CVE-2015-2319 (published 2018-01-08T19:29Z)

The TLS stack in Mono before 3.12.1 makes it easier for remote attackers to conduct cipher-downgrade attacks to EXPORT_RSA ciphers via crafted TLS traffic, related to the "FREAK" issue, a different vulnerability than CVE-2015-0204.

Severity: MEDIUM
CVSS v2 base score: 5.0 (AV:N/AC:L/Au:N/C:P/I:N/A:N)
CVSS v3 base score: 7.5, HIGH (CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N)

Weakness information:
cwe_id: CWE-295
cwe_name: Improper Certificate Validation
description: The product does not validate, or incorrectly validates, a certificate.
extended_description: When a certificate is invalid or malicious, it might allow an attacker to spoof a trusted entity by interfering in the communication path between the host and client. The product might connect to a malicious host while believing it is a trusted host, or the product might be deceived into accepting spoofed data that appears to originate from a trusted host.
         

Fix information:
repo_url: https://github.com/mono/mono
commit_details: repo_url: https://github.com/mono/mono
author: Sebastien Pouliot
author_date: 2015-03-06 10:35:27-05:00
msg: Remove the EXPORT ciphers and related code path

    That was still useful in 2003/2004 but the technical and legal landscape
    changed a lot since then. Removing the old, limited key size, cipher
    suites also allow removed additional parts of the code that deals with
    them.
repository: repo_url: https://github.com/mono/mono
repo_name: mono/mono
description: Mono open source ECMA CLI, C# and .NET implementation.
repo_language: C#
owner: mono
file_changes: filename: CipherSuiteFactory.cs
change_type: ModificationType.MODIFY
diff: @@ -116,14 +116,14 @@ private static CipherSuiteCollection GetTls1SupportedCiphers()
 			scs.Add((0x00 << 0x08) | 0x09, "TLS_RSA_WITH_DES_CBC_SHA", CipherAlgorithmType.Des, HashAlgorithmType.Sha1, ExchangeAlgorithmType.RsaKeyX, false, true, 8, 8, 56, 8, 8);
 			
 			// Supported exportable ciphers
-			scs.Add((0x00 << 0x08) | 0x03, "TLS_RSA_EXPORT_WITH_RC4_40_MD5", CipherAlgorithmType.Rc4, HashAlgorithmType.Md5, ExchangeAlgorithmType.RsaKeyX, true, false, 5, 16, 40, 0, 0);
-			scs.Add((0x00 << 0x08) | 0x06, "TLS_RSA_EXPORT_WITH_RC2_CBC_40_MD5", CipherAlgorithmType.Rc2, HashAlgorithmType.Md5, ExchangeAlgorithmType.RsaKeyX, true, true, 5, 16, 40, 8, 8);
-			scs.Add((0x00 << 0x08) | 0x08, "TLS_RSA_EXPORT_WITH_DES40_CBC_SHA", CipherAlgorithmType.Des, HashAlgorithmType.Sha1, ExchangeAlgorithmType.RsaKeyX, true, true, 5, 8, 40, 8, 8);
-			scs.Add((0x00 << 0x08) | 0x60, "TLS_RSA_EXPORT_WITH_RC4_56_MD5", CipherAlgorithmType.Rc4, HashAlgorithmType.Md5, ExchangeAlgorithmType.RsaKeyX, true, false, 7, 16, 56, 0, 0);
-			scs.Add((0x00 << 0x08) | 0x61, "TLS_RSA_EXPORT_WITH_RC2_CBC_56_MD5", CipherAlgorithmType.Rc2, HashAlgorithmType.Md5, ExchangeAlgorithmType.RsaKeyX, true, true, 7, 16, 56, 8, 8);
+			// scs.Add((0x00 << 0x08) | 0x03, "TLS_RSA_EXPORT_WITH_RC4_40_MD5", CipherAlgorithmType.Rc4, HashAlgorithmType.Md5, ExchangeAlgorithmType.RsaKeyX, true, false, 5, 16, 40, 0, 0);
+			// scs.Add((0x00 << 0x08) | 0x06, "TLS_RSA_EXPORT_WITH_RC2_CBC_40_MD5", CipherAlgorithmType.Rc2, HashAlgorithmType.Md5, ExchangeAlgorithmType.RsaKeyX, true, true, 5, 16, 40, 8, 8);
+			// scs.Add((0x00 << 0x08) | 0x08, "TLS_RSA_EXPORT_WITH_DES40_CBC_SHA", CipherAlgorithmType.Des, HashAlgorithmType.Sha1, ExchangeAlgorithmType.RsaKeyX, true, true, 5, 8, 40, 8, 8);
+			// scs.Add((0x00 << 0x08) | 0x60, "TLS_RSA_EXPORT_WITH_RC4_56_MD5", CipherAlgorithmType.Rc4, HashAlgorithmType.Md5, ExchangeAlgorithmType.RsaKeyX, true, false, 7, 16, 56, 0, 0);
+			// scs.Add((0x00 << 0x08) | 0x61, "TLS_RSA_EXPORT_WITH_RC2_CBC_56_MD5", CipherAlgorithmType.Rc2, HashAlgorithmType.Md5, ExchangeAlgorithmType.RsaKeyX, true, true, 7, 16, 56, 8, 8);
 			// 56 bits but we use 64 bits because of parity (DES is really 56 bits)
-			scs.Add((0x00 << 0x08) | 0x62, "TLS_RSA_EXPORT_WITH_DES_CBC_56_SHA", CipherAlgorithmType.Des, HashAlgorithmType.Sha1, ExchangeAlgorithmType.RsaKeyX, true, true, 8, 8, 64, 8, 8); 
-			scs.Add((0x00 << 0x08) | 0x64, "TLS_RSA_EXPORT_WITH_RC4_56_SHA", CipherAlgorithmType.Rc4, HashAlgorithmType.Sha1, ExchangeAlgorithmType.RsaKeyX, true, false, 7, 16, 56, 0, 0);
+			// scs.Add((0x00 << 0x08) | 0x62, "TLS_RSA_EXPORT_WITH_DES_CBC_56_SHA", CipherAlgorithmType.Des, HashAlgorithmType.Sha1, ExchangeAlgorithmType.RsaKeyX, true, true, 8, 8, 64, 8, 8);
+			// scs.Add((0x00 << 0x08) | 0x64, "TLS_RSA_EXPORT_WITH_RC4_56_SHA", CipherAlgorithmType.Rc4, HashAlgorithmType.Sha1, ExchangeAlgorithmType.RsaKeyX, true, false, 7, 16, 56, 0, 0);
 			
 			// Default CipherSuite
 			// scs.Add(0, "TLS_NULL_WITH_NULL_NULL", CipherAlgorithmType.None, HashAlgorithmType.None, ExchangeAlgorithmType.None, true, false, 0, 0, 0, 0, 0);
@@ -195,14 +195,14 @@ private static CipherSuiteCollection GetSsl3SupportedCiphers()
 			scs.Add((0x00 << 0x08) | 0x09, "SSL_RSA_WITH_DES_CBC_SHA", CipherAlgorithmType.Des, HashAlgorithmType.Sha1, ExchangeAlgorithmType.RsaKeyX, false, true, 8, 8, 56, 8, 8);
 
 			// Supported exportable ciphers
-			scs.Add((0x00 << 0x08) | 0x03, "SSL_RSA_EXPORT_WITH_RC4_40_MD5", CipherAlgorithmType.Rc4, HashAlgorithmType.Md5, ExchangeAlgorithmType.RsaKeyX, true, false, 5, 16, 40, 0, 0);
-			scs.Add((0x00 << 0x08) | 0x06, "SSL_RSA_EXPORT_WITH_RC2_CBC_40_MD5", CipherAlgorithmType.Rc2, HashAlgorithmType.Md5, ExchangeAlgorithmType.RsaKeyX, true, true, 5, 16, 40, 8, 8);
-			scs.Add((0x00 << 0x08) | 0x08, "SSL_RSA_EXPORT_WITH_DES40_CBC_SHA", CipherAlgorithmType.Des, HashAlgorithmType.Sha1, ExchangeAlgorithmType.RsaKeyX, true, true, 5, 8, 40, 8, 8);
-			scs.Add((0x00 << 0x08) | 0x60, "SSL_RSA_EXPORT_WITH_RC4_56_MD5", CipherAlgorithmType.Rc4, HashAlgorithmType.Md5, ExchangeAlgorithmType.RsaKeyX, true, false, 7, 16, 56, 0, 0);
-			scs.Add((0x00 << 0x08) | 0x61, "SSL_RSA_EXPORT_WITH_RC2_CBC_56_MD5", CipherAlgorithmType.Rc2, HashAlgorithmType.Md5, ExchangeAlgorithmType.RsaKeyX, true, true, 7, 16, 56, 8, 8);
+			// scs.Add((0x00 << 0x08) | 0x03, "SSL_RSA_EXPORT_WITH_RC4_40_MD5", CipherAlgorithmType.Rc4, HashAlgorithmType.Md5, ExchangeAlgorithmType.RsaKeyX, true, false, 5, 16, 40, 0, 0);
+			// scs.Add((0x00 << 0x08) | 0x06, "SSL_RSA_EXPORT_WITH_RC2_CBC_40_MD5", CipherAlgorithmType.Rc2, HashAlgorithmType.Md5, ExchangeAlgorithmType.RsaKeyX, true, true, 5, 16, 40, 8, 8);
+			// scs.Add((0x00 << 0x08) | 0x08, "SSL_RSA_EXPORT_WITH_DES40_CBC_SHA", CipherAlgorithmType.Des, HashAlgorithmType.Sha1, ExchangeAlgorithmType.RsaKeyX, true, true, 5, 8, 40, 8, 8);
+			// scs.Add((0x00 << 0x08) | 0x60, "SSL_RSA_EXPORT_WITH_RC4_56_MD5", CipherAlgorithmType.Rc4, HashAlgorithmType.Md5, ExchangeAlgorithmType.RsaKeyX, true, false, 7, 16, 56, 0, 0);
+			// scs.Add((0x00 << 0x08) | 0x61, "SSL_RSA_EXPORT_WITH_RC2_CBC_56_MD5", CipherAlgorithmType.Rc2, HashAlgorithmType.Md5, ExchangeAlgorithmType.RsaKeyX, true, true, 7, 16, 56, 8, 8);
 			// 56 bits but we use 64 bits because of parity (DES is really 56 bits)
-			scs.Add((0x00 << 0x08) | 0x62, "SSL_RSA_EXPORT_WITH_DES_CBC_56_SHA", CipherAlgorithmType.Des, HashAlgorithmType.Sha1, ExchangeAlgorithmType.RsaKeyX, true, true, 8, 8, 64, 8, 8); 
-			scs.Add((0x00 << 0x08) | 0x64, "SSL_RSA_EXPORT_WITH_RC4_56_SHA", CipherAlgorithmType.Rc4, HashAlgorithmType.Sha1, ExchangeAlgorithmType.RsaKeyX, true, false, 7, 16, 56, 0, 0);
+			// scs.Add((0x00 << 0x08) | 0x62, "SSL_RSA_EXPORT_WITH_DES_CBC_56_SHA", CipherAlgorithmType.Des, HashAlgorithmType.Sha1, ExchangeAlgorithmType.RsaKeyX, true, true, 8, 8, 64, 8, 8);
+			// scs.Add((0x00 << 0x08) | 0x64, "SSL_RSA_EXPORT_WITH_RC4_56_SHA", CipherAlgorithmType.Rc4, HashAlgorithmType.Sha1, ExchangeAlgorithmType.RsaKeyX, true, false, 7, 16, 56, 0, 0);
 
 			// Default CipherSuite
 			// scs.Add(0, "SSL_NULL_WITH_NULL_NULL", CipherAlgorithmType.None, HashAlgorithmType.None, true, false, 0, 0, 0, 0, 0);

programming_language: Go
filename: ClientRecordProtocol.cs
change_type: ModificationType.MODIFY
diff: @@ -159,13 +159,6 @@ private HandshakeMessage createClientHandshakeMessage(HandshakeType type)
 						break;
 					return new TlsServerCertificate(this.context, buffer);
 
-					// Optional
-				case HandshakeType.ServerKeyExchange:
-					// only for RSA_EXPORT
-					if (last == HandshakeType.Certificate && context.Current.Cipher.IsExportable)
-						return new TlsServerKeyExchange(this.context, buffer);
-					break;
-
 					// Optional
 				case HandshakeType.CertificateRequest:
 					if (last == HandshakeType.ServerKeyExchange || last == HandshakeType.Certificate)

programming_language: Go
filename: SslCipherSuite.cs
change_type: ModificationType.MODIFY
diff: @@ -190,59 +190,15 @@ public override void ComputeKeys()
 			this.Context.ClientWriteKey = keyBlock.ReadBytes(this.KeyMaterialSize);
 			this.Context.ServerWriteKey = keyBlock.ReadBytes(this.KeyMaterialSize);
 
-			if (!this.IsExportable)
+			if (this.IvSize != 0)
 			{
-				if (this.IvSize != 0)
-				{
-					this.Context.ClientWriteIV = keyBlock.ReadBytes(this.IvSize);
-					this.Context.ServerWriteIV = keyBlock.ReadBytes(this.IvSize);
-				}
-				else
-				{
-					this.Context.ClientWriteIV = CipherSuite.EmptyArray;
-					this.Context.ServerWriteIV = CipherSuite.EmptyArray;
-				}
+				this.Context.ClientWriteIV = keyBlock.ReadBytes(this.IvSize);
+				this.Context.ServerWriteIV = keyBlock.ReadBytes(this.IvSize);
 			}
 			else
 			{
-				HashAlgorithm md5 = MD5.Create();
-
-				int keySize = (md5.HashSize >> 3); //in bytes not bits
-				byte[] temp = new byte [keySize];
-
-				// Generate final write keys
-				md5.TransformBlock(this.Context.ClientWriteKey, 0, this.Context.ClientWriteKey.Length, temp, 0);
-				md5.TransformFinalBlock(this.Context.RandomCS, 0, this.Context.RandomCS.Length);
-				byte[] finalClientWriteKey = new byte[this.ExpandedKeyMaterialSize];
-				Buffer.BlockCopy(md5.Hash, 0, finalClientWriteKey, 0, this.ExpandedKeyMaterialSize);
-
-				md5.Initialize();
-				md5.TransformBlock(this.Context.ServerWriteKey, 0, this.Context.ServerWriteKey.Length, temp, 0);
-				md5.TransformFinalBlock(this.Context.RandomSC, 0, this.Context.RandomSC.Length);
-				byte[] finalServerWriteKey = new byte[this.ExpandedKeyMaterialSize];
-				Buffer.BlockCopy(md5.Hash, 0, finalServerWriteKey, 0, this.ExpandedKeyMaterialSize);
-				
-				this.Context.ClientWriteKey = finalClientWriteKey;
-				this.Context.ServerWriteKey = finalServerWriteKey;
-
-				// Generate IV keys
-				if (this.IvSize > 0) 
-				{
-					md5.Initialize();
-					temp = md5.ComputeHash(this.Context.RandomCS, 0, this.Context.RandomCS.Length);
-					this.Context.ClientWriteIV = new byte[this.IvSize];
-					Buffer.BlockCopy(temp, 0, this.Context.ClientWriteIV, 0, this.IvSize);
-
-					md5.Initialize();
-					temp = md5.ComputeHash(this.Context.RandomSC, 0, this.Context.RandomSC.Length);
-					this.Context.ServerWriteIV = new byte[this.IvSize];
-					Buffer.BlockCopy(temp, 0, this.Context.ServerWriteIV, 0, this.IvSize);
-				}
-				else 
-				{
-					this.Context.ClientWriteIV = CipherSuite.EmptyArray;
-					this.Context.ServerWriteIV = CipherSuite.EmptyArray;
-				}
+				this.Context.ClientWriteIV = CipherSuite.EmptyArray;
+				this.Context.ServerWriteIV = CipherSuite.EmptyArray;
 			}
 
 			DebugHelper.WriteLine(">>>> KeyBlock", keyBlock.ToArray());

programming_language: C#
filename: SslServerStream.cs
change_type: ModificationType.MODIFY
diff: @@ -233,16 +233,8 @@ internal override void EndNegotiateHandshake(IAsyncResult asyncResult)
 			// Send ServerCertificate message
 			this.protocol.SendRecord(HandshakeType.Certificate);
 
-			// If the negotiated cipher is a KeyEx cipher send ServerKeyExchange
-			if (this.context.Negotiating.Cipher.IsExportable)
-			{
-				this.protocol.SendRecord(HandshakeType.ServerKeyExchange);
-			}
-
-			// If the negotiated cipher is a KeyEx cipher or
-			// the client certificate is required send the CertificateRequest message
-			if (this.context.Negotiating.Cipher.IsExportable ||
-				((ServerContext)this.context).ClientCertificateRequired ||
+			// If the client certificate is required send the CertificateRequest message
+			if (((ServerContext)this.context).ClientCertificateRequired ||
 				((ServerContext)this.context).RequestClientCertificate)
 			{
 				this.protocol.SendRecord(HandshakeType.CertificateRequest);

programming_language: C#
filename: TlsCipherSuite.cs
change_type: ModificationType.MODIFY
diff: @@ -123,45 +123,15 @@ public override void ComputeKeys()
 			this.Context.ClientWriteKey = keyBlock.ReadBytes(this.KeyMaterialSize);
 			this.Context.ServerWriteKey = keyBlock.ReadBytes(this.KeyMaterialSize);
 
-			if (!this.IsExportable)
+			if (this.IvSize != 0)
 			{
-				if (this.IvSize != 0)
-				{
-					this.Context.ClientWriteIV = keyBlock.ReadBytes(this.IvSize);
-					this.Context.ServerWriteIV = keyBlock.ReadBytes(this.IvSize);
-				}
-				else
-				{
-					this.Context.ClientWriteIV = CipherSuite.EmptyArray;
-					this.Context.ServerWriteIV = CipherSuite.EmptyArray;
-				}
+				this.Context.ClientWriteIV = keyBlock.ReadBytes(this.IvSize);
+				this.Context.ServerWriteIV = keyBlock.ReadBytes(this.IvSize);
 			}
 			else
 			{
-				// Generate final write keys
-				byte[] finalClientWriteKey	= PRF(this.Context.ClientWriteKey, "client write key", this.Context.RandomCS, this.ExpandedKeyMaterialSize);
-				byte[] finalServerWriteKey	= PRF(this.Context.ServerWriteKey, "server write key", this.Context.RandomCS, this.ExpandedKeyMaterialSize);
-				
-				this.Context.ClientWriteKey	= finalClientWriteKey;
-				this.Context.ServerWriteKey	= finalServerWriteKey;
-
-				if (this.IvSize > 0) 
-				{
-					// Generate IV block
-					byte[] ivBlock = PRF(CipherSuite.EmptyArray, "IV block", this.Context.RandomCS, this.IvSize*2);
-
-					// Generate IV keys
-					this.Context.ClientWriteIV = new byte[this.IvSize];				
-					Buffer.BlockCopy(ivBlock, 0, this.Context.ClientWriteIV, 0, this.Context.ClientWriteIV.Length);
-
-					this.Context.ServerWriteIV = new byte[this.IvSize];
-					Buffer.BlockCopy(ivBlock, this.IvSize, this.Context.ServerWriteIV, 0, this.Context.ServerWriteIV.Length);
-				}
-				else 
-				{
-					this.Context.ClientWriteIV = CipherSuite.EmptyArray;
-					this.Context.ServerWriteIV = CipherSuite.EmptyArray;
-				}
+				this.Context.ClientWriteIV = CipherSuite.EmptyArray;
+				this.Context.ServerWriteIV = CipherSuite.EmptyArray;
 			}
 
 			DebugHelper.WriteLine(">>>> KeyBlock", keyBlock.ToArray());

programming_language: C#