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Internet Engineering Task Force (IETF)                       E. RescorlaRequest for Comments: 5746                                    RTFM, Inc.Updates:5246,4366,4347,4346,2246                             M. RayCategory: Standards Track                                    S. DispensaISSN: 2070-1721                                              PhoneFactor                                                                N. Oskov                                                               Microsoft                                                           February 2010Transport Layer Security (TLS) Renegotiation Indication ExtensionAbstract   Secure Socket Layer (SSL) and Transport Layer Security (TLS)   renegotiation are vulnerable to an attack in which the attacker forms   a TLS connection with the target server, injects content of his   choice, and then splices in a new TLS connection from a client.  The   server treats the client's initial TLS handshake as a renegotiation   and thus believes that the initial data transmitted by the attacker   is from the same entity as the subsequent client data.  This   specification defines a TLS extension to cryptographically tie   renegotiations to the TLS connections they are being performed over,   thus preventing this attack.Status of This Memo   This is an Internet Standards Track document.   This document is a product of the Internet Engineering Task Force   (IETF).  It represents the consensus of the IETF community.  It has   received public review and has been approved for publication by the   Internet Engineering Steering Group (IESG).  Further information on   Internet Standards is available inSection 2 of RFC 5741.   Information about the current status of this document, any errata,   and how to provide feedback on it may be obtained athttp://www.rfc-editor.org/info/rfc5746.Rescorla, et al.             Standards Track                    [Page 1]

RFC 5746               TLS Renegotiation Extension         February 2010Copyright Notice   Copyright (c) 2010 IETF Trust and the persons identified as the   document authors.  All rights reserved.   This document is subject toBCP 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 Contents1. Introduction ....................................................32. Conventions Used in This Document ...............................43. Secure Renegotiation Definition .................................43.1. Additional Connection State ................................43.2. Extension Definition .......................................5      3.3. Renegotiation Protection Request Signaling Cipher           Suite Value ................................................63.4. Client Behavior: Initial Handshake .........................63.5. Client Behavior: Secure Renegotiation ......................73.6. Server Behavior: Initial Handshake .........................73.7. Server Behavior: Secure Renegotiation ......................84. Backward Compatibility ..........................................94.1. Client Considerations ......................................94.2. Client Behavior: Legacy (Insecure) Renegotiation ..........104.3. Server Considerations .....................................104.4. Server Behavior: Legacy (Insecure) Renegotiation ..........114.5. SSLv3 .....................................................115. Security Considerations ........................................126. IANA Considerations ............................................137. Acknowledgements ...............................................138. References .....................................................138.1. Normative References ......................................138.2. Informative References ....................................13Rescorla, et al.             Standards Track                    [Page 2]

RFC 5746               TLS Renegotiation Extension         February 20101.  Introduction   TLS [RFC5246] allows either the client or the server to initiate   renegotiation -- a new handshake that establishes new cryptographic   parameters.  Unfortunately, although the new handshake is carried out   using the cryptographic parameters established by the original   handshake, there is no cryptographic binding between the two.  This   creates the opportunity for an attack in which the attacker who can   intercept a client's transport layer connection can inject traffic of   his own as a prefix to the client's interaction with the server.  One   form of this attack [Ray09] proceeds as shown below:   Client                        Attacker                        Server   ------                        -------                         ------                                     <----------- Handshake ---------->                                     <======= Initial Traffic ========>   <--------------------------  Handshake ============================>   <======================== Client Traffic ==========================>   To start the attack, the attacker forms a TLS connection to the   server (perhaps in response to an initial intercepted connection from   the client).  He then sends any traffic of his choice to the server.   This may involve multiple requests and responses at the application   layer, or may simply be a partial application layer request intended   to prefix the client's data.  This traffic is shown with == to   indicate it is encrypted.  He then allows the client's TLS handshake   to proceed with the server.  The handshake is in the clear to the   attacker but encrypted over the attacker's TLS connection to the   server.  Once the handshake has completed, the client communicates   with the server over the newly established security parameters with   the server.  The attacker cannot read this traffic, but the server   believes that the initial traffic to and from the attacker is the   same as that to and from the client.   If certificate-based client authentication is used, the server will   see a stream of bytes where the initial bytes are protected but   unauthenticated by TLS and subsequent bytes are authenticated by TLS   and bound to the client's certificate.  In some protocols (notably   HTTPS), no distinction is made between pre- and post-authentication   stages and the bytes are handled uniformly, resulting in the server   believing that the initial traffic corresponds to the authenticated   client identity.  Even without certificate-based authentication, a   variety of attacks may be possible in which the attacker convinces   the server to accept data from it as data from the client.  For   instance, if HTTPS [RFC2818] is in use with HTTP cookies [RFC2965],   the attacker may be able to generate a request of his choice   validated by the client's cookie.Rescorla, et al.             Standards Track                    [Page 3]

RFC 5746               TLS Renegotiation Extension         February 2010   Some protocols -- such as IMAP or SMTP -- have more explicit   transitions between authenticated and unauthenticated phases and   require that the protocol state machine be partly or fully reset at   such transitions.  If strictly followed, these rules may limit the   effect of attacks.  Unfortunately, there is no requirement for state   machine resets at TLS renegotiation, and thus there is still a   potential window of vulnerability, for instance, by prefixing a   command that writes to an area visible by the attacker with a command   by the client that includes his password, thus making the client's   password visible to the attacker (note that this precise attack does   not work with challenge-response authentication schemes, but other   attacks may be possible).  Similar attacks are available with SMTP,   and in fact do not necessarily require the attacker to have an   account on the target server.   It is important to note that in both cases these attacks are possible   because the client sends unsolicited authentication information   without requiring any specific data from the server over the TLS   connection.  Protocols that require a round trip to the server over   TLS before the client sends sensitive information are likely to be   less vulnerable.   These attacks can be prevented by cryptographically binding   renegotiation handshakes to the enclosing TLS cryptographic   parameters, thus allowing the server to differentiate renegotiation   from initial negotiation, as well as preventing renegotiations from   being spliced in between connections.  An attempt by an attacker to   inject himself as described above will result in a mismatch of the   cryptographic binding and can thus be detected.  The data used in the   extension is similar to, but not the same as, the data used in the   tls-unique and/or tls-unique-for-telnet channel bindings described in   [TLS-CHANNEL-BINDINGS]; however, this extension is not a general-   purposeRFC 5056 [RFC5056] channel binding facility.2.  Conventions Used in This Document   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].3.  Secure Renegotiation Definition3.1.  Additional Connection State   Both client and server need to store three additional values for each   TLS connection state (seeRFC 5246, Section 6.1).  Note that these   values are specific to connection (not a TLS session cache entry).Rescorla, et al.             Standards Track                    [Page 4]

RFC 5746               TLS Renegotiation Extension         February 2010   o  a "secure_renegotiation" flag, indicating whether secure      renegotiation is in use for this connection.   o  "client_verify_data":  the verify_data from the Finished message      sent by the client on the immediately previous handshake.  For      currently defined TLS versions and cipher suites, this will be a      12-byte value; for SSLv3, this will be a 36-byte value.   o  "server_verify_data":  the verify_data from the Finished message      sent by the server on the immediately previous handshake.3.2.  Extension Definition   This document defines a new TLS extension, "renegotiation_info" (with   extension type 0xff01), which contains a cryptographic binding to the   enclosing TLS connection (if any) for which the renegotiation is   being performed.  The "extension data" field of this extension   contains a "RenegotiationInfo" structure:      struct {          opaque renegotiated_connection<0..255>;      } RenegotiationInfo;   The contents of this extension are specified as follows.   o  If this is the initial handshake for a connection, then the      "renegotiated_connection" field is of zero length in both the      ClientHello and the ServerHello.  Thus, the entire encoding of the      extension is ff 01 00 01 00.  The first two octets represent the      extension type, the third and fourth octets the length of the      extension itself, and the final octet the zero length byte for the      "renegotiated_connection" field.   o  For ClientHellos that are renegotiating, this field contains the      "client_verify_data" specified inSection 3.1.   o  For ServerHellos that are renegotiating, this field contains the      concatenation of client_verify_data and server_verify_data.  For      current versions of TLS, this will be a 24-byte value (for SSLv3,      it will be a 72-byte value).   This extension also can be used with Datagram TLS (DTLS) [RFC4347].   Although, for editorial simplicity, this document refers to TLS, all   requirements in this document apply equally to DTLS.Rescorla, et al.             Standards Track                    [Page 5]

RFC 5746               TLS Renegotiation Extension         February 20103.3.  Renegotiation Protection Request Signaling Cipher Suite Value   Both the SSLv3 and TLS 1.0/TLS 1.1 specifications require   implementations to ignore data following the ClientHello (i.e.,   extensions) if they do not understand it.  However, some SSLv3 and   TLS 1.0 implementations incorrectly fail the handshake in such a   case.  This means that clients that offer the "renegotiation_info"   extension may encounter handshake failures.  In order to enhance   compatibility with such servers, this document defines a second   signaling mechanism via a special Signaling Cipher Suite Value (SCSV)   "TLS_EMPTY_RENEGOTIATION_INFO_SCSV", with code point {0x00, 0xFF}.   This SCSV is not a true cipher suite (it does not correspond to any   valid set of algorithms) and cannot be negotiated.  Instead, it has   the same semantics as an empty "renegotiation_info" extension, as   described in the following sections.  Because SSLv3 and TLS   implementations reliably ignore unknown cipher suites, the SCSV may   be safely sent to any server.  The SCSV can also be included in the   SSLv2 backward compatible CLIENT-HELLO (seeAppendix E.2 of   [RFC5246]).   Note:  a minimal client that does not support renegotiation at all   can simply use the SCSV in all initial handshakes.  The rules in the   following sections will cause any compliant server to abort the   handshake when it sees an apparent attempt at renegotiation by such a   client.3.4.  Client Behavior: Initial Handshake   Note that this section andSection 3.5 apply to both full handshakes   and session resumption handshakes.   o  The client MUST include either an empty "renegotiation_info"      extension, or the TLS_EMPTY_RENEGOTIATION_INFO_SCSV signaling      cipher suite value in the ClientHello.  Including both is NOT      RECOMMENDED.   o  When a ServerHello is received, the client MUST check if it      includes the "renegotiation_info" extension:      *  If the extension is not present, the server does not support         secure renegotiation; set secure_renegotiation flag to FALSE.         In this case, some clients may want to terminate the handshake         instead of continuing; seeSection 4.1 for discussion.Rescorla, et al.             Standards Track                    [Page 6]

RFC 5746               TLS Renegotiation Extension         February 2010      *  If the extension is present, set the secure_renegotiation flag         to TRUE.  The client MUST then verify that the length of the         "renegotiated_connection" field is zero, and if it is not, MUST         abort the handshake (by sending a fatal handshake_failure         alert).         Note: later inSection 3, "abort the handshake" is used as         shorthand for "send a fatal handshake_failure alert and         terminate the connection".   o  When the handshake has completed, the client needs to save the      client_verify_data and server_verify_data values for future use.3.5.  Client Behavior: Secure Renegotiation   This text applies if the connection's "secure_renegotiation" flag is   set to TRUE (if it is set to FALSE, seeSection 4.2).   o  The client MUST include the "renegotiation_info" extension in the      ClientHello, containing the saved client_verify_data.  The SCSV      MUST NOT be included.   o  When a ServerHello is received, the client MUST verify that the      "renegotiation_info" extension is present; if it is not, the      client MUST abort the handshake.   o  The client MUST then verify that the first half of the      "renegotiated_connection" field is equal to the saved      client_verify_data value, and the second half is equal to the      saved server_verify_data value.  If they are not, the client MUST      abort the handshake.   o  When the handshake has completed, the client needs to save the new      client_verify_data and server_verify_data values.3.6.  Server Behavior: Initial Handshake   Note that this section andSection 3.7 apply to both full handshakes   and session-resumption handshakes.   o  When a ClientHello is received, the server MUST check if it      includes the TLS_EMPTY_RENEGOTIATION_INFO_SCSV SCSV.  If it does,      set the secure_renegotiation flag to TRUE.Rescorla, et al.             Standards Track                    [Page 7]

RFC 5746               TLS Renegotiation Extension         February 2010   o  The server MUST check if the "renegotiation_info" extension is      included in the ClientHello.  If the extension is present, set      secure_renegotiation flag to TRUE.  The server MUST then verify      that the length of the "renegotiated_connection" field is zero,      and if it is not, MUST abort the handshake.   o  If neither the TLS_EMPTY_RENEGOTIATION_INFO_SCSV SCSV nor the      "renegotiation_info" extension was included, set the      secure_renegotiation flag to FALSE.  In this case, some servers      may want to terminate the handshake instead of continuing; seeSection 4.3 for discussion.   o  If the secure_renegotiation flag is set to TRUE, the server MUST      include an empty "renegotiation_info" extension in the ServerHello      message.   o  When the handshake has completed, the server needs to save the      client_verify_data and server_verify_data values for future use.   TLS servers implementing this specification MUST ignore any unknown   extensions offered by the client and they MUST accept version numbers   higher than their highest version number and negotiate the highest   common version.  These two requirements reiterate preexisting   requirements inRFC 5246 and are merely stated here in the interest   of forward compatibility.   Note that sending a "renegotiation_info" extension in response to a   ClientHello containing only the SCSV is an explicit exception to the   prohibition inRFC 5246, Section 7.4.1.4, on the server sending   unsolicited extensions and is only allowed because the client is   signaling its willingness to receive the extension via the   TLS_EMPTY_RENEGOTIATION_INFO_SCSV SCSV.  TLS implementations MUST   continue to comply withSection 7.4.1.4 for all other extensions.3.7.  Server Behavior: Secure Renegotiation   This text applies if the connection's "secure_renegotiation" flag is   set to TRUE (if it is set to FALSE, seeSection 4.4).   o  When a ClientHello is received, the server MUST verify that it      does not contain the TLS_EMPTY_RENEGOTIATION_INFO_SCSV SCSV.  If      the SCSV is present, the server MUST abort the handshake.   o  The server MUST verify that the "renegotiation_info" extension is      present; if it is not, the server MUST abort the handshake.Rescorla, et al.             Standards Track                    [Page 8]

RFC 5746               TLS Renegotiation Extension         February 2010   o  The server MUST verify that the value of the      "renegotiated_connection" field is equal to the saved      client_verify_data value; if it is not, the server MUST abort the      handshake.   o  The server MUST include a "renegotiation_info" extension      containing the saved client_verify_data and server_verify_data in      the ServerHello.   o  When the handshake has completed, the server needs to save the new      client_verify_data and server_verify_data values.4.  Backward Compatibility   Existing implementations that do not support this extension are   widely deployed and, in general, must interoperate with newer   implementations that do support it.  This section describes   considerations for backward compatible interoperation.4.1.  Client Considerations   If a client offers the "renegotiation_info" extension or the   TLS_EMPTY_RENEGOTIATION_INFO_SCSV SCSV and the server does not reply   with "renegotiation_info" in the ServerHello, then this indicates   that the server does not support secure renegotiation.  Because some   attacks (seeSection 1) look like a single handshake to the client,   the client cannot determine whether or not the connection is under   attack.  Note, however, that merely because the server does not   acknowledge the extension does not mean that it is vulnerable; it   might choose to reject all renegotiations and simply not signal it.   However, it is not possible for the client to determine purely via   TLS mechanisms whether or not this is the case.   If clients wish to ensure that such attacks are impossible, they need   to terminate the connection immediately upon failure to receive the   extension without completing the handshake.  Such clients MUST   generate a fatal "handshake_failure" alert prior to terminating the   connection.  However, it is expected that many TLS servers that do   not support renegotiation (and thus are not vulnerable) will not   support this extension either, so in general, clients that implement   this behavior will encounter interoperability problems.  There is no   set of client behaviors that will guarantee security and achieve   maximum interoperability during the transition period.  Clients need   to choose one or the other preference when dealing with potentially   un-upgraded servers.Rescorla, et al.             Standards Track                    [Page 9]

RFC 5746               TLS Renegotiation Extension         February 20104.2.  Client Behavior: Legacy (Insecure) Renegotiation   This text applies if the connection's "secure_renegotiation" flag is   set to FALSE.   It is possible that un-upgraded servers will request that the client   renegotiate.  It is RECOMMENDED that clients refuse this   renegotiation request.  Clients that do so MUST respond to such   requests with a "no_renegotiation" alert (RFC 5246 requires this   alert to be at the "warning" level).  It is possible that the   apparently un-upgraded server is in fact an attacker who is then   allowing the client to renegotiate with a different, legitimate,   upgraded server.  If clients nevertheless choose to renegotiate, they   MUST behave as described below.   Clients that choose to renegotiate MUST provide either the   TLS_EMPTY_RENEGOTIATION_INFO_SCSV SCSV or "renegotiation_info" in   their ClientHello.  In a legitimate renegotiation with an un-upgraded   server, that server should ignore both of these signals.  However, if   the server (incorrectly) fails to ignore extensions, sending the   "renegotiation_info" extension may cause a handshake failure.  Thus,   it is permitted, though NOT RECOMMENDED, for the client to simply   send the SCSV.  This is the only situation in which clients are   permitted to not send the "renegotiation_info" extension in a   ClientHello that is used for renegotiation.   Note that in the case of a downgrade attack, if this is an initial   handshake from the server's perspective, then use of the SCSV from   the client precludes detection of this attack by the server (if this   is a renegotiation from the server's perspective, then it will detect   the attack).  However, the attack will be detected by the client when   the server sends an empty "renegotiation_info" extension and the   client is expecting one containing the previous verify_data.  By   contrast, if the client sends the "renegotiation_info" extension,   then the server will immediately detect the attack.   When the ServerHello is received, the client MUST verify that it does   not contain the "renegotiation_info" extension.  If it does, the   client MUST abort the handshake.  (Because the server has already   indicated it does not support secure renegotiation, the only way that   this can happen is if the server is broken or there is an attack.)4.3.  Server Considerations   If the client does not offer the "renegotiation_info" extension or   the TLS_EMPTY_RENEGOTIATION_INFO_SCSV SCSV, then this indicates that   the client does not support secure renegotiation.  Although the   attack described inSection 1 looks like two handshakes to theRescorla, et al.             Standards Track                   [Page 10]

RFC 5746               TLS Renegotiation Extension         February 2010   server, other attacks may be possible in which the renegotiation is   seen only by the client.  If servers wish to ensure that such attacks   are impossible, they need to terminate the connection immediately   upon failure to negotiate the use of secure renegotiation.  Servers   that do choose to allow connections from unpatched clients can still   prevent the attack described inSection 1 by refusing to renegotiate   over those connections.   In order to enable clients to probe, even servers that do not support   renegotiation MUST implement the minimal version of the extension   described in this document for initial handshakes, thus signaling   that they have been upgraded.4.4.  Server Behavior: Legacy (Insecure) Renegotiation   This text applies if the connection's "secure_renegotiation" flag is   set to FALSE.   It is RECOMMENDED that servers not permit legacy renegotiation.  If   servers nevertheless do permit it, they MUST follow the requirements   in this section.   o  When a ClientHello is received, the server MUST verify that it      does not contain the TLS_EMPTY_RENEGOTIATION_INFO_SCSV SCSV.  If      the SCSV is present, the server MUST abort the handshake.   o  The server MUST verify that the "renegotiation_info" extension is      not present; if it is, the server MUST abort the handshake.4.5.  SSLv3   While SSLv3 is not a protocol under IETF change control (see   [SSLv3]), it was the original basis for TLS and most TLS   implementations also support SSLv3.  The IETF encourages SSLv3   implementations to adopt the "renegotiation_info" extension and SCSV   as defined in this document.  The semantics of the SCSV and extension   are identical to TLS stacks except for the size of the verify_data   values, which are 36 bytes long each.  Note that this will require   adding at least minimal extension processing to such stacks.  Clients   that support SSLv3 and offer secure renegotiation (either via SCSV or   "renegotiation_info") MUST accept the "renegotiation_info" extension   from the server, even if the server version is {0x03, 0x00}, and   behave as described in this specification.  TLS servers that support   secure renegotiation and support SSLv3 MUST accept SCSV or the   "renegotiation_info" extension and respond as described in this   specification even if the offered client version is {0x03, 0x00}.   SSLv3 does not define the "no_renegotiation" alert (and doesRescorla, et al.             Standards Track                   [Page 11]

RFC 5746               TLS Renegotiation Extension         February 2010   not offer a way to indicate a refusal to renegotiate at a "warning"   level).  SSLv3 clients that refuse renegotiation SHOULD use a fatal   handshake_failure alert.5.  Security Considerations   The extension described in this document prevents an attack on TLS.   If this extension is not used, TLS renegotiation is subject to an   attack in which the attacker can inject their own conversation with   the TLS server as a prefix to the client's conversation.  This attack   is invisible to the client and looks like an ordinary renegotiation   to the server.  The extension defined in this document allows   renegotiation to be performed safely.  Servers SHOULD NOT allow   clients to renegotiate without using this extension.  Many servers   can mitigate this attack simply by refusing to renegotiate at all.   While this extension mitigates the man-in-the-middle attack described   in the overview, it does not resolve all possible problems an   application may face if it is unaware of renegotiation.  For example,   during renegotiation, either the client or the server can present a   different certificate than was used earlier.  This may come as a   surprise to application developers (who might have expected, for   example, that a "getPeerCertificates()" API call returns the same   value if called twice), and might be handled in an insecure way.   TLS implementations SHOULD provide a mechanism to disable and enable   renegotiation.   TLS implementers are encouraged to clearly document how renegotiation   interacts with the APIs offered to applications (for example, which   API calls might return different values on different calls, or which   callbacks might get called multiple times).   To make life simpler for applications that use renegotiation but do   not expect the certificate to change once it has been authenticated,   TLS implementations may also wish to offer the applications the   option to abort the renegotiation if the peer tries to authenticate   with a different certificate and/or different server name (in the   server_name extension) than was used earlier.  TLS implementations   may alternatively offer the option to disable renegotiation once the   client certificate has been authenticated.  However, enabling these   options by default for all applications could break existing   applications that depend on using renegotiation to change from one   certificate to another.  (For example, long-lived TLS connections   could change to a renewed certificate; or renegotiation could select   a different cipher suite that requires using a different   certificate.)Rescorla, et al.             Standards Track                   [Page 12]

RFC 5746               TLS Renegotiation Extension         February 2010   Finally, designers of applications that depend on renegotiation are   reminded that many TLS APIs represent application data as a simple   octet stream; applications may not be able to determine exactly which   application data octets were received before, during, or after   renegotiation.  Especially if the peer presents a different   certificate during renegotiation, care is needed when specifying how   the application should handle the data.6.  IANA Considerations   IANA has added the extension code point 65281 (0xff01), which has   been used for prototype implementations, for the "renegotiation_info"   extension to the TLS ExtensionType values registry.   IANA has added TLS cipher suite number 0x00,0xFF with name   TLS_EMPTY_RENEGOTIATION_INFO_SCSV to the TLS Cipher Suite registry.7.  Acknowledgements   This vulnerability was originally discovered by Marsh Ray and   independently rediscovered by Martin Rex.  The general concept behind   the extension described here was independently invented by Steve   Dispensa, Nasko Oskov, and Eric Rescorla with refinements from Nelson   Bolyard, Pasi Eronen, Michael D'Errico, Stephen Farrell, Michael   Gray, David-Sarah Hopwood, Ben Laurie, David Makepeace, Bodo Moeller,   Martin Rex, Peter Robinson, Jesse Walker, Nico Williams, and other   members of the Project Mogul team and the TLS WG.8.  References8.1.  Normative References   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate              Requirement Levels",BCP 14,RFC 2119, March 1997.   [RFC5246]  Dierks, T. and E. Rescorla, "The Transport Layer Security              (TLS) Protocol Version 1.2",RFC 5246, August 2008.8.2.  Informative References   [RFC4347]  Rescorla, E. and N. Modadugu, "Datagram Transport Layer              Security",RFC 4347, April 2006.   [RFC5056]  Williams, N., "On the Use of Channel Bindings to Secure              Channels",RFC 5056, November 2007.Rescorla, et al.             Standards Track                   [Page 13]

RFC 5746               TLS Renegotiation Extension         February 2010   [TLS-CHANNEL-BINDINGS]              Altman, J., Williams, N., and L. Zhu, "Channel Bindings              for TLS", Work in Progress, October 2009.   [RFC2818]  Rescorla, E., "HTTP Over TLS",RFC 2818, May 2000.   [RFC2965]  Kristol, D. and L. Montulli, "HTTP State Management              Mechanism",RFC 2965, October 2000.   [Ray09]    Ray, M., "Authentication Gap in TLS Renegotiation",              November 2009, <http://extendedsubset.com/?p=8>.   [SSLv3]    Freier, A., Karlton, P., and P. Kocher, "The SSL Protocol              Version 3.0", Work in Progress, November 1996.Rescorla, et al.             Standards Track                   [Page 14]

RFC 5746               TLS Renegotiation Extension         February 2010Authors' Addresses   Eric Rescorla   RTFM, Inc.   2064 Edgewood Drive   Palo Alto, CA  94303   USA   EMail:  ekr@rtfm.com   Marsh Ray   PhoneFactor   7301 W 129th Street   Overland Park, KS  66213   USA   EMail:  marsh@extendedsubset.com   Steve Dispensa   PhoneFactor   7301 W 129th Street   Overland Park, KS  66213   USA   EMail:  dispensa@phonefactor.com   Nasko Oskov   Microsoft   One Microsoft Way   Redmond, WA  98052   USA   EMail:  nasko.oskov@microsoft.comRescorla, et al.             Standards Track                   [Page 15]