dnsval.conf(3)                Programmer's Manual               dnsval.conf(3)

       dnsval.conf, resolv.conf, root.hints - Configuration policy for the
       DNSSEC validator library libval(3)

       val_add_valpolicy - Dynamically add a new policy to the validator

       val_remove_valpolicy - Remove a dynamically added policy from the
       validator context

           int val_add_valpolicy(val_context_t *context,
                           void *policy_definition,
                           val_policy_entry_t **pol);

           int val_remove_valpolicy(val_context_t *context,
                           val_policy_entry_t *pol);

           typedef struct {
               char *keyword;
               char *zone;
               char *value;
               long ttl;
           } libval_policy_definition_t;

       Applications can use local policy to influence the validation outcome.
       Examples of local policy elements include trust anchors for different
       zones and untrusted algorithms for cryptographic keys and hashes.
       Local policy may vary for different applications and operating

       The val_add_valpolicy() function can be used to dynamically add a new
       policy for a given context (the policies are not added persistently to
       the system configuration). The policy_definition field contains an
       implementation-specific definition of the validator policy to be added.
       For the libval library this is represented by the
       libval_policy_definition_t structure, which contains four fields:
       keyword, zone and value arguments are identical to keyword, zone and
       additional-data defined below for dnsval.conf.  ttl specifies the
       duration in seconds for which the policy is kept in effect.  A tt value
       of -1 adds to policy to the context indefinitely.  A handle to the
       newly added policy is returned in *pol.  This structure is opaque to
       the applications; applications must not modify the contents of the
       memory returned in *pol.

       Applications may also revoke the effects of a newly added policy, pol,
       before the expiry of its timeout interval using the
       val_remove_valpolicy() policy.

       The validator library reads configuration information from three
       separate files, resolv.conf, root.hints, and dnsval.conf.

           The nameserver and search options are supported in the resolv.conf

           This nameserver option is used to specify the IP address of the
           name server to which queries must be sent by default.  For example,


           A number of additional fields can be specified to qualify the name
           server. For example, in the following line:

               nameserver [][example.tsigkey:hmac-md5.sig-alg.reg.int:300:0jnu3SdsMvzzlmTDPYRceA==]:8053

           example.tsigkey refers to the TSIG key name;
           hmac-md5.sig-alg.reg.int refers to the TSIG algorithm, 300 is the
           TSIG fudge factor. and the key is specified as a base64 encoded
           value.  The value 8053 refers to the port number.

           The values for the TSIG algorithm and the fudge factor in the above
           example are the defaults. They may be omitted as follows:

               nameserver [][example.tsigkey:::0jnu3SdsMvzzlmTDPYRceA==]:8053

           The TSIG portion may also be left out entirely, in which case the
           representation is as follows:

               nameserver []:8053

           This search option is used to specify the search path for issuing
           queries.  For example,

               search test.dnssec-tools.org dnssec-tools.org

           The forward option is used to redirect queries for names that match
           a given zone name to the provided name server.  For example,

               forward test.dnssec-tools.org

           If the resolv.conf file contains no name servers, the validator
           tries to recursively answer the query using information present in

           The root.hints file contains bootstrapping information for the
           resolver while it attempts to recursively answer queries.  The
           contents of this file may be generated by the following command:

               dig @e.root-servers.net . ns > root.hints

           The dnsval.conf file contains the validator policy.  It consists of
           a sequence of the following "policy-fragments":

               <label> <keyword> <additional-data>;

           Policies are identified by simple text strings called labels, which
           must be unique within the configuration system.  For example,
           "browser" could be used as the label that defines the validator
           policy for all web-browsers in a system.  A label value of ":"
           identifies the default policy, the policy that is used when a NULL
           context is specified as the ctx parameter for interfaces listed in
           libval(3), val_getaddrinfo(3), and val_gethostbyname(3).  The
           default policy must be unique within the configuration system.

           keyword specifies the policy component within the policy fragment.
           The format of additional-data depends on the keyword specified.

           If multiple policy fragments are defined for the same label and
           keyword combination then the first definition in the file is used.

           The following keywords are defined for dnsval.conf:

               For the "trust-anchor" attribute additional-data is a sequence
               of ordered pairs, each consisting of the zone name and the
               RDATA portion for the trust anchor with an optional prefix.
               Trust anchors may be either DNSKEY or DS records, the prefix in
               the RDATA is use to indicate what type of record it is.  DNSKEY
               is assumed if no prefix is specified.

               An example is given below.

                   browser trust-anchor
                       .   DS  19036  8  2  \
                       example.com   257 3 5 AQO8XS4y9r77X 9SHBmrx MoJf1Pf9\
                           AT9Mr/L5BBGtO9/e9f/zl4FFgM2l B6M2 XEm6mp6 mit4tzp\
                           B/sAEQw1McYz6bJdKkTiqtuWTCfDmgQhI6 /Ha0 Ef GPNSqn\
                           Y 99FmbSeWNIRaa4fgSCVFhvbrYq1nXkNVy QPeEVHk oDNCA\
                           lr qOA3lw==

               For the "zone-security-expectation" attribute additional-data
               is a sequence of <domain name,value> tuples representing the
               security expectation for names in that domain, where value can
               be one of the following:

                   Ignore DNSSEC validation for names under this domain.

                   Perform DNSSEC validation of answers received for names
                   under this domain.

                   Reject all answers received for names under this domain.

               This zone-security-expectation DNSSEC validator policy
               construct makes it possible to define various islands of trust
               for DNSSEC-enabled zones and to ignore or validate data from
               selected zones. The default zone security expectation for a
               domain is "validate".  In the following example, for DNSSEC
               validator contexts created with a DNSSEC validator policy label
               of "browser", the DNSSEC validation is only performed for names
               under the example.com domain; names under the somebogus.org
               domain are always considered to be untrusted and DNSSEC
               validation for all other domain names is ignored.

                   browser zone-security-expectation
                       example.com  validate
                       somebogusname.org untrusted
                       . ignore

               For the "provably-insecure-status" attribute additional-data is
               a sequence of  <domain name,value> tuples representing the
               validity of the provably insecure condition, where value is one
               of the following:

                   Treat the provably insecure condition as valid.

                   Treat the provably insecure condition as invalid.

               The default value for the provably insecure status for a domain
               is "trusted".  In the following example, for DNSSEC validator
               contexts created with the default label, the provably insecure
               condition is treated as valid for all domains except the net
               domain, where this condition is treated as invalid.

                   : provably-insecure-status
                       . trusted
                       net untrusted

               For the "clock-skew" attribute additional-data is a sequence of
               the domain name and the number of seconds of clock-skew
               acceptable for signatures on names in that domain. A clock skew
               value of -1 has the effect of turning off inception and
               expiration time checks on signatures from that domain. The
               default clock skew is 0.  In the following example, for DNSSEC
               validator contexts created with the "mta" label, signature
               inception and expiration checks are disabled for all names
               under the example.com domain.

                   mta clock-skew
                       example.com -1

           nsec3-max-iter [only if LIBVAL_NSEC3 is enabled]
               Specifies the maximum number of iterations allowable while
               computing the NSEC3 hash for a zone.  A value of -1 does not
               place a maximum limit on the number of iterations.  This is
               also the default setting for a zone.

           dlv-trust-points [only if LIBVAL_DLV is enabled]
               Specifies the DLV tree for the target zone. In the following
               example, libval will use the DLV registry defined at
               dlv.isc.org. for all queries under the root that do not give us
               a trustworthy answer using the normal DNSSEC mechanism, and
               have a zone-security-expectation of validate.

                   dlv dlv-trust-points
                       .   dlv.isc.org.

               In order for DLV to be used in the above example, there must
               also be a trust-anchor policy defined for the dlv registry,
               with the zone-security-expectation policy for registry set to

                   dlv trust-anchor
                       dlv.isc.org DS  19297  5  2  \

           Apart from zone-specific configuration options, it is also possible
           to configure global options for the validation in dnsval.conf.
           Global options can be specified using the construct below.

                   keyowrd1 value1
                   keyword2 value2

           There can only be one global-options construct defined for
           dnsval.conf.  If multiple constructs are defined, only the first is

           The following keywords are defined for global-options in

               This option has been deprecated. Use trust-oob-answers instead.

               If the value against this option is yes then, for all answers
               returned using some out-of-band mechanism (e.g. a file store
               such as /etc/hosts), the value returned from the
               val_istrusted() function (see libval(3)) is greater than one.

               In querying various name servers, libsres will also attempt
               multiple EDNS0 sizes, ending with a query that has EDNS0
               disabled (i.e. no CD bit set).  The following EDNS0 sizes are
               tried by default: 4096, 1492, 512 The "edns0-size" policy knob
               can be used to change the largest EDNS0 size that is attempted.

               This option allows the administrator of the dnsval.conf to
               control whether libval uses user-specified values in
               environmental variables while determining libval policy and log
               targets. See the section below on overriding dnsval.conf
               policies for additional details on this option.

               This option allows the administrator of the dnsval.conf file to
               control whether libval will automatically look for a validation
               policy with a label equal to the application name in
               dnsval.conf. See the section below on overriding dnsval.conf
               policies for additional details on this option.

               The default validation behavior is to look for any
               authentication chain that validates successfully. Thus if there
               are trust anchors for example.com and test.example.com the
               validator will return success if the authentication chain can
               be anchored to the example.com trust anchor, even if the trust
               anchor for test.example.com does not match. In cases where this
               is not desirable, the closest-ta-only option can be used.

               If this option is set to yes then the validation algorithm
               terminates at the closest matching TA.

               This option is used to control whether libval will attempt to
               fall back to a recursive lookup of the name if the response
               from the caching name server returned an error. By default this
               options is set to yes; it can be turned off by setting this
               option to no.

               This option is used in conjunction with the
               VAL_QUERY_SKIP_CACHE query flag. When queries have this flag
               enabled they would normally skip cached entries. However, max-
               refresh can throttle how often queries are actually sent on the
               wire. Whe this option is set to a positive value a new query is
               only sent out if the cached value was stored more than (the
               value specified by) max-refresh seconds ago. If max-refresh is
               0, then the cache is always skipped. If the value is -1 the
               cache is never skipped. The default value for max-refresh is 60
               seconds. That means that two queries sent with the the
               VAL_QUERY_SKIP_CACHE flag set less than a minute apart will
               only result in one query seen on the wire.

               This option is used to control the network protocol that libval
               uses to send queries out to various name servers. If the value
               is set to ipv6, libval uses only IPv6; if it is set to ipv4
               libval uses only IPv4. The default is any, which causes libval
               to send over any of the available protocols for the given name

               This option overrides the default resolver timeout value with
               the value provided.

               This option overrides the default resolver retry value with the
               value provided.

           log This option controls the level of logging and the log target
               for libval.  The value expected against this option is the same
               as that specified for val_add_log_optarg (see libval(3)).

           An example global-options construct is given below:

                   trust-oob-answers yes
                   edns0-size 4096
                   env-policy enable
                   app-policy enable
                   log 5:stderr

       libval first looks at resolver options present in the resolv.conf file
       specfied at the time of running configure. If this file is absent,
       libval looks at /etc/resolv.conf file for resolver options.

       This allows users with a simple way of overriding resolver policies.
       The system-specific resolv.conf can remain unchanged, while any
       additional policies that may have to be specified for libval can be
       used in the configure-supplied resolv.conf file.

       libval provides three ways for tailoring dnsval.conf policies for a
       given environment.

       Multiple include files
           libval allows additional dnsval.conf files to be included with a
           given dnsval.conf file.  The option is specified as follows:

               include /path/to/override/file/dnsval.conf

           The files are read in breadth-first. The policies are evaluated in
           a manner that gives the last-defined policy more precedence over
           earlier ones. Therefore, an administrator may supply a dnsval.conf
           with default policies including another file from the user's home
           directory. The included file may be used for overriding policies
           specified in the base dnsval.conf file.

       Application-name policies
           If the app-policy global option is not disabled, libval
           automatically looks for a policy in dnsval.conf with a label value
           constructed from the name of the application.  For example,
           dnsval.conf may be defined with validator policies for the foo
           label.  The foo application, when run, will use the policy defined
           against the foo label during its validation operation.

       Policies through environment
           If the env-policy global option is not disabled, libval looks at
           the VAL_CONTEXT_LABEL and VAL_LOG_TARGET environmental variables in
           order to determine the validator policy label and log target.

       Validator Label Precedence
           There are effectively four different types of polic-labels that can
           be applied by libval: application-name policies, policies through
           VAL_CONTEXT_LABEL, and labels specified by the application (either
           NULL or non-NULL). The precedence of applying these labels is
           defined with the following rules:

           1. If env-policy is "override", use the label specified in the
           VAL_CONTEXT_LABEL env variable (if defined).

           2. If env-policy is "enable" and the policy specified by the
           application  is NULL, use the label specified in the
           VAL_CONTEXT_LABEL env variable (if defined).

           3. if app-policy is "override", use the label generated from the
           application name.  If this policy label does not exist in the
           configuration system, use the default policy.

           4. if app-policy is "enable" and the policy specified by the
           application is NULL, use the label generated from the application

           5. If policy specified by the application is not NULL, use this

           6. Use default policy

           The following use-cases can therefore be defined

           locked-down system with single policy
               An administrator that wants to (and is able to) lock down a
               system to a particular validator policy, must set the env-
               policy and app-policy global options to disable.  This also
               requires that administrators are able to lock down the system
               to specific applications and that these applications are not
               written in a way that would allow them to specify non-NULL
               policy labels during context creation. (see val_create_context
               in libval(3)).

           locked-down system with app-specific policies
               An administrator that wants to (and is able to) lock down a
               system to a particular dnsval.conf file, but wishes to use
               different policies for different applications must set the app-
               policy to override and the env-policy to disable. The
               administrator must also define policies for various application
               names in dnval.conf; for applications that don't have a policy
               with a label corresponding to its name, the default policy is

               The administrator may set the app-policy to enable if non-NULL
               policies specified by the application during validator context
               creation is deemed acceptable.

           User controlled
               An administrator can set env-policy to override to give the
               user complete control over which policy label is used during
               validation. The validation policy is read through the
               VAL_CONTEXT_LABEL environment variable.

               If VAL_CONTEXT_LABEL is specified globally for the system, the
               administrator may instead choose the env-policy global option
               to be enable instead of override. In this case, the label given
               in VAL_CONTEXT_LABEL is used only when the policy specified by
               the application is non-NULL.

               The label in VAL_CONTEXT_LABEL is used only if it is defined.
               If this value is NULL, libval will read other policy labels as
               guided by the precedence rules listed above.




       Copyright 2004-2013 SPARTA, Inc.  All rights reserved.  See the COPYING
       file included with the dnssec-tools package for details.


       http://www.dnssec-tools.org http://www.dnssec-tools.org

perl v5.26.2                      2018-08-08                    dnsval.conf(3)