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By default, when a TLS connection is established, the SSLContext will
enable all available ciphersuites. This may not be appropriate in
situations where export restrictions apply and higher grade
ciphersuites are prohibitied.
This change allows a caller to configure a restricted set of
ciphersuites to be used when establishing TLS connections.
Callers use the JSSEContextFactory.setRestrictedCipherSuites() method
to configure a list of ciphersuites. Any ciphersuites which are not
included in the list will be excluded in subsequent TLS connections.
If the JSSEContextFactory.setRestrictedCipherSuites() is never called,
or called with a null parameter, then no restriction will apply.
Test-information:
Validated that by calling the new method to restrict the available
ciphers, TLS connections initiated by Stroke only propose ciphersuites
in the restricted list, and connections fail when the server fails to
find an acceptable cipher.
Change-Id: Id0b4b19553a6f386cda27a71f0172410d899218e
Signed-off-by: Nick Hudson <nick.hudson@isode.com>
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Note that TLS won't be enabled with this patch unless you uncomment the
change in PlatformTLSFactories. With that comment removed, then a new
CoreClient session will attempt to negotiate TLS if the server supports
it.
Further changes are required to support this properly, as there
appears not to be comprehensive support in the CoreClient class for
dealing with situations when the server's certificate is not acceptable.
There's also no support yet for setting up client certificates.
Further changes will also be needed (see below) to support full
parsing of subjectAltNames from server certificates.
Significant changes are as follows
- TLSProceed - FIXME comments removed
- JavaConnection - changed so that it reads bytes from the socket's
InputStream, rather than reading chars and then constructing a
String out of them from which a byte array is then extracted.
While this seemed to work for non-binary data (e.g. non-encrypted
XMPP sessions), it breaks when you start sending binary (i.e. TLS)
data.
- JavaTLSConnectionFactory - implemented
- PlatformTLSFactories - By having this return a JSSEContextFactory, then
this will cause the client to try TLS if possible. But because other
changes are needed to make this work properly, the current code still
returns null.
- JSSEContext - new class which uses an SSLEngine to handle TLS handshake
and subsequent encryption/decryption. This is the main substance of
the SSL implementation
Note the "hack" in here to cope with SSLEngine requiring that some data
be sent from the application before it will do a TLS handshake
- JSSEContextFactory - just creates JSSEContexts
- JavaCertificate - this wraps an X509Certificate and does *some* of the
parsing of a certificate to look for stuff that is expected when
verifying an XMPP server certificate (RFC 6120 and RFC 6125). Note that
the JDK classes for parsing certificates don't provide an easy way
to decode "OTHER" subjectAltNames, and so this implementation does
not find XMPP or SRV subjectaltnames from the server certificate. This
will need extra work.
- JavaTrustManager - obtains the server certificate from the TLS handshake
and verifies it. Currently the only verification done is to check that
it's in date. More work will be needed to perform proper validation
- Where necessary, Remko's copyright comments were changed from GNU to
"All rights reserved". Isode copyright notices updated to "2012"
Test-information:
Set up XMPP server with its own certificate, and checked that TLS gets
negotiated and starts OK (provided the server cert contains e.g. a DNS
subjectAltName matching its own name). Subsequent operation appears
to be as expected.
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