X-Git-Url: https://git.exim.org/exim.git/blobdiff_plain/2dd9a491d1ff0ddc6e6fc22d6db3e9d8ba191f64..41c494e2465efadc2e82002a07430e8aec85bc9b:/doc/doc-docbook/spec.xfpt

diff --git a/doc/doc-docbook/spec.xfpt b/doc/doc-docbook/spec.xfpt
index d7a7f8516..cbb7045a3 100644
--- a/doc/doc-docbook/spec.xfpt
+++ b/doc/doc-docbook/spec.xfpt
@@ -228,6 +228,14 @@
   <secondary>failure report</secondary>
   <see><emphasis>bounce message</emphasis></see>
 </indexterm>
+<indexterm role="concept">
+  <primary>de-tainting</primary>
+  <see><emphasis>tainting, de-tainting</emphasis></see>
+</indexterm>
+<indexterm role="concept">
+  <primary>detainting</primary>
+  <see><emphasis>tainting, de-tainting</emphasis></see>
+</indexterm>
 <indexterm role="concept">
   <primary>dialup</primary>
   <see><emphasis>intermittently connected hosts</emphasis></see>
@@ -9474,7 +9482,22 @@ reasons,
 .cindex "tainted data" expansion
 .cindex expansion "tainted data"
 and expansion of data deriving from the sender (&"tainted data"&)
-is not permitted.
+.new
+is not permitted (including acessing a file using a tainted name).
+The main config option &%allow_insecure_tainted_data%& can be used as
+mitigation during uprades to more secure configurations.
+.wen
+
+.new
+Common ways of obtaining untainted equivalents of variables with
+tainted values
+.cindex "tainted data" "de-tainting"
+come down to using the tainted value as a lookup key in a trusted database.
+This database could be the filesystem structure,
+or the password file,
+or accessed via a DBMS.
+Specific methods are indexed under &"de-tainting"&.
+.wen
 
 
 
@@ -14410,6 +14433,8 @@ listed in more than one group.
 
 .section "Miscellaneous" "SECID96"
 .table2
+.row &%add_environment%&             "environment variables"
+.row &%allow_insecure_tainted_data%& "turn taint errors into warnings"
 .row &%bi_command%&                  "to run for &%-bi%& command line option"
 .row &%debug_store%&                 "do extra internal checks"
 .row &%disable_ipv6%&                "do no IPv6 processing"
@@ -15017,6 +15042,18 @@ domains (defined in the named domain list &%local_domains%& in the default
 configuration). This &"magic string"& matches the domain literal form of all
 the local host's IP addresses.
 
+.new
+.option allow_insecure_tainted_data main boolean false
+.cindex "de-tainting"
+.oindex "allow_insecure_tainted_data"
+The handling of tainted data may break older (pre 4.94) configurations.
+Setting this option to "true" turns taint errors (which result in a temporary
+message rejection) into warnings. This option is meant as mitigation only
+and deprecated already today. Future releases of Exim may ignore it.
+The &%taint%& log selector can be used to suppress even the warnings.
+.wen
+
+
 
 .option allow_mx_to_ip main boolean false
 .cindex "MX record" "pointing to IP address"
@@ -25408,11 +25445,14 @@ BDAT will not be used in conjunction with a transport filter.
 .option hosts_try_dane smtp "host list&!!" *
 .cindex DANE "transport options"
 .cindex DANE "attempting for certain servers"
-If built with DANE support, Exim  will require that a DNSSEC-validated
-TLSA record is present for any host matching the list,
-and that a DANE-verified TLS connection is made. See
-the &%dnssec_request_domains%& router and transport options.
-There will be no fallback to in-clear communication.
+.new
+If built with DANE support, Exim  will look up a
+TLSA record for any host matching the list,
+If one is found and that lookup was DNSSEC-validated,
+then Exim requires that a DANE-verified TLS connection is made for that host;
+there will be no fallback to in-clear communication.
+.wen
+See the &%dnssec_request_domains%& router and transport options.
 See section &<<SECDANE>>&.
 
 .option hosts_try_fastopen smtp "host list&!!" *
@@ -27643,7 +27683,14 @@ fixed_plain:
   client_send = ^username^mysecret
 .endd
 The lack of colons means that the entire text is sent with the AUTH
-command, with the circumflex characters converted to NULs. A similar example
+command, with the circumflex characters converted to NULs.
+.new
+Note that due to the ambiguity of parsing three consectutive circumflex characters
+there is no way to provide a password having a leading circumflex.
+.wen
+
+
+A similar example
 that uses the LOGIN mechanism is:
 .code
 fixed_login:
@@ -38149,6 +38196,7 @@ selection marked by asterisks:
 &` smtp_protocol_error        `&  SMTP protocol errors
 &` smtp_syntax_error          `&  SMTP syntax errors
 &` subject                    `&  contents of &'Subject:'& on <= lines
+&`*taint                      `&  taint errors or warnings
 &`*tls_certificate_verified   `&  certificate verification status
 &`*tls_cipher                 `&  TLS cipher suite on <= and => lines
 &` tls_peerdn                 `&  TLS peer DN on <= and => lines
@@ -38542,6 +38590,11 @@ using a CA trust anchor,
 &`CA=dane`& if using a DNS trust anchor,
 and &`CV=no`& if not.
 .next
+.cindex "log" "Taint warnings"
+&%taint%&: Log warnings about tainted data. This selector can't be
+turned of if &%allow_insecure_tainted_data%& is false (which is the
+default).
+.next
 .cindex "log" "TLS cipher"
 .cindex "TLS" "logging cipher"
 &%tls_cipher%&: When a message is sent or received over an encrypted