +52,11 @@
 {
 	switch (errorCode) {
 	case OFTLSStreamErrorCodeInitializationFailed:
 		return @"Initialization of TLS context failed";
 	case OFTLSStreamErrorCodeCertificateVerificationFailed:
-		return @"Verification of the certificate failed";
+		return @"Failed to verify certificate";
 	case OFTLSStreamErrorCodeCertificateIssuerUntrusted:
 		return @"The certificate has an untrusted or unknown issuer";
 	case OFTLSStreamErrorCodeCertificateNameMismatch:
 		return @"The certificate is for a different name";
 	case OFTLSStreamErrorCodeCertificatedExpired:

Index: src/tls/OFOpenSSLTLSStream.m
==================================================================
--- src/tls/OFOpenSSLTLSStream.m
+++ src/tls/OFOpenSSLTLSStream.m
@@ -21,10 +21,12 @@
 
 #include <errno.h>
 
 #import "OFOpenSSLTLSStream.h"
 #import "OFData.h"
+
+#include <openssl/err.h>
 
 #import "OFAlreadyOpenException.h"
 #import "OFInitializationFailedException.h"
 #import "OFNotOpenException.h"
 #import "OFReadFailedException.h"
@@ -33,10 +35,48 @@
 
 #define bufferSize OFOpenSSLTLSStreamBufferSize
 
 int _ObjFWTLS_reference;
 static SSL_CTX *clientContext;
+
+static OFTLSStreamErrorCode
+verifyResultToErrorCode(const SSL *SSL_)
+{
+	switch (SSL_get_verify_result(SSL_)) {
+	case X509_V_ERR_UNABLE_TO_GET_ISSUER_CERT:
+	case X509_V_ERR_UNABLE_TO_GET_ISSUER_CERT_LOCALLY:
+	case X509_V_ERR_DEPTH_ZERO_SELF_SIGNED_CERT:
+	case X509_V_ERR_SELF_SIGNED_CERT_IN_CHAIN:
+	case X509_V_ERR_CERT_UNTRUSTED:
+		return OFTLSStreamErrorCodeCertificateIssuerUntrusted;
+	case X509_V_ERR_HOSTNAME_MISMATCH:
+		return OFTLSStreamErrorCodeCertificateNameMismatch;
+	case X509_V_ERR_CERT_NOT_YET_VALID:
+	case X509_V_ERR_CERT_HAS_EXPIRED:
+		return OFTLSStreamErrorCodeCertificatedExpired;
+	case X509_V_ERR_CERT_REVOKED:
+		return OFTLSStreamErrorCodeCertificateRevoked;
+	}
+
+	return OFTLSStreamErrorCodeCertificateVerificationFailed;
+}
+
+static OFTLSStreamErrorCode
+errToErrorCode(const SSL *SSL_)
+{
+	unsigned long err = ERR_get_error();
+
+	switch (ERR_GET_LIB(err)) {
+	case ERR_LIB_SSL:
+		switch (ERR_GET_REASON(err)) {
+		case SSL_R_CERTIFICATE_VERIFY_FAILED:
+			return verifyResultToErrorCode(SSL_);
+		}
+	}
+
+	return OFTLSStreamErrorCodeUnknown;
+}
 
 @implementation OFOpenSSLTLSStream
 + (void)load
 {
 	if (OFTLSStreamImplementation == Nil)
@@ -112,10 +152,11 @@
 	size_t bytesRead;
 
 	if (!_handshakeDone)
 		@throw [OFNotOpenException exceptionWithObject: self];
 
+	ERR_clear_error();
 	ret = SSL_read_ex(_SSL, buffer, length, &bytesRead);
 
 	while (BIO_ctrl_pending(_writeBIO) > 0) {
 		int tmp = BIO_read(_writeBIO, _buffer, bufferSize);
 
@@ -143,10 +184,11 @@
 				if (e.errNo == EWOULDBLOCK || e.errNo != EAGAIN)
 					return 0;
 			}
 		}
 
+		ERR_clear_error();
 		ret = SSL_read_ex(_SSL, buffer, length, &bytesRead);
 
 		while (BIO_ctrl_pending(_writeBIO) > 0) {
 			int tmp = BIO_read(_writeBIO, _buffer, bufferSize);
 
@@ -174,10 +216,12 @@
 	int ret;
 	size_t bytesWritten;
 
 	if (!_handshakeDone)
 		@throw [OFNotOpenException exceptionWithObject: self];
+
+	ERR_clear_error();
 
 	if ((ret = SSL_write_ex(_SSL, buffer, length, &bytesWritten)) != 1) {
 		/* FIXME: Translate error to errNo */
 		int errNo = 0;
 
@@ -270,10 +314,11 @@
 			    exceptionWithStream: self
 					   host: host
 				      errorCode: initFailedErrorCode];
 	}
 
+	ERR_clear_error();
 	status = SSL_do_handshake(_SSL);
 
 	while (BIO_ctrl_pending(_writeBIO) > 0) {
 		int tmp = BIO_read(_writeBIO, _buffer, bufferSize);
 
@@ -298,12 +343,17 @@
 			[_underlyingStream asyncWriteData: [OFData data]
 					      runLoopMode: runLoopMode];
 			[_delegate retain];
 			objc_autoreleasePoolPop(pool);
 			return;
+		case SSL_ERROR_SSL:
+			exception = [OFTLSHandshakeFailedException
+			    exceptionWithStream: self
+					   host: host
+				      errorCode: errToErrorCode(_SSL)];
+			break;
 		default:
-			/* FIXME: Map to better errors */
 			exception = [OFTLSHandshakeFailedException
 			    exceptionWithStream: self
 					   host: host
 				      errorCode: OFTLSStreamErrorCodeUnknown];
 			break;
@@ -331,10 +381,11 @@
 
 		OFEnsure(length <= INT_MAX);
 		OFEnsure(BIO_write(_readBIO, buffer, (int)length) ==
 		    (int)length);
 
+		ERR_clear_error();
 		status = SSL_do_handshake(_SSL);
 
 		while (BIO_ctrl_pending(_writeBIO) > 0) {
 			int tmp = BIO_read(_writeBIO, buffer, bufferSize);
 
@@ -354,10 +405,16 @@
 				OFRunLoopMode runLoopMode =
 				    [OFRunLoop currentRunLoop].currentMode;
 				[_underlyingStream asyncWriteData: [OFData data]
 						      runLoopMode: runLoopMode];
 				return false;
+			case SSL_ERROR_SSL:
+				exception = [OFTLSHandshakeFailedException
+				    exceptionWithStream: self
+						   host: _host
+					      errorCode: errToErrorCode(_SSL)];
+				break;
 			default:
 				exception = [OFTLSHandshakeFailedException
 				    exceptionWithStream: self
 						   host: _host
 					      errorCode: unknownErrorCode];
@@ -395,10 +452,11 @@
 
 			[_underlyingStream writeBuffer: _buffer length: tmp];
 			[_underlyingStream flushWriteBuffer];
 		}
 
+		ERR_clear_error();
 		status = SSL_do_handshake(_SSL);
 
 		while (BIO_ctrl_pending(_writeBIO) > 0) {
 			int tmp = BIO_read(_writeBIO, _buffer, bufferSize);
 
@@ -420,10 +478,16 @@
 						 length: bufferSize
 					    runLoopMode: runLoopMode];
 				return nil;
 			case SSL_ERROR_WANT_WRITE:
 				return data;
+			case SSL_ERROR_SSL:
+				exception = [OFTLSHandshakeFailedException
+				    exceptionWithStream: self
+						   host: _host
+					      errorCode: errToErrorCode(_SSL)];
+				break;
 			default:
 				exception = [OFTLSHandshakeFailedException
 				    exceptionWithStream: self
 						   host: _host
 					      errorCode: unknownErrorCode];