Docs: more info on taint

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

diff --git a/doc/doc-docbook/spec.xfpt b/doc/doc-docbook/spec.xfpt
index 28c8b14626e0a59ee0297c98a58b17160788ffe5..ccfa4424af467d75b478db3fc4a67a06218c45d5 100644 (file)
--- a/doc/doc-docbook/spec.xfpt
+++ b/doc/doc-docbook/spec.xfpt
@@ -8061,8 +8061,8 @@ For MySQL, PostgreSQL and Redis lookups (but not currently for Oracle and InterB
 it is possible to specify a list of servers with an individual query. This is
 done by appending a comma-separated option to the query type:
 .display
-.endd
 &`,servers=`&&'server1:server2:server3:...'&
+.endd
 Each item in the list may take one of two forms:
 .olist
 If it contains no slashes it is assumed to be just a host name. The appropriate
@@ -8096,7 +8096,7 @@ option, you can still update it by a query of this form:
 ${lookup pgsql,servers=master/db/name/pw {UPDATE ...} }
 .endd
 
-An older syntax places the servers speciification before the qury,
+An older syntax places the servers specification before the query,
 semicolon separated:
 .code
 ${lookup mysql{servers=master; UPDATE ...} }
@@ -9453,10 +9453,22 @@ the data type.  ACL rules always expand strings.  A couple of expansion
 conditions do not expand some of the brace-delimited branches, for security
 reasons,
 .cindex "tainted data" expansion
+.cindex "tainted data" definition
 .cindex expansion "tainted data"
 and expansion of data deriving from the sender (&"tainted data"&)
 is not permitted.
 
+.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 filestem structure,
+or the password file,
+or accessed via a DBMS.
+Specific methods are indexed under &"de-tainting"&.
+.wen
+
 
 
 .section "Literal text in expanded strings" "SECTlittext"
@@ -10168,6 +10180,18 @@ extracted is used.
 You can use &`fail`& instead of {<&'string3'&>} as in a string extract.
 
 
+.new
+.vitem &*${listquote{*&<&'separator'&>&*}{*&<&'string'&>&*}}*&
+.cindex quoting "for list"
+.cindex list quoting
+This item doubles any occurrence of the separator character
+in the given string.
+An empty string is replaced with a single space.
+This converts the string into a safe form for use as a list element,
+in a list using the given separator.
+.wen
+
+
 .vitem "&*${lookup{*&<&'key'&>&*}&~*&<&'search&~type'&>&*&~&&&
         {*&<&'file'&>&*}&~{*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&"
 This is the first of one of two different types of lookup item, which are both
@@ -11933,15 +11957,12 @@ request, for a password, so the data consists of just two strings.
 
 There can be problems if any of the strings are permitted to contain colon
 characters. In the usual way, these have to be doubled to avoid being taken as
-separators. If the data is being inserted from a variable, the &%sg%& expansion
-item can be used to double any existing colons. For example, the configuration
+separators.
+The &%listquote%& expansion item can be used for this.
+For example, the configuration
 of a LOGIN authenticator might contain this setting:
 .code
-server_condition = ${if pam{$auth1:${sg{$auth2}{:}{::}}}}
-.endd
-For a PLAIN authenticator you could use:
-.code
-server_condition = ${if pam{$auth2:${sg{$auth3}{:}{::}}}}
+server_condition = ${if pam{$auth1:${listquote{:}{$auth2}}}}
 .endd
 In some operating systems, PAM authentication can be done only from a process
 running as root. Since Exim is running as the Exim user when receiving