Warn about insecure SSL connections.

Fixed GH-313

src/AppleTLSSession.cc

@@ -43,6 +43,7 @@
 #include "LogFactory.h"
 #include "a2functional.h"
 #include "fmt.h"
+#include "message.h"
 
 #define ioErr -36
 #define paramErr -50
@@ -85,7 +86,7 @@ static inline const char* protoToString(SSLProtocol proto)
   case kSSLProtocol2:
     return "SSLv2 (!)";
   case kSSLProtocol3:
-    return "SSLv3";
+    return "SSLv3 (!)";
   case kTLSProtocol1:
     return "TLSv1";
   case kTLSProtocol11:
@@ -731,6 +732,17 @@ int AppleTLSSession::tlsConnect(const std::string& hostname,
                   hostname.c_str(),
                   protoToString(proto),
                   suiteToString(suite).c_str()));
+  switch (proto) {
+    case kSSLProtocol2:
+    case kSSLProtocol3: {
+      std::string protoAndSuite = protoToString(proto);
+      protoAndSuite += " " + suiteToString(suite);
+      A2_LOG_WARN(fmt(MSG_WARN_OLD_TLS_CONNECTION, protoAndSuite.c_str()));
+      break;
+    }
+    default:
+      break;
+  }
 
   return TLS_ERR_OK;
 }

src/LibgnutlsTLSSession.cc

@@ -39,6 +39,9 @@
 #include "TLSContext.h"
 #include "util.h"
 #include "SocketCore.h"
+#include "LogFactory.h"
+#include "fmt.h"
+#include "message.h"
 
 namespace aria2 {
 
@@ -297,6 +300,24 @@ int GnuTLSSession::tlsConnect(const std::string& hostname,
       return TLS_ERR_ERROR;
     }
   }
+  auto proto = gnutls_protocol_get_version(sslSession_);
+  switch(proto) {
+    case GNUTLS_SSL3: {
+      std::string protoAndSuite = gnutls_protocol_get_name(proto);
+      protoAndSuite += " ";
+      protoAndSuite += gnutls_cipher_suite_get_name(
+          gnutls_kx_get(sslSession_),
+          gnutls_cipher_get(sslSession_),
+          gnutls_mac_get(sslSession_)
+          );
+      A2_LOG_WARN(fmt(MSG_WARN_OLD_TLS_CONNECTION, protoAndSuite.c_str()));
+      break;
+    }
+
+    default:
+      break;
+  }
+
   return TLS_ERR_OK;
 }
 

src/LibsslTLSSession.cc

@@ -267,6 +267,26 @@ int OpenSSLTLSSession::tlsConnect(const std::string& hostname,
       return TLS_ERR_ERROR;
     }
   }
+
+  switch(SSL_version(ssl_)) {
+    case SSL3_VERSION:
+    case SSL2_VERSION: {
+      std::string protoAndSuite = "Unknown";
+      auto cipher = SSL_get_current_cipher(ssl_);
+      if(cipher) {
+        auto buf = make_unique<char[]>(256);
+        auto cipherstr = SSL_CIPHER_description(cipher, buf.get(), 256);
+        if(cipherstr) {
+          protoAndSuite = cipherstr;
+        }
+      }
+      A2_LOG_WARN(fmt(MSG_WARN_OLD_TLS_CONNECTION, protoAndSuite.c_str()));
+      break;
+    }
+    default:
+      break;
+  }
+
   return TLS_ERR_OK;
 }
 

src/WinTLSSession.cc

@@ -119,6 +119,17 @@ inline static std::string getCipherSuite(CtxtHandle* handle)
   return "Unknown";
 }
 
+inline static uint32_t getProtocolVersion(CtxtHandle* handle)
+{
+  WinSecPkgContext_CipherInfo info = {SECPKGCONTEXT_CIPHERINFO_V1};
+  if (QueryContextAttributes(handle, SECPKG_ATTR_CIPHER_INFO, &info) ==
+      SEC_E_OK) {
+    return info.dwProtocol;
+  }
+  // XXX Assume the best?!
+  return std::numeric_limits<uint32_t>::max();
+}
+
 } // namespace
 
 namespace aria2 {
@@ -808,14 +819,31 @@ restart:
   }
   // Fall through
 
-  case st_handshake_done:
+  case st_handshake_done: {
     // All ready now :D
     state_ = st_connected;
     A2_LOG_INFO(
         fmt("WinTLS: connected with: %s", getCipherSuite(&handle_).c_str()));
+    auto proto = getProtocolVersion(&handle_);
+    if (proto < 0x301) {
+      std::string protoAndSuite;
+      switch (proto) {
+      case 0x300:
+        protoAndSuite = "SSLv3";
+        break;
+      default:
+        protoAndSuite = "Unknown";
+        break;
+      }
+      protoAndSuite += " " + getCipherSuite(&handle_);
+      A2_LOG_WARN(fmt(MSG_WARN_OLD_TLS_CONNECTION, protoAndSuite.c_str()));
+    }
+
     return TLS_ERR_OK;
   }
 
+  }
+
   A2_LOG_ERROR("WinTLS: Unreachable reached during tlsConnect! This is a bug!");
   state_ = st_error;
   return TLS_ERR_ERROR;

src/message.h

@@ -183,6 +183,10 @@
 #define MSG_WARN_NO_CA_CERT                                             \
   _("You may encounter the certificate verification error with HTTPS server." \
     " See --ca-certificate and --check-certificate option.")
+#define MSG_WARN_OLD_TLS_CONNECTION \
+  _("aria2c had to connect to the server using an old and vulnerable cipher" \
+    " suite. The integrity and confidentiality of the connection might be" \
+    " compromised.\nProtocol and cipher suite: %s")
 #define MSG_SHOW_FILES _("Printing the contents of file '%s'...")
 #define MSG_NOT_TORRENT_METALINK _("This file is neither Torrent nor Metalink" \
                                    " file. Skipping.")