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@ -20,11 +20,11 @@ Expires: 29 October 2024
Abstract Abstract
This document describes a common output format of Passive DNS Servers This document describes a common output format of Passive DNS Servers
that clients can query. The output format description also includes which clients can query. The output format description includes also
a common semantic for each Passive DNS system. By having multiple in addition a common semantic for each Passive DNS system. By having
Passive DNS Systems adhere to the same output format for queries, multiple Passive DNS Systems adhere to the same output format for
users of multiple Passive DNS servers will be able to combine result queries, users of multiple Passive DNS servers will be able to
sets easily. combine result sets easily.
Status of This Memo Status of This Memo
@ -118,20 +118,20 @@ Internet-Draft Passive DNS - Common Output Format April 2024
Passive DNS is a technique described by Florian Weimer in 2005 in Passive DNS is a technique described by Florian Weimer in 2005 in
Passive DNS replication, F Weimer - 17th Annual FIRST Conference on Passive DNS replication, F Weimer - 17th Annual FIRST Conference on
Computer Security [WEIMERPDNS]. Since then, multiple Passive DNS Computer Security [WEIMERPDNS]. Since then multiple Passive DNS
implementations were created and have evolved over time. Users of implementations were created and evolved over time. Users of these
these Passive DNS servers may query a server (often via WHOIS Passive DNS servers may query a server (often via WHOIS [RFC3912] or
[RFC3912] or HTTP REST [REST]), parse the results, and process them HTTP REST [REST]), parse the results and process them in other
in other applications. applications.
There are multiple implementations of Passive DNS software. Users of There are multiple implementations of Passive DNS software. Users of
Passive DNS query each implementation and aggregate the results for passive DNS query each implementation and aggregate the results for
their search. This document describes the output format of four their search. This document describes the output format of four
Passive DNS Systems ([DNSDB], [DNSDBQ], [PDNSCERTAT], [PDNSCIRCL] and Passive DNS Systems ([DNSDB], [DNSDBQ], [PDNSCERTAT], [PDNSCIRCL] and
[PDNSCOF]) that are in use today and that already share a nearly [PDNSCOF]) which are in use today and which already share a nearly
identical output format. As the format and the meaning of output identical output format. As the format and the meaning of output
fields from each Passive DNS need to be consistent, this document fields from each Passive DNS need to be consistent, we propose in
proposes a solution to commonly name each field along with its this document a solution to commonly name each field along with their
corresponding interpretation. The format follows a simple key-value corresponding interpretation. The format follows a simple key-value
structure in JSON [RFC4627] format. The benefit of having a structure in JSON [RFC4627] format. The benefit of having a
consistent Passive DNS output format is that multiple client consistent Passive DNS output format is that multiple client
@ -141,8 +141,8 @@ Internet-Draft Passive DNS - Common Output Format April 2024
standardization. The document does not describe the protocol (e.g. standardization. The document does not describe the protocol (e.g.
WHOIS [RFC3912], HTTP REST [REST]) nor the query format used to query WHOIS [RFC3912], HTTP REST [REST]) nor the query format used to query
the Passive DNS. Neither does this document describe "pre-recursor" the Passive DNS. Neither does this document describe "pre-recursor"
Passive DNS Systems. Each of these are separate topics and deserve Passive DNS Systems. Both of these are separate topics and deserve
their own RFC documents. This document describes the current best their own RFC document. The document describes the current best
practices implemented in various Passive DNS server implementations. practices implemented in various Passive DNS server implementations.
1.1. Requirements Language 1.1. Requirements Language
@ -153,15 +153,15 @@ Internet-Draft Passive DNS - Common Output Format April 2024
2. Limitation 2. Limitation
As Passive DNS servers can include protection mechanisms for their As a Passive DNS servers can include protection mechanisms for their
operation, results might be different due to those protection operation, results might be different due to those protection
measures. These mechanisms filter out DNS answers if they fail some measures. These mechanisms filter out DNS answers if they fail some
criteria. The bailiwick algorithm [BAILIWICK] protects the Passive criteria. The bailiwick algorithm [BAILIWICK] protects the Passive
DNS Database from cache poisoning attacks [CACHEPOISONING]. Another DNS Database from cache poisoning attacks [CACHEPOISONING]. Another
limitation that clients querying the database need to be aware of is limitation that clients querying the database need to be aware of is
that each query simply gets a snapshot-in-time answer at the time of that each query simply gets a snapshot-answer of the time of
querying. Clients MUST NOT rely on existing answers from different querying. Clients MUST NOT rely on consistent answers. Nor must
Passive DNS database. Nor should they assume that answers will be they assume that answers must be identical across multiple Passive
@ -170,7 +170,7 @@ Dulaunoy, et al. Expires 29 October 2024 [Page 3]
Internet-Draft Passive DNS - Common Output Format April 2024 Internet-Draft Passive DNS - Common Output Format April 2024
identical across multiple Passive DNS Servers. DNS Servers.
3. Common Output Format 3. Common Output Format
@ -226,9 +226,9 @@ Dulaunoy, et al. Expires 29 October 2024 [Page 4]
Internet-Draft Passive DNS - Common Output Format April 2024 Internet-Draft Passive DNS - Common Output Format April 2024
Note that value is defined in JSON [RFC4627] and has the same Note that value is defined in JSON [RFC4627] and has the exact same
specification as there. The same goes for the definition of string. specification as there. The same goes for the definition of string.
Note the changed definition of ws does not include CR or LF as those Note the changed definition of ws dows not include CR or LF as those
are NOT allowed in NDJSON, and thus the definition here MUST be used are NOT allowed in NDJSON, and thus the definition here MUST be used
for other ABNF defitions in JSON [RFC4627]. for other ABNF defitions in JSON [RFC4627].
@ -433,7 +433,7 @@ Internet-Draft Passive DNS - Common Output Format April 2024
6. Privacy Considerations 6. Privacy Considerations
Passive DNS Servers capture DNS answers from multiple collection Passive DNS Servers capture DNS answers from multiple collecting
points ("sensors") which are located on the Internet-facing side of points ("sensors") which are located on the Internet-facing side of
DNS recursors ("post-recursor passive DNS"). In this process, they DNS recursors ("post-recursor passive DNS"). In this process, they
intentionally omit the source IP, source port, destination IP and intentionally omit the source IP, source port, destination IP and
@ -451,15 +451,15 @@ Internet-Draft Passive DNS - Common Output Format April 2024
Servers are able to find out much about the actual person querying Servers are able to find out much about the actual person querying
the DNS records. In this sense, passive DNS Servers are similar to the DNS records nor who actually sent the query. In this sense,
keeping an archive of all previous phone books - if public DNS passive DNS Servers are similar to keeping an archive of all previous
records can be compared to phone numbers - as they often are. phone books - if public DNS records can be compared to phone numbers
Nevertheless, the authors strongly encourage Passive DNS implementors - as they often are. Nevertheless, the authors strongly encourage
to take special care of privacy issues. bortzmeyer-dnsop-dns-privacy Passive DNS implementors to take special care of privacy issues.
is an excellent starting point for this. Finally, the overall bortzmeyer-dnsop-dns-privacy is an excellent starting point for this.
recommendations in RFC6973 [RFC6973] should be taken into Finally, the overall recommendations in RFC6973 [RFC6973] should be
consideration when designing any application which uses Passive DNS taken into consideration when designing any application which uses
data. Passive DNS data.
In the scope of the General Data Protection Regulation (GDPR - In the scope of the General Data Protection Regulation (GDPR -
Directive 95/46/EC), operators of Passive DNS Server needs to ensure Directive 95/46/EC), operators of Passive DNS Server needs to ensure

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@ -144,21 +144,21 @@
<abstract> <abstract>
<t>This document describes a common output format of Passive DNS Servers that clients can query. The output format description also includes a common semantic for each Passive DNS system. By having multiple Passive DNS Systems adhere to the same output format for queries, users of multiple Passive DNS servers will be able to combine result sets easily.</t> <t>This document describes a common output format of Passive DNS Servers which clients can query. The output format description includes also in addition a common semantic for each Passive DNS system. By having multiple Passive DNS Systems adhere to the same output format for queries, users of multiple Passive DNS servers will be able to combine result sets easily.</t>
</abstract> </abstract>
</front> </front>
<middle> <middle>
<section title="Introduction"> <section title="Introduction">
<t>Passive DNS is a technique described by Florian Weimer in 2005 in <xref target="WEIMERPDNS">Passive DNS replication, F Weimer - 17th Annual FIRST Conference on Computer Security</xref>. Since then, multiple Passive DNS implementations were created and have evolved over time. Users of these Passive DNS servers may query a server (often via <xref target="RFC3912">WHOIS</xref> or HTTP <xref target="REST">REST</xref>), parse the results, and process them in other applications.</t> <t>Passive DNS is a technique described by Florian Weimer in 2005 in <xref target="WEIMERPDNS">Passive DNS replication, F Weimer - 17th Annual FIRST Conference on Computer Security</xref>. Since then multiple Passive DNS implementations were created and evolved over time. Users of these Passive DNS servers may query a server (often via <xref target="RFC3912">WHOIS</xref> or HTTP <xref target="REST">REST</xref>), parse the results and process them in other applications.</t>
<t> <t>
There are multiple implementations of Passive DNS software. Users of Passive DNS query each implementation and aggregate the results for their search. This document describes the output format of four Passive DNS Systems (<xref target="DNSDB"/>, <xref target="DNSDBQ"/>, <xref target="PDNSCERTAT"/>, <xref target="PDNSCIRCL"/> and <xref target="PDNSCOF"/>) that are in use today and that already share a nearly identical output format. There are multiple implementations of Passive DNS software. Users of passive DNS query each implementation and aggregate the results for their search. This document describes the output format of four Passive DNS Systems (<xref target="DNSDB"/>, <xref target="DNSDBQ"/>, <xref target="PDNSCERTAT"/>, <xref target="PDNSCIRCL"/> and <xref target="PDNSCOF"/>) which are in use today and which already share a nearly identical output format.
As the format and the meaning of output fields from each Passive DNS need to be consistent, this document proposes a solution to commonly name each field along with its corresponding interpretation. The format follows a simple key-value structure in <xref target="RFC4627">JSON</xref> format. As the format and the meaning of output fields from each Passive DNS need to be consistent, we propose in this document a solution to commonly name each field along with their corresponding interpretation. The format follows a simple key-value structure in <xref target="RFC4627">JSON</xref> format.
The benefit of having a consistent Passive DNS output format is that multiple client implementations can query different servers without having to have a separate parser for each The benefit of having a consistent Passive DNS output format is that multiple client implementations can query different servers without having to have a separate parser for each
individual server. <xref target="PDNSCLIENT">passivedns-client</xref> currently implements multiple parsers due to a lack of standardization. individual server. <xref target="PDNSCLIENT">passivedns-client</xref> currently implements multiple parsers due to a lack of standardization.
The document does not describe the protocol (e.g. <xref target="RFC3912">WHOIS</xref>, HTTP <xref target="REST">REST</xref>) nor the query format used to query the Passive DNS. Neither does this document describe "pre-recursor" Passive DNS Systems. Each of these are separate topics and deserve their own RFC documents. This document describes the current best practices implemented in various Passive DNS server implementations. The document does not describe the protocol (e.g. <xref target="RFC3912">WHOIS</xref>, HTTP <xref target="REST">REST</xref>) nor the query format used to query the Passive DNS. Neither does this document describe "pre-recursor" Passive DNS Systems. Both of these are separate topics and deserve their own RFC document. The document describes the current best practices implemented in various Passive DNS server implementations.
</t> </t>
<section title="Requirements Language"> <section title="Requirements Language">
@ -170,9 +170,9 @@ The document does not describe the protocol (e.g. <xref target="RFC3912">WHOIS</
</section> </section>
<section title="Limitation"> <section title="Limitation">
<t> As Passive DNS servers can include protection mechanisms for their operation, results might be different due to those protection measures. These mechanisms filter out DNS answers if they fail some criteria. The <xref target="BAILIWICK">bailiwick algorithm</xref> protects the Passive DNS Database from <xref target="CACHEPOISONING">cache poisoning attacks</xref>. <t> As a Passive DNS servers can include protection mechanisms for their operation, results might be different due to those protection measures. These mechanisms filter out DNS answers if they fail some criteria. The <xref target="BAILIWICK">bailiwick algorithm</xref> protects the Passive DNS Database from <xref target="CACHEPOISONING">cache poisoning attacks</xref>.
Another limitation that clients querying the database need to be aware of is that each query simply gets a snapshot-in-time answer at the time of querying. Clients MUST NOT rely on existing answers from different Passive DNS database. Nor should they assume that answers will be identical across multiple Passive DNS Servers. Another limitation that clients querying the database need to be aware of is that each query simply gets a snapshot-answer of the time of querying. Clients MUST NOT rely on consistent answers. Nor must they assume that answers must be identical across multiple Passive DNS Servers.
</t> </t>
</section> </section>
<section title="Common Output Format"> <section title="Common Output Format">
@ -206,7 +206,7 @@ ws = *(
) )
]]></artwork></figure> ]]></artwork></figure>
<t>Note that value is defined in <xref target="RFC4627">JSON</xref> and has the same specification as there. The same goes for the definition of string. Note the changed definition of ws does not include CR or LF as those are NOT allowed in NDJSON, and thus the definition here MUST be used for other ABNF defitions in <xref target="RFC4627">JSON</xref>.</t> <t>Note that value is defined in <xref target="RFC4627">JSON</xref> and has the exact same specification as there. The same goes for the definition of string. Note the changed definition of ws dows not include CR or LF as those are NOT allowed in NDJSON, and thus the definition here MUST be used for other ABNF defitions in <xref target="RFC4627">JSON</xref>.</t>
</section> </section>
<section title="Mandatory Fields"> <section title="Mandatory Fields">
<t>Implementation MUST support all the mandatory fields.</t> <t>Implementation MUST support all the mandatory fields.</t>
@ -297,7 +297,7 @@ ws = *(
</section> </section>
<section anchor="Privacy" title="Privacy Considerations"> <section anchor="Privacy" title="Privacy Considerations">
<t>Passive DNS Servers capture DNS answers from multiple collection points ("sensors") which are located on the Internet-facing side of DNS recursors ("post-recursor passive DNS"). In this process, they intentionally omit the source IP, source port, destination IP and destination port from the captured packets. Since the data is captured "post-recursor", the timing information (who queries what) is lost, since the recursor will cache the results. Furthermore, since multiple sensors feed into a passive DNS server, the resulting data gets mixed together, reducing the likelihood that Passive DNS Servers are able to find out much about the actual person querying the DNS records. In this sense, passive DNS Servers are similar to keeping an archive of all previous phone books - if public DNS records can be compared to phone numbers - as they often are. <t>Passive DNS Servers capture DNS answers from multiple collecting points ("sensors") which are located on the Internet-facing side of DNS recursors ("post-recursor passive DNS"). In this process, they intentionally omit the source IP, source port, destination IP and destination port from the captured packets. Since the data is captured "post-recursor", the timing information (who queries what) is lost, since the recursor will cache the results. Furthermore, since multiple sensors feed into a passive DNS server, the resulting data gets mixed together, reducing the likelihood that Passive DNS Servers are able to find out much about the actual person querying the DNS records nor who actually sent the query. In this sense, passive DNS Servers are similar to keeping an archive of all previous phone books - if public DNS records can be compared to phone numbers - as they often are.
Nevertheless, the authors strongly encourage Passive DNS implementors to take special care of privacy issues. bortzmeyer-dnsop-dns-privacy is an excellent starting point for this. Nevertheless, the authors strongly encourage Passive DNS implementors to take special care of privacy issues. bortzmeyer-dnsop-dns-privacy is an excellent starting point for this.
Finally, the overall recommendations in <xref target="RFC6973">RFC6973</xref> should be taken into consideration when designing any application which uses Passive DNS data.</t> Finally, the overall recommendations in <xref target="RFC6973">RFC6973</xref> should be taken into consideration when designing any application which uses Passive DNS data.</t>