DKIM: dkim_verify_min_keysizes option

[users/heiko/exim.git] / doc / doc-docbook / spec.xfpt

diff --git a/doc/doc-docbook/spec.xfpt b/doc/doc-docbook/spec.xfpt
index c54437181b2bc1bfd83c2109fd4bf07f54b88550..bf042ac2f2c8ade48994ed9e780f45e202773b41 100644 (file)
--- a/doc/doc-docbook/spec.xfpt
+++ b/doc/doc-docbook/spec.xfpt
@@ -10285,21 +10285,37 @@ ${readsocket{/socket/name}{request string}{3s}}
 .endd
 
 The third argument is a list of options, of which the first element is the timeout
 .endd
 
 The third argument is a list of options, of which the first element is the timeout

-and must be present if the argument is given.
+and must be present if any options are given.

 Further elements are options of form &'name=value'&.
 Further elements are options of form &'name=value'&.

-Two option types is currently recognised: shutdown and tls.
-The first defines whether (the default)
-or not a shutdown is done on the connection after sending the request.
-Example, to not do so (preferred, eg. by some webservers):
+Example:

 .code
 ${readsocket{/socket/name}{request string}{3s:shutdown=no}}
 .endd
 .code
 ${readsocket{/socket/name}{request string}{3s:shutdown=no}}
 .endd

-The second, tls, controls the use of TLS on the connection.  Example:
-.code
-${readsocket{/socket/name}{request string}{3s:tls=yes}}
-.endd
-The default is to not use TLS.
+
+.new
+The following option names are recognised:
+.ilist
+&*cache*&
+Defines if the result data can be cached for use by a later identical
+request in the same process.
+Values are &"yes"& or &"no"& (the default).
+If not, all cached results for this connection specification
+will be invalidated.
+
+.next
+&*shutdown*&
+Defines whether or not a write-shutdown is done on the connection after
+sending the request. Values are &"yes"& (the default) or &"no"&
+(preferred, eg. by some webservers).
+
+.next
+&*tls*&
+Controls the use of TLS on the connection.
+Values are &"yes"& or &"no"& (the default).

 If it is enabled, a shutdown as descripbed above is never done.
 If it is enabled, a shutdown as descripbed above is never done.

+.endlist
+.wen
+

 
 A fourth argument allows you to change any newlines that are in the data
 that is read, in the same way as for &%readfile%& (see above). This example
 
 A fourth argument allows you to change any newlines that are in the data
 that is read, in the same way as for &%readfile%& (see above). This example


@@ -14574,6 +14590,7 @@ See also the &'Policy controls'& section above.
 .table2
 .row &%dkim_verify_hashes%&          "DKIM hash methods accepted for signatures"
 .row &%dkim_verify_keytypes%&        "DKIM key types accepted for signatures"
 .table2
 .row &%dkim_verify_hashes%&          "DKIM hash methods accepted for signatures"
 .row &%dkim_verify_keytypes%&        "DKIM key types accepted for signatures"

+.row &%dkim_verify_min_keysizes%&    "DKIM key sizes accepted for signatures"

 .row &%dkim_verify_signers%&         "DKIM domains for which DKIM ACL is run"
 .row &%host_lookup%&                 "host name looked up for these hosts"
 .row &%host_lookup_order%&           "order of DNS and local name lookups"
 .row &%dkim_verify_signers%&         "DKIM domains for which DKIM ACL is run"
 .row &%host_lookup%&                 "host name looked up for these hosts"
 .row &%host_lookup_order%&           "order of DNS and local name lookups"


@@ -15348,6 +15365,16 @@ This option gives a list of key types which are acceptable in signatures,
 and an order of processing.
 Signatures with algorithms not in the list will be ignored.
 
 and an order of processing.
 Signatures with algorithms not in the list will be ignored.
 

+
+.new
+.option dkim_verify_min_keysizes main "string list" "rsa=1024 ed25519=250"
+This option gives a list of key sizes which are acceptable in signatures.
+The list is keyed by the algorithm type for the key; the values are in bits.
+Signatures with keys smaller than given by this option will fail verification.
+
+The default enforces the RFC 8301 minimum key size for RSA signatures.
+.wen
+

 .option dkim_verify_minimal main boolean false
 If set to true, verification of signatures will terminate after the
 first success.
 .option dkim_verify_minimal main boolean false
 If set to true, verification of signatures will terminate after the
 first success.


@@ -40717,6 +40744,10 @@ Notes from the key record (tag n=).
 
 .vitem &%$dkim_key_length%&
 Number of bits in the key.
 
 .vitem &%$dkim_key_length%&
 Number of bits in the key.

+.new
+Valid only once the key is loaded, which is at the time the header signature
+is verified, which is after the body hash is.
+.wen

 
 Note that RFC 8301 says:
 .code
 
 Note that RFC 8301 says:
 .code


@@ -40724,9 +40755,8 @@ Verifiers MUST NOT consider signatures using RSA keys of
 less than 1024 bits as valid signatures.
 .endd
 
 less than 1024 bits as valid signatures.
 .endd
 

-To enforce this you must have a DKIM ACL which checks this variable
-and overwrites the &$dkim_verify_status$& variable as discussed above.
-As EC keys are much smaller, the check should only do this for RSA keys.
+This is enforced by the default setting for the &%dkim_verify_min_keysizes%&
+option.

 
 .endlist
 
 
 .endlist