X-Git-Url: https://git.exim.org/users/jgh/exim.git/blobdiff_plain/0719afe27105e35ad40805dabb66dbbcb44dab52..eb445b049c9b78cbe187b9cb3c318d65862d4851:/doc/doc-docbook/spec.xfpt?ds=sidebyside diff --git a/doc/doc-docbook/spec.xfpt b/doc/doc-docbook/spec.xfpt index c29ab47ba..f455c9f0c 100644 --- a/doc/doc-docbook/spec.xfpt +++ b/doc/doc-docbook/spec.xfpt @@ -9154,6 +9154,7 @@ If the ACL returns defer the result is a forced-fail. Otherwise the expansion f .vitem "&*${authresults{*&<&'authserv-id'&>&*}}*&" .cindex authentication "results header" .cindex headers "authentication-results:" +.cindex authentication "expansion item" This item returns a string suitable for insertion as an &'Authentication-Results"'& header line. @@ -9172,6 +9173,7 @@ Example use (as an ACL modifier): .code add_header = :at_start:${authresults {$primary_hostname}} .endd +This is safe even if no authentication reselts are available. .wen @@ -11593,10 +11595,15 @@ preserve some of the authentication information in the variable user/password authenticator configuration might preserve the user name for use in the routers. Note that this is not the same information that is saved in &$sender_host_authenticated$&. + When a message is submitted locally (that is, not over a TCP connection) the value of &$authenticated_id$& is normally the login name of the calling process. However, a trusted user can override this by means of the &%-oMai%& command line option. +.new +This second case also sets up inforamtion used by the +&$authresults$& expansion item. +.wen .vitem &$authenticated_fail_id$& .cindex "authentication" "fail" "id" @@ -11936,6 +11943,13 @@ lookup succeeds, but there is a lookup problem such as a timeout when checking the result, the name is not accepted, and &$host_lookup_deferred$& is set to &"1"&. See also &$sender_host_name$&. +.new +.cindex authentication "expansion item" +Performing these checks sets up information used by the +&$authresults$& expansion item. +.wen + + .vitem &$host_lookup_failed$& .vindex "&$host_lookup_failed$&" See &$host_lookup_deferred$&. @@ -23927,6 +23941,24 @@ For testing purposes, this value can be overridden by the &%-oB%& command line option. +.new +.option dane_require_tls_ciphers smtp string&!! unset +.cindex "TLS" "requiring specific ciphers for DANE" +.cindex "cipher" "requiring specific" +.cindex DANE "TLS ciphers" +This option may be used to override &%tls_require_ciphers%& for connections +where DANE has been determined to be in effect. +If not set, then &%tls_require_ciphers%& will be used. +Normal SMTP delivery is not able to make strong demands of TLS cipher +configuration, because delivery will fall back to plaintext. Once DANE has +been determined to be in effect, there is no plaintext fallback and making the +TLS cipherlist configuration stronger will increase security, rather than +counter-intuitively decreasing it. +If the option expands to be empty or is forced to fail, then it will +be treated as unset and &%tls_require_ciphers%& will be used instead. +.wen + + .option data_timeout smtp time 5m This sets a timeout for the transmission of each block in the data portion of the message. As a result, the overall timeout for a message depends on the size @@ -26105,6 +26137,12 @@ public name) of the authenticator driver that successfully authenticated the client from which the message was received. This variable is empty if there was no successful authentication. +.new +.cindex authentication "expansion item" +Successful authentication sets up information used by the +&$authresults$& expansion item. +.wen + @@ -28082,8 +28120,7 @@ that DNS lookups they do for the server have not been tampered with. The domain to this server, its A record, its TLSA record and any associated CNAME records must all be covered by DNSSEC. 2) add TLSA DNS records. These say what the server certificate for a TLS connection should be. -3) offer a server certificate, or certificate chain, in TLS connections which is traceable to the one -defined by (one of?) the TSLA records +3) offer a server certificate, or certificate chain, in TLS connections which is is anchored by one of the TLSA records. There are no changes to Exim specific to server-side operation of DANE. Support for client-side operation of DANE can be included at compile time by defining SUPPORT_DANE=yes @@ -28138,8 +28175,9 @@ This modification of hosts_request_ocsp is only done if it has the default value those who use &%hosts_require_ocsp%&, should consider the interaction with DANE in their OCSP settings. -For client-side DANE there are two new smtp transport options, &%hosts_try_dane%& and &%hosts_require_dane%&. -The latter variant will result in failure if the target host is not DNSSEC-secured. +For client-side DANE there are three new smtp transport options, &%hosts_try_dane%&, &%hosts_require_dane%& +and &%dane_require_tls_ciphers%&. +The require variant will result in failure if the target host is not DNSSEC-secured. DANE will only be usable if the target host has DNSSEC-secured MX, A and TLSA records. @@ -28148,6 +28186,14 @@ If a TLSA lookup is done and succeeds, a DANE-verified TLS connection will be required for the host. If it does not, the host will not be used; there is no fallback to non-DANE or non-TLS. +If DANE is requested and usable, then the TLS cipher list configuration +prefers to use the option &%dane_require_tls_ciphers%& and falls +back to &%tls_require_ciphers%& only if that is unset. +This lets you configure "decent crypto" for DANE and "better than nothing +crypto" as the default. Note though that while GnuTLS lets the string control +which versions of TLS/SSL will be negotiated, OpenSSL does not and you're +limited to ciphersuite constraints. + If DANE is requested and useable (see above) the following transport options are ignored: .code hosts_require_tls @@ -31812,9 +31858,7 @@ If the value of &%av_scanner%& starts with a dollar character, it is expanded before use. The usual list-parsing of the content (see &<>&) applies. The following scanner types are supported in this release, -.new though individual ones can be included or not at build time: -.wen .vlist .vitem &%avast%& @@ -31828,11 +31872,22 @@ which can be either a full path to a UNIX socket, or host and port specifiers separated by white space. The host may be a name or an IP address; the port is either a single number or a pair of numbers with a dash between. -Any further options are given, on separate lines, -to the daemon as options before the main scan command. +A list of options may follow. These options are interpreted on the +Exim's side of the malware scanner, or are given on separate lines to +the daemon as options before the main scan command. + +.new +.cindex &`pass_unscanned`& "avast" +If &`pass_unscanned`& +is set, any files the Avast scanner can't scan (e.g. +decompression bombs, or invalid archives) are considered clean. Use with +care. +.wen + For example: .code av_scanner = avast:/var/run/avast/scan.sock:FLAGS -fullfiles:SENSITIVITY -pup +av_scanner = avast:/var/run/avast/scan.sock:pass_unscanned:FLAGS -fullfiles:SENSITIVITY -pup av_scanner = avast:192.168.2.22 5036 .endd If you omit the argument, the default path @@ -31849,8 +31904,9 @@ $ socat UNIX:/var/run/avast/scan.sock STDIO: PACK .endd -Only the first virus detected will be reported. - +If the scanner returns a temporary failure (e.g. license issues, or +permission problems), the message is deferred and a paniclog entry is +written. The usual &`defer_ok`& option is available. .vitem &%aveserver%& .cindex "virus scanners" "Kaspersky" @@ -31901,7 +31957,7 @@ av_scanner = clamd:192.0.2.3 1234 : 192.0.2.4 1234 If the value of av_scanner points to a UNIX socket file or contains the &`local`& option, then the ClamAV interface will pass a filename containing the data -to be scanned, which will should normally result in less I/O happening and be +to be scanned, which should normally result in less I/O happening and be more efficient. Normally in the TCP case, the data is streamed to ClamAV as Exim does not assume that there is a common filesystem with the remote host. @@ -38917,6 +38973,21 @@ is set. .endlist .new +To generate keys under OpenSSL: +.code +openssl genrsa -out dkim_rsa.private 2048 +openssl rsa -in dkim_rsa.private -out /dev/stdout -pubout -outform PEM +.endd +Take the base-64 lines from the output of the second command, concatenated, +for the DNS TXT record. +See section 3.6 of RFC6376 for the record specification. + +Under GnuTLS: +.code +certtool --generate-privkey --rsa --bits=2048 --password='' -8 --outfile=dkim_rsa.private +certtool --load-privkey=dkim_rsa.private --pubkey-info +.endd + Note that RFC 8301 says: .code Signers MUST use RSA keys of at least 1024 bits for all keys. @@ -38931,6 +39002,18 @@ As they are a recent development, users should consider dual-signing for some transition period. The "_CRYPTO_SIGN_ED25519" macro will be defined if support is present for EC keys. + +OpenSSL 1.1.1 and GnuTLS 3.6.0 can create Ed25519 private keys: +.code +openssl genpkey -algorithm ed25519 -out dkim_ed25519.private +certtool --generate-privkey --key-type=ed25519 --outfile=dkim_ed25519.private +.endd + +To produce the required public key value for a DNS record: +.code +openssl pkey -outform DER -pubout -in dkim_ed25519.private | tail -c +13 | base64 +certtool --load_privkey=dkim_ed25519.private --pubkey_info --outder | tail -c +13 | base64 +.endd .wen .option dkim_hash smtp string&!! sha256 @@ -39001,6 +39084,12 @@ To evaluate the signature in the ACL a large number of expansion variables containing the signature status and its details are set up during the runtime of the ACL. +.new +.cindex authentication "expansion item" +Performing verification sets up information used by the +&$authresults$& expansion item. +.wen + Calling the ACL only for existing signatures is not sufficient to build more advanced policies. For that reason, the global option &%dkim_verify_signers%&, and a global expansion variable @@ -39261,6 +39350,12 @@ There is no Exim involvement on the trasmission of messages; publishing certain DNS records is all that is required. For verification, an ACL condition and an expansion lookup are provided. +.new +.cindex authentication "expansion item" +Performing verification sets up information used by the +&$authresults$& expansion item. +.wen + .cindex SPF "ACL condition" .cindex ACL "spf condition" @@ -39290,18 +39385,11 @@ its domain as well. This should be treated like "none". .vitem &%permerror%& This indicates a syntax error in the SPF record of the queried domain. -You may deny messages when this occurs. (Changed in 4.83) +You may deny messages when this occurs. .vitem &%temperror%& This indicates a temporary error during all processing, including Exim's SPF processing. You may defer messages when this occurs. -(Changed in 4.83) - -.vitem &%err_temp%& -Same as permerror, deprecated in 4.83, will be removed in a future release. - -.vitem &%err_perm%& -Same as temperror, deprecated in 4.83, will be removed in a future release. .endlist You can prefix each string with an exclamation mark to invert