[Pkg-mono-svn-commits] [mono] 01/04: Mono's implementation of the SSL/TLS stack failed to check the order of the handshake messages. Which would allow various attacks on the protocol to succeed. ("SKIP-TLS" attack). (Closes: #780751, CVE-2015-2318)
Jo Shields
directhex at moszumanska.debian.org
Thu Mar 19 11:59:39 UTC 2015
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directhex pushed a commit to branch master
in repository mono.
commit 037e3b590b640b1e0dc0c8814672155feb4a10bf
Author: Jo Shields <jo.shields at xamarin.com>
Date: Thu Mar 19 09:35:36 2015 +0000
Mono's implementation of the SSL/TLS stack failed to check the order of the handshake messages. Which would allow various attacks on the protocol to succeed. ("SKIP-TLS" attack). (Closes: #780751, CVE-2015-2318)
(cherry picked from commit 74ceb8e2fd6039a93c1bef4b02f3dcb76498ef26)
---
.../ClientRecordProtocol.cs | 33 ++++++++++++++++---
.../Mono.Security.Protocol.Tls/Context.cs | 2 ++
.../Mono.Security.Protocol.Tls/RecordProtocol.cs | 5 ++-
.../ServerRecordProtocol.cs | 37 ++++++++++++++++------
4 files changed, 59 insertions(+), 18 deletions(-)
diff --git a/mcs/class/Mono.Security/Mono.Security.Protocol.Tls/ClientRecordProtocol.cs b/mcs/class/Mono.Security/Mono.Security.Protocol.Tls/ClientRecordProtocol.cs
index 7cece50..acaa0c2 100644
--- a/mcs/class/Mono.Security/Mono.Security.Protocol.Tls/ClientRecordProtocol.cs
+++ b/mcs/class/Mono.Security/Mono.Security.Protocol.Tls/ClientRecordProtocol.cs
@@ -129,6 +129,7 @@ namespace Mono.Security.Protocol.Tls
HandshakeType type, byte[] buffer)
{
ClientContext context = (ClientContext)this.context;
+ var last = context.LastHandshakeMsg;
switch (type)
{
@@ -148,23 +149,44 @@ namespace Mono.Security.Protocol.Tls
return null;
case HandshakeType.ServerHello:
+ if (last != HandshakeType.HelloRequest)
+ break;
return new TlsServerHello(this.context, buffer);
+ // Optional
case HandshakeType.Certificate:
+ if (last != HandshakeType.ServerHello)
+ break;
return new TlsServerCertificate(this.context, buffer);
+ // Optional
case HandshakeType.ServerKeyExchange:
- return new TlsServerKeyExchange(this.context, buffer);
+ // only for RSA_EXPORT
+ if (last == HandshakeType.Certificate && context.Current.Cipher.IsExportable)
+ return new TlsServerKeyExchange(this.context, buffer);
+ break;
+ // Optional
case HandshakeType.CertificateRequest:
- return new TlsServerCertificateRequest(this.context, buffer);
+ if (last == HandshakeType.ServerKeyExchange || last == HandshakeType.Certificate)
+ return new TlsServerCertificateRequest(this.context, buffer);
+ break;
case HandshakeType.ServerHelloDone:
- return new TlsServerHelloDone(this.context, buffer);
+ if (last == HandshakeType.CertificateRequest || last == HandshakeType.Certificate || last == HandshakeType.ServerHello)
+ return new TlsServerHelloDone(this.context, buffer);
+ break;
case HandshakeType.Finished:
- return new TlsServerFinished(this.context, buffer);
-
+ // depends if a full (ServerHelloDone) or an abbreviated handshake (ServerHello) is being done
+ bool check = context.AbbreviatedHandshake ? (last == HandshakeType.ServerHello) : (last == HandshakeType.ServerHelloDone);
+ // ChangeCipherSpecDone is not an handshake message (it's a content type) but still needs to be happens before finished
+ if (check && context.ChangeCipherSpecDone) {
+ context.ChangeCipherSpecDone = false;
+ return new TlsServerFinished (this.context, buffer);
+ }
+ break;
+
default:
throw new TlsException(
AlertDescription.UnexpectedMessage,
@@ -172,6 +194,7 @@ namespace Mono.Security.Protocol.Tls
"Unknown server handshake message received ({0})",
type.ToString()));
}
+ throw new TlsException (AlertDescription.HandshakeFailiure, String.Format ("Protocol error, unexpected protocol transition from {0} to {1}", last, type));
}
#endregion
diff --git a/mcs/class/Mono.Security/Mono.Security.Protocol.Tls/Context.cs b/mcs/class/Mono.Security/Mono.Security.Protocol.Tls/Context.cs
index 792a997..4e02812 100644
--- a/mcs/class/Mono.Security/Mono.Security.Protocol.Tls/Context.cs
+++ b/mcs/class/Mono.Security/Mono.Security.Protocol.Tls/Context.cs
@@ -122,6 +122,8 @@ namespace Mono.Security.Protocol.Tls
set { this.protocolNegotiated = value; }
}
+ public bool ChangeCipherSpecDone { get; set; }
+
public SecurityProtocolType SecurityProtocol
{
get
diff --git a/mcs/class/Mono.Security/Mono.Security.Protocol.Tls/RecordProtocol.cs b/mcs/class/Mono.Security/Mono.Security.Protocol.Tls/RecordProtocol.cs
index 9ef45da..cfab5ed 100644
--- a/mcs/class/Mono.Security/Mono.Security.Protocol.Tls/RecordProtocol.cs
+++ b/mcs/class/Mono.Security/Mono.Security.Protocol.Tls/RecordProtocol.cs
@@ -88,6 +88,8 @@ namespace Mono.Security.Protocol.Tls
} else {
ctx.StartSwitchingSecurityParameters (false);
}
+
+ ctx.ChangeCipherSpecDone = true;
}
public virtual HandshakeMessage GetMessage(HandshakeType type)
@@ -348,9 +350,6 @@ namespace Mono.Security.Protocol.Tls
// Try to read the Record Content Type
int type = internalResult.InitialBuffer[0];
- // Set last handshake message received to None
- this.context.LastHandshakeMsg = HandshakeType.ClientHello;
-
ContentType contentType = (ContentType)type;
byte[] buffer = this.ReadRecordBuffer(type, record);
if (buffer == null)
diff --git a/mcs/class/Mono.Security/Mono.Security.Protocol.Tls/ServerRecordProtocol.cs b/mcs/class/Mono.Security/Mono.Security.Protocol.Tls/ServerRecordProtocol.cs
index 6e316dc..31c2547 100644
--- a/mcs/class/Mono.Security/Mono.Security.Protocol.Tls/ServerRecordProtocol.cs
+++ b/mcs/class/Mono.Security/Mono.Security.Protocol.Tls/ServerRecordProtocol.cs
@@ -33,6 +33,8 @@ namespace Mono.Security.Protocol.Tls
{
internal class ServerRecordProtocol : RecordProtocol
{
+ TlsClientCertificate cert;
+
#region Constructors
public ServerRecordProtocol(
@@ -93,30 +95,45 @@ namespace Mono.Security.Protocol.Tls
private HandshakeMessage createClientHandshakeMessage(
HandshakeType type, byte[] buffer)
{
+ var last = context.LastHandshakeMsg;
switch (type)
{
case HandshakeType.ClientHello:
return new TlsClientHello(this.context, buffer);
case HandshakeType.Certificate:
- return new TlsClientCertificate(this.context, buffer);
+ if (last != HandshakeType.ClientHello)
+ break;
+ cert = new TlsClientCertificate(this.context, buffer);
+ return cert;
case HandshakeType.ClientKeyExchange:
- return new TlsClientKeyExchange(this.context, buffer);
+ if (last == HandshakeType.ClientHello || last == HandshakeType.Certificate)
+ return new TlsClientKeyExchange(this.context, buffer);
+ break;
case HandshakeType.CertificateVerify:
- return new TlsClientCertificateVerify(this.context, buffer);
+ if (last == HandshakeType.ClientKeyExchange && cert != null)
+ return new TlsClientCertificateVerify(this.context, buffer);
+ break;
case HandshakeType.Finished:
- return new TlsClientFinished(this.context, buffer);
-
+ // Certificates are optional, but if provided, they should send a CertificateVerify
+ bool check = (cert == null) ? (last == HandshakeType.ClientKeyExchange) : (last == HandshakeType.CertificateVerify);
+ // ChangeCipherSpecDone is not an handshake message (it's a content type) but still needs to be happens before finished
+ if (check && context.ChangeCipherSpecDone) {
+ context.ChangeCipherSpecDone = false;
+ return new TlsClientFinished(this.context, buffer);
+ }
+ break;
+
default:
- throw new TlsException(
- AlertDescription.UnexpectedMessage,
- String.Format(CultureInfo.CurrentUICulture,
- "Unknown server handshake message received ({0})",
- type.ToString()));
+ throw new TlsException(AlertDescription.UnexpectedMessage, String.Format(CultureInfo.CurrentUICulture,
+ "Unknown server handshake message received ({0})",
+ type.ToString()));
+ break;
}
+ throw new TlsException (AlertDescription.HandshakeFailiure, String.Format ("Protocol error, unexpected protocol transition from {0} to {1}", last, type));
}
private HandshakeMessage createServerHandshakeMessage(
--
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