Versions (on both hosts):
Postfix 2.5.6
Linked against OpenSSL 0.9.8c (debian etch with security-fixes backported)
as well as OpenSSL 0.9.8j (makes no difference)
Configured with Command: (the OpenSSL 0.9.8j variant, the first one used
the openssl installed in /usr/)
make makefiles CCARGS='-DHAS_PCRE -DUSE_TLS -I/opt/openssl/include
-I/usr/local/include' OPT='-O' DEBUG='' 'AUXLIBS=-L/usr/local/lib -lpcre
-L/opt/openssl/lib -lssl -lcrypto -L/usr/local/lib'
Setup:
1. Smarthost with TLS Certificate User auth (for relaying) ("wurzel")
2. Mailrelay (TLS Client) with Client-Certificate authenticating through TLS.
(dynamic hosts...)
Because the CRLs are not accessible online i put the crl.pem-files into
the ssl-subdir together with the certificates and c_rehash symlinked them
correctly. Postfix does not access them, however.
With my old PKI and certificates (soon to expire!) it worked flawlessly.
However it uses potentially insecure algorithms and far too short
keysizes (1024).
So i just set up a new PKI using the momentarily recommended Algorithms
and keysizes (4096 bit RSA, SHA256 digest) as well als the current BCP and
RFC recommendations for the Certificates and generated new certificates
for both Mailservers, but the mailserver bails out with the folowing
error messages.
(New PKI structure is: RootCA -signed-> PubCA -signed-> both MTA's certs.
Both CA certs are in the respective ssl directories (strace confirmed
accessibility) and c_hashed.)
I forced IPv4 for sake of log readability. IPv6 connects show the same problem.
Using the new certificates on both sides:
Feb 7 22:57:31 wurzel postfix/smtpd[28735]: connect from ppp-82-135-84-112.dyna
mic.mnet-online.de[82.135.84.112]
Feb 7 22:57:31 wurzel postfix/smtpd[28735]: setting up TLS connection from ppp-
82-135-84-112.dynamic.mnet-online.de[82.135.84.112]
Feb 7 22:57:31 wurzel postfix/smtpd[28735]: certificate verification failed for
ppp-82-135-84-112.dynamic.mnet-online.de[82.135.84.112]: untrusted issuer /C=DE
/ST=Bavaria/L=Munich/O=Jor's Net/OU=PKI/CN=Jor's Net Root CA/emailaddress...@jor
s.net
Feb 7 22:57:31 wurzel postfix/smtpd[28735]: SSL_accept error from ppp-82-135-84
-112.dynamic.mnet-online.de[82.135.84.112]: -1
Feb 7 22:57:31 wurzel postfix/smtpd[28735]: warning: TLS library problem: 28735
:error:0D0C50A1:asn1 encoding routines:ASN1_item_verify:unknown message digest a
lgorithm:a_verify.c:146:
Feb 7 22:57:31 wurzel postfix/smtpd[28735]: warning: TLS library problem: 28735
:error:0D0C50A1:asn1 encoding routines:ASN1_item_verify:unknown message digest a
lgorithm:a_verify.c:146:
Feb 7 22:57:31 wurzel postfix/smtpd[28735]: lost connection after STARTTLS from
ppp-82-135-84-112.dynamic.mnet-online.de[82.135.84.112]
Feb 7 22:57:31 wurzel postfix/smtpd[28735]: disconnect from ppp-82-135-84-112.d
ynamic.mnet-online.de[82.135.84.112]
Switching back to the old certs (both CA and client/server cert) on both MTAs:
Feb 7 22:57:58 wurzel postfix/smtpd[28735]: setting up TLS connection from ppp-
82-135-84-112.dynamic.mnet-online.de[82.135.84.112]
Feb 7 22:57:58 wurzel postfix/smtpd[28735]: ppp-82-135-84-112.dynamic.mnet-onli
ne.de[82.135.84.112]: Trusted: subject_CN=hal.m.jors.net, issuer=Jors.net CA, fi
ngerprint=3A:E2:AF:C5:ED:3E:12:FE:89:B3:6D:66:76:0B:91:78:43:EE:E1:95
Feb 7 22:57:58 wurzel postfix/smtpd[28735]: Trusted TLS connection established
from ppp-82-135-84-112.dynamic.mnet-online.de[82.135.84.112]: TLSv1 with cipher
DHE-RSA-AES256-SHA (256/256 bits)
Relevant configuration: (/etc/postfix/ssl is symlinked to /usr/lib/ssl)
relay_clientcerts = hash:/etc/postfix/relay_clientcerts
smtpd_use_tls = yes
smtpd_tls_loglevel = 1
smtpd_tls_ask_ccert = yes
smtpd_tls_security_level = may
smtpd_tls_auth_only = yes
smtpd_tls_received_header = yes
smtpd_tls_cert_file = /etc/postfix/ssl/rm.pem
smtpd_tls_key_file = $smtpd_tls_cert_file
smtpd_tls_CApath = /etc/postfix/ssl/
smtpd_tls_scert_verifydepth = 2
smtpd_tls_exclude_ciphers = aNULL
smtpd_tls_mandatory_exclude_ciphers = RC4
smtp_use_tls = yes
smtp_tls_enforce_peername = yes
smtp_tls_loglevel = 1
smtp_tls_security_level = may
smtp_tls_policy_maps = hash:/etc/postfix/tls_policy
smtp_tls_note_starttls_offer = yes
smtp_tls_cert_file = /etc/postfix/ssl/rm.pem
smtp_tls_key_file = $smtp_tls_cert_file
smtp_tls_CApath = /etc/postfix/ssl/
smtp_tls_scert_verifydepth = 2
smtp_tls_exclude_ciphers = aNULL
smtp_tls_mandatory_exclude_ciphers = RC4
(config is the same on both MTAsl, only the cert_file path points
to the correct file of course, which contains both Cert and Key.)
On the Client:
# cat tls_policy
[rm.jors.net] secure ciphers=high match=rm.jors.net:hostname
On the Server:
# cat tls_policy
[hal.m.jors.net] secure ciphers=high match=hal.m.jors.net:hostname
[hal.home.jors.net] secure ciphers=high match=hal.m.jors.net:hostname
Since the Certfiles are a lot of data, i put them on my Webserver:
http://jors.net/postfix/ (in the subdir new/ and old/ respectively).
I also tried using a test CA with SHA1 as signature hash Algorithm
(with 2048bit RSA keys) and siginign the certs using SHA1 only, but
that made no difference (I erased the test CA and certs after the
unsucessfull attempts)
Systems are of course NTP-time synched, all other use-cases for the
new Certificates (HTTPS, 802.1X WPA2 WLAN, S/MIME) work without
any Problems. (https://rw.jors.net/, the CRL is not yet online due
to DNS glitches)
Juergen
--
Juergen Meier
