Hello,

I came across a strange problem with my Dovecot 2.1.7 installation (updated Debian Wheezy) in regards to SSL/TLS connections.

My configuration is as follows:

$ dovecot -n | grep ssl
service imap-login {
    ssl = yes
    ...
}
ssl_cert = <......
ssl_cipher_list =
EDH+CAMELLIA:EDH+aRSA:EECDH+aRSA+AESGCM:EECDH+aRSA+SHA384:EECDH+aRSA+SHA256:EECDH:+CAMELLIA256:+AES256:+CAMELLIA128:+AES128:+SSLv3:!aNULL:!eNULL:!LOW:!3DES:!MD5:!EXP:!PSK:!DSS:!RC4:!SEED:!ECDSA:CAMELLIA256-SHA:AES256-SHA:CAMELLIA128-SHA:AES128-SHA
ssl_key = <......
ssl_protocols = !SSLv3 !SSLv2

This cipherstring has been taken from https://bettercrypto.org/static/applied-crypto-hardening.pdf. But this is not the problem, when I comment it out, Dovecot still behaves the same way.

When I enable verbose_ssl I get this:

2015-03-15 08:27:39 imap-login: Warning: SSL: where=0x10, ret=1: before/accept initialization [$CLIENTIP]
2015-03-15 08:27:39 imap-login: Warning: SSL: where=0x2001, ret=1: before/accept initialization [$CLIENTIP]
2015-03-15 08:27:39 imap-login: Warning: SSL: where=0x2002, ret=-1: unknown state [$CLIENTIP]
2015-03-15 08:27:39 imap-login: Warning: SSL: where=0x2001, ret=1: SSLv3 read client hello A [$CLIENTIP]
2015-03-15 08:27:39 imap-login: Warning: SSL: where=0x2001, ret=1: SSLv3 write server hello A [$CLIENTIP]
2015-03-15 08:27:39 imap-login: Warning: SSL: where=0x2001, ret=1: SSLv3 write certificate A [$CLIENTIP]
2015-03-15 08:27:39 imap-login: Warning: SSL: where=0x2001, ret=1: SSLv3 write server done A [$CLIENTIP]
2015-03-15 08:27:39 imap-login: Warning: SSL: where=0x2001, ret=1: SSLv3 flush data [$CLIENTIP]
2015-03-15 08:27:39 imap-login: Warning: SSL: where=0x2002, ret=-1: SSLv3 read client certificate A [$CLIENTIP]
2015-03-15 08:27:39 imap-login: Warning: SSL: where=0x2002, ret=-1: SSLv3 read client certificate A [$CLIENTIP]
2015-03-15 08:27:39 imap-login: Warning: SSL: where=0x2001, ret=1: SSLv3 read client key exchange A [$CLIENTIP]
2015-03-15 08:27:39 imap-login: Warning: SSL: where=0x2001, ret=1: SSLv3 read finished A [$CLIENTIP]
2015-03-15 08:27:39 imap-login: Warning: SSL: where=0x2001, ret=1: SSLv3 write change cipher spec A [$CLIENTIP]
2015-03-15 08:27:39 imap-login: Warning: SSL: where=0x2001, ret=1: SSLv3 write finished A [$CLIENTIP]
2015-03-15 08:27:39 imap-login: Warning: SSL: where=0x2001, ret=1: SSLv3 flush data [$CLIENTIP]
2015-03-15 08:27:39 imap-login: Warning: SSL: where=0x20, ret=1: SSL negotiation finished successfully [$CLIENTIP]
2015-03-15 08:27:39 imap-login: Warning: SSL: where=0x2002, ret=1: SSL negotiation finished successfully [$CLIENTIP]

Is this right? Is SSLv3 used on this connection?

But when I explicitely test for SSLv3 support I get

$ openssl s_client -connect $SERVERIP:993 -ssl3

CONNECTED(00000003)
140683835029160:error:14094410:SSL routines:SSL3_READ_BYTES:sslv3 alert handshake failure:s3_pkt.c:1260:SSL alert number 40
140683835029160:error:1409E0E5:SSL routines:SSL3_WRITE_BYTES:ssl handshake failure:s3_pkt.c:598:
---
no peer certificate available
---
No client certificate CA names sent
---
SSL handshake has read 7 bytes and written 0 bytes
---
New, (NONE), Cipher is (NONE)
Secure Renegotiation IS NOT supported
Compression: NONE
Expansion: NONE
SSL-Session:
    Protocol  : SSLv3
    Cipher    : 0000
    Session-ID: 
    Session-ID-ctx: 
    Master-Key: 
    Key-Arg   : None
    PSK identity: None
    PSK identity hint: None
    SRP username: None
    Start Time: 1426411304
    Timeout   : 7200 (sec)
    Verify return code: 0 (ok)
---

Where I got this from says "if you you get a handshake failure, then you don't support SSLv3". But in my case the following output kinda says, that I do support it - with a ciphers of (NONE)?

In regards to libraries

$ ldd /usr/lib/dovecot/imap-login  | grep ssl
	libssl.so.1.0.0 => /usr/lib/x86_64-linux-gnu/libssl.so.1.0.0 (0x00007f1f55025000)

$ dpkg -l | grep ssl
ii  libcrypt-openssl-bignum-perl         0.04-3                        amd64        Access OpenSSL multiprecision integer arithmetic libraries
ii  libcrypt-openssl-dsa-perl            0.13-6                        amd64        module which implements the DSA signature verification system
ii  libcrypt-openssl-rsa-perl            0.28-1                        amd64        module for RSA encryption using OpenSSL
ii  libcrypt-ssleay-perl                 0.58-1                        amd64        OpenSSL support for LWP
ii  libio-socket-ssl-perl                1.76-2                        all          Perl module implementing object oriented interface to SSL sockets
ii  libnet-ssleay-perl                   1.48-1+b1                     amd64        Perl module for Secure Sockets Layer (SSL)
rc  libssl0.9.8                          0.9.8o-4squeeze14             amd64        SSL shared libraries
ii  libssl1.0.0:amd64                    1.0.1e-2+deb7u14              amd64        SSL shared libraries
ii  openssl                              1.0.1e-2+deb7u14              amd64        Secure Socket Layer (SSL) binary and related cryptographic tools
ii  openssl-blacklist                    0.5-3                         all          Blacklists for  OpenSSL RSA keys and tools
ii  python-openssl                       0.13-2+deb7u1                 amd64        Python 2 wrapper around the OpenSSL library
ii  ssl-cert                             1.0.32                        all          simple debconf wrapper for OpenSSL
ii  ssl-cert-check                       3.22-1                        all          proactively handling X.509 certificate expiration
ii  sslmate                              0.6.2-1                       all          Buy and manage SSL certificates from the command line

My NginX is using the same library, and this does indeed support TLSv2, so what I am doing wrong in my Dovecot configuration?

Any clues?

Regards

Thomas

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