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Created attachment 1045132[details]
DSA certificates for reproducer
Description of problem:
When the clients and servers use 2048 or 3072 bit DSA certificates with GnuTLS and TLS1.1, the connection is rejected.
Version-Release number of selected component (if applicable):
nss-3.19.1-5.el7_1.x86_64
gnutls-3.3.8-12.el7.x86_64
openssl-1.0.1e-42.el7_1.6.x86_64
How reproducible:
Always
Steps to Reproduce:
1. tar xzf ~/dsa-certificates.tar.gz
2. cd dsa-certificates/
3. Pick a server and a client, start them:
# openssl server
openssl s_server -key dsa-server/key.pem -cert dsa-server/cert.pem -CAfile <(cat ca/cert.pem dsa-ca/cert.pem) -cipher EDH-DSS-DES-CBC3-SHA -Verify 1
# NSS server
/usr/lib64/nss/unsupported-tools/selfserv -d sql:./nssdb/ -p 4433 -V tls1.0: -c :0013 -H 1 -rr -S dsa-server
# GnuTLS server
gnutls-serv --http -p 4433 --x509keyfile dsa-server/key.pem --x509certfile <(cat dsa-server/cert.pem dsa-ca/cert.pem) --x509cafile <(cat ca/cert.pem dsa-ca/cert.pem) --require-client-cert --verify-client-cert
# openssl client
openssl s_client -CAfile ca/cert.pem -cipher EDH-DSS-DES-CBC3-SHA -connect localhost:4433 -cert dsa-client/cert.pem -key dsa-client/key.pem -tls1_1
# NSS client
/usr/lib64/nss/unsupported-tools/tstclnt -h localhost -p 4433 -d sql:./nsscl/ -c :0013 -V tls1.0:tls1.1 -n dsa-client
# GnuTLS client
gnutls-cli --x509cafile ca/cert.pem --x509keyfile dsa-client/key.pem --x509certfile dsa-client/cert.pem --priority NORMAL:-VERS-TLS1.2 -p 4433 localhost
Actual results:
Connections between GnuTLS and any other implementation fail, connections between NSS and OpenSSL work.
Expected results:
All combinations should work
Additional info:
When used with 1024 bit DSA certificates, the connections work as expected.
While the bug is filed for GnuTLS, I'm not sure if this is actually GnuTLS fault, but since OpenSSL and NSS do interoperate with each other, other implementations will likely aim for same behaviour...
Comment 3Nikos Mavrogiannopoulos
2015-07-02 10:40:17 UTC
That non-interoperation is intentional. According to DSS standard you cannot use 2048+ bit keys with SHA1, and given that TLS 1.1 only uses SHA1 it cannot be used with those keys.
That's the reason gnutls doesn't interoperate. It refuses to violate the DSS standard. I have described that in a TLS profile (not adopted by the TLS WG):
https://tools.ietf.org/html/draft-mavrogiannopoulos-tls-dss-01
So I believe the bug should be reported against openssl and NSS which violate DSS.
Comment 4Nikos Mavrogiannopoulos
2015-07-02 10:41:05 UTC
(to clarify the above message, the SHA1 with DSS refers to the ServerKeyExchange signature)
I agree with Nikos here, that the fix should be in NSS and OpenSSL if anywhere. We should simply declare the DSS support in TLS for keys >= 2048bits as experimental and non-interoperable due to missing standards.
The DSS should be considered a legacy anyway and it does not make sense to spend too many resources on it.
(In reply to Tomas Mraz from comment #5)
> I agree with Nikos here, that the fix should be in NSS and OpenSSL if
> anywhere. We should simply declare the DSS support in TLS for keys >=
> 2048bits as experimental and non-interoperable due to missing standards.
>
> The DSS should be considered a legacy anyway and it does not make sense to
> spend too many resources on it.
It's only the TLS 1.0 and TLS 1.1 with >= 2048 bit DSA that is lacking standards.
TLS 1.2 has provisions for DSA keys of this size and FIPS requirements can be easily met there.
(e.g DSA is listed as /the/ reason why the signature algorithms and hash algorithms are listed in pairs, not as two separate lists in Signature Algorithms extension)
So, yes, I agree that we should declare very specific combinations as unsupported (>= 2048 DSA with TLS 1.1), even if they appear to sometimes work (but violate standards). And then declare some combinations as experimental (any DSA with TLS 1.2).
Created attachment 1045132 [details] DSA certificates for reproducer Description of problem: When the clients and servers use 2048 or 3072 bit DSA certificates with GnuTLS and TLS1.1, the connection is rejected. Version-Release number of selected component (if applicable): nss-3.19.1-5.el7_1.x86_64 gnutls-3.3.8-12.el7.x86_64 openssl-1.0.1e-42.el7_1.6.x86_64 How reproducible: Always Steps to Reproduce: 1. tar xzf ~/dsa-certificates.tar.gz 2. cd dsa-certificates/ 3. Pick a server and a client, start them: # openssl server openssl s_server -key dsa-server/key.pem -cert dsa-server/cert.pem -CAfile <(cat ca/cert.pem dsa-ca/cert.pem) -cipher EDH-DSS-DES-CBC3-SHA -Verify 1 # NSS server /usr/lib64/nss/unsupported-tools/selfserv -d sql:./nssdb/ -p 4433 -V tls1.0: -c :0013 -H 1 -rr -S dsa-server # GnuTLS server gnutls-serv --http -p 4433 --x509keyfile dsa-server/key.pem --x509certfile <(cat dsa-server/cert.pem dsa-ca/cert.pem) --x509cafile <(cat ca/cert.pem dsa-ca/cert.pem) --require-client-cert --verify-client-cert # openssl client openssl s_client -CAfile ca/cert.pem -cipher EDH-DSS-DES-CBC3-SHA -connect localhost:4433 -cert dsa-client/cert.pem -key dsa-client/key.pem -tls1_1 # NSS client /usr/lib64/nss/unsupported-tools/tstclnt -h localhost -p 4433 -d sql:./nsscl/ -c :0013 -V tls1.0:tls1.1 -n dsa-client # GnuTLS client gnutls-cli --x509cafile ca/cert.pem --x509keyfile dsa-client/key.pem --x509certfile dsa-client/cert.pem --priority NORMAL:-VERS-TLS1.2 -p 4433 localhost Actual results: Connections between GnuTLS and any other implementation fail, connections between NSS and OpenSSL work. Expected results: All combinations should work Additional info: When used with 1024 bit DSA certificates, the connections work as expected. While the bug is filed for GnuTLS, I'm not sure if this is actually GnuTLS fault, but since OpenSSL and NSS do interoperate with each other, other implementations will likely aim for same behaviour...