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Network Working Group                                     W. Hoehlhubmer
Internet-Draft                                              Nov 17, 2013
Category: Best Current Practice
Intended status: Standards Track
Expires: May 18, 2014


                  Informational Add-on for HTTP over
            the Secure Sockets Layer (SSL) Protocol and/or
             the Transport Layer Security (TLS) Protocol
                   draft-hoehlhubmer-https-addon-03

Abstract

   This document describes an Add-on for websites providing encrypted
   connectivity (HTTP over TLS).

   The Add-on has two parts,  one for the Domain Name System (DNS) -
   storing the X.509 certificate hashes - and one for the webserver
   itself - an additional webpage providing specific informations.

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 May 18, 2014.

Copyright Notice

   Copyright (c) 2013 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




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   (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. Requirements Notation  . . . . . . . . . . . . . . . . . . .   4
   2.  Implementing this Add-on  . . . . . . . . . . . . . . . . . .   4
   2.1.  Implementing the DNS part . . . . . . . . . . . . . . . . .   5
   2.1.1.  Calculating the Hashes  . . . . . . . . . . . . . . . . .   5
   2.1.1.1.  Calculating the Packed form . . . . . . . . . . . . . .   6
   2.1.2.  Arbitrary String Attribute Syntax . . . . . . . . . . . .   6
   2.1.3.  DNS-entry Namespace   . . . . . . . . . . . . . . . . . .   7
   2.2.  Implementing the HTTP part  . . . . . . . . . . . . . . . .   8
   2.2.1.  Webpage Content . . . . . . . . . . . . . . . . . . . . .   9
   2.2.2.  Formating and Presenting the webpage  . . . . . . . . . .  10
   3.  Verification Procedure for the DNS part . . . . . . . . . . .  10
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  11
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .  11
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  11
   7.  Recommendations . . . . . . . . . . . . . . . . . . . . . . .  11
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  12
   8.1.  Normative References  . . . . . . . . . . . . . . . . . . .  12
   8.2.  Informative References  . . . . . . . . . . . . . . . . . .  12
   9.  Discussions . . . . . . . . . . . . . . . . . . . . . . . . .  15
   A.  Example certificates  . . . . . . . . . . . . . . . . . . . .  16
   A.1.  The DER-encoded CA certificate  . . . . . . . . . . . . . .  16
   A.1.1.  The CA's public key . . . . . . . . . . . . . . . . . . .  16
   A.2.  The DER-encoded SSL certificate . . . . . . . . . . . . . .  17
   B.  Script Examples for the Add-on webpage  . . . . . . . . . . .  18
   B.1.  PHP-script  . . . . . . . . . . . . . . . . . . . . . . . .  18
   B.2.  CGI-script: A BASH shell script . . . . . . . . . . . . . .  19
   B.3.  CGI-script: A compiled C program  . . . . . . . . . . . . .  19
   C.  Sample Content of the Add-on webpage  . . . . . . . . . . . .  22
   C.1.  A complete sample content . . . . . . . . . . . . . . . . .  22
   C.1a.  ...,  the client certificate part  . . . . . . . . . . . .  23
   C.2.  Picking another cipher suite  . . . . . . . . . . . . . . .  23
   C.2a.  ...,  and one more . . . . . . . . . . . . . . . . . . . .  23
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  24







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1. Introduction

   HTTP over TLS [HTTPTLS] is not limited to e.g.  electronic banking
   sites.  E-commerce is also using this technology on their websites
   for encrypted communication between clients (users) and them.

   A list of a few encryption algorithms:

   (1) Advanced Encryption Standard (AES)
   (2) Data Encryption Standard (DES, 3DES)
   (3) Ron's Code 4 (RC4)
   (4) ...

   As an example a list of some kinds of the Camellia encryption
   algorithm [CAMELLIA] (names taken from OpenSSL help [OPENSSL]):

   (1) CAMELLIA-128-CBC: 128-bit Camellia encryption in CBC mode
   (2) CAMELLIA-128-ECB: 128-bit Camellia encryption in ECB mode
   (3) CAMELLIA-192-CBC: 192-bit Camellia encryption in CBC mode
   (4) CAMELLIA-192-ECB: 192-bit Camellia encryption in ECB mode
   (5) CAMELLIA-256-CBC: 256-bit Camellia encryption in CBC mode
   (6) CAMELLIA-256-ECB: 256-bit Camellia encryption in ECB mode
   (7) ...

   A list of possible secure layer used:

   (1) The Secure Sockets Layer (SSL) Protocol:
       (1a) Version 2.0 [SSLv2]
       (1b) Version 3.0 [SSLv3]

   (2) The Transport Layer Security (TLS) Protocol:
       (2a) Version 1.0 [TLSv1.0]
       (2b) Version 1.1 [TLSv1.1]
       (2c) Version 1.2 [TLSv1.2]

   A list of possible Ciphersuites for Transport Layer Security (TLS):

   (1) Pre-Shared Key Cipher Suites [RFC4279]
   (2) Elliptic Curve Cryptography (ECC) Cipher Suites [RFC4492]
   (3) Pre-Shared Key Cipher Suites with NULL Encryption [RFC4785]
   (4) AES Galois Counter Mode (GCM) Cipher Suites [RFC5288]
   (5) DES and IDEA Cipher Suites [RFC5469]
   (6) ECDHE_PSK Cipher Suites [RFC5489]
   (7) Camellia Cipher Suites [RFC5932]
   (8) ...






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   A list of possible Hashing Algorithms:

   (1) the [MD2] Message-Digest Algorithm (historic see [RFC6149])
   (2) the [MD4] Message-Digest Algorithm (historic see [RFC6150])
   (3) the [MD5] Message-Digest Algorithm used commonly in past
   (4) the US Secure Hash Algorithm 1 [SHA1]
   (5) more US Secure Hash Algorithms [RFC6234]
   (6) ...

   Only the X.509 Certificates [PKIX] are static,  all other
   informations depend on the capabilities of the used web browser.

   Not every browser allows you to view all these informations,
   especially the Cipher Suite the browser has picked for use.

   With most browsers let you view the used X.509 certificates of the
   actual session,  but you have no direct comparison if they are the
   correct ones.

   It is a good practice to show these informations on the website.

   The X.509 certificates which are shown by the browser and those,
   that are shown in this Add-on webpage MUST match;  with other words:
   if they do not match, there is going on a man-in-the-middle attack.

   To give the browser,  a plug-in,  or just a stand-alone program
   the ability to verify,  that the X.509 certificate is correct,
   the Fingerprint and/or Hash of the X.509 certificates are stored
   in the Domain Name System (DNS) [DNS-1,DNS-2] as arbitrary string
   attributes as specified in [RFC1464].

1.1. Requirements Notation

   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 RFC 2119 [RFC2119].

2.  Implementing this Add-on

   This Add-on has two parts.

   Section 2.1.  describes the implementation of the neccessary entries
   in the Domain Name System (DNS).

   Section 2.2.  describes the implementation of the additional webpage.






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2.1.  Implementing the DNS part

2.1.1  Calculating the Hashes

   For calculating the hashes use either [SHA1] or SHA-224,  SHA-256,
   SHA-384,  or SHA-512 as specified in  [RFC6234].

   Take each X.509 certificate of the whole chain and calculate the
   hash of the DER-encoded certificate.

   The example certificates of Appendix A give these SHA-224 hashes
   in hex:

   CA:  00fcc1bb4d09a392f5729a0c1e1ed4247db6b21da1fca9bf6d218db4
   SSL:  eacbdc6c27cba4ecc87b4e953b56c6987d87430b682b1f13031b04de

   and these SHA-512 hashes in hex:

   CA:  6744023893a9a046e713b5615bcf1a267a41da13712f4eb964e496754bd94310
   5a5a3a8b9b071dea25f90fa7aa9c877dcc2ec81a7c97b640b30dd35083252078
   SSL:  df0dee228b19aa1eac6d2227d11cb243562058db5a4041b208ed77028699874
   7ed7ba08026791961d338cb2063f3485ec9fe07d5631a8a1b1da34025cb8962f5

   Concatenate the binary form of the calculated hashes in the correct
   order beginning at the root.

   Generate the Base64 encoding [RFC4648] from the concatenated hashes.

   This example gives the following Base64 from the concatenated
   SHA-224 hashes:

   APzBu00Jo5L1cpoMHh7UJH22sh2h/Km/bSGNtOrL3Gwny6TsyHtOlTtWxph9h0ML
   aCsfEwMbBN4=

   and from the SHA-512 hashes:

   Z0QCOJOpoEbnE7VhW88aJnpB2hNxL065ZOSWdUvZQxBaWjqLmwcd6iX5D6eqnId9
   zC7IGnyXtkCzDdNQgyUgeN8N7iKLGaoerG0iJ9EcskNWIFjbWkBBsgjtdwKGmYdH
   7XuggCZ5GWHTOMsgY/NIXsn+B9VjGoobHaNAJcuJYvU=

   Due to size limitations as specified in [DNS-2] Section 2.3.4.  and
   the Syntax as specified in Section 2.1.2.  below
   this Base64 encoded hash MUST NOT be longer than 214 octets.









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   This table shows when to use the packed form of calculation explained
   in next Section 2.1.1.1.

      +-----------+--------------+
      | Hashing   | X.509        |
      | algorithm | certificates |
      +-----------+--------------+
      | SHA-1     | 9 or more    |
      +-----------+--------------+
      | SHA-224   | 6 or more    |
      +-----------+--------------+
      | SHA-256   | 6 or more    |
      +-----------+--------------+
      | SHA-384   | 4 or more    |
      +-----------+--------------+
      | SHA-512   | 3 or more    |
      +-----------+--------------+

2.1.1.1.  Calculating the Packed form

   The calculation is the same except, that the binary form of the
   concatenated hashes is hashed again using the SHA-512 algorithm.

   Generate the Base64 encoding from this SHA-512 hash.

   The example from the previous Section 2.1.1.  has only two X.509
   certificates.  There would not be any need of packing this by
   hashing again.

   The Base64 encoding of this packed SHA-512 hash is the following:

   4iBTHcxpK4GG0thWbLaq9gQx2UmFDPI2DJDWyeKYk3RmUwS+nkuCXYXR6ED4iGy4
   Ftl5nFcsta9rwMvsaQx/wg==

2.1.2  Arbitrary String Attribute Syntax

   The syntax for a complete arbitrary string attribute, using the
   ABNF notation and core rules of [RFC5234], is:

      attribute = DQUOTE attr-algo *SP
                         attr-count *SP
                         attr-hashes *SP
                         attr-packed DQUOTE

      attr-algo = "algo=" hash-algo ";"
      attr-count = "count=" cert-count ";"
      attr-hashes = "hashes=" cert-hashes ";"
      attr-packed = "packed=" packed-form ";"



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      hash-algo = 1*("sha1" / "sha224" / "sha256" / "sha384" / "sha512")
                          ; possible hashing algorithms

      cert-count = 1DIGIT ; number of X.509 certificates of
                          ;  the whole certificates chain

      cert-hashes = base64string
                          ; base64 encoding of the certificates
                          ;  hashes

      packed-form = 1BIT  ; "0" non-packed base64 encoded hashes,
                          ; "1" packed base64 encoded hashes

      base64string = 1*(ALPHA / DIGIT / "+" / "/") [ "=" [ "=" ] ]

      separator = %x3B    ; ";"

   The example from Section 2.1.1.  gives these:

   "algo=SHA224; count=2; hashes=APzBu00Jo5L1cpoMHh7UJH22sh2h/Km/bSG
   NtOrL3Gwny6TsyHtOlTtWxph9h0MLaCsfEwMbBN4=; packed=0;"

   "algo=SHA512; count=2; hashes=Z0QCOJOpoEbnE7VhW88aJnpB2hNxL065ZOS
   WdUvZQxBaWjqLmwcd6iX5D6eqnId9zC7IGnyXtkCzDdNQgyUgeN8N7iKLGaoerG0i
   J9EcskNWIFjbWkBBsgjtdwKGmYdH7XuggCZ5GWHTOMsgY/NIXsn+B9VjGoobHaNAJ
   cuJYvU=; packed=0;"

   "algo=SHA512; count=2; hashes=4iBTHcxpK4GG0thWbLaq9gQx2UmFDPI2DJD
   WyeKYk3RmUwS+nkuCXYXR6ED4iGy4Ftl5nFcsta9rwMvsaQx/wg==; packed=1;"

   All three are valid.  Using the non packed form SHOULD be
   preferred.

2.1.3.  DNS-entry Namespace

   For this Add-on a subdomain named "_sslcert" is used.

      INFORMATIVE OPERATIONAL NOTE: Wildcard DNS records (e.g.,
      *._sslcert.example.com) are only used in context with
      Wildcard X.509 certificates.  Note also that wildcards within
      domains (e.g., s._sslcert.*.example.com) are not supported by
      the DNS.









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   The DNS entries for this example look like these:

   ; IPv4 address
   www.example.com.           IN A 192.0.2.1

   ; IPv6 address
   www.example.com.           IN AAAA 2001:db8::1

   ; X.509 certificates hashes, SHA-224
   www._sslcert.example.com.  IN TXT "algo=SHA224; count=2; hashes=A
   PzBu00Jo5L1cpoMHh7UJH22sh2h/Km/bSGNtOrL3Gwny6TsyHtOlTtWxph9h0MLaC
   sfEwMbBN4=; packed=0;"

   ; X.509 certificates hashes, SHA-512
   www._sslcert.example.com.  IN TXT "algo=SHA512; count=2; hashes=Z
   0QCOJOpoEbnE7VhW88aJnpB2hNxL065ZOSWdUvZQxBaWjqLmwcd6iX5D6eqnId9zC
   7IGnyXtkCzDdNQgyUgeN8N7iKLGaoerG0iJ9EcskNWIFjbWkBBsgjtdwKGmYdH7Xu
   ggCZ5GWHTOMsgY/NIXsn+B9VjGoobHaNAJcuJYvU=; packed=0;"

   ; X.509 certificates hashes, SHA-512, packed
   www._sslcert.example.com.  IN TXT "algo=SHA512; count=2; hashes=4
   iBTHcxpK4GG0thWbLaq9gQx2UmFDPI2DJDWyeKYk3RmUwS+nkuCXYXR6ED4iGy4Ft
   l5nFcsta9rwMvsaQx/wg==; packed=1;"

2.2.  Implementing the HTTP part

   This Add-on is just one page of the website.  Its content MUST be
   completely generated on server side.  The Common Gateway Interface
   [CGI1.1] is RECOMMENDED to be used.  There MUST exist at least one
   relative reference to this page as defined in [RFC3986] Section 4.2.

   For doing so see the sample scripts from Appendix B.
   To see how this Add-on works,  see [MYADDON].


















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2.2.1.  Webpage Content

   The informations MUST be the following:

   (1) The actual date and time

   (2) The cipher specification name

   (3) Number of cipher bits (actually used)
   (4) Number of cipher bits (possible)

   (5) The SSL Protocol version: SSLv2,  SSLv3,
       TLSv1.0,  TLSv1.1,  TLSv1.2, ...

   (6) If cipher is an export cipher: false, true
   (7) If secure renegotiation is supported: false, true

   (8) Algorithm used for the public key of server's certificate
   (9) Algorithm used for the signature of server's certificate
   (10) Issuer DN of server's certificate
   (11) Subject DN in server's certificate
   (12) The serial of the server certificate
   (13) The version of the server certificate
   (14) Validity of server's certificate (start time)
   (15) Validity of server's certificate (end time)

   (16) Client certificate verification:
        NONE, SUCCESS, GENEROUS or FAILED:reason

   (17) SSL compression method negotiated: NULL when disabled

   For connections where X.509 certificates are used for authentication
   these informations are RECOMMENDED:

   (18) Algorithm used for the public key of client's certificate
   (19) Algorithm used for the signature of client's certificate
   (20) Issuer DN of client's certificate
   (21) Subject DN in client's certificate
   (22) The serial of the client certificate
   (23) The version of the client certificate
   (24) Validity of client's certificate (start time)
   (25) Validity of client's certificate (end time)
   (26) Number of days until client's certificate expires

   This information MAY be given:

   (27) The hex-encoded SSL session id
   (28) Contents of the SNI TLS extension (if supplied with ClientHello)



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   These OPTIONAL informations depend on the used software:

   (29) The SSL-module program version: e.g. Apache mod_ssl version
   (30) The SSL program version: e.g. OpenSSL version

   See Appendix C for a sample content.

2.2.2.  Formating and Presenting the webpage

   You SHALL present this information simple,  plain Text is enough.
   When using HTML,  only relative references as defined in [RFC3986]
   Section 4.2.  MAY be used.  It is RECOMMENDED to use only a subset
   of [HTML2.0].

   The actual date and time SHALL be formatted as specified in [RFC5322]
   Section 3.3.  The time MUST NOT differ with more than 5 seconds from
   the real date/time.

   Any translation or sorting the order of this content is OPTIONAL.

3.  Verification Procedure for the DNS part

   When the webbrowser or a plug-in honors the additional DNS entries,
   it SHOULD give a warning to the user:

   (1) when it doesn't find the entry
   (2) when the entry doesn't match

   In case the DNS entries were retrieved by [DNSSEC] instead of simple
   DNS,  then the user MUST give a permission to go further, when one
   of the two scenarios occurs.




















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4.  IANA Considerations

   There are no requests for IANA actions in this document.

5.  Security Considerations

   When implementing the HTTP part as a popup window in the browser,
   this information MUST also be available with enabled popup-blocker.

   The implementation MUST NOT use any scripts, that run on client side:
   e.g. Javascript, ...

   There SHOULD also be no references to other websites inside this
   Add-on page.

6.  Acknowledgements

7.  Recommendations

   [DNSSEC] SHOULD be used for the DNS part.

   Using a standardized URL for the HTTP part is RECOMMENDED,
   for more see Discussions at Section 9.




























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8.  References

8.1.  Normative References

   [DNS-1]     Mockapetris, P., "Domain names - concepts and
               facilities", STD 13, RFC 1034, November 1987.

   [DNS-2]     Mockapetris, P., "Domain names - implementation and
               specification", STD 13, RFC 1035, November 1987.

   [PKIX]      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, May 2008.

8.2.  Informative References

   [CAMELLIA]  Matsui, M., Nakajima, J., and S. Moriai, "A Description
               of the Camellia Encryption Algorithm", RFC 3713,
               April 2004.

   [DNSSEC]    Arends, R., Austein, R., Larson, M., Massey, D., and
               S. Rose, "DNS Security Introduction and Requirements",
               RFC 4033, March 2005.

   [HTTPTLS]   Rescorla, E., "HTTP over TLS", RFC 2818, May 2000.

























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   [CGI1.1]    Robinson, D. and K. Coar, "The Common Gateway Interface
               (CGI) Version 1.1", RFC 3875, October 2004.

   [HTML2.0]   Berners-Lee, T. and D. Connolly, "Hypertext Markup
               Language - 2.0", RFC 1866, November 1995.

   [MD2]       Kaliski, B., "The MD2 Message-Digest Algorithm",
               RFC 1319, April 1992.

   [MD4]       Rivest, R., "The MD4 Message-Digest Algorithm", RFC 1320,
               April 1992.

   [MD5]       Rivest, R., "The MD5 Message-Digest Algorithm", RFC 1321,
               April 1992.

   [SHA1]      Eastlake 3rd, D. and P. Jones, "US Secure Hash
               Algorithm 1 (SHA1)", RFC 3174, September 2001.

   [SSLv2]     Hickman, Kipp, "The SSL Protocol", Netscape
               Communications Corp., Feb 9, 1995.

   [SSLv3]     Freier, A., Karlton, P., and P. Kocher, "The Secure
               Sockets Layer (SSL) Protocol Version 3.0", RFC 6101,
               August 2011.

   [TLS1.0]    Dierks, T. and C. Allen, "The TLS Protocol Version 1.0",
               RFC 2246, January 1999.

   [TLS1.1]    Dierks, T. and E. Rescorla, "The Transport Layer Security
               (TLS) Protocol Version 1.1", RFC 4346, April 2006.

   [TLS1.2]    Dierks, T. and E. Rescorla, "The Transport Layer Security
               (TLS) Protocol Version 1.2", RFC 5246, August 2008.

   [OPENSSL]   OpenSSL Cryptography and SSL/TLS Toolkit at
               http://www.openssl.org/

   [RFC1464]   Rosenbaum, R., "Using the Domain Name System To Store
               Arbitrary String Attributes", RFC 1464, May 1993.

   [RFC2119]   Bradner, S., "Key words for use in RFCs to Indicate
               Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC3986]   Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
               Resource Identifier (URI): Generic Syntax", STD 66,
               RFC 3986, January 2005.





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   [RFC4279]   Eronen, P., Ed., and H. Tschofenig, Ed., "Pre-Shared Key
               Ciphersuites for Transport Layer Security (TLS)",
               RFC 4279, December 2005.

   [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,
               May 2006.

   [RFC4648]   Josefsson, S., "The Base16, Base32, and Base64 Data
               Encodings", RFC 4648, October 2006.

   [RFC4785]   Blumenthal, U. and P. Goel, "Pre-Shared Key (PSK)
               Ciphersuites with NULL Encryption for Transport Layer
               Security (TLS)", RFC 4785, January 2007.

   [RFC5234]   Crocker, D., Ed., and P. Overell, "Augmented BNF for
               Syntax Specifications: ABNF", STD 68, RFC 5234,
               January 2008.

   [RFC5288]   Salowey, J., Choudhury, A., and D. McGrew, "AES Galois
               Counter Mode (GCM) Cipher Suites for TLS", RFC 5288,
               August 2008.

   [RFC5322]   Resnick, P., Ed., "Internet Message Format", RFC 5322,
               October 2008.

   [RFC5469]   Eronen, P., Ed., "DES and IDEA Cipher Suites for
               Transport Layer Security (TLS)", RFC 5469, February
               2009.

   [RFC5489]   Badra, M. and I. Hajjeh, "ECDHE_PSK Cipher Suites for
               Transport Layer Security (TLS)", RFC 5489, March 2009.

   [RFC5932]   Kato, A., Kanda, M., and S. Kanno, "Camellia Cipher
               Suites for TLS", RFC 5932, June 2010.

   [RFC6149]   Turner, S. and L. Chen, "MD2 to Historic Status",
               RFC 6149, March 2011.

   [RFC6150]   Turner, S. and L. Chen, "MD4 to Historic Status",
               RFC 6150, March 2011.

   [RFC6234]   Eastlake 3rd, D. and T. Hansen, "US Secure Hash
               Algorithms (SHA and SHA-based HMAC and HKDF)", RFC 6234,
               May 2011.





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   [MYADDON]   A working implementation of this Add-on on my website at
               https://ssl.mathemainzel.info/sslinfo/

9.  Discussions

   It would be good to have a standardized URL for this Add-on webpage;
   e.g.  https://www.example.com/sslinfo/

   Placing an Absolute URI as defined in [RFC3986] Section 4.3.
   outside the encrypted website part is RECOMMENDED.









































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A.  Example certificates

A.1.  The DER-encoded CA certificate

   This section contains the full, DER-encoded certificate, in hex.

   1010600634021010601500010016400004020010020000010064600044061030
   5210311000676700040100240503000003050703001300301105240300300400
   1023026455010061007060001406002125011412051407066557047545063562
   0120610110600014060021250114130514130665570475450635620671250721
   5101006100706000140600212501140305100706755702016404050301706000
   6427030067030460030460030060030060030060013532033415030464031462
   0310610324630324710550710434600054610044600014060021250114060264
   0203045503002000301605240300500400342306752306255507111703054703
   0024003022052403005404005423067523062555071117052547064556030564
   0300200030160524030014040034230675220721570414400301011176010064
   6000440610305210311000676700040100240100140010660103000010460110
   0402000201071316115226031524061442141373010143166673165250141015
   0517401044541316341204240165050550721355741560520432570444641506
   6212130607367410244201373701137307300614742302406311650507617510
   2115172574007434061225113362175757116071145403104350137377010514
   1601271540621072141376071226201714071567250673200574521157610255
   1515761102656314564700175211011417064417277604020203762405372207
   4623073516001402000001121401030143030141003017052403011435000401
   0023770300050004031774010070600014060165250004171774010020040010
   0300300101646000140601652500201600202607142401206117056206232514
   4163006736034416141314025571166561030336003037052403021435014004
   0130600122000305630710241527610715441573100070151460710747020704
   5315735500646000440610305210311000676700040100240500140010060100
   6000064104177605102053130121063016051615111404042507164044160755
   0150730227030737461373310202221205130644631422570426040372570324
   0106623304640504442010640207527417434210564615636511027014202013
   2210113030032353130707014732025533023174116127173702002647127304
   0476341541621070161534751436560126630235111776670102040261610302
   2317534312263011522403605011472510677411363503034305034010220600
   0114

A.1.1.  The CA's public key

   This section contains the DER-encoded public RSA key of the CA who
   signed the example SSL certificate.  It is included with the purpose
   of simplifying verifications of the example certificate.









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   1004600302370030150250110442061736060004150004010000051004030002
   1510046000121110060114700011316205223202106317554306170213542012
   4355006752160302026123116211012263042641035035076132025273127734
   0321061311111433211362420211671576051754270030220115660317170424
   5007663504657407620401636511241717114216762603477300163416431317
   7610046276053421031340106330103616110277003645152763150335025156
   1705370466331044530717371234551653130460031222201773611013651121
   00151077111527047171001167000403000400

A.2.  The DER-encoded SSL certificate

   This section contains the full, DER-encoded certificate, in hex.

   1010601044021010601710010016400004020010020004010064600044061030
   5210311000676700040100240503000003050703001300301105240300300400
   1023026455010061007060001406002125011412051407066557047545063562
   0120610110600014060021250114130514130665570475450635620671250721
   5101006100706000140600212501140305100706755702016404050301706000
   6427030067030460030460030060030060030060013532033415030460031462
   0310610324630324710550710234600054610044600014060021250114060264
   0203045503003000302605240300140400742307356702716707414506654106
   6160027145067543030155117601006460004406103052103110006767000401
   0024010014001066010300001046011004020002010306350224351562760733
   0201553513736613223202707401572412765103062504052411220602401605
   6252132200177140167322136432161133067275017065117657147015104103
   1320470130561271570461311722030710130570270727500270640500641707
   7207510002302210257601600417462415564614327511176510662500200211
   5031053744134352077175044205021561031707012630025157134361044574
   1710160201730353711402010574261455531607560014020000011214011222
   0110046003024100301105240301143500100400006000706000140601652500
   0417177401002004001003120005016460001406016525002016002026052024
   1211441111160234400147731747170770361023170065521711200303340030
   3705240302143501400401306001220003056307102415276107154415731000
   7015146071074702070453157355015060001406016525002021030023101021
   0734170735670624560605700701550625540614560665570114600014060165
   2500204503001400301202541000040600240500140703000100302305240302
   0035006004005060004060003006100547000414000402006460004406103052
   1031100067670004010024050014001006011050000731771510471102230437
   5505451502743711211417637417525600233317671301440610514700054013
   6261147431115322066751112110124235015435164317163765135144110577
   0257050063051220501411621312461723760237531632761446601276110760
   3316177002764501554414156702511613457713274417152503620402713116
   4416066704165331145672012711066756161622041305033711123071177333
   077143130262053202136157121506006646000106







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B.  Script Examples for the Add-on webpage

   Use the following script examples as a template for your
   implementation of this Add-on webpage.

   The first two examples generate identical content in plain
   ASCII-text,  the third example makes use of HTML and is a
   compiled C program.

   Script Examples:

   B.1.  PHP-script
   B.2.  CGI-script: A BASH shell script,  for most Linux systems
   B.3.  CGI-script: A compiled C program,  for any other system


B.1.  PHP-script

   <CODE BEGINS>
   <?php

   header( "Content-type: text/plain" );

   print "SSL informations: " . date( "r" ) . "\r\n";
   print "================\r\n\r\n";

   if ( isset( $_SERVER['HTTPS'] ) && ( $_SERVER['HTTPS'] == "on" ) ) {
     $list = array( );
     $nmbrOfValues = 0;

     foreach ( $_SERVER as $key => $value ) {
       if ( substr( $key, 0, 4 ) == "SSL_" ) {
         $list[ $nmbrOfValues++ ] = $key . "=" . $value;
       }
     }

     sort( $list );   // sort content before printing ...

     for ( $iter = 0; $iter < $nmbrOfValues; $iter++ ) {
       print $list[ $iter ] . "\r\n";
     }
   }
   else {
     echo "No SSL information available.\r\n";
   }
   ?>
   <CODE ENDS>




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B.2.  CGI-script: A BASH shell script,  for most Linux systems

   <CODE BEGINS>
   #!/bin/bash

   printf "Content-type: text/plain\n\n"

   printf "SSL informations: $(date --rfc-2822)\n"
   printf "================\n\n"

   if [ "$HTTPS" == "on" ]; then
     env | grep --regexp="^SSL_" | sort
   else
     printf "No SSL information available.\n"
   fi
   <CODE ENDS>


B.3.  CGI-script: A compiled C program,  for any other system

   This CGI-script is a compiled C program,  and in comparison to the
   other 2 examples,  it makes use of HTML.

   For compiling this program any C compiler SHOULD be suitable.  Be
   sure your runtime supports the function strftime with standard format
   specifiers.

   <CODE BEGINS>
   #include <stdio.h>
   #include <stdlib.h>
   #include <string.h>
   #include <time.h>

   #ifdef __linux__
   #include <unistd.h>
   #endif

   const char* pszHtmlEndPart [ ] = { "<HR>",
     "<ADDRESS>https at www.example.com Port 443</ADDRESS>",
     "</BODY>",
     "</HTML>" };

   const char* pszHtmlBeginPart[ ] = {
     "<!DOCTYPE HTML PUBLIC \"-//IETF//DTD HTML 2.0//EN\">",
     "<HTML>",
     "<HEAD>",
     "<TITLE>SSL informations</TITLE>",
     "</HEAD>",



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     "<BODY>",
     "<H3>SSL informations</H3>" };

   /* function prototype used for sorting */
   int compareFunc( const void* pvd1, const void* pvd2 );

   int main( int argc, char* argv[ ], char** envp )
   {                               /* char* envp[ ] */
     char* * ppszContent;
     char* * ppsz;
     char* psz;
     char szDateTime[ 80 ];
     int i, nCount;

     time_t tnow = time( NULL );
     struct tm* tmnow = localtime( &tnow );

     strftime( szDateTime, sizeof( szDateTime ) - 4,
       "%a, %d %b %Y %H:%M:%S %z", tmnow );

     printf( "Content-type: text/html; charset=ISO-8859-1\r\n\r\n" );

     nCount = sizeof( pszHtmlBeginPart ) / sizeof( char* );
     for ( i = 0; i < nCount; i++ )
       printf( "%s\r\n", pszHtmlBeginPart[ i ] );

     printf( "<B>SSL informations</B>: %s\r\n", szDateTime );
     printf( "<P>\r\n" );

     if ( ( psz = getenv( "HTTPS" ) ) && ( strcmp( psz, "on" ) == 0 ) )
     {
       /* count relevant values ... */
       ppsz = envp;
       nCount = 0;
       while ( ppsz && *ppsz )
       {
         if ( strncmp( *ppsz, "SSL_", 4 ) == 0 )
           nCount++;
         ppsz++;
       }

       /* allocate memory */
       ppszContent = (char* *) calloc( nCount, sizeof( char* ) );








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       if ( ppszContent )
       {
         /* extract relevant values from environment ... */
         i = 0;
         ppsz = envp;
         while ( ppsz && *ppsz )
         {
           if ( strncmp( *ppsz, "SSL_", 4 ) == 0 )
             *( ppszContent + i++ ) = *ppsz;
           ppsz++;
         }

         /* sort content */
         qsort( (void*) ppszContent, nCount, sizeof( char* ),
           compareFunc );

         printf( "<CODE>\r\n" );

         /* output sorted content */
         for ( i = 0; i < nCount; i++ )
           printf( "%s<BR>\r\n", *( ppszContent + i ) );

         printf( "</CODE>\r\n" );

         /* free up memory */
         free( (void*) ppszContent );
       }
       else
         printf( "Internal error (unable to allocate memory).\r\n" );
     }
     else
       printf( "No SSL information available.\r\n" );

     nCount = sizeof( pszHtmlEndPart ) / sizeof( char* );
     for ( i = 0; i < nCount; i++ )
       printf( "%s\r\n", pszHtmlEndPart[ i ] );

     return 0;
   }

   /* comparison function for sorting */
   int compareFunc( const void* pvd1, const void* pvd2 )
   {
     return strcmp( *( (char* *) pvd1 ), *( (char* *) pvd2 ) );
   }
   <CODE ENDS>





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C.  Sample Content of the Add-on webpage

   The first example shows a complete sample content in sorted order.
   The second example shows the client certificate part,  in case client
   certificate authentication is used.
   The other two examples show only the part that may differ when the
   browser picks another cipher suite.

   For meaning of the numbers in brackets of the examples see
   Section 2.2.1.

   C.1.  A complete sample content
   C.1a.  ...,  the client certificate part
   C.2.  Picking another cipher suite
   C.2a.  ...,  and one more


C.1.  A complete sample content

   SSL informations: Thu, 01 Jan 1970 00:00:00 +0000               (1)
   ================

   SSL_CIPHER=AES256-SHA                                           (2)
   SSL_CIPHER_ALGKEYSIZE=256                                       (4)
   SSL_CIPHER_EXPORT=false                                         (6)
   SSL_CIPHER_USEKEYSIZE=256                                       (3)
   SSL_CLIENT_VERIFY=NONE                                          (16)
   SSL_COMPRESS_METHOD=NULL                                        (17)
   SSL_PROTOCOL=TLSv1                                              (5)
   SSL_SECURE_RENEG=true                                           (7)
   SSL_SERVER_A_KEY=rsaEncryption                                  (8)
   SSL_SERVER_A_SIG=sha1WithRSAEncryption                          (9)
   SSL_SERVER_I_DN=/C=--/O=SomeOrg/OU=SomeOrgUnit/CN=Root CA       (10)
   SSL_SERVER_I_DN_C=--                                            (10)
   SSL_SERVER_I_DN_CN=Root CA                                      (10)
   SSL_SERVER_I_DN_O=SomeOrg                                       (10)
   SSL_SERVER_I_DN_OU=SomeOrgUnit                                  (10)
   SSL_SERVER_M_SERIAL=01                                          (12)
   SSL_SERVER_M_VERSION=3                                          (13)
   SSL_SERVER_S_DN=/C=--/CN=www.example.com                        (11)
   SSL_SERVER_S_DN_C=--                                            (11)
   SSL_SERVER_S_DN_CN=www.example.com                              (11)
   SSL_SERVER_V_END=Dec 31 23:59:59 1970 GMT                       (15)
   SSL_SERVER_V_START=Jan 01 00:00:00 1970 GMT                     (14)
   SSL_SESSION_ID=0123456789ABCDEF0123456789ABCDEF0123456789ABCDEF (27)
   SSL_TLS_SNI=www.example.com                                     (28)
   SSL_VERSION_INTERFACE=mod_ssl/2.2.15                            (29)
   SSL_VERSION_LIBRARY=OpenSSL/1.0.0-fips                          (30)



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C.1a.  ...,  the client certificate part

   ...
   SSL_CLIENT_A_KEY=rsaEncryption                                  (18)
   SSL_CLIENT_A_SIG=sha1WithRSAEncryption                          (19)
   SSL_CLIENT_I_DN=/C=--/O=SomeOrg/OU=SomeOrgUnit/CN=Root CA       (20)
   SSL_CLIENT_I_DN_C=--                                            (20)
   SSL_CLIENT_I_DN_CN=Root CA                                      (20)
   SSL_CLIENT_I_DN_O=SomeOrg                                       (20)
   SSL_CLIENT_I_DN_OU=SomeOrgUnit                                  (20)
   SSL_CLIENT_M_SERIAL=02                                          (22)
   SSL_CLIENT_M_VERSION=3                                          (23)
   SSL_CLIENT_S_DN=/CN=Name/emailAddress=name@example.com          (21)
   SSL_CLIENT_S_DN_CN=Name                                         (21)
   SSL_CLIENT_S_DN_Email=name@example.com                          (21)
   SSL_CLIENT_VERIFY=SUCCESS                                       (16)
   SSL_CLIENT_V_END=Dec 31 23:59:59 1970 GMT                       (25)
   SSL_CLIENT_V_REMAIN=365                                         (26)
   SSL_CLIENT_V_START=Jan 01 00:00:00 1970 GMT                     (24)
   ...


C.2.  Picking another cipher suite

   ...
   SSL_CIPHER=RC4-MD5
   SSL_CIPHER_ALGKEYSIZE=128
   SSL_CIPHER_EXPORT=false
   SSL_CIPHER_USEKEYSIZE=128
   ...
   SSL_PROTOCOL=SSLv3
   SSL_SECURE_RENEG=false
   ...

C.2a.  ...,  and one more

   ...
   SSL_CIPHER=AES128-SHA256
   SSL_CIPHER_ALGKEYSIZE=128
   SSL_CIPHER_EXPORT=false
   SSL_CIPHER_USEKEYSIZE=128
   ...
   SSL_PROTOCOL=TLSv1.2
   SSL_SECURE_RENEG=true
   ...






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Author's Address

   Walter Hoehlhubmer
   Lederergasse 47a
   A-4020 Linz
   Austria, EUROPE

   EMail: walter.h@mathemainzel.info











































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Html markup produced by rfcmarkup 1.129c, available from https://tools.ietf.org/tools/rfcmarkup/