Internet DRAFT - draft-ietf-uta-smtp-tlsrpt
draft-ietf-uta-smtp-tlsrpt
Using TLS in Applications D. Margolis
Internet-Draft Google, Inc
Intended status: Standards Track A. Brotman
Expires: December 16, 2018 Comcast, Inc
B. Ramakrishnan
Yahoo!, Inc
J. Jones
Microsoft, Inc
M. Risher
Google, Inc
June 14, 2018
SMTP TLS Reporting
draft-ietf-uta-smtp-tlsrpt-23
Abstract
A number of protocols exist for establishing encrypted channels
between SMTP Mail Transfer Agents, including STARTTLS, DANE TLSA, and
MTA-STS. These protocols can fail due to misconfiguration or active
attack, leading to undelivered messages or delivery over unencrypted
or unauthenticated channels. This document describes a reporting
mechanism and format by which sending systems can share statistics
and specific information about potential failures with recipient
domains. Recipient domains can then use this information to both
detect potential attacks and diagnose unintentional
misconfigurations.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on December 16, 2018.
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Copyright Notice
Copyright (c) 2018 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
(http://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 Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4
2. Related Technologies . . . . . . . . . . . . . . . . . . . . 4
3. Reporting Policy . . . . . . . . . . . . . . . . . . . . . . 5
3.1. Example Reporting Policy . . . . . . . . . . . . . . . . 7
3.1.1. Report using MAILTO . . . . . . . . . . . . . . . . . 7
3.1.2. Report using HTTPS . . . . . . . . . . . . . . . . . 7
4. Reporting Schema . . . . . . . . . . . . . . . . . . . . . . 7
4.1. Report Time-frame . . . . . . . . . . . . . . . . . . . . 8
4.2. Delivery Summary . . . . . . . . . . . . . . . . . . . . 9
4.2.1. Success Count . . . . . . . . . . . . . . . . . . . . 9
4.2.2. Failure Count . . . . . . . . . . . . . . . . . . . . 9
4.3. Result Types . . . . . . . . . . . . . . . . . . . . . . 9
4.3.1. Negotiation Failures . . . . . . . . . . . . . . . . 10
4.3.2. Policy Failures . . . . . . . . . . . . . . . . . . . 10
4.3.3. General Failures . . . . . . . . . . . . . . . . . . 11
4.3.4. Transient Failures . . . . . . . . . . . . . . . . . 11
4.4. JSON Report Schema . . . . . . . . . . . . . . . . . . . 11
4.5. Policy Samples . . . . . . . . . . . . . . . . . . . . . 14
5. Report Delivery . . . . . . . . . . . . . . . . . . . . . . . 15
5.1. Report Filename . . . . . . . . . . . . . . . . . . . . . 15
5.2. Compression . . . . . . . . . . . . . . . . . . . . . . . 16
5.3. Email Transport . . . . . . . . . . . . . . . . . . . . . 16
5.3.1. Example Report . . . . . . . . . . . . . . . . . . . 17
5.4. HTTPS Transport . . . . . . . . . . . . . . . . . . . . . 18
5.5. Delivery Retry . . . . . . . . . . . . . . . . . . . . . 19
5.6. Metadata Variances . . . . . . . . . . . . . . . . . . . 19
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19
6.1. Message headers . . . . . . . . . . . . . . . . . . . . . 19
6.2. Report Type . . . . . . . . . . . . . . . . . . . . . . . 19
6.3. +gzip Media Type Suffix . . . . . . . . . . . . . . . . . 20
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6.4. application/tlsrpt+json Media Type . . . . . . . . . . . 21
6.5. application/tlsrpt+gzip Media Type . . . . . . . . . . . 23
6.6. STARTTLS Validation Result Types . . . . . . . . . . . . 24
7. Security Considerations . . . . . . . . . . . . . . . . . . . 24
8. Privacy Considerations . . . . . . . . . . . . . . . . . . . 26
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 26
9.1. Normative References . . . . . . . . . . . . . . . . . . 26
9.2. Informative References . . . . . . . . . . . . . . . . . 28
9.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Appendix A. Example Reporting Policy . . . . . . . . . . . . . . 30
A.1. Report using MAILTO . . . . . . . . . . . . . . . . . . . 30
A.2. Report using HTTPS . . . . . . . . . . . . . . . . . . . 30
Appendix B. Example JSON Report . . . . . . . . . . . . . . . . 30
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 32
1. Introduction
The STARTTLS extension to SMTP [RFC3207] allows SMTP clients and
hosts to establish secure SMTP sessions over TLS. The protocol
design uses an approach that has come to be known as "Opportunistic
Security" (OS) [RFC7435]. This method maintains interoperability
with clients that do not support STARTTLS, but means that any
attacker could potentially eavesdrop on a session. An attacker could
perform a downgrade or interception attack by deleting parts of the
SMTP session (such as the "250 STARTTLS" response) or redirect the
entire SMTP session (perhaps by overwriting the resolved MX record of
the delivery domain).
Because such "downgrade attacks" are not necessarily apparent to the
receiving MTA, this document defines a mechanism for sending domains
to report on failures at multiple stages of the MTA-to-MTA
conversation.
Recipient domains may also use the mechanisms defined by MTA-STS
[I-D.ietf-uta-mta-sts] or DANE [RFC6698] to publish additional
encryption and authentication requirements; this document defines a
mechanism for sending domains that are compatible with MTA-STS or
DANE to share success and failure statistics with recipient domains.
Specifically, this document defines a reporting schema that covers
failures in routing, DNS resolution, STARTTLS negotiation, and both
DANE [RFC6698] and MTA-STS [I-D.ietf-uta-mta-sts] policy validation
errors, and a standard TXT record that recipient domains can use to
indicate where reports in this format should be sent. The report can
also serve as a heartbeat that systems are successfully negotiating
TLS during sessions as expected.
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This document is intended as a companion to the specification for
SMTP MTA Strict Transport Security [I-D.ietf-uta-mta-sts], as well as
adds reporting abilities for those implementing DANE [RFC7672].
1.1. 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.
We also define the following terms for further use in this document:
o MTA-STS Policy: A mechanism by which administrators can specify
the expected TLS availability, presented identity, and desired
actions for a given email recipient domain. MTA-STS is defined in
[I-D.ietf-uta-mta-sts].
o DANE Policy: A mechanism by which administrators can use DNSSEC to
commit an MTA to support STARTTLS and to publish criteria to be
used to validate its presented certificates. DANE for SMTP is
defined in [RFC7672], with the base specification in [RFC6698]
(updated in [RFC7671].
o TLSRPT Policy: A policy specifying the endpoint to which sending
MTAs should deliver reports.
o Policy Domain: The domain against which an MTA-STS or DANE Policy
is defined. For MTA-STS this is typically the same as the
envelope recipient domain [RFC5321], but when mail is routed to a
"smarthost" gateway by local policy, the "smarthost" domain name
is used instead. For DANE the Policy Domain is the "TLSA base
domain" of the receiving SMTP server as described in RFC7672 [1]
and RFC6698 [2].
o Sending MTA: The MTA initiating the relay of an email message.
o Aggregate Report URI (rua): A comma-separated list of locations
where the report is to be submitted.
2. Related Technologies
o This document is intended as a companion to the specification for
SMTP MTA Strict Transport Security [I-D.ietf-uta-mta-sts].
o SMTP-TLSRPT defines a mechanism for sending domains that are
compatible with MTA-STS or DANE to share success and failure
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statistics with recipient domains. DANE is defined in [RFC6698]
and MTA-STS is defined in [I-D.ietf-uta-mta-sts].
3. Reporting Policy
A domain publishes a record to its DNS indicating that it wishes to
receive reports. These SMTP TLSRPT policies are distributed via DNS
from the Policy Domain's zone, as TXT records (similar to DMARC
policies) under the name "_smtp._tls". For example, for the Policy
Domain "example.com", the recipient's TLSRPT policy can be retrieved
from "_smtp._tls.example.com".
Policies consist of the following directives:
o "v": This document defines version 1 of TLSRPT, for which this
value MUST be equal to "TLSRPTv1". Other versions may be defined
in later documents.
o "rua": A URI specifying the endpoint to which aggregate
information about policy validation results should be sent (see
Section 4, "Reporting Schema", for more information). Two URI
schemes are supported: "mailto" and "https". As with DMARC
[RFC7489], the policy domain can specify a comma-separated list of
URIs.
o In the case of "https", reports should be submitted via POST
([RFC7231]) to the specified URI. Report submitters MAY ignore
certificate validation errors when submitting reports via https.
o In the case of "mailto", reports should be submitted to the
specified email address ([RFC6068]). When sending failure reports
via SMTP, sending MTAs MUST deliver reports despite any TLS-
related failures and SHOULD NOT include this SMTP session in the
next report. When sending failure reports via HTTPS, sending MTAs
MAY deliver reports despite any TLS-related faliures. This may
mean that the reports are delivered in the clear. Reports sent
via SMTP MUST contain a valid DKIM [RFC6376] signature by the
reporting domain. Reports lacking such a signature MUST be
ignored by the recipient. DKIM signatures must not use the "l="
attribute to limit the body length used in the signature. The
DKIM TXT record must contain the appropriate service type
declaration, "s=tlsrpt", and if not present the receiving system
SHOULD ignore reports signed using this record.
The formal definition of the "_smtp._tls" TXT record, defined using
[RFC5234] & [RFC7405], is as follows:
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tlsrpt-record = tlsrpt-version 1*(field-delim tlsrpt-field)
[field-delim]
field-delim = *WSP ";" *WSP
tlsrpt-field = tlsrpt-rua / ; Note that the
tlsrpt-extension ; tlsrpt-rua record is
; required.
tlsrpt-version = %s"v=TLSRPTv1"
tlsrpt-rua = %s"rua="
tlsrpt-uri *(*WSP "," *WSP tlsrpt-uri)
tlsrpt-uri = URI
; "URI" is imported from [RFC3986];
; commas (ASCII 0x2C), exclamation
; points (ASCII 0x21), and semicolons
; (ASCII 0x3B) MUST be encoded
tlsrpt-extension = tlsrpt-ext-name "=" tlsrpt-ext-value
tlsrpt-ext-name = (ALPHA / DIGIT) *31(ALPHA /
DIGIT / "_" / "-" / ".")
tlsrpt-ext-value = 1*(%x21-3A / %x3C / %x3E-7E)
; chars excluding "=", ";", SP, and control
; chars
If multiple TXT records for "_smtp._tls" are returned by the
resolver, records which do not begin with "v=TLSRPTv1;" are
discarded. If the number of resulting records is not one, senders
MUST assume the recipient domain does not implement TLSRPT. If the
resulting TXT record contains multiple strings (as described in
Section 3.1.3 of [RFC4408]), then the record MUST be treated as if
those strings are concatenated together without adding spaces.
The record supports the abillity to declare more than one rua, and if
there exists more than one, the reporter MAY attempt to deliver to
each of the supported rua destinations. A receiver MAY opt to only
attempt delivery to one of the endpoints, however the report SHOULD
NOT be considered successfully delivered until one of the endpoints
accepts delivery of the report.
Parsers MUST accept TXT records which are syntactically valid (i.e.
valid key-value pairs separated by semi-colons) and implementing a
superset of this specification, in which case unknown fields SHALL be
ignored.
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3.1. Example Reporting Policy
3.1.1. Report using MAILTO
_smtp._tls.example.com. IN TXT \
"v=TLSRPTv1;rua=mailto:reports@example.com"
3.1.2. Report using HTTPS
_smtp._tls.example.com. IN TXT \
"v=TLSRPTv1; \
rua=https://reporting.example.com/v1/tlsrpt"
4. Reporting Schema
The report is composed as a plain text file encoded in the I-JSON
format ([RFC7493]).
Aggregate reports contain the following fields:
o Report metadata:
* The organization responsible for the report
* Contact information for one or more responsible parties for the
contents of the report
* A unique identifier for the report
* The reporting date range for the report
o Policy, consisting of:
* One of the following policy types: (1) The MTA-STS policy
applied (as a string) (2) The DANE TLSA record applied (as a
string, with each RR entry of the RRset listed and separated by
a semicolon) (3) The literal string "no-policy-found", if
neither a DANE nor MTA-STS policy could be found.
* The domain for which the policy is applied
* The MX host
o Aggregate counts, comprising result type, sending MTA IP,
receiving MTA hostname, session count, and an optional additional
information field containing a URI for recipients to review
further information on a failure type.
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Note that the failure types are non-exclusive; an aggregate report
may contain overlapping "counts" of failure types when a single send
attempt encountered multiple errors. Reporters may report multiple
applied policies (for example, an MTA-STS policy and a DANE TLSA
record for the same domain and MX). Because of this, even in the
case where only a single policy was applied, the "policies" field of
the report body MUST be an array and not a singular value.
In the case of multiple failure types, the "failure-details" array
would contain multiple entries. Each entry would have its own set of
infomation pertaining to that failure type.
4.1. Report Time-frame
The report SHOULD cover a full day, from 0000-2400 UTC. This should
allow for easier correlation of failure events. To avoid a Denial of
Service against the system processing the reports, the reports should
be delivered after some delay, perhaps several hours.
As an example, a sending site might want to introduce a random delay
of up to four hours:
func generate_sleep_delay() {
min_delay = 1
max_delay = 14400
rand = random(min_delay,max_delay)
return rand
}
func generate_report(policy_domain) {
do_rpt_work(policy_domain)
send_rpt(policy_domain)
}
func generate_tlsrpt() {
sleep(generate_sleep_delay())
for policy_domain in list_of_tlsrpt_enabled_domains {
generate_report(policy_domain)
}
}
A sending site might wish to introduce a random delay per destination
site, up to four hours:
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func generate_sleep_delay() {
min_delay = 1
max_delay = 14400
rand = random(min_delay,max_delay)
return rand
}
func generate_report(policy_domain) {
sleep(generate_sleep_delay())
do_rpt_work(policy_domain)
send_rpt(policy_domain)
}
func generate_tlsrpt() {
for policy_domain in list_of_tlsrpt_enabled_domains {
generate_report(policy_domain)
}
}
4.2. Delivery Summary
4.2.1. Success Count
o "total-successful-session-count": This indicates that the sending
MTA was able to successfully negotiate a policy-compliant TLS
connection, and serves to provide a "heartbeat" to receiving
domains that reporting is functional and tabulating correctly.
This field contains an aggregate count of successful connections
for the reporting system.
4.2.2. Failure Count
o "total-failure-session-count": This indicates that the sending MTA
was unable to successfully establish a connection with the
receiving platform. Section 4.3, "Result Types", will elaborate
on the failed negotiation attempts. This field contains an
aggregate count of failed connections.
4.3. Result Types
The list of result types will start with the minimal set below, and
is expected to grow over time based on real-world experience. The
initial set is:
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4.3.1. Negotiation Failures
o "starttls-not-supported": This indicates that the recipient MX did
not support STARTTLS.
o "certificate-host-mismatch": This indicates that the certificate
presented did not adhere to the constraints specified in the MTA-
STS or DANE policy, e.g. if the MX hostname does not match any
identities listed in the Subject Alternate Name (SAN) [RFC5280].
o "certificate-expired": This indicates that the certificate has
expired.
o "certificate-not-trusted": This a label that covers multiple
certificate related failures that include, but not limited to
errors such as untrusted/unknown CAs, certificate name
constraints, certificate chain errors etc. When using this
declaration, the reporting MTA SHOULD utilize the "failure-reason-
code" to provide more information to the receiving entity.
o "validation-failure": This indicates a general failure for a
reason not matching a category above. When using this
declaration, the reporting MTA SHOULD utilize the "failure-reason-
code" to provide more information to the receiving entity.
4.3.2. Policy Failures
4.3.2.1. DANE-specific Policy Failures
o "tlsa-invalid": This indicates a validation error in the TLSA
record associated with a DANE policy. None of the records in the
RRset were found to be valid.
o "dnssec-invalid": This would indicate that no valid records were
returned from the recursive resolver. The request returned with
SERVFAIL for the requested TLSA record.
o "dane-required": This indicates that the sending system is
configured to require DANE TLSA records for all the MX hosts of
the destination domain, but no DNSSEC-validated TLSA records were
present for the MX host that is the subject of the report.
Mandatory DANE for SMTP is described in section 6 of [RFC7672].
Such policies may be created by mutual agreement between two
organizations that frequently exchange sensitive content via
email.
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4.3.2.2. MTA-STS-specific Policy Failures
o "sts-policy-invalid": This indicates a validation error for the
overall MTA-STS policy.
o "sts-webpki-invalid": This indicates that the MTA-STS policy could
not be authenticated using PKIX validation.
4.3.3. General Failures
When a negotiation failure can not be categorized into one of the
"Negotiation Failures" stated above, the reporter SHOULD use the
"validation-failure" category. As TLS grows and becomes more
complex, new mechanisms may not be easily categorized. This allows
for a generic feedback category. When this category is used, the
reporter SHOULD also use the "failure-reason-code" to give some
feedback to the receiving entity. This is intended to be a short
text field, and the contents of the field should be an error code or
error text, such as "X509_V_ERR_UNHANDLED_CRITICAL_CRL_EXTENSION".
4.3.4. Transient Failures
Transient errors due to too-busy network, TCP timeouts, etc. are not
required to be reported.
4.4. JSON Report Schema
The JSON schema is derived from the HPKP JSON schema [RFC7469] (cf.
Section 3)
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{
"organization-name": organization-name,
"date-range": {
"start-datetime": date-time,
"end-datetime": date-time
},
"contact-info": email-address,
"report-id": report-id,
"policies": [{
"policy": {
"policy-type": policy-type,
"policy-string": policy-string,
"policy-domain": domain,
"mx-host": mx-host-pattern
},
"summary": {
"total-successful-session-count": total-successful-session-count,
"total-failure-session-count": total-failure-session-count
},
"failure-details": [
{
"result-type": result-type,
"sending-mta-ip": ip-address,
"receiving-mx-hostname": receiving-mx-hostname,
"receiving-mx-helo": receiving-mx-helo,
"receiving-ip": receiving-ip,
"failed-session-count": failed-session-count,
"additional-information": additional-info-uri,
"failure-reason-code": failure-reason-code
}
]
}
]
}
JSON Report Format
o "organization-name": The name of the organization responsible for
the report. It is provided as a string.
o "date-time": The date-time indicates the start- and end-times for
the report range. It is provided as a string formatted according
to Section 5.6, "Internet Date/Time Format", of [RFC3339]. The
report should be for a full UTC day, 0000-2400.
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o "email-address": The contact information for a responsible party
of the report. It is provided as a string formatted according to
Section 3.4.1, "Addr-Spec", of [RFC5321].
o "report-id": A unique identifier for the report. Report authors
may use whatever scheme they prefer to generate a unique
identifier. It is provided as a string.
o "policy-type": The type of policy that was applied by the sending
domain. Presently, the only three valid choices are "tlsa",
"sts", and the literal string "no-policy-found". It is provided
as a string.
o "policy-string": An encoding of the applied policy as a JSON array
of strings, whether TLSA record ([RFC6698] section 2.3) or MTA-STS
policy. Examples follow in the next section.
o "domain": The Policy Domain is the domain against which the MTA-
STS or DANE policy is defined. In the case of Internationalized
Domain Names ([RFC5891]), the domain MUST consist of the Punycode-
encoded A-labels ([RFC3492]) and not the U-labels.
o "mx-host-pattern": The pattern of MX hostnames from the applied
policy. It is provided as a string, and is interpreted in the
same manner as the "Checking of Wildcard Certificates" rules in
Section 6.4.3 of [RFC6125]. In the case of Internationalized
Domain Names ([RFC5891]), the domain MUST consist of the Punycode-
encoded A-labels ([RFC3492]) and not the U-labels.
o "result-type": A value from Section 4.3, "Result Types", above.
o "ip-address": The IP address of the sending MTA that attempted the
STARTTLS connection. It is provided as a string representation of
an IPv4 (see below) or IPv6 ([RFC5952]) address in dot-decimal or
colon-hexadecimal notation.
o "receiving-mx-hostname": The hostname of the receiving MTA MX
record with which the sending MTA attempted to negotiate a
STARTTLS connection.
o "receiving-mx-helo": (optional) The HELO or EHLO string from the
banner announced during the reported session.
o "receiving-ip": The destination IP address that was using when
creating the outbound session. It is provided as a string
representation of an IPv4 (see below) or IPv6 ([RFC5952]) address
in dot-decimal or colon-hexadecimal notation.
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o "total-successful-session-count": The aggregate count (integer,
encoded as a JSON number) of successfully negotiated TLS-enabled
connections to the receiving site.
o "total-failure-session-count": The aggregate count (integer,
encoded as a JSON number) of failures to negotiate a TLS-enabled
connection to the receiving site.
o "failed-session-count": The number of (attempted) sessions that
match the relevant "result-type" for this section (integer,
encoded as a JSON number).
o "additional-info-uri": An optional URI [RFC3986] pointing to
additional information around the relevant "result-type". For
example, this URI might host the complete certificate chain
presented during an attempted STARTTLS session.
o "failure-reason-code": A text field to include a TLS-related error
code or error message.
For report purposes, an IPv4 Address is defined via the following
ABNF:
IPv4address = dec-octet "." dec-octet "." dec-octet "." dec-octet
dec-octet = DIGIT ; 0-9
/ %x31-39 DIGIT ; 10-99
/ "1" 2DIGIT ; 100-199
/ "2" %x30-34 DIGIT ; 200-249
/ "25" %x30-35 ; 250-255
4.5. Policy Samples
Part of the report body includes the policy that is applied when
attemping relay to the destination.
For DANE TLSA policies, this is a JSON array of strings each
representing the RDATA of a single TLSA resource record as a space-
separated list of its four TLSA fields; the fields are in
presentation format (defined in [RFC6698] Section 2.2) with no
internal spaces or grouping parentheses:
[
"3 0 1 1F850A337E6DB9C609C522D136A475638CC43E1ED424F8EEC8513D747D1D085D",
"3 0 1 12350A337E6DB9C6123522D136A475638CC43E1ED424F8EEC8513D747D1D1234"
]
For MTA-STS policies, this is an array of JSON strings that
represents the policy that is declared by the receiving site,
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including any errors that may be present. Note that where there are
multiple "mx" values, they must be listed as separate "mx" elements
in the policy array, rather as a single nested "mx" sub-array.
[
"version: STSv1",
"mode: testing",
"mx: mx1.example.com",
"mx: mx2.example.com",
"mx: mx.backup-example.com",
"max_age: 604800"
]
5. Report Delivery
Reports can be delivered either as an email message via SMTP or via
HTTP POST.
5.1. Report Filename
The filename is RECOMMENDED to be constructed using the following
ABNF:
filename = sender "!" policy-domain "!" begin-timestamp
"!" end-timestamp [ "!" unique-id ] "." extension
unique-id = 1*(ALPHA / DIGIT)
sender = domain ; From the [RFC5321] that is used
; as the domain for the `contact-info`
; address in the report body
policy-domain = domain
begin-timestamp = 1*DIGIT
; seconds since 00:00:00 UTC January 1, 1970
; indicating start of the time range contained
; in the report
end-timestamp = 1*DIGIT
; seconds since 00:00:00 UTC January 1, 1970
; indicating end of the time range contained
; in the report
extension = "json" / "json.gz"
The extension MUST be "json" for a plain JSON file, or "json.gz" for
a JSON file compressed using GZIP.
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"unique-id" allows an optional unique ID generated by the Sending MTA
to distinguish among multiple reports generated simultaneously by
different sources within the same Policy Domain. For example, this
is a possible filename for a compressed report to the Policy Domain
"example.net" from the Sending MTA "mail.sndr.example.com":
"mail.sndr.example.com!example.net!1470013207!1470186007!001.json.gz"
5.2. Compression
The report SHOULD be subjected to GZIP [RFC1952] compression for both
email and HTTPS transport. Declining to apply compression can cause
the report to be too large for a receiver to process (a commonly
observed receiver limit is ten megabytes); compressing the file
increases the chances of acceptance of the report at some compute
cost.
5.3. Email Transport
The report MAY be delivered by email. To make the reports machine-
parsable for the receivers, we define a top-level media type
"multipart/report" with a new parameter "report-type="tlsrpt"".
Inside it, there are two parts: The first part is human readable,
typically "text/plain", and the second part is machine readable with
a new media type defined called "application/tlsrpt+json". If
compressed, the report should use the media type "application/
tlsrpt+gzip".
In addition, the following two new top level message header fields
are defined:
"TLS-Report-Domain: Receiver-Domain"
"TLS-Report-Submitter: Sender-Domain"
The "TLS-Report-Submitter" value MUST match the value found in the
[RFC5321] domain from the "contact-info" from the report body. These
message headers MUST be included and should allow for easy searching
for all reports submitted by a report domain or a particular
submitter, for example in IMAP [RFC3501]:
"s SEARCH HEADER "TLS-Report-Domain" "example.com""
It is presumed that the aggregate reporting address will be equipped
to process new message header fields and extract MIME parts with the
prescribed media type and filename, and ignore the rest. These
additional headers SHOULD be included in the DKIM [RFC6376] signature
for the message.
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The [RFC5322].Subject field for report submissions SHOULD conform to
the following ABNF:
tlsrpt-subject = %s"Report" FWS ; "Report"
%s"Domain:" FWS ; "Domain:"
domain-name FWS ; per [RFC6376]
%s"Submitter:" FWS ; "Submitter:"
domain-name FWS ; per [RFC6376]
%s"Report-ID:" FWS ; "Report-ID:
"<" id-left "@" id-right ">" ; per [RFC5322]
[CFWS] ; per [RFC5322]
; (as with FWS)
The first domain-name indicates the DNS domain name about which the
report was generated. The second domain-name indicates the DNS
domain name representing the Sending MTA generating the report. The
purpose of the Report-ID: portion of the field is to enable the
Policy Domain to identify and ignore duplicate reports that might be
sent by a Sending MTA.
For instance, this is a possible Subject field for a report to the
Policy Domain "example.net" from the Sending MTA
"mail.sender.example.com". It is line-wrapped as allowed by
[RFC5322]:
Subject: Report Domain: example.net
Submitter: mail.sender.example.com
Report-ID: <735ff.e317+bf22029@mailexample.net>
5.3.1. Example Report
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From: tlsrpt@mail.sender.example.com
Date: Fri, May 09 2017 16:54:30 -0800
To: mts-sts-tlsrpt@example.net
Subject: Report Domain: example.net
Submitter: mail.sender.example.com
Report-ID: <735ff.e317+bf22029@example.net>
TLS-Report-Domain: example.net
TLS-Report-Submitter: mail.sender.example.com
MIME-Version: 1.0
Content-Type: multipart/report; report-type="tlsrpt";
boundary="----=_NextPart_000_024E_01CC9B0A.AFE54C00"
Content-Language: en-us
This is a multipart message in MIME format.
------=_NextPart_000_024E_01CC9B0A.AFE54C00
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 7bit
This is an aggregate TLS report from mail.sender.example.com
------=_NextPart_000_024E_01CC9B0A.AFE54C00
Content-Type: application/tlsrpt+gzip
Content-Transfer-Encoding: base64
Content-Disposition: attachment;
filename="mail.sender.example!example.com!
1013662812!1013749130.json.gz"
<gzipped content of report>
------=_NextPart_000_024E_01CC9B0A.AFE54C00--
...
Note that, when sending failure reports via SMTP, sending MTAs MUST
NOT honor MTA-STS or DANE TLSA failures.
5.4. HTTPS Transport
The report MAY be delivered by POST to HTTPS. If compressed, the
report SHOULD use the media type "application/tlsrpt+gzip", and
"application/tlsrpt+json" otherwise (see section Section 6, "IANA
Considerations").
The receiving system MUST return a "successful" response from its
HTTPS server, typically a 200 or 201 HTTP code [RFC7321]. Other
codes could indicate a delivery failure, and may be retried as per
local sender policy. The receiving system is not expected to process
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reports at receipt time, and MAY store them for processing at a later
time.
5.5. Delivery Retry
In the event of a delivery failure, regardless of the delivery
method, a sender SHOULD attempt redelivery for up to 24hrs after the
initial attempt. As previously stated the reports are optional, so
while it is ideal to attempt redelivery, it is not required. If
multiple retries are attempted, ideally they SHOULD be done with
exponential backoff.
5.6. Metadata Variances
As stated above, there are a variable number of ways to declare
information about the data therein. If any of items declared via
subject or filename disagree with the report, the report MUST be
considered the authoritative source.
6. IANA Considerations
The following are the IANA considerations discussed in this document.
6.1. Message headers
Below is the Internet Assigned Numbers Authority (IANA) Permanent
Message Header Field registration information per [RFC3864].
Header field name: TLS-Report-Domain
Applicable protocol: mail
Status: standard
Author/Change controller: IETF
Specification document(s): this one
Header field name: TLS-Report-Submitter
Applicable protocol: mail
Status: standard
Author/Change controller: IETF
Specification document(s): this one
6.2. Report Type
This document creates a new registry for "report-type" parameter to
the Content-Type header field for the "multipart/report" top-level
media type defined in [RFC6522].
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The registry name is "Report Type Registry", and the procedure for
updating the registry will be "Specification Required".
An entry in this registry should contain:
o the report-type being registered
o one or more registered media-types that can be used with this
report-type
o the document containing the registration action
o an optional comment
The initial entries are:
Report-Type: tlsrpt Media Type: application/tlsrpt+gzip, application/
tlsrpt+json Registered By: [RFCXXXX] Comment: Media types suitable
for use with this report-type are defined in Sections 6.4 and 6.5 of
[RFCXXXX]
Report-Type: disposition-notification Media Type: message/
disposition-notification Registered By: [RFC8098] Section 10
Report-Type: disposition-notification Media Type: message/global-
disposition-notification Registered By: [RFC6533] Section 6
Report-Type: delivery-status Media Type: message/delivery-status
Registered By: [RFC3464] Appendix D
Report-Type: delivery-status Media Type: message/global-delivery-
status Registered By: [RFC6533] Section 6
6.3. +gzip Media Type Suffix
This document registers a new media type suffix "+gzip". The GZIP
format is a public domain, cross-platform, interoperable file storage
and transfer format, specified in [RFC1952]; it supports compression
and is used as the underlying representation by a variety of file
formats. The media type "application/gzip" has been registered for
such files. The suffix "+gzip" MAY be used with any media type whose
representation follows that established for "application/gzip". The
media type structured syntax suffix registration form follows:
Type name: GZIP file storage and transfer format
+suffix: +gzip
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References: [RFC1952][RFC6713]
Encoding considerations: GZIP is a binary encoding.
Fragment identifier considerations: The syntax and semantics of
fragment identifiers specified for +gzip SHOULD be as specified for
"application/gzip". (At publication of this document, there is no
fragment identification syntax defined for "application/gzip".) The
syntax and semantics for fragment identifiers for a specific "xxx/
yyy+gzip" SHOULD be processed as follows:
For cases defined in +gzip, where the fragment identifier
resolves per the +gzip rules, then process as specified in
+gzip.
For cases defined in +gzip, where the fragment identifier does
not resolve per the +gzip rules, then process as specified in
"xxx/yyy+gzip".
For cases not defined in +gzip, then process as specified in
"xxx/yyy+gzip".
Interoperability considerations: n/a
Security considerations: GZIP format doesn't provide confidentiality
protection. Integrity protection is provided by and Adler-32
checksum, which is not cryptographically strong. See also security
considerations of [RFC6713]. Each individual media type registered
with a +gzip suffix can have additional security considerations.
Additionally, GZIP objects can contain multiple files and associated
paths. File paths must be validated when the files are extracted; a
malicious file path could otherwise cause the extractor to overwrite
application or system files.
Contact: art@ietf.org
Author/Change controller: Internet Engineering Task Force
(mailto:iesg@ietf.org).
6.4. application/tlsrpt+json Media Type
This document registers multiple media types, beginning with Table 1
below.
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+-------------+----------------+-------------+-------------------+
| Type | Subtype | File extn | Specification |
+-------------+----------------+-------------+-------------------+
| application | tlsrpt+json | .json | Section 5.3 |
+-------------+----------------+-------------+-------------------+
Table 1: SMTP TLS Reporting Media Type
Type name: application
Subtype name: tlsrpt+json
Required parameters: n/a
Optional parameters: n/a
Encoding considerations: Encoding considerations are identical to
those specified for the "application/json" media type. See
[RFC7493].
Security considerations: Security considerations relating to SMTP TLS
Reporting are discussed in Section 7.
Interoperability considerations: This document specifies format of
conforming messages and the interpretation thereof.
Published specification: Section 5.3 of this document.
Applications that use this media type: Mail User Agents (MUA) and
Mail Transfer Agents.
Additional information:
Magic number(s): n/a
File extension(s): ".json"
Macintosh file type code(s): n/a
Person & email address to contact for further information: See
Authors' Addresses section.
Intended usage: COMMON
Restrictions on usage: n/a
Author: See Authors' Addresses section.
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Change controller: Internet Engineering Task Force
(mailto:iesg@ietf.org).
6.5. application/tlsrpt+gzip Media Type
+-------------+----------------+-------------+-------------------+
| Type | Subtype | File extn | Specification |
+-------------+----------------+-------------+-------------------+
| application | tlsrpt+gzip | .gz | Section 5.3 |
+-------------+----------------+-------------+-------------------+
Table 2: SMTP TLS Reporting Media Type
Type name: application
Subtype name: tlsrpt+gzip
Required parameters: n/a
Optional parameters: n/a
Encoding considerations: Binary
Security considerations: Security considerations relating to SMTP TLS
Reporting are discussed in Section 7. Security considerations
related to gzip compression are discussed in [RFC6713].
Interoperability considerations: This document specifies format of
conforming messages and the interpretation thereof.
Published specification: Section 5.3 of this document.
Applications that use this media type: Mail User Agents (MUA) and
Mail Transfer Agents.
Additional information:
Magic number(s): The first two bytes are 0x1f, 0x8b.
File extension(s): ".gz"
Macintosh file type code(s): n/a
Person & email address to contact for further information: See
Authors' Addresses section.
Intended usage: COMMON
Restrictions on usage: n/a
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Author: See Authors' Addresses section.
Change controller: Internet Engineering Task Force
(mailto:iesg@ietf.org).
6.6. STARTTLS Validation Result Types
This document creates a new registry, "STARTTLS Validation Result
Types". The initial entries in the registry are:
+-------------------------------+-----------+
| Result Type | Desc |
+-------------------------------+-----------+
| "starttls-not-supported" | 4.3 |
| "certificate-host-mismatch" | 4.3 |
| "certificate-expired" | 4.3 |
| "tlsa-invalid" | 4.3 |
| "dnssec-invalid" | 4.3 |
| "dane-required" | 4.3 |
| "certificate-not-trusted" | 4.3 |
| "sts-policy-invalid" | 4.3 |
| "sts-webpki-invalid" | 4.3 |
| "validation-failure" | 4.3 |
+-------------------------------+-----------+
The above entries are described in section Section 4.3, "Result
Types." New result types can be added to this registry using "Expert
Review" IANA registration policy.
7. Security Considerations
SMTP TLS Reporting provides transparency into misconfigurations or
attempts to intercept or tamper with mail between hosts who support
STARTTLS. There are several security risks presented by the
existence of this reporting channel:
o Flooding of the Aggregate report URI (rua) endpoint: An attacker
could flood the endpoint with excessive reporting traffic and
prevent the receiving domain from accepting additional reports.
This type of Denial-of-Service attack would limit visibility into
STARTTLS failures, leaving the receiving domain blind to an
ongoing attack.
o Untrusted content: An attacker could inject malicious code into
the report, opening a vulnerability in the receiving domain.
Implementers are advised to take precautions against evaluating
the contents of the report.
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o Report snooping: An attacker could create a bogus TLSRPT record to
receive statistics about a domain the attacker does not own.
Since an attacker able to poison DNS is already able to receive
counts of SMTP connections (and, absent DANE or MTA-STS policies,
actual SMTP message payloads), this does not present a significant
new vulnerability.
o Ignoring HTTPS validation when submitting reports: When reporting
benign misconfigurations, it is likely that a misconfigured SMTP
server may also mean a misconfigured HTTPS server; as a result,
reporters who required HTTPS validity on the reporting endpoint
may fail to alert administrators about such misconfigurations.
Conversely, in the event of an actual attack, an attacker who
wished to create a gap in reporting and could intercept HTTPS
reports could, just as easily, simply thwart the resolution of the
TLSRPT TXT record or establishment of the TCP session to the HTTPS
endpoint. Furthermore, such a man-in-the-middle attacker could
discover most or all of the metadata exposed in a report merely
through passive observation. As a result, we consider the risks
of failure to deliver reports on misconfigurations to outweigh
those of attackers intercepting reports.
o Reports as DDoS: TLSRPT allows specifying destinations for the
reports that are outside the authority of the Policy Domain, which
allows domains to delegate processing of reports to a partner
organization. However, an attacker who controls the Policy Domain
DNS could also use this mechanism to direct the reports to an
unwitting victim, flooding that victim with excessive reports.
DMARC [RFC7489] defines a solution for verifying delegation to
avoid such attacks; the need for this is greater with DMARC,
however, because DMARC allows an attacker to trigger reports to a
target from an innocent third party by sending that third party
mail (which triggers a report from the third party to the target).
In the case of TLSRPT, the attacker would have to induce the third
party to send the attacker mail in order to trigger reports from
the third party to the victim; this reduces the risk of such an
attack and the need for a verification mechanism.
Finally, because TLSRPT is intended to help administrators discover
man-in-the-middle attacks against transport-layer encryption,
including attacks designed to thwart negotiation of encrypted
connections (by downgrading opportunistic encryption or, in the case
of MTA-STS, preventing discovery of a new MTA-STS policy), we must
also consider the risk that an adversary who can induce such a
downgrade attack can also prevent discovery of the TLSRPT TXT record
(and thus prevent discovery of the successful downgrade attack).
Administrators are thus encouraged to deploy TLSRPT TXT records with
a large TTL (reducing the window for successful application of
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transient attacks against DNS resolution of the record) or to deploy
DNSSEC on the deploying zone.
8. Privacy Considerations
MTAs are generally considered public knowledge, however, the
internals of how those MTAs are configured and the users of those
MTAs may not be as public. It should be noted that when providing a
receiving site with information, it may reveal information about the
sender's configuration, or even information about the senders
themselves. Consider that by sending a report, it might disclose
your SSL library version as the inability to negotiate a session may
be a known incompatbility between two library versions, or perhaps
commonly used in a operating system release that is centered in a
certain region. The risk may be minimal, but should be considered.
9. References
9.1. Normative References
[I-D.ietf-uta-mta-sts]
Margolis, D., Risher, M., Ramakrishnan, B., Brotman, A.,
and J. Jones, "SMTP MTA Strict Transport Security (MTA-
STS)", draft-ietf-uta-mta-sts-19 (work in progress), May
2018.
[RFC1952] Deutsch, P., "GZIP file format specification version 4.3",
RFC 1952, DOI 10.17487/RFC1952, May 1996,
<https://www.rfc-editor.org/info/rfc1952>.
[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>.
[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>.
[RFC3492] Costello, A., "Punycode: A Bootstring encoding of Unicode
for Internationalized Domain Names in Applications
(IDNA)", RFC 3492, DOI 10.17487/RFC3492, March 2003,
<https://www.rfc-editor.org/info/rfc3492>.
[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>.
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[RFC4408] Wong, M. and W. Schlitt, "Sender Policy Framework (SPF)
for Authorizing Use of Domains in E-Mail, Version 1",
RFC 4408, DOI 10.17487/RFC4408, April 2006,
<https://www.rfc-editor.org/info/rfc4408>.
[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>.
[RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
Housley, R., and W. Polk, "Internet X.509 Public Key
Infrastructure Certificate and Certificate Revocation List
(CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008,
<https://www.rfc-editor.org/info/rfc5280>.
[RFC5321] Klensin, J., "Simple Mail Transfer Protocol", RFC 5321,
DOI 10.17487/RFC5321, October 2008, <https://www.rfc-
editor.org/info/rfc5321>.
[RFC5322] Resnick, P., Ed., "Internet Message Format", RFC 5322,
DOI 10.17487/RFC5322, October 2008, <https://www.rfc-
editor.org/info/rfc5322>.
[RFC5891] Klensin, J., "Internationalized Domain Names in
Applications (IDNA): Protocol", RFC 5891,
DOI 10.17487/RFC5891, August 2010, <https://www.rfc-
editor.org/info/rfc5891>.
[RFC5952] Kawamura, S. and M. Kawashima, "A Recommendation for IPv6
Address Text Representation", RFC 5952,
DOI 10.17487/RFC5952, August 2010, <https://www.rfc-
editor.org/info/rfc5952>.
[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>.
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[RFC6376] Crocker, D., Ed., Hansen, T., Ed., and M. Kucherawy, Ed.,
"DomainKeys Identified Mail (DKIM) Signatures", STD 76,
RFC 6376, DOI 10.17487/RFC6376, September 2011,
<https://www.rfc-editor.org/info/rfc6376>.
[RFC6522] Kucherawy, M., Ed., "The Multipart/Report Media Type for
the Reporting of Mail System Administrative Messages",
STD 73, RFC 6522, DOI 10.17487/RFC6522, January 2012,
<https://www.rfc-editor.org/info/rfc6522>.
[RFC6698] Hoffman, P. and J. Schlyter, "The DNS-Based Authentication
of Named Entities (DANE) Transport Layer Security (TLS)
Protocol: TLSA", RFC 6698, DOI 10.17487/RFC6698, August
2012, <https://www.rfc-editor.org/info/rfc6698>.
[RFC6713] Levine, J., "The 'application/zlib' and 'application/gzip'
Media Types", RFC 6713, DOI 10.17487/RFC6713, August 2012,
<https://www.rfc-editor.org/info/rfc6713>.
[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>.
[RFC7493] Bray, T., Ed., "The I-JSON Message Format", RFC 7493,
DOI 10.17487/RFC7493, March 2015, <https://www.rfc-
editor.org/info/rfc7493>.
[RFC7672] Dukhovni, V. and W. Hardaker, "SMTP Security via
Opportunistic DNS-Based Authentication of Named Entities
(DANE) Transport Layer Security (TLS)", RFC 7672,
DOI 10.17487/RFC7672, October 2015, <https://www.rfc-
editor.org/info/rfc7672>.
[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>.
9.2. Informative References
[RFC3207] Hoffman, P., "SMTP Service Extension for Secure SMTP over
Transport Layer Security", RFC 3207, DOI 10.17487/RFC3207,
February 2002, <https://www.rfc-editor.org/info/rfc3207>.
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[RFC3464] Moore, K. and G. Vaudreuil, "An Extensible Message Format
for Delivery Status Notifications", RFC 3464,
DOI 10.17487/RFC3464, January 2003, <https://www.rfc-
editor.org/info/rfc3464>.
[RFC3501] Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL - VERSION
4rev1", RFC 3501, DOI 10.17487/RFC3501, March 2003,
<https://www.rfc-editor.org/info/rfc3501>.
[RFC3864] Klyne, G., Nottingham, M., and J. Mogul, "Registration
Procedures for Message Header Fields", BCP 90, RFC 3864,
DOI 10.17487/RFC3864, September 2004, <https://www.rfc-
editor.org/info/rfc3864>.
[RFC6533] Hansen, T., Ed., Newman, C., and A. Melnikov,
"Internationalized Delivery Status and Disposition
Notifications", RFC 6533, DOI 10.17487/RFC6533, February
2012, <https://www.rfc-editor.org/info/rfc6533>.
[RFC7321] McGrew, D. and P. Hoffman, "Cryptographic Algorithm
Implementation Requirements and Usage Guidance for
Encapsulating Security Payload (ESP) and Authentication
Header (AH)", RFC 7321, DOI 10.17487/RFC7321, August 2014,
<https://www.rfc-editor.org/info/rfc7321>.
[RFC7435] Dukhovni, V., "Opportunistic Security: Some Protection
Most of the Time", RFC 7435, DOI 10.17487/RFC7435,
December 2014, <https://www.rfc-editor.org/info/rfc7435>.
[RFC7469] Evans, C., Palmer, C., and R. Sleevi, "Public Key Pinning
Extension for HTTP", RFC 7469, DOI 10.17487/RFC7469, April
2015, <https://www.rfc-editor.org/info/rfc7469>.
[RFC7489] Kucherawy, M., Ed. and E. Zwicky, Ed., "Domain-based
Message Authentication, Reporting, and Conformance
(DMARC)", RFC 7489, DOI 10.17487/RFC7489, March 2015,
<https://www.rfc-editor.org/info/rfc7489>.
[RFC8098] Hansen, T., Ed. and A. Melnikov, Ed., "Message Disposition
Notification", STD 85, RFC 8098, DOI 10.17487/RFC8098,
February 2017, <https://www.rfc-editor.org/info/rfc8098>.
9.3. URIs
[1] Section 2.2.3
[2] Section 3
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Appendix A. Example Reporting Policy
A.1. Report using MAILTO
_smtp._tls.mail.example.com. IN TXT \
"v=TLSRPTv1;rua=mailto:reports@example.com"
A.2. Report using HTTPS
_smtp._tls.mail.example.com. IN TXT \
"v=TLSRPTv1; \
rua=https://reporting.example.com/v1/tlsrpt"
Appendix B. Example JSON Report
Below is an example JSON report for messages from Company-X to
Company-Y, where 100 sessions were attempted to Company Y servers
with an expired certificate and 200 sessions were attempted to
Company Y servers that did not successfully respond to the "STARTTLS"
command. Additionally 3 sessions failed due to
"X509_V_ERR_PROXY_PATH_LENGTH_EXCEEDED".
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{
"organization-name": "Company-X",
"date-range": {
"start-datetime": "2016-04-01T00:00:00Z",
"end-datetime": "2016-04-01T23:59:59Z"
},
"contact-info": "sts-reporting@company-x.example",
"report-id": "5065427c-23d3-47ca-b6e0-946ea0e8c4be",
"policies": [{
"policy": {
"policy-type": "sts",
"policy-string": ["version: STSv1","mode: testing",
"mx: *.mail.company-y.example","max_age: 86400"],
"policy-domain": "company-y.example",
"mx-host": "*.mail.company-y.example"
},
"summary": {
"total-successful-session-count": 5326,
"total-failure-session-count": 303
},
"failure-details": [{
"result-type": "certificate-expired",
"sending-mta-ip": "2001:db8:abcd:0012::1",
"receiving-mx-hostname": "mx1.mail.company-y.example",
"failed-session-count": 100
}, {
"result-type": "starttls-not-supported",
"sending-mta-ip": "2001:db8:abcd:0013::1",
"receiving-mx-hostname": "mx2.mail.company-y.example",
"receiving-ip": "203.0.113.56",
"failed-session-count": 200,
"additional-information": "https://reports.company-x.example/
report_info ? id = 5065427 c - 23 d3# StarttlsNotSupported "
}, {
"result-type": "validation-failure",
"sending-mta-ip": "198.51.100.62",
"receiving-ip": "203.0.113.58",
"receiving-mx-hostname": "mx-backup.mail.company-y.example",
"failed-session-count": 3,
"failure-error-code": "X509_V_ERR_PROXY_PATH_LENGTH_EXCEEDED"
}]
}]
}
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Authors' Addresses
Daniel Margolis
Google, Inc
Email: dmargolis@google.com
Alexander Brotman
Comcast, Inc
Email: alex_brotman@comcast.com
Binu Ramakrishnan
Yahoo!, Inc
Email: rbinu@oath.com
Janet Jones
Microsoft, Inc
Email: janet.jones@microsoft.com
Mark Risher
Google, Inc
Email: risher@google.com
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