--- 1/draft-ietf-httpbis-encryption-encoding-00.txt 2016-03-20 23:15:54.974580874 -0700 +++ 2/draft-ietf-httpbis-encryption-encoding-01.txt 2016-03-20 23:15:55.018581962 -0700 @@ -1,98 +1,111 @@ -Network Working Group M. Thomson +HTTP Working Group M. Thomson Internet-Draft Mozilla -Intended status: Standards Track December 22, 2015 -Expires: June 24, 2016 +Intended status: Standards Track March 20, 2016 +Expires: September 21, 2016 Encrypted Content-Encoding for HTTP - draft-ietf-httpbis-encryption-encoding-00 + draft-ietf-httpbis-encryption-encoding-01 Abstract This memo introduces a content-coding for HTTP that allows message payloads to be encrypted. +Note to Readers + + Discussion of this draft takes place on the HTTP working group + mailing list (ietf-http-wg@w3.org), which is archived at + https://lists.w3.org/Archives/Public/ietf-http-wg/ . + + Working Group information can be found at http://httpwg.github.io/ ; + source code and issues list for this draft can be found at + https://github.com/httpwg/http-extensions/labels/encryption . + 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 June 24, 2016. + This Internet-Draft will expire on September 21, 2016. Copyright Notice - Copyright (c) 2015 IETF Trust and the persons identified as the + Copyright (c) 2016 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 . . . . . . . . . . . . . . . . . . . . . . . . 2 + 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Notational Conventions . . . . . . . . . . . . . . . . . 3 - 2. The "aesgcm128" HTTP Content Encoding . . . . . . . . . . . . 3 + 2. The "aesgcm" HTTP Content Encoding . . . . . . . . . . . . . 4 3. The Encryption HTTP Header Field . . . . . . . . . . . . . . 5 3.1. Encryption Header Field Parameters . . . . . . . . . . . 6 - 3.2. Content Encryption Key Derivation . . . . . . . . . . . . 6 + 3.2. Content Encryption Key Derivation . . . . . . . . . . . . 7 3.3. Nonce Derivation . . . . . . . . . . . . . . . . . . . . 7 4. Crypto-Key Header Field . . . . . . . . . . . . . . . . . . . 8 - 4.1. Explicit Key . . . . . . . . . . . . . . . . . . . . . . 8 + 4.1. Explicit Key . . . . . . . . . . . . . . . . . . . . . . 9 4.2. Diffie-Hellman . . . . . . . . . . . . . . . . . . . . . 9 4.3. Pre-shared Authentication Secrets . . . . . . . . . . . . 10 5. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 11 5.1. Successful GET Response . . . . . . . . . . . . . . . . . 11 - 5.2. Encryption and Compression . . . . . . . . . . . . . . . 11 - 5.3. Encryption with More Than One Key . . . . . . . . . . . . 11 + 5.2. Encryption and Compression . . . . . . . . . . . . . . . 12 + 5.3. Encryption with More Than One Key . . . . . . . . . . . . 12 5.4. Encryption with Explicit Key . . . . . . . . . . . . . . 12 - 5.5. Diffie-Hellman Encryption . . . . . . . . . . . . . . . . 12 - 6. Security Considerations . . . . . . . . . . . . . . . . . . . 13 - 6.1. Key and Nonce Reuse . . . . . . . . . . . . . . . . . . . 13 - 6.2. Content Integrity . . . . . . . . . . . . . . . . . . . . 13 - 6.3. Leaking Information in Headers . . . . . . . . . . . . . 14 - 6.4. Poisoning Storage . . . . . . . . . . . . . . . . . . . . 14 - 6.5. Sizing and Timing Attacks . . . . . . . . . . . . . . . . 15 - 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15 - 7.1. The "aesgcm128" HTTP Content Encoding . . . . . . . . . . 15 - 7.2. Encryption Header Fields . . . . . . . . . . . . . . . . 15 - 7.3. The HTTP Encryption Parameter Registry . . . . . . . . . 16 - 7.3.1. keyid . . . . . . . . . . . . . . . . . . . . . . . . 16 - 7.3.2. salt . . . . . . . . . . . . . . . . . . . . . . . . 16 - 7.3.3. rs . . . . . . . . . . . . . . . . . . . . . . . . . 17 - 7.4. The HTTP Crypto-Key Parameter Registry . . . . . . . . . 17 - 7.4.1. keyid . . . . . . . . . . . . . . . . . . . . . . . . 17 - 7.4.2. aesgcm128 . . . . . . . . . . . . . . . . . . . . . . 17 - 7.4.3. dh . . . . . . . . . . . . . . . . . . . . . . . . . 18 - 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 18 - 8.1. Normative References . . . . . . . . . . . . . . . . . . 18 - 8.2. Informative References . . . . . . . . . . . . . . . . . 19 - Appendix A. JWE Mapping . . . . . . . . . . . . . . . . . . . . 20 - Appendix B. Acknowledgements . . . . . . . . . . . . . . . . . . 21 - Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 21 + 5.5. Encryption with Multiple Records . . . . . . . . . . . . 13 + 5.6. Diffie-Hellman Encryption . . . . . . . . . . . . . . . . 13 + 5.7. Diffie-Hellman with Authentication Secret . . . . . . . . 14 + 6. Security Considerations . . . . . . . . . . . . . . . . . . . 14 + 6.1. Key and Nonce Reuse . . . . . . . . . . . . . . . . . . . 15 + 6.2. Content Integrity . . . . . . . . . . . . . . . . . . . . 15 + 6.3. Leaking Information in Headers . . . . . . . . . . . . . 15 + 6.4. Poisoning Storage . . . . . . . . . . . . . . . . . . . . 16 + 6.5. Sizing and Timing Attacks . . . . . . . . . . . . . . . . 16 + 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16 + 7.1. The "aesgcm" HTTP Content Encoding . . . . . . . . . . . 16 + 7.2. Encryption Header Fields . . . . . . . . . . . . . . . . 17 + 7.3. The HTTP Encryption Parameter Registry . . . . . . . . . 17 + 7.3.1. keyid . . . . . . . . . . . . . . . . . . . . . . . . 18 + 7.3.2. salt . . . . . . . . . . . . . . . . . . . . . . . . 18 + 7.3.3. rs . . . . . . . . . . . . . . . . . . . . . . . . . 18 + 7.4. The HTTP Crypto-Key Parameter Registry . . . . . . . . . 18 + 7.4.1. keyid . . . . . . . . . . . . . . . . . . . . . . . . 19 + 7.4.2. aesgcm . . . . . . . . . . . . . . . . . . . . . . . 19 + 7.4.3. dh . . . . . . . . . . . . . . . . . . . . . . . . . 19 + 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 19 + 8.1. Normative References . . . . . . . . . . . . . . . . . . 19 + 8.2. Informative References . . . . . . . . . . . . . . . . . 20 + Appendix A. JWE Mapping . . . . . . . . . . . . . . . . . . . . 21 + Appendix B. Intermediate Values for Encryption . . . . . . . . . 22 + Appendix C. Acknowledgements . . . . . . . . . . . . . . . . . . 23 + Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 23 1. Introduction It is sometimes desirable to encrypt the contents of a HTTP message (request or response) so that when the payload is stored (e.g., with a HTTP PUT), only someone with the appropriate key can read it. For example, it might be necessary to store a file on a server without exposing its contents to that server. Furthermore, that same file could be replicated to other servers (to make it more resistant @@ -123,45 +136,47 @@ identify keys will depend on the use case. Though a complete key management system is not described, this document defines an Crypto- Key header field that can be used to convey keying material. 1.1. Notational Conventions The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119]. -2. The "aesgcm128" HTTP Content Encoding + Base64url encoding is defined in Section 2 of [RFC7515]. - The "aesgcm128" HTTP content-coding indicates that a payload has been +2. The "aesgcm" HTTP Content Encoding + + The "aesgcm" HTTP content-coding indicates that a payload has been encrypted using Advanced Encryption Standard (AES) in Galois/Counter Mode (GCM) as identified as AEAD_AES_128_GCM in [RFC5116], Section 5.1. The AEAD_AES_128_GCM algorithm uses a 128 bit content encryption key. When this content-coding is in use, the Encryption header field (Section 3) describes how encryption has been applied. The Crypto- Key header field (Section 4) can be included to describe how the content encryption key is derived or retrieved. - The "aesgcm128" content-coding uses a single fixed set of encryption + The "aesgcm" content-coding uses a single fixed set of encryption primitives. Cipher suite agility is achieved by defining a new content-coding scheme. This ensures that only the HTTP Accept- Encoding header field is necessary to negotiate the use of encryption. - The "aesgcm128" content-coding uses a fixed record size. The - resulting encoding is a series of fixed-size records, with a final - record that is one or more octets shorter than a fixed sized record. + The "aesgcm" content-coding uses a fixed record size. The resulting + encoding is a series of fixed-size records, with a final record that + is one or more octets shorter than a fixed sized record. - +------+ input of between rs-256 - | data | and rs-1 octets + +------+ input of between rs-65537 + | data | and rs-2 octets +------+ (one fewer for the last record) | v +-----+-----------+ | pad | data | add padding to form plaintext +-----+-----------+ | v +--------------------+ | ciphertext | encrypt with AEAD_AES_128_GCM @@ -174,26 +189,26 @@ field. AEAD_AES_128_GCM expands ciphertext to be 16 octets longer than its input plaintext. Therefore, the length of each enciphered record other than the last is equal to the value of the "rs" parameter plus 16 octets. A receiver MUST fail to decrypt if the final record ciphertext is 16 octets or less in size. Valid records always contain at least one byte of padding and a 16 octet authentication tag. - Each record contains between 1 and 256 octets of padding, inserted + Each record contains between 2 and 65537 octets of padding, inserted into a record before the enciphered content. Padding consists of a - length byte, followed that number of zero-valued octets. A receiver - MUST fail to decrypt if any padding octet other than the first is - non-zero, or a record has more padding than the record size can - accommodate. + two octet unsigned integer in network byte order, followed that + number of zero-valued octets. A receiver MUST fail to decrypt if any + padding octet other than the first two are non-zero, or a record has + more padding than the record size can accommodate. The nonce for each record is a 96-bit value constructed from the record sequence number and the input keying material. Nonce derivation is covered in Section 3.3. The additional data passed to each invocation of AEAD_AES_128_GCM is a zero-length octet sequence. A sequence of full-sized records can be truncated to produce a shorter sequence of records with valid authentication tags. To @@ -245,28 +260,28 @@ The following parameters are used in determining the content encryption key that is used for encryption: keyid: The "keyid" parameter contains a string that identifies the keying material that is used. The "keyid" parameter SHOULD be included, unless key identification is guaranteed by other means. The "keyid" parameter MUST be used if keying material included in an Crypto-Key header field is needed to derive the content encryption key. - salt: The "salt" parameter contains a base64 URL-encoded octets that - is used as salt in deriving a unique content encryption key (see - Section 3.2). The "salt" parameter MUST be present, and MUST be - exactly 16 octets long when decoded. The "salt" parameter MUST - NOT be reused for two different payload bodies that have the same - input keying material; generating a random salt for every - application of the content encoding ensures that content - encryption key reuse is highly unlikely. + salt: The "salt" parameter contains a base64url-encoded octets + [RFC7515] that is used as salt in deriving a unique content + encryption key (see Section 3.2). The "salt" parameter MUST be + present, and MUST be exactly 16 octets long when decoded. The + "salt" parameter MUST NOT be reused for two different payload + bodies that have the same input keying material; generating a + random salt for every application of the content encoding ensures + that content encryption key reuse is highly unlikely. rs: The "rs" parameter contains a positive decimal integer that describes the record size in octets. This value MUST be greater than 1. If the "rs" parameter is absent, the record size defaults to 4096 octets. 3.2. Content Encryption Key Derivation In order to allow the reuse of keying material for multiple different HTTP messages, a content encryption key is derived for each message. @@ -276,24 +291,24 @@ The decoded value of the "salt" parameter is the salt input to HKDF function. The keying material identified by the "keyid" parameter is the input keying material (IKM) to HKDF. Input keying material can either be prearranged, or can be described using the Crypto-Key header field (Section 4). The first step of HKDF is therefore: PRK = HMAC-SHA-256(salt, IKM) The info parameter to HKDF is set to the ASCII-encoded string - "Content-Encoding: aesgcm128", a single zero octet and an optional + "Content-Encoding: aesgcm", a single zero octet and an optional context string: - cek_info = "Content-Encoding: aesgcm128" || 0x00 || context + cek_info = "Content-Encoding: aesgcm" || 0x00 || context Unless otherwise specified, the context is a zero length octet sequence. Specifications that use this content encoding MAY specify the use of an expanded context to cover additional inputs in the key derivation. AEAD_AES_128_GCM requires a 16 octet (128 bit) content encryption key, so the length (L) parameter to HKDF is 16. The second step of HKDF can therefore be simplified to the first 16 octets of a single HMAC: @@ -335,22 +350,22 @@ The Crypto-Key header field uses the extended ABNF syntax defined in Section 1.2 of [RFC7230] and the "parameter" rule from [RFC7231]. Crypto-Key = #crypto_key_params crypto_key_params = [ parameter *( ";" parameter ) ] keyid: The "keyid" parameter corresponds to the "keyid" parameter in the Encryption header field. - aesgcm128: The "aesgcm128" parameter contains the URL-safe base64 - [RFC4648] octets of the input keying material. + aesgcm: The "aesgcm" parameter contains the base64url-encoded octets + [RFC7515] of the input keying material. dh: The "dh" parameter contains an ephemeral Diffie-Hellman share. This form of the header field can be used to encrypt content for a specific recipient. Crypto-Key header field values with multiple instances of the same parameter name are invalid. The input keying material used by the key derivation (see Section 3.2) can be determined based on the information in the @@ -363,26 +378,26 @@ Note that different methods for determining input keying material will produce different amounts of data. The HKDF process ensures that the final content encryption key is the necessary size. Alternative methods for determining input keying material MAY be defined by specifications that use this content-encoding. 4.1. Explicit Key - The "aesgcm128" parameter is decoded and used as the input keying - material for the "aesgcm128" content encoding. The "aesgcm128" - parameter MUST decode to at least 16 octets in order to be used as - input keying material for "aesgcm128" content encoding. + The "aesgcm" parameter is decoded and used as the input keying + material for the "aesgcm" content encoding. The "aesgcm" parameter + MUST decode to at least 16 octets in order to be used as input keying + material for "aesgcm" content encoding. - Other key determination parameters can be ignored if the "aesgcm128" + Other key determination parameters can be ignored if the "aesgcm" parameter is present. 4.2. Diffie-Hellman The "dh" parameter is included to describe a Diffie-Hellman share, either modp (or finite field) Diffie-Hellman [DH] or elliptic curve Diffie-Hellman (ECDH) [RFC4492]. This share is combined with other information at the recipient to determine the HKDF input keying material. In order for the exchange @@ -421,23 +436,23 @@ context = label || 0x00 || length(recipient_public) || recipient_public || length(sender_public) || sender_public The two length fields are encoded as a two octet unsigned integer in network byte order. Specifications that rely on an Diffie-Hellman exchange for determining input keying material MUST either specify the parameters - for Diffie-Hellman (group parameters, or curves and point format) - that are used, or describe how those parameters are negotiated - between sender and receiver. + for Diffie-Hellman (label, group parameters, or curves and point + format) that are used, or describe how those parameters are + negotiated between sender and receiver. 4.3. Pre-shared Authentication Secrets Key derivation MAY be extended to include an additional authentication secret. Such a secret is shared between the sender and receiver of a message using other means. A pre-shared authentication secret is not explicitly signaled in either the Encryption or Crypto-Key header fields. Use of this additional step depends on prior agreement. @@ -462,112 +477,160 @@ provided to the final key derivation stages. Alternatively, this phase can be viewed as always having a zero-length context. Note that in the absence of an authentication secret, the input keying material is simply the raw keying material: IKM = raw_key 5. Examples + This section shows a few examples of the content encoding. + + Note: All binary values in the examples in this section use the URL + and filename safe variant of base64 [RFC4648]. This includes the + bodies of requests. Whitespace in these values is added to fit + formatting constraints. + 5.1. Successful GET Response HTTP/1.1 200 OK Content-Type: application/octet-stream - Content-Encoding: aesgcm128 + Content-Encoding: aesgcm Connection: close Encryption: keyid="http://example.org/bob/keys/123"; salt="XZwpw6o37R-6qoZjw6KwAw" [encrypted payload] Here, a successful HTTP GET response has been encrypted using input keying material that is identified by a URI. Note that the media type has been changed to "application/octet- stream" to avoid exposing information about the content. 5.2. Encryption and Compression + In this example, a response is first compressed, then encrypted. + Note that this particular encoding might compromise confidentiality + if the contents of the response could be influenced by an attacker. + HTTP/1.1 200 OK Content-Type: text/html - Content-Encoding: aesgcm128, gzip + Content-Encoding: gzip, aesgcm Transfer-Encoding: chunked Encryption: keyid="mailto:me@example.com"; salt="m2hJ_NttRtFyUiMRPwfpHA" [encrypted payload] 5.3. Encryption with More Than One Key + Here, a PUT request has been encrypted twice with different input + keying material; decrypting twice is necessary to read the content. + The outer layer of encryption uses a 1200 octet record size. + PUT /thing HTTP/1.1 Host: storage.example.com Content-Type: application/http - Content-Encoding: aesgcm128, aesgcm128 - Content-Length: 1234 + Content-Encoding: aesgcm, aesgcm + Content-Length: 1235 Encryption: keyid="mailto:me@example.com"; salt="NfzOeuV5USPRA-n_9s1Lag", keyid="http://example.org/bob/keys/123"; salt="bDMSGoc2uobK_IhavSHsHA"; rs=1200 [encrypted payload] - Here, a PUT request has been encrypted twice with different input - keying material; decrypting twice is necessary to read the content. - The outer layer of encryption uses a 1200 octet record size. 5.4. Encryption with Explicit Key + This example shows the UTF-8 encoded string "I am the walrus" + encrypted using an directly provided value for the input keying + material. The content body contains a single record only and is + shown here using base64url encoding for presentation reasons. + HTTP/1.1 200 OK - Content-Length: 32 - Content-Encoding: aesgcm128 + Content-Length: 33 + Content-Encoding: aesgcm Encryption: keyid="a1"; salt="vr0o6Uq3w_KDWeatc27mUg" - Crypto-Key: keyid="a1"; aesgcm128="csPJEXBYA5U-Tal9EdJi-w" + Crypto-Key: keyid="a1"; aesgcm="csPJEXBYA5U-Tal9EdJi-w" - fuag8ThIRIazSHKUqJ5OduR75UgEUuM76J8UFwadEvg + VDeU0XxaJkOJDAxPl7h9JD5V8N43RorP7PfpPdZZQuwF - This example shows the string "I am the walrus" encrypted using an - directly provided value for the input keying material. The content - body contains a single record only and is shown here encoded in URL- - safe base64 for presentation reasons only. +5.5. Encryption with Multiple Records -5.5. Diffie-Hellman Encryption + This example shows the same encrypted message, but split into records + of 10 octets each. The first record includes a single additional + octet of padding, which causes the end of the content to align with a + record boundary, forcing the creation of a third record that contains + only padding. HTTP/1.1 200 OK - Content-Length: 32 - Content-Encoding: aesgcm128 + Content-Length: 70 + Content-Encoding: aesgcm + Encryption: keyid="a1"; salt="4pdat984KmT9BWsU3np0nw"; rs=10 + Crypto-Key: keyid="a1"; aesgcm="BO3ZVPxUlnLORbVGMpbT1Q" + + uzLfrZ4cbMTC6hlUqHz4NvWZshFlTN3o2RLr6FrIuOKEfl2VrM_jYgoiIyEo + Zvc-ZGwV-RMJejG4M6ZfGysBAdhpPqrLzw + +5.6. Diffie-Hellman Encryption + + HTTP/1.1 200 OK + Content-Length: 33 + Content-Encoding: aesgcm Encryption: keyid="dhkey"; salt="Qg61ZJRva_XBE9IEUelU3A" Crypto-Key: keyid="dhkey"; dh="BDgpRKok2GZZDmS4r63vbJSUtcQx4Fq1V58-6-3NbZzS TlZsQiCEDTQy3CZ0ZMsqeqsEb7qW2blQHA4S48fynTk" - G6j_sfKg0qebO62yXpTCayN2KV24QitNiTvLgcFiEj0 + yqD2bapcx14XxUbtwjiGx69eHE3Yd6AqXcwBpT2Kd1uy This example shows the same string, "I am the walrus", encrypted using ECDH over the P-256 curve [FIPS186], which is identified with the label "P-256" encoded in ASCII. The content body is shown here - encoded in URL-safe base64 for presentation reasons only. + encoded in URL-safe base64url for presentation reasons only. The receiver (in this case, the HTTP client) uses a key pair that is identified by the string "dhkey" and the sender (the server) uses a key pair for which the public share is included in the "dh" parameter above. The keys shown below use uncompressed points [X9.62] encoded - using URL-safe base64. Line wrapping is added for presentation - purposes only. + using base64url. Line wrapping is added for presentation purposes + only. Receiver: private key: 9FWl15_QUQAWDaD3k3l50ZBZQJ4au27F1V4F0uLSD_M public key: BCEkBjzL8Z3C-oi2Q7oE5t2Np-p7osjGLg93qUP0wvqR T21EEWyf0cQDQcakQMqz4hQKYOQ3il2nNZct4HgAUQU Sender: private key: vG7TmzUX9NfVR4XUGBkLAFu8iDyQe-q_165JkkN0Vlw public key: +5.7. Diffie-Hellman with Authentication Secret + + This example shows the same receiver key pair from Section 5.6, but + with a shared authentication secret of "R29vIGdvbyBnJyBqb29iIQ". + + HTTP/1.1 200 OK + Content-Length: 33 + Content-Encoding: aesgcm + Encryption: keyid="dhkey"; salt="lngarbyKfMoi9Z75xYXmkg" + Crypto-Key: keyid="dhkey"; + dh="BNoRDbb84JGm8g5Z5CFxurSqsXWJ11ItfXEWYVLE85Y7 + CYkDjXsIEc4aqxYaQ1G8BqkXCJ6DPpDrWtdWj_mugHU" + + 6nqAQUME8hNqw5J3kl8cpVVJylXKYqZOeseZG8UueKpA + + The sender's private key used in this example is "nCScek-QpEjmOOlT- + rQ38nZzvdPlqa00Zy0i6m2OJvY". Intermediate values for this example + are included in Appendix B. + 6. Security Considerations This mechanism assumes the presence of a key management framework that is used to manage the distribution of keys between valid senders and receivers. Defining key management is part of composing this mechanism into a larger application, protocol, or framework. Implementation of cryptography - and key management in particular - can be difficult. For instance, implementations need to account for the potential for exposing keying material on side channels, such as @@ -656,27 +719,26 @@ so on, may leak sensitive information. This risk can be mitigated through the use of the padding that this mechanism provides. Alternatively, splitting up content into segments and storing the separately might reduce exposure. HTTP/2 [RFC7540] combined with TLS [RFC5246] might be used to hide the size of individual messages. 7. IANA Considerations -7.1. The "aesgcm128" HTTP Content Encoding +7.1. The "aesgcm" HTTP Content Encoding This memo registers the "encrypted" HTTP content-coding in the HTTP Content Codings Registry, as detailed in Section 2. - o Name: aesgcm128 - + o Name: aesgcm o Description: AES-GCM encryption with a 128-bit content encryption key o Reference: this specification 7.2. Encryption Header Fields This memo registers the "Encryption" HTTP header field in the Permanent Message Header Registry, as detailed in Section 3. @@ -746,21 +808,21 @@ o Purpose: The size of the encrypted records. o Reference: this document 7.4. The HTTP Crypto-Key Parameter Registry This memo establishes a registry for parameters used by the "Crypto- Key" header field under the "Hypertext Transfer Protocol (HTTP) Parameters" grouping. The "Hypertext Transfer Protocol (HTTP) - Encryption Parameters" operates under an "Specification Required" + Crypto-Key Parameters" operates under an "Specification Required" policy [RFC5226]. Entries in this registry are expected to include the following information: o Parameter Name: The name of the parameter. o Purpose: A brief description of the purpose of the parameter. o Reference: A reference to a specification that defines the @@ -769,26 +831,26 @@ The initial contents of this registry are: 7.4.1. keyid o Parameter Name: keyid o Purpose: Identify the key that is in use. o Reference: this document -7.4.2. aesgcm128 +7.4.2. aesgcm - o Parameter Name: aesgcm128 + o Parameter Name: aesgcm o Purpose: Provide an explicit input keying material value for the - aesgcm128 content encoding. + aesgcm content encoding. o Reference: this document 7.4.3. dh o Parameter Name: dh o Purpose: Carry a modp or elliptic curve Diffie-Hellman share used to derive input keying material. @@ -812,43 +874,43 @@ Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC4492] Blake-Wilson, S., Bolyard, N., Gupta, V., Hawk, C., and B. Moeller, "Elliptic Curve Cryptography (ECC) Cipher Suites for Transport Layer Security (TLS)", RFC 4492, DOI 10.17487/RFC4492, May 2006, . - [RFC4648] Josefsson, S., "The Base16, Base32, and Base64 Data - Encodings", RFC 4648, DOI 10.17487/RFC4648, October 2006, - . - [RFC5116] McGrew, D., "An Interface and Algorithms for Authenticated Encryption", RFC 5116, DOI 10.17487/RFC5116, January 2008, . [RFC5869] Krawczyk, H. and P. Eronen, "HMAC-based Extract-and-Expand Key Derivation Function (HKDF)", RFC 5869, DOI 10.17487/RFC5869, May 2010, . [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, . [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, . + [RFC7515] Jones, M., Bradley, J., and N. Sakimura, "JSON Web + Signature (JWS)", RFC 7515, DOI 10.17487/RFC7515, May + 2015, . + 8.2. Informative References [FIPS186] National Institute of Standards and Technology (NIST), "Digital Signature Standard (DSS)", NIST PUB 186-4 , July 2013. [RFC4880] Callas, J., Donnerhacke, L., Finney, H., Shaw, D., and R. Thayer, "OpenPGP Message Format", RFC 4880, DOI 10.17487/RFC4880, November 2007, . @@ -889,25 +951,25 @@ [X9.62] ANSI, "Public Key Cryptography For The Financial Services Industry: The Elliptic Curve Digital Signature Algorithm (ECDSA)", ANSI X9.62 , 1998. [XMLENC] Eastlake, D., Reagle, J., Imamura, T., Dillaway, B., and E. Simon, "XML Encryption Syntax and Processing", W3C REC , December 2002, . Appendix A. JWE Mapping - The "aesgcm128" content encoding can be considered as a sequence of - JSON Web Encryption (JWE) objects [RFC7516], each corresponding to a - single fixed size record. The following transformations are applied - to a JWE object that might be expressed using the JWE Compact - Serialization: + The "aesgcm" content encoding can be considered as a sequence of JSON + Web Encryption (JWE) objects [RFC7516], each corresponding to a + single fixed size record that includes leading padding. The + following transformations are applied to a JWE object that might be + expressed using the JWE Compact Serialization: o The JWE Protected Header is fixed to a value { "alg": "dir", "enc": "A128GCM" }, describing direct encryption using AES-GCM with a 128-bit content encryption key. This header is not transmitted, it is instead implied by the value of the Content- Encoding header field. o The JWE Encrypted Key is empty, as stipulated by the direct encryption algorithm. @@ -917,28 +979,80 @@ Section 3.3). This value is also not transmitted. o The final value is the concatenated JWE Ciphertext and the JWE Authentication Tag, both expressed without URL-safe Base 64 encoding. The "." separator is omitted, since the length of these fields is known. Thus, the example in Section 5.4 can be rendered using the JWE Compact Serialization as: - eyAiYWxnIjogImRpciIsICJlbmMiOiAiQTEyOEdDTSIgfQ..AAAAAAAAAAAAAAAA. - LwTC-fwdKh8de0smD2jfzA.eh1vURhu65M2lxhctbbntA - Where the first line represents the fixed JWE Protected Header, JWE - Encrypted Key, and JWE Initialization Vector, all of which are - determined algorithmically. The second line contains the encoded - body, split into JWE Ciphertext and JWE Authentication Tag. + eyAiYWxnIjogImRpciIsICJlbmMiOiAiQTEyOEdDTSIgfQ..31iQYc1v4a36EgyJ. + VDeU0XxaJkOJDAxPl7h9JD4.VfDeN0aKz-z36T3WWULsBQ -Appendix B. Acknowledgements + Where the first line represents the fixed JWE Protected Header, an + empty JWE Encrypted Key, and the algorithmically-determined JWE + Initialization Vector. The second line contains the encoded body, + split into JWE Ciphertext and JWE Authentication Tag. + +Appendix B. Intermediate Values for Encryption + + The intermediate values calculated for the example in Section 5.7 are + shown here. The following are inputs to the calculation: + + Plaintext: SSBhbSB0aGUgd2FscnVz + + Sender public key: BNoRDbb84JGm8g5Z5CFxurSqsXWJ11ItfXEWYVLE85Y7 + CYkDjXsIEc4aqxYaQ1G8BqkXCJ6DPpDrWtdWj_mugHU + + Sender private key: nCScek-QpEjmOOlT-rQ38nZzvdPlqa00Zy0i6m2OJvY + + Receiver public key: BCEkBjzL8Z3C-oi2Q7oE5t2Np-p7osjGLg93qUP0wvqR + T21EEWyf0cQDQcakQMqz4hQKYOQ3il2nNZct4HgAUQU + + Receiver private key: 9FWl15_QUQAWDaD3k3l50ZBZQJ4au27F1V4F0uLSD_M + + Salt: lngarbyKfMoi9Z75xYXmkg + Note that knowledge of just one of the private keys is necessary. + The sender randomly generates the salt value, whereas salt is input + to the receiver. + + This produces the following intermediate values: + + Shared secret (raw_key): RNjC-NVW4BGJbxWPW7G2mowsLeDa53LYKYm4-NOQ6Y + + Input keying material (IKM): EhpZec37Ptm4IRD5-jtZ0q6r1iK5vYmY1tZwtN8 + fbZY + + Context for content encryption key derivation: + Q29udGVudC1FbmNvZGluZzogYWVzZ2NtAFAtMjU2AABB BCEkBjzL8Z3C- + oi2Q7oE5t2Np-p7osjGLg93qUP0wvqR + T21EEWyf0cQDQcakQMqz4hQKYOQ3il2nNZct4HgAUQUA + QQTaEQ22_OCRpvIOWeQhcbq0qrF1iddSLX1xFmFSxPOW + OwmJA417CBHOGqsWGkNRvAapFwiegz6Q61rXVo_5roB1 + + Content encryption key (CEK): AN2-xhvFWeYh5z0fcDu0Ww + + Context for nonce derivation: Q29udGVudC1FbmNvZGluZzogbm9uY2UAUC0yNT + YAAEEE ISQGPMvxncL6iLZDugTm3Y2n6nuiyMYuD3epQ_TC-pFP + bUQRbJ_RxANBxqRAyrPiFApg5DeKXac1ly3geABRBQBB + BNoRDbb84JGm8g5Z5CFxurSqsXWJ11ItfXEWYVLE85Y7 + CYkDjXsIEc4aqxYaQ1G8BqkXCJ6DPpDrWtdWj_mugHU + + Base nonce: JY1Okw5rw1Drkg9J + + When the CEK and nonce are used with AES GCM and the padded plaintext + of AABJIGFtIHRoZSB3YWxydXM, the final ciphertext is + 6nqAQUME8hNqw5J3kl8cpVVJylXKYqZOeseZG8UueKpA, as shown in the + example. + +Appendix C. Acknowledgements Mark Nottingham was an original author of this document. The following people provided valuable input: Richard Barnes, David Benjamin, Peter Beverloo, Mike Jones, Stephen Farrell, Adam Langley, John Mattsson, Eric Rescorla, and Jim Schaad. Author's Address Martin Thomson