On Monday, November 13, 2023 8:34:04 PM CET Manuel Bouyer wrote: > Hello > I'm facing an issue with postfix+openssl3 which may be critical (depending > on how it can be fixed). > > Now my postfix setup fails to send mails with > Nov 13 20:20:53 comore postfix/smtp[6449]: warning: TLS library problem: > error:0A00018E:SSL routines::ca md too > weak:/usr/src/crypto/external/bsd/openssl/dist/ssl/statem/statem_lib.c:984: > > From what I understood, this is the remote certificate which is not accepted: > openssl 3 deprecated some signature algorithm, which are no longer accepted > with @SECLEVEL=1 (which is the default). > In server's certificate chain all but the last one are signed with > sha384WithRSAEncryption (which should be OK). The last one (the root > certificate) is signed with RSA-SHA1 and I don't think this will change > soon: > 3 s:C = GB, ST = Greater Manchester, L = Salford, O = Comodo CA Limited, CN > = A > AA Certificate Services > i:C = GB, ST = Greater Manchester, L = Salford, O = Comodo CA Limited, CN > = A > AA Certificate Services > a:PKEY: rsaEncryption, 2048 (bit); sigalg: RSA-SHA1 > v:NotBefore: Jan 1 00:00:00 2004 GMT; NotAfter: Dec 31 23:59:59 2028 GMT > > So, as far as I understand, we end up with a postfix installation which > can't talk to servers with valid certificates.
NIST has been sunsetting SHA1 for a long time, 2016 in fact. In many cases, there is a better trust chain for Comodo intermediary certificates and admins should be installing those. Joerg
