Re: Multi-domain certificates and TLS
Hi, When the Subject Alternative Name extension is present in a server certificate, Postfix will use the first domain listed in that extension as the verified peer name, unless one of the other domains satisfies the matching rules for the destination TLS policy. Aug 6 09:44:20 smtp01 postfix/smtp[24772]: setting up TLS connection to mail.messaging.microsoft.com Aug 6 09:44:20 smtp01 postfix/smtp[24772]: Peer verification: CommonName in certificate does not match: mail.global.frontbridge.com != mail.messaging.microsoft.com Aug 6 09:44:20 smtp01 postfix/smtp[24772]: TLS connection established to mail.messaging.microsoft.com: TLSv1 with cipher RC4-SHA (128/128 bits) Aug 6 09:44:20 smtp01 postfix/smtp[24772]: 03C221880003: to=t...@example1.com, relay=mail.messaging.microsoft.com[65.55.88.22], delay=1, status=deferred (TLS-failure: Could not verify certificate) Looks like they recently migrated from Postfix SMTP servers to Microsoft Exchange: Yes, I believe that is the case. Connected to mail.messaging.microsoft.com[65.55.88.22]:25 ... mail.messaging.microsoft.com[65.55.88.22]:25: subjectAltName: mail.global.frontbridge.com mail.messaging.microsoft.com[65.55.88.22]:25: subjectAltName: *.outlook.com mail.messaging.microsoft.com[65.55.88.22]:25: subjectAltName: *.exchangelabs.com mail.messaging.microsoft.com[65.55.88.22]:25: subjectAltName: *.bigfish.com mail.messaging.microsoft.com[65.55.88.22]:25: Matched subjectAltName: *.messaging.microsoft.com mail.messaging.microsoft.com[65.55.88.22]:25 CommonName mail.global.frontbridge.com mail.messaging.microsoft.com[65.55.88.22]:25: Matched subject_CN=*.messaging.microsoft.com, issuer_CN=Cybertrust SureServer Standard Validation CA ... What is your TLS policy for this destination? The wildcard Subject Alt Name *.messaging.microsoft.com should match mail.messaging.microsoft.com if you are configured to check for that... At least it does when I test it as you see above. If I understand correctly, the vendor uses mail.messaging.microsoft.com for their hosted email, which use mail.global.frontbridge.com to actually process the mail? In any case, we'd like to use forced TLS (MUST_NOPEERMATCH) for connections to this vendor. I believe this would mean we would also need to add *.messaging.microsoft.com to smtp_tls_per_site. How would this affect other connections to mail.messaging.microsoft.com that weren't using TLS? Below is the full cert chain, with the first cert fully decoded, if that's useful: Yes, thanks. Much thanks, Alex
Re: Multi-domain certificates and TLS
On Tue, Aug 24, 2010 at 05:35:42PM -0400, Alex wrote: mail.messaging.microsoft.com[65.55.88.22]:25: Matched subject_CN=*.messaging.microsoft.com, issuer_CN=Cybertrust SureServer Standard Validation CA ... What is your TLS policy for this destination? The wildcard Subject Alt Name *.messaging.microsoft.com should match mail.messaging.microsoft.com if you are configured to check for that... At least it does when I test it as you see above. If I understand correctly, the vendor uses mail.messaging.microsoft.com for their hosted email, which use mail.global.frontbridge.com to actually process the mail? No. The MX records have typically been mail.global.frontbridge.com, but this has the same IP addresses as mail.messaging.microsoft.com, so the two are interchangeable, and both appear in the Subject Altname of the certificate. My question is about *your* TLS policy settings. In any case, we'd like to use forced TLS (MUST_NOPEERMATCH) for connections to this vendor. I believe this would mean we would also need to add *.messaging.microsoft.com to smtp_tls_per_site. The use of MUST_NOPEERMATCH is obsolete and no longer suppported. You should not be using the old tls_per_site policies with Postfix 2.3 or later. You should not be using Postfix 2.2 or earlier with non-trivial TLS policies. You have not shown your configuration settings for this destination, and have not supplied postconf -n output. Without these, no further help is possible. -- Viktor.
Re: Multi-domain certificates and TLS
On Fri, Aug 20, 2010 at 10:30:48PM -0400, Alex wrote: I posted a message a few days ago, and still haven't been able to figure this out. I believe this is a result of the certificate having multiple DNS names and my TLS configuration not properly supporting that. Could that be the case? When the Subject Alternative Name extension is present in a server certificate, Postfix will use the first domain listed in that extension as the verified peer name, unless one of the other domains satisfies the matching rules for the destination TLS policy. Aug 6 09:44:20 smtp01 postfix/smtp[24772]: setting up TLS connection to mail.messaging.microsoft.com Aug 6 09:44:20 smtp01 postfix/smtp[24772]: Peer verification: CommonName in certificate does not match: mail.global.frontbridge.com != mail.messaging.microsoft.com Aug 6 09:44:20 smtp01 postfix/smtp[24772]: TLS connection established to mail.messaging.microsoft.com: TLSv1 with cipher RC4-SHA (128/128 bits) Aug 6 09:44:20 smtp01 postfix/smtp[24772]: 03C221880003: to=t...@example1.com, relay=mail.messaging.microsoft.com[65.55.88.22], delay=1, status=deferred (TLS-failure: Could not verify certificate) Looks like they recently migrated from Postfix SMTP servers to Microsoft Exchange: Connected to mail.messaging.microsoft.com[65.55.88.22]:25 220 TX2EHSMHS001.bigfish.com Microsoft ESMTP MAIL Service ready at Mon, 23 Aug 2010 13:37:27 + EHLO amnesiac.example.com 250-TX2EHSMHS001.bigfish.com Hello [192.0.2.1] 250-SIZE 157286400 250-PIPELINING 250-ENHANCEDSTATUSCODES 250-STARTTLS 250-AUTH 250-8BITMIME 250-BINARYMIME 250 CHUNKING STARTTLS 220 2.0.0 SMTP server ready mail.messaging.microsoft.com[65.55.88.22]:25: subjectAltName: mail.global.frontbridge.com mail.messaging.microsoft.com[65.55.88.22]:25: subjectAltName: *.outlook.com mail.messaging.microsoft.com[65.55.88.22]:25: subjectAltName: *.exchangelabs.com mail.messaging.microsoft.com[65.55.88.22]:25: subjectAltName: *.bigfish.com mail.messaging.microsoft.com[65.55.88.22]:25: Matched subjectAltName: *.messaging.microsoft.com mail.messaging.microsoft.com[65.55.88.22]:25 CommonName mail.global.frontbridge.com mail.messaging.microsoft.com[65.55.88.22]:25: Matched subject_CN=*.messaging.microsoft.com, issuer_CN=Cybertrust SureServer Standard Validation CA mail.messaging.microsoft.com[65.55.88.22]:25 sha1 fingerprint A8:5E:1B:DB:FF:98:13:64:B6:14:64:6F:74:BA:B5:0B:43:FA:C8:59 Verified TLS connection established to mail.messaging.microsoft.com[65.55.88.22]:25: TLSv1 with cipher AES128-SHA (128/128 bits) What is your TLS policy for this destination? The wildcard Subject Alt Name *.messaging.microsoft.com should match mail.messaging.microsoft.com if you are configured to check for that... At least it does when I test it as you see above. Below is the full cert chain, with the first cert fully decoded, if that's useful: --- Certificate chain 0 s:/C=US/ST=Washington/L=Redmond/O=Microsoft Corporation/OU=Forefront Online Protection for Exchange/emailaddress=supp...@frontbridge.com/CN=mail.global.frontbridge.com i:/O=Cybertrust Inc/CN=Cybertrust SureServer Standard Validation CA Certificate: Data: Version: 3 (0x2) Serial Number: 01:00:00:00:00:01:2a:00:ad:2e:87 Signature Algorithm: sha1WithRSAEncryption Issuer: O=Cybertrust Inc, CN=Cybertrust SureServer Standard Validation CA Validity Not Before: Jul 23 18:32:50 2010 GMT Not After : Jul 23 18:32:50 2011 GMT Subject: C=US, ST=Washington, L=Redmond, O=Microsoft Corporation, OU=Forefront Online Protection for Exchange/emailaddress=supp...@frontbridge.com, CN=mail.global.frontbridge.com Subject Public Key Info: Public Key Algorithm: rsaEncryption RSA Public Key: (2048 bit) Modulus (2048 bit): 00:cd:0f:0d:38:d8:30:e3:06:56:22:5a:27:57:6e: 60:5b:8b:1a:92:1a:d8:d8:ca:c1:41:2d:a2:68:a5: 14:ff:ac:96:71:83:c4:73:ea:ef:3d:b1:7a:2b:c6: 10:0c:22:c8:21:44:47:8c:c5:c8:bf:df:ea:4f:af: 83:eb:d3:b8:6b:6b:17:fa:7f:d0:81:42:40:cb:e5: ac:8e:e0:34:5f:65:7b:48:8c:2f:9b:f2:5b:e9:fc: 34:98:d0:21:e8:65:0f:52:df:7c:20:ae:7f:6d:d8: 49:ba:82:b5:3e:2a:d2:8f:78:f1:11:8f:c8:de:d7: 6c:1f:92:46:10:24:04:86:15:a5:50:c9:d5:62:0b: 4e:45:da:73:a4:b1:09:c0:1b:1e:2d:64:de:d9:0e: 2e:c2:b2:de:03:e3:d7:a6:2c:ae:b7:44:23:44:5e: b0:ff:45:87:4a:03:ce:b4:22:07:a2:4a:06:cc:8c: 0e:1d:5f:e6:a1:03:d8:de:71:d4:85:84:f5:5f:92: 73:bc:a9:00:68:1e:5c:40:62:55:d8:19:8f:7f:5b: ac:a0:7f:ec:2d:34:c7:64:aa:fc:00:6c:a0:51:6c: 87:23:fb:c1:30:d4:f5:f9:a9:07:0a:07:c0:71:70: 08:06:25:20:ec:77:b9:a8:4d:00:1f:3b:93:ad:79:
Re: Multi-domain certificates and TLS
Alex: Aug 6 09:44:20 smtp01 postfix/smtp[24772]: setting up TLS connection to mail.messaging.microsoft.com Aug 6 09:44:20 smtp01 postfix/smtp[24772]: Peer verification: CommonName in certificate does not match: mail.global.frontbridge.com != mail.messaging.microsoft.com The certificate CommonName is mail.global.frontbridge.com. This is easily demonstrated with $ openssl s_client -connect 65.55.88.22:25 -starttls smtp Why do you believe that the server certificate has MULTIPLE names? Wietse
