[pfx] Re: TLS Library Problem? (SSL_accept error from ...)
The /usr/share/crypto-policies/DEFAULT/opensslcnf.txt on RHEL 9 looks identical to what you posted for Fedora. I am not a RHEL expert but I have not see any references to opt out of the crypto policy on a per application basis. You can customize an existing crypto policy or create your own. I think as long as people are follow best practices of running Postfix on a dedicated system they should be able to tweak the system-wide policy should they really need to do so, absent any options for granular application configuration. Comparing the DEFAULT policy with the LEGACY policy seems to reduce the security of the system by allowing "..SHA-1 in the TLS hash, signature and algorithm. CBC-mode ciphers are allowed to be used with SSH. Applications using GNUTLS allow certificates with SHA-1" Other than this the TLS, IKEv2, SSH2 protocols are the same as DEFAULT. The RSA keys and Diffie-Hellman parameters are also the same. On Fri, May 5, 2023 at 8:30 PM Viktor Dukhovni via Postfix-users < postfix-users@postfix.org> wrote: > On Fri, May 05, 2023 at 08:28:48PM -0400, Viktor Dukhovni via > Postfix-users wrote: > > > You should of course also share ( > https://www.postfix.org/DEBUG_README.html#mail) > > > > $ postconf -nf > > $ postconf -Mf > > > > without any changes in whitespace, including line breaks. Attaching > > these as text files may be simplest if your mail client won't coöperate. > > And, if applicable, post the content of: > > /usr/share/crypto-policies/DEFAULT/opensslcnf.txt > > Which on a sample Fedora36 system holds: > > CipherString = > @SECLEVEL=2:kEECDH:kRSA:kEDH:kPSK:kDHEPSK:kECDHEPSK:kRSAPSK:-aDSS:-3DES:!DES:!RC4:!RC2:!IDEA:-SEED:!eNULL:!aNULL:!MD5:-SHA384:-CAMELLIA:-ARIA:-AESCCM8 > Ciphersuites = > TLS_AES_256_GCM_SHA384:TLS_CHACHA20_POLY1305_SHA256:TLS_AES_128_GCM_SHA256:TLS_AES_128_CCM_SHA256 > TLS.MinProtocol = TLSv1.2 > TLS.MaxProtocol = TLSv1.3 > DTLS.MinProtocol = DTLSv1.2 > DTLS.MaxProtocol = DTLSv1.2 > SignatureAlgorithms = > ECDSA+SHA256:ECDSA+SHA384:ECDSA+SHA512:ed25519:ed448:rsa_pss_pss_sha256:rsa_pss_pss_sha384:rsa_pss_pss_sha512:rsa_pss_rsae_sha256:rsa_pss_rsae_sha384:rsa_pss_rsae_sha512:RSA+SHA256:RSA+SHA384:RSA+SHA512:ECDSA+SHA224:RSA+SHA224 > > [openssl_init] > alg_section = evp_properties > > [evp_properties] > rh-allow-sha1-signatures = yes > > Postfix (at least in a default configuration) is not affected by: > > CipherString > TLS.MinProtocol > TLS.MaxProtocol > DTLS.MinProtocol > DTLS.MaxProtocol > > But currently has no controls to override: > > # TLS 1.3 ciphersuites (not a priority to fine-tune) > Ciphersuites = ... > > # TLS 1.2 signature algorithm negotiation (the RH list is fine) > SignatureAlgorithms = ... > > # If this is set to "no", TLS 1.0 key exchange is likely to break. > # In some cases certificate verification may break. > rh-allow-sha1-signatures = yes > > I don't even know whether RedHat exposes any mechanisms for applications > to opt-out of crypto policy and use only application-driven OpenSSL > configuration. This is should perhaps be looked into in the Postfix 3.9 > timeframe. > > -- > Viktor. > ___ > Postfix-users mailing list -- postfix-users@postfix.org > To unsubscribe send an email to postfix-users-le...@postfix.org > ___ Postfix-users mailing list -- postfix-users@postfix.org To unsubscribe send an email to postfix-users-le...@postfix.org
[pfx] Re: TLS Library Problem? (SSL_accept error from ...)
Thank you so much for the suggestion to review the crypto setting as this indeed a RedHat based distribution. I confirmed it is set to "default" which means “The default system-wide cryptographic policy level offers secure settings for current threat models. It allows the TLS 1.2 and 1.3 protocols, as well as the IKEv2 and SSH2 protocols. The RSA keys and Diffie-Hellman parameters are accepted if they are at least 2048 bits long.” Source: https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/9/html/security_hardening/using-the-system-wide-cryptographic-policies_security-hardening The system in question was located and is an older than dirt system running a LONG obsolete version of Gentoo. My best guess is that the system was accidentally powered on during a generator test due to a former employee not properly decommissioning the system many years ago. The configuration change that I wrote about (disabling the STARTTLS keyword for the IP address) did allow my Postfix gateways to route email without any issue. I am going to guess the age or configuration of the system is to blame. I have started the official process to pull the plug on the server so it can be wiped and recycled. On Fri, May 5, 2023 at 7:29 PM Viktor Dukhovni via Postfix-users < postfix-users@postfix.org> wrote: > On Fri, May 05, 2023 at 06:55:23PM -0500, E R via Postfix-users wrote: > > > postfix/smtpd[1234567]: SSL_accept error from > xxx.xxx.xxx[yyy.yyy.yyy.yyy]: -1 > > postfix/smtpd[1234567]: warning: TLS library problem: > > error:0398:digital envelope routines::invalid > digest:crypto/evp/m_sigver.c:343: > > postfix/smtpd[1234567]: warning: TLS library problem: > > error:0A0C0103:SSL routines::internal > error:ssl/statem/statem_srvr.c:2684: > > This problem may be worth further analysis. It appears that OpenSSL has > chosen a signature algorithm (public key algorithm + digest method, e.g. > RSA with SHA256, ...) at the TLS layer, but failed to initialise a > signature context at the crypto API layer. This is odd, because the > known TLS layer combinations should map to known crypto layer > primitives. > > Are you on a RedHat system perhaps? RedHat's latest releases have > turned up crypto policy to "11", and may refuse to, for example, support > RSA with SHA1. The remote client may have one of the really dated TLS > stacks that doesn't know how to do anything better. > > If your system is a RHEL or recent Fedora or similar system, or perhaps > by now other distributions have joined the club, then you'll to find the > relevant crypto policy file and dial it down a bit (on an MTA doing > opportunistic TLS, RSA with SHA1 is better than cleartext). > > Similar considerations may apply not only to MTAs but also to validating > DNS resolvers, and perhaps other applications. > > The various distributions may publish instructions on recommnded ways to > tune the crypto policy. > > If all the above is false lead, then the problem is more mysterious, and > perhaps a PCAP file capturing a failed handshake would be a good next > step. > > You should of course also share ( > https://www.postfix.org/DEBUG_README.html#mail) > > $ postconf -nf > $ postconf -Mf > > without any changes in whitespace, including line breaks. Attaching > these as text files may be simplest if your mail client won't coöperate. > > -- > Viktor. > ___ > Postfix-users mailing list -- postfix-users@postfix.org > To unsubscribe send an email to postfix-users-le...@postfix.org > ___ Postfix-users mailing list -- postfix-users@postfix.org To unsubscribe send an email to postfix-users-le...@postfix.org
[pfx] TLS Library Problem? (SSL_accept error from ...)
I have setup Postfix so that internally I offer TLS to systems but do not require it since I have no control over their configuration. I did extensive testing to ensure that the mail gateway supports TLS and accepts email from another Postfix system where TLS is disabled. But today I found a system failing to route email through the Postfix gateway today that has me baffled. My best guess based on searching the archives is that there may be a defect in the remote system that is causing the issue. I looked at the documentation and I think the next step would be to configure the smtpd_discard_ehlo_keyword_address_maps option and use a CIDR file for the mapping. (i.e. smtpd_discard_ehlo_keyword_address_maps = cidr:/etc/postfix/smtpd_discard_ehlo_keyword_address_maps). The contents of the file would be the IP address of the system and the STARTTLS keyword if I want to disable TLS for this IP (i.e. 123.456.789.123 STARTTLS). I tested this on my test system with good ole telnet and it seems to have the effect I desired. Am I missing anything? [snippet from main.cf] smtpd_tls_security_level = may [snippet from log] May 05 16:27:59 zzz postfix/smtpd[1234567]: connect from xxx.xxx.xxx[yyy.yyy.yyy.yyy] May 05 16:27:59 zzz postfix/smtpd[1234567]: SSL_accept error from xxx.xxx.xxx[yyy.yyy.yyy.yyy]: -1 May 05 16:27:59 zzz postfix/smtpd[1234567]: warning: TLS library problem: error:0398:digital envelope routines::invalid digest:crypto/evp/m_sigver.c:343: May 05 16:27:59 zzz postfix/smtpd[1234567]: warning: TLS library problem: error:0A0C0103:SSL routines::internal error:ssl/statem/statem_srvr.c:2684: May 05 16:27:59 zzz postfix/smtpd[1234567]: lost connection after STARTTLS from xxx.xxx.xxx[yyy.yyy.yyy.yyy] ___ Postfix-users mailing list -- postfix-users@postfix.org To unsubscribe send an email to postfix-users-le...@postfix.org
