security.txt: A File Format to Aid in Security Vulnerability Disclosure

Internet Engineering Task Force (IETF)                         E. Foudil
Request for Comments: 9116
Category: Informational                                  Y. Shafranovich
ISSN: 2070-1721                                 Nightwatch Cybersecurity
                                                              April 2022


       A File Format to Aid in Security Vulnerability Disclosure

Abstract

   When security vulnerabilities are discovered by researchers, proper
   reporting channels are often lacking.  As a result, vulnerabilities
   may be left unreported.  This document defines a machine-parsable
   format ("security.txt") to help organizations describe their
   vulnerability disclosure practices to make it easier for researchers
   to report vulnerabilities.

Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for informational purposes.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Not all documents
   approved by the IESG are candidates for any level of Internet
   Standard; see Section 2 of RFC 7841.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   https://www.rfc-editor.org/info/rfc9116.

Copyright Notice

   Copyright (c) 2022 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Revised BSD License text as described in Section 4.e of the
   Trust Legal Provisions and are provided without warranty as described
   in the Revised BSD License.

Table of Contents

   1.  Introduction
     1.1.  Motivation, Prior Work, and Scope
     1.2.  Terminology
   2.  The Specification
     2.1.  Comments
     2.2.  Line Separator
     2.3.  Digital Signature
     2.4.  Extensibility
     2.5.  Field Definitions
       2.5.1.  Acknowledgments
       2.5.2.  Canonical
       2.5.3.  Contact
       2.5.4.  Encryption
       2.5.5.  Expires
       2.5.6.  Hiring
       2.5.7.  Policy
       2.5.8.  Preferred-Languages
     2.6.  Example of an Unsigned "security.txt" File
     2.7.  Example of a Signed "security.txt" File
   3.  Location of the security.txt File
     3.1.  Scope of the File
   4.  File Format Description and ABNF Grammar
   5.  Security Considerations
     5.1.  Compromised Files and Incident Response
     5.2.  Redirects
     5.3.  Incorrect or Stale Information
     5.4.  Intentionally Malformed Files, Resources, and Reports
     5.5.  No Implied Permission for Testing
     5.6.  Multi-User Environments
     5.7.  Protecting Data in Transit
     5.8.  Spam and Spurious Reports
   6.  IANA Considerations
     6.1.  Well-Known URIs Registry
     6.2.  Registry for security.txt Fields
   7.  References
     7.1.  Normative References
     7.2.  Informative References
   Acknowledgments
   Authors' Addresses

1.  Introduction

1.1.  Motivation, Prior Work, and Scope

   Many security researchers encounter situations where they are unable
   to report security vulnerabilities to organizations because there are
   no reporting channels to contact the owner of a particular resource,
   and no information is available about the vulnerability disclosure
   practices of such owner.

   As per Section 4 of [RFC2142], there is an existing convention of
   using the <SECURITY@domain> email address for communications
   regarding security issues.  That convention provides only a single,
   email-based channel of communication per domain and does not provide
   a way for domain owners to publish information about their security
   disclosure practices.

   There are also contact conventions prescribed for Internet Service
   Providers (ISPs) in Section 2 of [RFC3013], for Computer Security
   Incident Response Teams (CSIRTs) in Section 3.2 of [RFC2350], and for
   site operators in Section 5.2 of [RFC2196].  As per [RFC7485], there
   is also contact information provided by Regional Internet Registries
   (RIRs) and domain registries for owners of IP addresses, Autonomous
   System Numbers (ASNs), and domain names.  However, none of these
   tackle the issue of how security researchers can locate contact
   information and vulnerability disclosure practices for organizations
   in order to report vulnerabilities.

   In this document, we define a richer, machine-parsable, and more
   extensible way for organizations to communicate information about
   their security disclosure practices and ways to contact them.  Other
   details of vulnerability disclosure are outside the scope of this
   document.  Readers are encouraged to consult other documents such as
   [ISO.29147.2018] or [CERT.CVD].

   As per [CERT.CVD], "vulnerability response" refers to reports of
   product vulnerabilities, which is related to but distinct from
   reports of network intrusions and compromised websites ("incident
   response").  The mechanism defined in this document is intended to be
   used for the former ("vulnerability response").  If implementors want
   to utilize this mechanism for incident response, they should be aware
   of additional security considerations discussed in Section 5.1.

   The "security.txt" file is intended to be complementary and not a
   substitute or replacement for other public resources maintained by
   organizations regarding their security disclosure practices.

1.2.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

   The term "researcher" corresponds to the terms "finder" and
   "reporter" in [ISO.29147.2018] and [CERT.CVD].  The term
   "organization" corresponds to the term "vendor" in [ISO.29147.2018]
   and [CERT.CVD].

   The term "implementors" includes all parties involved in the
   vulnerability disclosure process.

2.  The Specification

   This document defines a text file to be placed in a known location
   that provides information about vulnerability disclosure practices of
   a particular organization.  The format of this file is machine
   parsable and MUST follow the ABNF grammar defined in Section 4.  This
   file is intended to help security researchers when disclosing
   security vulnerabilities.

   By convention, the file is named "security.txt".  The location and
   scope are described in Section 3.

   This text file contains multiple fields with different values.  A
   field contains a "name", which is the first part of a field all the
   way up to the colon (for example: "Contact:") and follows the syntax
   defined for "field-name" in Section 3.6.8 of [RFC5322].  Field names
   are case insensitive (as per Section 2.3 of [RFC5234]).  The "value"
   comes after the field name (for example:
   "mailto:security@example.com") and follows the syntax defined for
   "unstructured" in Section 3.2.5 of [RFC5322].  The file MAY also
   contain blank lines.

   A field MUST always consist of a name and a value (for example:
   "Contact: mailto:security@example.com").  A "security.txt" file can
   have an unlimited number of fields.  Each field MUST appear on its
   own line.  Unless otherwise specified by the field definition,
   multiple values MUST NOT be chained together for a single field.
   Unless otherwise indicated in a definition of a particular field, a
   field MAY appear multiple times.

   Implementors should be aware that some of the fields may contain URIs
   using percent-encoding (as per Section 2.1 of [RFC3986]).

2.1.  Comments

   Any line beginning with the "#" (%x23) symbol MUST be interpreted as
   a comment.  The content of the comment may contain any ASCII or
   Unicode characters in the %x21-7E and %x80-FFFFF ranges plus the tab
   (%x09) and space (%x20) characters.

   Example:

   # This is a comment.

2.2.  Line Separator

   Every line MUST end with either a carriage return and line feed
   characters (CRLF / %x0D %x0A) or just a line feed character (LF /
   %x0A).

2.3.  Digital Signature

   It is RECOMMENDED that a "security.txt" file be digitally signed
   using an OpenPGP cleartext signature as described in Section 7 of
   [RFC4880].  When digital signatures are used, it is also RECOMMENDED
   that organizations use the "Canonical" field (as per Section 2.5.2),
   thus allowing the digital signature to authenticate the location of
   the file.

   When it comes to verifying the key used to generate the signature, it
   is always the security researcher's responsibility to make sure the
   key being used is indeed one they trust.

2.4.  Extensibility

   Like many other formats and protocols, this format may need to be
   changed over time to fit the ever-changing landscape of the Internet.
   Therefore, extensibility is provided via an IANA registry for fields
   as defined in Section 6.2.  Any fields registered via that process
   MUST be considered optional.  To encourage extensibility and
   interoperability, researchers MUST ignore any fields they do not
   explicitly support.

   In general, implementors should "be conservative in what you do, be
   liberal in what you accept from others" (as per [RFC0793]).

2.5.  Field Definitions

   Unless otherwise stated, all fields MUST be considered optional.

2.5.1.  Acknowledgments

   The "Acknowledgments" field indicates a link to a page where security
   researchers are recognized for their reports.  The page being
   referenced should list security researchers that reported security
   vulnerabilities and collaborated to remediate them.  Organizations
   should be careful to limit the vulnerability information being
   published in order to prevent future attacks.

   If this field indicates a web URI, then it MUST begin with "https://"
   (as per Section 2.7.2 of [RFC7230]).

   Example:

   Acknowledgments: https://example.com/hall-of-fame.html

   Example security acknowledgments page:

   We would like to thank the following researchers:

   (2017-04-15) Frank Denis - Reflected cross-site scripting
   (2017-01-02) Alice Quinn  - SQL injection
   (2016-12-24) John Buchner - Stored cross-site scripting
   (2016-06-10) Anna Richmond - A server configuration issue

2.5.2.  Canonical

   The "Canonical" field indicates the canonical URIs where the
   "security.txt" file is located, which is usually something like
   "https://example.com/.well-known/security.txt".  If this field
   indicates a web URI, then it MUST begin with "https://" (as per
   Section 2.7.2 of [RFC7230]).

   While this field indicates that a "security.txt" retrieved from a
   given URI is intended to apply to that URI, it MUST NOT be
   interpreted to apply to all canonical URIs listed within the file.
   Researchers SHOULD use an additional trust mechanism such as a
   digital signature (as per Section 2.3) to make the determination that
   a particular canonical URI is applicable.

   If this field appears within a "security.txt" file and the URI used
   to retrieve that file is not listed within any canonical fields, then
   the contents of the file SHOULD NOT be trusted.

   Canonical: https://www.example.com/.well-known/security.txt
   Canonical: https://someserver.example.com/.well-known/security.txt

2.5.3.  Contact

   The "Contact" field indicates a method that researchers should use
   for reporting security vulnerabilities such as an email address, a
   phone number, and/or a web page with contact information.  This field
   MUST always be present in a "security.txt" file.  If this field
   indicates a web URI, then it MUST begin with "https://" (as per
   Section 2.7.2 of [RFC7230]).  Security email addresses should use the
   conventions defined in Section 4 of [RFC2142].

   The value MUST follow the URI syntax described in Section 3 of
   [RFC3986].  This means that "mailto" and "tel" URI schemes must be
   used when specifying email addresses and telephone numbers, as
   defined in [RFC6068] and [RFC3966].  When the value of this field is
   an email address, it is RECOMMENDED that encryption be used (as per
   Section 2.5.4).

   These SHOULD be listed in order of preference, with the first
   occurrence being the preferred method of contact, the second
   occurrence being the second most preferred method of contact, etc.
   In the example below, the first email address
   ("security@example.com") is the preferred method of contact.

   Contact: mailto:security@example.com
   Contact: mailto:security%2Buri%2Bencoded@example.com
   Contact: tel:+1-201-555-0123
   Contact: https://example.com/security-contact.html

2.5.4.  Encryption

   The "Encryption" field indicates an encryption key that security
   researchers should use for encrypted communication.  Keys MUST NOT
   appear in this field.  Instead, the value of this field MUST be a URI
   pointing to a location where the key can be retrieved.  If this field
   indicates a web URI, then it MUST begin with "https://" (as per
   Section 2.7.2 of [RFC7230]).

   When it comes to verifying the authenticity of the key, it is always
   the security researcher's responsibility to make sure the key being
   specified is indeed one they trust.  Researchers must not assume that
   this key is used to generate the digital signature referenced in
   Section 2.3.

   Example of an OpenPGP key available from a web server:

   Encryption: https://example.com/pgp-key.txt

   Example of an OpenPGP key available from an OPENPGPKEY DNS record:

Encryption: dns:5d2d37ab76d47d36._openpgpkey.example.com?type=OPENPGPKEY

   Example of an OpenPGP key being referenced by its fingerprint:

   Encryption: openpgp4fpr:5f2de5521c63a801ab59ccb603d49de44b29100f

2.5.5.  Expires

   The "Expires" field indicates the date and time after which the data
   contained in the "security.txt" file is considered stale and should
   not be used (as per Section 5.3).  The value of this field is
   formatted according to the Internet profiles of [ISO.8601-1] and
   [ISO.8601-2] as defined in [RFC3339].  It is RECOMMENDED that the
   value of this field be less than a year into the future to avoid
   staleness.

   This field MUST always be present and MUST NOT appear more than once.

   Expires: 2021-12-31T18:37:07z

2.5.6.  Hiring

   The "Hiring" field is used for linking to the vendor's security-
   related job positions.  If this field indicates a web URI, then it
   MUST begin with "https://" (as per Section 2.7.2 of [RFC7230]).

   Hiring: https://example.com/jobs.html

2.5.7.  Policy

   The "Policy" field indicates a link to where the vulnerability
   disclosure policy is located.  This can help security researchers
   understand the organization's vulnerability reporting practices.  If
   this field indicates a web URI, then it MUST begin with "https://"
   (as per Section 2.7.2 of [RFC7230]).

   Example:

   Policy: https://example.com/disclosure-policy.html

2.5.8.  Preferred-Languages

   The "Preferred-Languages" field can be used to indicate a set of
   natural languages that are preferred when submitting security
   reports.  This set MAY list multiple values, separated by commas.  If
   this field is included, then at least one value MUST be listed.  The
   values within this set are language tags (as defined in [RFC5646]).
   If this field is absent, security researchers may assume that English
   is the language to be used (as per Section 4.5 of [RFC2277]).

   The order in which they appear is not an indication of priority; the
   listed languages are intended to have equal priority.

   This field MUST NOT appear more than once.

   Example (English, Spanish and French):

   Preferred-Languages: en, es, fr

2.6.  Example of an Unsigned "security.txt" File

   # Our security address
   Contact: mailto:security@example.com

   # Our OpenPGP key
   Encryption: https://example.com/pgp-key.txt

   # Our security policy
   Policy: https://example.com/security-policy.html

   # Our security acknowledgments page
   Acknowledgments: https://example.com/hall-of-fame.html

   Expires: 2021-12-31T18:37:07z

2.7.  Example of a Signed "security.txt" File

   -----BEGIN PGP SIGNED MESSAGE-----
   Hash: SHA256

   # Canonical URI
   Canonical: https://example.com/.well-known/security.txt

   # Our security address
   Contact: mailto:security@example.com

   # Our OpenPGP key
   Encryption: https://example.com/pgp-key.txt

   # Our security policy
   Policy: https://example.com/security-policy.html

   # Our security acknowledgments page
   Acknowledgments: https://example.com/hall-of-fame.html

   Expires: 2021-12-31T18:37:07z
   -----BEGIN PGP SIGNATURE-----
   Version: GnuPG v2.2

   [signature]
   -----END PGP SIGNATURE-----

3.  Location of the security.txt File

   For web-based services, organizations MUST place the "security.txt"
   file under the "/.well-known/" path, e.g., https://example.com/.well-
   known/security.txt as per [RFC8615] of a domain name or IP address.
   For legacy compatibility, a "security.txt" file might be placed at
   the top-level path or redirect (as per Section 6.4 of [RFC7231]) to
   the "security.txt" file under the "/.well-known/" path.  If a
   "security.txt" file is present in both locations, the one in the
   "/.well-known/" path MUST be used.

   The file MUST be accessed via HTTP 1.0 or a higher version, and the
   file access MUST use the "https" scheme (as per Section 2.7.2 of
   [RFC7230]).  It MUST have a Content-Type of "text/plain" with the
   default charset parameter set to "utf-8" (as per Section 4.1.3 of
   [RFC2046]).

   Retrieval of "security.txt" files and resources indicated within such
   files may result in a redirect (as per Section 6.4 of [RFC7231]).
   Researchers should perform additional analysis (as per Section 5.2)
   to make sure these redirects are not malicious or pointing to
   resources controlled by an attacker.

3.1.  Scope of the File

   A "security.txt" file MUST only apply to the domain or IP address in
   the URI used to retrieve it, not to any of its subdomains or parent
   domains.  A "security.txt" file MAY also apply to products and
   services provided by the organization publishing the file.

   As per Section 1.1, this specification is intended for a
   vulnerability response.  If implementors want to use this for an
   incident response, they should be aware of additional security
   considerations discussed in Section 5.1.

   Organizations SHOULD use the policy directive (as per Section 2.5.7)
   to provide additional details regarding the scope and details of
   their vulnerability disclosure process.

   Some examples appear below:

   # The following only applies to example.com.
   https://example.com/.well-known/security.txt

   # This only applies to subdomain.example.com.
   https://subdomain.example.com/.well-known/security.txt

   # This security.txt file applies to IPv4 address of 192.0.2.0.
   https://192.0.2.0/.well-known/security.txt

   # This security.txt file applies to IPv6 address of 2001:db8:8:4::2.
   https://[2001:db8:8:4::2]/.well-known/security.txt

4.  File Format Description and ABNF Grammar

   The file format of the "security.txt" file MUST be plain text (MIME
   type "text/plain") as defined in Section 4.1.3 of [RFC2046] and MUST
   be encoded using UTF-8 [RFC3629] in Net-Unicode form [RFC5198].

   The format of this file MUST follow the ABNF definition below (which
   incorporates the core ABNF rules from [RFC5234] and uses the case-
   sensitive string support from [RFC7405]).

   body             =  signed / unsigned

   unsigned       =  *line (contact-field eol) ; one or more required
                     *line (expires-field eol) ; exactly one required
                     *line [lang-field eol] *line ; exactly one optional
                     ; order of fields within the file is not important
                     ; except that if contact-field appears more
                     ; than once, the order of those indicates
                     ; priority (see Section 3.5.3)

   ; signed is the production that should match the OpenPGP clearsigned
   ; document
   signed           =  cleartext-header
                       1*(hash-header)
                       CRLF
                       cleartext
                       signature

   cleartext-header =  %s"-----BEGIN PGP SIGNED MESSAGE-----" CRLF

   hash-header      =  %s"Hash: " hash-alg *("," hash-alg) CRLF

   hash-alg         =  token
                         ; imported from RFC 2045; see RFC 4880 Section
                         ; 10.3.3 for a pointer to the registry of
                         ; valid values

   ;cleartext       =  1*( UTF8-octets [CR] LF)
                         ; dash-escaped per RFC 4880 Section 7.1

   cleartext        =  *((line-dash / line-from / line-nodash) [CR] LF)

   line-dash        =  ("- ") "-" *UTF8-char-not-cr
                          ; MUST include initial "- "

   line-from        =  ["- "] "From " *UTF8-char-not-cr
                         ; SHOULD include initial "- "

   line-nodash      =  ["- "] *UTF8-char-not-cr
                         ; MAY include initial "- "

   UTF8-char-not-dash =  UTF8-1-not-dash / UTF8-2 / UTF8-3 / UTF8-4
   UTF8-1-not-dash  =  %x00-2C / %x2E-7F
   UTF8-char-not-cr =  UTF8-1-not-cr / UTF8-2 / UTF8-3 / UTF8-4
   UTF8-1-not-cr    =  %x00-0C / %x0E-7F

   ; UTF8 rules from RFC 3629
   UTF8-octets      =  *( UTF8-char )
   UTF8-char        =  UTF8-1 / UTF8-2 / UTF8-3 / UTF8-4
   UTF8-1           =  %x00-7F
   UTF8-2           =  %xC2-DF UTF8-tail
   UTF8-3           =  %xE0 %xA0-BF UTF8-tail / %xE1-EC 2( UTF8-tail ) /
                       %xED %x80-9F UTF8-tail / %xEE-EF 2( UTF8-tail )
   UTF8-4           =  %xF0 %x90-BF 2( UTF8-tail ) /
                       %xF1-F3 3( UTF8-tail ) /
                       %xF4 %x80-8F 2( UTF8-tail )
   UTF8-tail        =  %x80-BF

   signature        =  armor-header
                       armor-keys
                       CRLF
                       signature-data
                       armor-tail

   armor-header     =  %s"-----BEGIN PGP SIGNATURE-----" CRLF

   armor-keys       =  *(token ": " *( VCHAR / WSP ) CRLF)
                         ; Armor Header Keys from RFC 4880

   armor-tail       =  %s"-----END PGP SIGNATURE-----" CRLF

   signature-data   =  1*(1*(ALPHA / DIGIT / "=" / "+" / "/") CRLF)
                         ; base64; see RFC 4648
                         ; includes RFC 4880 checksum

   line             =  [ (field / comment) ] eol

   eol              =  *WSP [CR] LF

   field            =  ; optional fields
                       ack-field /
                       can-field /
                       contact-field / ; optional repeated instances
                       encryption-field /
                       hiring-field /
                       policy-field /
                       ext-field

   fs               =  ":"

   comment          =  "#" *(WSP / VCHAR / %x80-FFFFF)

   ack-field        =  "Acknowledgments" fs SP uri

   can-field        =  "Canonical" fs SP uri

   contact-field    =  "Contact" fs SP uri

   expires-field    =  "Expires" fs SP date-time

   encryption-field =  "Encryption" fs SP uri

   hiring-field     =  "Hiring" fs SP uri

   lang-field       =  "Preferred-Languages" fs SP lang-values

   policy-field     =  "Policy" fs SP uri

   date-time        =  < imported from Section 5.6 of [RFC3339] >

   lang-tag         =  < Language-Tag from Section 2.1 of [RFC5646] >

   lang-values      =  lang-tag *(*WSP "," *WSP lang-tag)

   uri              =  < URI as per Section 3 of [RFC3986] >

   ext-field        =  field-name fs SP unstructured

   field-name       =  < imported from Section 3.6.8 of [RFC5322] >

   unstructured     =  < imported from Section 3.2.5 of [RFC5322] >

   token            =  < imported from Section 5.1 of [RFC2045] >

   ALPHA            =  %x41-5A / %x61-7A   ; A-Z / a-z

   BIT              =  "0" / "1"

   CHAR             =  %x01-7F
                         ; any 7-bit US-ASCII character,
                         ;  excluding NUL

   CR               =  %x0D
                         ; carriage return

   CRLF             =  CR LF
                         ; Internet standard newline

   CTL              =  %x00-1F / %x7F
                         ; controls

   DIGIT            =  %x30-39
                         ; 0-9

   DQUOTE           =  %x22
                         ; " (Double Quote)

   HEXDIG           =  DIGIT / "A" / "B" / "C" / "D" / "E" / "F"

   HTAB             =  %x09
                         ; horizontal tab

   LF               =  %x0A
                         ; linefeed

   LWSP             =  *(WSP / CRLF WSP)
                         ; Use of this linear-white-space rule
                         ;  permits lines containing only white
                         ;  space that are no longer legal in
                         ;  mail headers and have caused
                         ;  interoperability problems in other
                         ;  contexts.
                         ; Do not use when defining mail
                         ;  headers and use with caution in
                         ;  other contexts.

   OCTET            =  %x00-FF
                         ; 8 bits of data

   SP               =  %x20

   VCHAR            =  %x21-7E
                         ; visible (printing) characters

   WSP              =  SP / HTAB
                         ; white space

   "ext-field" refers to extension fields, which are discussed in
   Section 2.4.

5.  Security Considerations

   Because of the use of URIs and well-known resources, security
   considerations of [RFC3986] and [RFC8615] apply here, in addition to
   the considerations outlined below.

5.1.  Compromised Files and Incident Response

   An attacker that has compromised a website is able to compromise the
   "security.txt" file as well or set up a redirect to their own site.
   This can result in security reports not being received by the
   organization or being sent to the attacker.

   To protect against this, organizations should use the "Canonical"
   field to indicate the locations of the file (as per Section 2.5.2),
   digitally sign their "security.txt" files (as per Section 2.3), and
   regularly monitor the file and the referenced resources to detect
   tampering.

   Security researchers should validate the "security.txt" file,
   including verifying the digital signature and checking any available
   historical records before using the information contained in the
   file.  If the "security.txt" file looks suspicious or compromised, it
   should not be used.

   While it is not recommended, implementors may choose to use the
   information published within a "security.txt" file for an incident
   response.  In such cases, extreme caution should be taken before
   trusting such information, since it may have been compromised by an
   attacker.  Researchers should use additional methods to verify such
   data including out-of-band verification of the Pretty Good Privacy
   (PGP) signature, DNSSEC-based approaches, etc.

5.2.  Redirects

   When retrieving the file and any resources referenced in the file,
   researchers should record any redirects since they can lead to a
   different domain or IP address controlled by an attacker.  Further
   inspection of such redirects is recommended before using the
   information contained within the file.

5.3.  Incorrect or Stale Information

   If information and resources referenced in a "security.txt" file are
   incorrect or not kept up to date, this can result in security reports
   not being received by the organization or sent to incorrect contacts,
   thus exposing possible security issues to third parties.  Not having
   a "security.txt" file may be preferable to having stale information
   in this file.  Organizations must use the "Expires" field (see
   Section 2.5.5) to indicate to researchers when the data in the file
   is no longer valid.

   Organizations should ensure that information in this file and any
   referenced resources such as web pages, email addresses, and
   telephone numbers are kept current, are accessible, are controlled by
   the organization, and are kept secure.

5.4.  Intentionally Malformed Files, Resources, and Reports

   It is possible for compromised or malicious sites to create files
   that are extraordinarily large or otherwise malformed in an attempt
   to discover or exploit weaknesses in the parsing code.  Researchers
   should make sure that any such code is robust against large or
   malformed files and fields, and they may choose to have the code not
   parse files larger than 32 KBs, those with fields longer than 2,048
   characters, or those containing more than 1,000 lines.  The ABNF
   grammar (as defined in Section 4) can also be used as a way to verify
   these files.

   The same concerns apply to any other resources referenced within
   "security.txt" files, as well as any security reports received as a
   result of publishing this file.  Such resources and reports may be
   hostile, malformed, or malicious.

5.5.  No Implied Permission for Testing

   The presence of a "security.txt" file might be interpreted by
   researchers as providing permission to do security testing against
   the domain or IP address where it is published or against products
   and services provided by the organization publishing the file.  This
   might result in increased testing against an organization by
   researchers.  On the other hand, a decision not to publish a
   "security.txt" file might be interpreted by the organization
   operating that website to be a way to signal to researchers that
   permission to test that particular site or project is denied.  This
   might result in pushback against researchers reporting security
   issues to that organization.

   Therefore, researchers shouldn't assume that the presence or absence
   of a "security.txt" file grants or denies permission for security
   testing.  Any such permission may be indicated in the company's
   vulnerability disclosure policy (as per Section 2.5.7) or a new field
   (as per Section 2.4).

5.6.  Multi-User Environments

   In multi-user / multi-tenant environments, it may be possible for a
   user to take over the location of the "security.txt" file.
   Organizations should reserve the "security.txt" namespace at the root
   to ensure no third party can create a page with the "security.txt"
   AND "/.well-known/security.txt" names.

5.7.  Protecting Data in Transit

   To protect a "security.txt" file from being tampered with in transit,
   implementors MUST use HTTPS (as per Section 2.7.2 of [RFC7230]) when
   serving the file itself and for retrieval of any web URIs referenced
   in it (except when otherwise noted in this specification).  As part
   of the TLS handshake, researchers should validate the provided X.509
   certificate in accordance with [RFC6125] and the following
   considerations:

   *  Matching is performed only against the DNS-ID identifiers.

   *  DNS domain names in server certificates MAY contain the wildcard
      character '*' as the complete leftmost label within the
      identifier.

   The certificate may also be checked for revocation via the Online
   Certificate Status Protocol (OCSP) [RFC6960], certificate revocation
   lists (CRLs), or similar mechanisms.

   In cases where the "security.txt" file cannot be served via HTTPS
   (such as localhost) or is being served with an invalid certificate,
   additional human validation is recommended since the contents may
   have been modified while in transit.

   As an additional layer of protection, it is also recommended that
   organizations digitally sign their "security.txt" file with OpenPGP
   (as per Section 2.3).  Also, to protect security reports from being
   tampered with or observed while in transit, organizations should
   specify encryption keys (as per Section 2.5.4) unless HTTPS is being
   used for report submission.

   However, the determination of validity of such keys is out of scope
   for this specification.  Security researchers need to establish other
   secure means to verify them.

5.8.  Spam and Spurious Reports

   Similar to concerns in [RFC2142], denial-of-service attacks via spam
   reports would become easier once a "security.txt" file is published
   by an organization.  In addition, there is an increased likelihood of
   reports being sent in an automated fashion and/or as a result of
   automated scans without human analysis.  Attackers can also use this
   file as a way to spam unrelated third parties by listing their
   resources and/or contact information.

   Organizations need to weigh the advantages of publishing this file
   versus the possible disadvantages and increased resources required to
   analyze security reports.

   Security researchers should review all information within the
   "security.txt" file before submitting reports in an automated fashion
   or reports resulting from automated scans.

6.  IANA Considerations

   Implementors should be aware that any resources referenced within a
   "security.txt" file MUST NOT point to the Well-Known URIs namespace
   unless they are registered with IANA (as per [RFC8615]).

6.1.  Well-Known URIs Registry

   IANA has updated the "Well-Known URIs" registry with the following
   additional values (using the template from [RFC8615]):

   URI suffix:  security.txt
   Change controller:  IETF
   Specification document(s):  RFC 9116
   Status:  permanent

6.2.  Registry for security.txt Fields

   IANA has created the "security.txt Fields" registry in accordance
   with [RFC8126].  This registry contains fields for use in
   "security.txt" files, defined by this specification.

   New registrations or updates MUST be published in accordance with the
   "Expert Review" guidelines as described in Sections 4.5 and 5 of
   [RFC8126].  Any new field thus registered is considered optional by
   this specification unless a new version of this specification is
   published.

   Designated experts should determine whether a proposed registration
   or update provides value to organizations and researchers using this
   format and makes sense in the context of industry-accepted
   vulnerability disclosure processes such as [ISO.29147.2018] and
   [CERT.CVD].

   New registrations and updates MUST contain the following information:

   1.  Name of the field being registered or updated

   2.  Short description of the field

   3.  Whether the field can appear more than once

   4.  New or updated status, which MUST be one of the following:

       current:  The field is in current use.
       deprecated:  The field has been in use, but new usage is
          discouraged.
       historic:  The field is no longer in current use.

   5.  Change controller

   6.  The document in which the specification of the field is published
       (if available)

   Existing registrations may be marked historic or deprecated, as
   appropriate, by a future update to this document.

   The initial registry contains these values:

   Field Name:  Acknowledgments
   Description:  link to page where security researchers are recognized
   Multiple Appearances:  yes
   Status:  current
   Change controller:  IETF
   Reference:  RFC 9116

   Field Name:  Canonical
   Description:  canonical URI for this file
   Multiple Appearances:  yes
   Status:  current
   Change controller:  IETF
   Reference:  RFC 9116

   Field Name:  Contact
   Description:  contact information to use for reporting
      vulnerabilities
   Multiple Appearances:  yes
   Status:  current
   Change controller:  IETF
   Reference:  RFC 9116

   Field Name:  Expires
   Description:  date and time after which this file is considered stale
   Multiple Appearances:  no
   Status:  current
   Change controller:  IETF
   Reference:  RFC 9116

   Field Name:  Encryption
   Description:  link to a key to be used for encrypted communication
   Multiple Appearances:  yes
   Status:  current
   Change controller:  IETF
   Reference:  RFC 9116

   Field Name:  Hiring
   Description:  link to the vendor's security-related job positions
   Multiple Appearances:  yes
   Status:  current
   Change controller:  IETF
   Reference:  RFC 9116

   Field Name:  Policy
   Description:  link to security policy page
   Multiple Appearances:  yes
   Status:  current
   Change controller:  IETF
   Reference:  RFC 9116

   Field Name:  Preferred-Languages
   Description:  list of preferred languages for security reports
   Multiple Appearances:  no
   Status:  current
   Change controller:  IETF
   Reference:  RFC 9116

7.  References

7.1.  Normative References

   [RFC2046]  Freed, N. and N. Borenstein, "Multipurpose Internet Mail
              Extensions (MIME) Part Two: Media Types", RFC 2046,
              DOI 10.17487/RFC2046, November 1996,
              <https://www.rfc-editor.org/info/rfc2046>.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC2142]  Crocker, D., "Mailbox Names for Common Services, Roles and
              Functions", RFC 2142, DOI 10.17487/RFC2142, May 1997,
              <https://www.rfc-editor.org/info/rfc2142>.

   [RFC2277]  Alvestrand, H., "IETF Policy on Character Sets and
              Languages", BCP 18, RFC 2277, DOI 10.17487/RFC2277,
              January 1998, <https://www.rfc-editor.org/info/rfc2277>.

   [RFC3339]  Klyne, G. and C. Newman, "Date and Time on the Internet:
              Timestamps", RFC 3339, DOI 10.17487/RFC3339, July 2002,
              <https://www.rfc-editor.org/info/rfc3339>.

   [RFC3629]  Yergeau, F., "UTF-8, a transformation format of ISO
              10646", STD 63, RFC 3629, DOI 10.17487/RFC3629, November
              2003, <https://www.rfc-editor.org/info/rfc3629>.

   [RFC3966]  Schulzrinne, H., "The tel URI for Telephone Numbers",
              RFC 3966, DOI 10.17487/RFC3966, December 2004,
              <https://www.rfc-editor.org/info/rfc3966>.

   [RFC3986]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
              Resource Identifier (URI): Generic Syntax", STD 66,
              RFC 3986, DOI 10.17487/RFC3986, January 2005,
              <https://www.rfc-editor.org/info/rfc3986>.

   [RFC4880]  Callas, J., Donnerhacke, L., Finney, H., Shaw, D., and R.
              Thayer, "OpenPGP Message Format", RFC 4880,
              DOI 10.17487/RFC4880, November 2007,
              <https://www.rfc-editor.org/info/rfc4880>.

   [RFC5198]  Klensin, J. and M. Padlipsky, "Unicode Format for Network
              Interchange", RFC 5198, DOI 10.17487/RFC5198, March 2008,
              <https://www.rfc-editor.org/info/rfc5198>.

   [RFC5234]  Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
              Specifications: ABNF", STD 68, RFC 5234,
              DOI 10.17487/RFC5234, January 2008,
              <https://www.rfc-editor.org/info/rfc5234>.

   [RFC5322]  Resnick, P., Ed., "Internet Message Format", RFC 5322,
              DOI 10.17487/RFC5322, October 2008,
              <https://www.rfc-editor.org/info/rfc5322>.

   [RFC5646]  Phillips, A., Ed. and M. Davis, Ed., "Tags for Identifying
              Languages", BCP 47, RFC 5646, DOI 10.17487/RFC5646,
              September 2009, <https://www.rfc-editor.org/info/rfc5646>.

   [RFC6068]  Duerst, M., Masinter, L., and J. Zawinski, "The 'mailto'
              URI Scheme", RFC 6068, DOI 10.17487/RFC6068, October 2010,
              <https://www.rfc-editor.org/info/rfc6068>.

   [RFC6125]  Saint-Andre, P. and J. Hodges, "Representation and
              Verification of Domain-Based Application Service Identity
              within Internet Public Key Infrastructure Using X.509
              (PKIX) Certificates in the Context of Transport Layer
              Security (TLS)", RFC 6125, DOI 10.17487/RFC6125, March
              2011, <https://www.rfc-editor.org/info/rfc6125>.

   [RFC6960]  Santesson, S., Myers, M., Ankney, R., Malpani, A.,
              Galperin, S., and C. Adams, "X.509 Internet Public Key
              Infrastructure Online Certificate Status Protocol - OCSP",
              RFC 6960, DOI 10.17487/RFC6960, June 2013,
              <https://www.rfc-editor.org/info/rfc6960>.

   [RFC7230]  Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
              Protocol (HTTP/1.1): Message Syntax and Routing",
              RFC 7230, DOI 10.17487/RFC7230, June 2014,
              <https://www.rfc-editor.org/info/rfc7230>.

   [RFC7231]  Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
              Protocol (HTTP/1.1): Semantics and Content", RFC 7231,
              DOI 10.17487/RFC7231, June 2014,
              <https://www.rfc-editor.org/info/rfc7231>.

   [RFC7405]  Kyzivat, P., "Case-Sensitive String Support in ABNF",
              RFC 7405, DOI 10.17487/RFC7405, December 2014,
              <https://www.rfc-editor.org/info/rfc7405>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

   [RFC8615]  Nottingham, M., "Well-Known Uniform Resource Identifiers
              (URIs)", RFC 8615, DOI 10.17487/RFC8615, May 2019,
              <https://www.rfc-editor.org/info/rfc8615>.

7.2.  Informative References

   [CERT.CVD] Software Engineering Institute, "The CERT Guide to
              Coordinated Vulnerability Disclosure", Carnegie Mellon
              University, CMU/SEI-2017-SR-022, August 2017.

   [ISO.29147.2018]
              ISO, "Information technology - Security techniques -
              Vulnerability disclosure", ISO/IEC 29147:2018, October
              2018.

   [ISO.8601-1]
              ISO, "Date and time - Representations for information
              interchange - Part 1: Basic rules", ISO 8601-1:2019,
              February 2019.

   [ISO.8601-2]
              ISO, "Date and time - Representations for information
              interchange - Part 2: Extensions", ISO 8601-2:2019,
              February 2019.

   [RFC0793]  Postel, J., "Transmission Control Protocol", STD 7,
              RFC 793, DOI 10.17487/RFC0793, September 1981,
              <https://www.rfc-editor.org/info/rfc793>.

   [RFC2196]  Fraser, B., "Site Security Handbook", FYI 8, RFC 2196,
              DOI 10.17487/RFC2196, September 1997,
              <https://www.rfc-editor.org/info/rfc2196>.

   [RFC2350]  Brownlee, N. and E. Guttman, "Expectations for Computer
              Security Incident Response", BCP 21, RFC 2350,
              DOI 10.17487/RFC2350, June 1998,
              <https://www.rfc-editor.org/info/rfc2350>.

   [RFC3013]  Killalea, T., "Recommended Internet Service Provider
              Security Services and Procedures", BCP 46, RFC 3013,
              DOI 10.17487/RFC3013, November 2000,
              <https://www.rfc-editor.org/info/rfc3013>.

   [RFC7485]  Zhou, L., Kong, N., Shen, S., Sheng, S., and A. Servin,
              "Inventory and Analysis of WHOIS Registration Objects",
              RFC 7485, DOI 10.17487/RFC7485, March 2015,
              <https://www.rfc-editor.org/info/rfc7485>.

   [RFC8126]  Cotton, M., Leiba, B., and T. Narten, "Guidelines for
              Writing an IANA Considerations Section in RFCs", BCP 26,
              RFC 8126, DOI 10.17487/RFC8126, June 2017,
              <https://www.rfc-editor.org/info/rfc8126>.

Acknowledgments

   The authors would like to acknowledge the help provided during the
   development of this document by Tom Hudson, Jobert Abma, Gerben
   Janssen van Doorn, Austin Heap, Stephane Bortzmeyer, Max Smith,
   Eduardo Vela, and Krzysztof Kotowicz.

   The authors would also like to acknowledge the feedback provided by
   multiple members of the IETF's LAST CALL, SAAG, and SECDISPATCH
   lists.

   Yakov Shafranovich would like to also thank L.T.S. (for everything).

Authors' Addresses

   Edwin Foudil
   Email: contact@edoverflow.com


   Yakov Shafranovich
   Nightwatch Cybersecurity
   Email: yakov+ietf@nightwatchcybersecurity.com