OpenID

The end user interacts with a relying party (such as a website) that provides an option to specify an OpenID for the purposes of authentication; an end user typically has previously registered an OpenID (e.g. alice.openid.example.org) with an OpenID provider (e.g. openid.example.org).[1]

The relying party typically transforms the OpenID into a canonical URL form (e.g. http://alice.openid.example.org/).

• With OpenID 1.0, the relying party then requests the HTML resource identified by the URL and reads an HTML link tag to discover the OpenID provider's URL (e.g. http://openid.example.org/openid-auth.php). The relying party also discovers whether to use a delegated identity (see below).
• With OpenID 2.0, the relying party discovers the OpenID provider URL by requesting the XRDS document (also called the Yadis document) with the content type application/xrds+xml; this document may be available at the target URL and is always available for a target XRI.

There are two modes in which the relying party may communicate with the OpenID provider:

• checkid_immediate, in which the relying party requests that the OpenID provider not interact with the end user. All communication is relayed through the end user's user-agent without explicitly notifying the end user.
• checkid_setup, in which the end user communicates with the OpenID provider via the same user-agent used to access the relying party.

The checkid_immediate mode can fall back to the checkid_setup mode if the operation cannot be automated.

First, the relying party and the OpenID provider (optionally) establish a shared secret, referenced by an associate handle, which the relying party then stores. If using the checkid_setup mode, the relying party redirects the end user's user-agent to the OpenID provider so the end user can authenticate directly with the OpenID provider.

The method of authentication may vary, but typically, an OpenID provider prompts the end user for a password or some cryptographic token, and then asks whether the end user trusts the relying party to receive the necessary identity details.

If the end user declines the OpenID provider's request to trust the relying party, then the user-agent is redirected back to the relying party with a message indicating that authentication was rejected; the relying party in turn refuses to authenticate the end user.

If the end user accepts the OpenID provider's request to trust the relying party, then the user-agent is redirected back to the relying party along with the end user's credentials. That relying party must then confirm that the credentials really came from the OpenID provider. If the relying party and OpenID provider had previously established a shared secret, then the relying party can validate the identity of the OpenID provider by comparing its copy of the shared secret against the one received along with the end user's credentials; such a relying party is called stateful because it stores the shared secret between sessions. In contrast, a stateless or dumb relying party must make one more background request (check_authentication) to ensure that the data indeed came from the OpenID provider.

After the OpenID has been verified, authentication is considered successful and the end user is considered logged into the relying party under the identity specified by the given OpenID (e.g. alice.openid.example.org). The relying party typically then stores the end user's OpenID along with the end user's other session information.

To obtain an OpenID-enabled URL that can be used to log into OpenID-enabled websites, a user registers an OpenID identifier with an identity provider. Identity providers offer the ability to register a URL (typically a third-level domain, e.g. username.example.com) that will automatically be configured with OpenID authentication service.

Once they have registered an OpenID, a user can also use an existing URL under their own control (such as a blog or home page) as an alias or "delegated identity". They simply insert the appropriate OpenID tags in the HTML[14] or serve a Yadis document.[15]

Starting with OpenID Authentication 2.0 (and some 1.1 implementations), there are two types of identifiers that can be used with OpenID: URLs and XRIs.

XRIs are a new form of Internet identifier designed specifically for cross-domain digital identity. For example, XRIs come in two forms—i-names and i-numbers—that are usually registered simultaneously as synonyms. I-names are reassignable (like domain names), while i-numbers are never reassigned. When an XRI i-name is used as an OpenID identifier, it is immediately resolved to the synonymous i-number (the CanonicalID element of the XRDS document). This i-number is the OpenID identifier stored by the relying party. In this way, both the user and the relying party are protected from the end user's OpenID identity ever being taken over by another party as can happen with a URL based on a reassignable DNS name.

The OpenID Foundation's board of directors has six community board members and eight corporate board members:[16]

OIDF is a global organization to promote digital identity and to encourage the further adoption of OpenID, the OIDF has encouraged the creation of member chapters. Member chapters are officially part of the Foundation and work within their own constituency to support the development and adoption of OpenID as a framework for user-centric identity on the internet.

The OIDF ensures that OpenID specifications are freely implementable therefore the OIDF requires all contributors to sign a contribution agreement. This agreement both grants a copyright license to the Foundation to publish the collective specifications and includes a patent non-assertion agreement. The non-assertion agreement states that the contributor will not sue someone for implementing OpenID specifications.

The OpenID trademark in the United States was assigned to the OpenID Foundation in March 2008.[17] It had been registered by NetMesh Inc. before the OpenID Foundation was operational.[18][19] In Europe, as of August 31, 2007, the OpenID trademark is registered to the OpenID Europe Foundation.[20]

The OpenID logo was designed by Randy "ydnar" Reddig, who in 2005 had expressed plans to transfer the rights to an OpenID organization.[21]

Since the original announcement of OpenID, the official site has stated:[22]

Nobody should own this. Nobody's planning on making any money from this. The goal is to release every part of this under the most liberal licenses possible, so there's no money or licensing or registering required to play. It benefits the community as a whole if something like this exists, and we're all a part of the community.

Sun Microsystems, VeriSign and a number of smaller companies involved in OpenID have issued patent non-assertion covenants covering OpenID 1.1 specifications. The covenants state that the companies will not assert any of their patents against OpenID implementations and will revoke their promises from anyone who threatens, or asserts, patents against OpenID implementors.[23][24]

In March, 2012, a research paper[25] reported two generic security issues in OpenID. Both issues allow an attacker to sign in to a victim's relying party accounts. For the first issue, OpenID and Google (an Identity Provider of OpenID) both published security advisories to address it.[26][27] Google's advisory says "An attacker could forge an OpenID request that doesn't ask for the user's email address, and then insert an unsigned email address into the IDPs response. If the attacker relays this response to a website that doesn't notice that this attribute is unsigned, the website may be tricked into logging the attacker in to any local account." The research paper claims that many popular websites have been confirmed vulnerable, including Yahoo! Mail, smartsheet.com, Zoho, manymoon.com, diigo.com. The researchers have notified the affected parties, who have then fixed their vulnerable code.

For the second issue, the paper called it "Data Type Confusion Logic Flaw", which also allows attackers to sign in to victims' RP accounts. Google and PayPal were initially confirmed vulnerable. OpenID published a vulnerability report[28] on the flaw. The report says Google and PayPal have applied fixes, and suggest other OpenID vendors to check their implementations.

Some observers have suggested that OpenID has security weaknesses and may prove vulnerable to phishing attacks.[29][30][31] For example, a malicious relaying party may forward the end user to a bogus identity provider authentication page asking that end user to input their credentials. On completion of this, the malicious party (who in this case also controls the bogus authentication page) could then have access to the end user's account with the identity provider, and then use that end user's OpenID to log into other services.

In an attempt to combat possible phishing attacks, some OpenID providers mandate that the end user needs to be authenticated with them prior to an attempt to authenticate with the relying party.[32] This relies on the end user knowing the policy of the identity provider. In December 2008, the OpenID Foundation approved version 1.0 of the Provider Authentication Policy Extension (PAPE), which "enables Relying Parties to request that OpenID Providers employ specified authentication policies when authenticating users and for OpenID Providers to inform the Relying Parties which policies were actually used."[33]

Other security issues identified with OpenID involve lack of privacy and failure to address the trust problem.[34] However, this problem is not unique to OpenID and is simply the state of the Internet as commonly used.

The Identity Provider does, however, get a log of your OpenID logins; they know when you logged into what website, making cross-site tracking much easier. A compromised OpenID account is also likely to be a more serious breach of privacy than a compromised account on a single site.

Another important vulnerability is present in the last step in the authentication scheme when TLS/SSL are not used: the redirect-URL from the identity provider to the relying party. The problem with this redirect is the fact that anyone who can obtain this URL (e.g. by sniffing the wire) can replay it and get logged into the site as the victim user. Some of the identity providers use nonces (a number used just once) to allow a user to log into the site once and fail all the consecutive attempts. The nonce solution works if the user is the first one to use the URL. However, a fast attacker who is sniffing the wire can obtain the URL and immediately reset a user's TCP connection (as an attacker is sniffing the wire and knows the required TCP sequence numbers) and then execute the replay attack as described above. Thus nonces only protect against passive attackers, but cannot prevent active attackers from executing the replay attack.[35] Use of TLS/SSL in the authentication process can significantly reduce this risk.

This can be restated as:

  IF (Both RP1 and RP2 have Bob as a client) AND       // a common case
     (Bob uses the same IDP with both RP1 and RP2) AND // a common case
     (RP1 does not use VPN/SSL/TLS to secure their connection with the client) // preventable!
  THEN
    RP2 could obtain credentials sufficient to impersonate Bob with RP1
  END-IF

On May 1, 2014, a bug dubbed "Covert Redirect related to OAuth 2.0 and OpenID" was disclosed.[36][37] It was discovered by mathematics doctoral student Wang Jing at the School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore.[38][39][40]

The announcement of OpenID is: "'Covert Redirect', publicized in May 2014, is an instance of attackers using open redirectors – a well-known threat, with well-known means of prevention. The OpenID Connect protocol mandates strict measures that preclude open redirectors to prevent this vulnerability."[41]

"The general consensus, so far, is that Covert Redirect is not as bad, but still a threat. Understanding what makes it dangerous requires a basic understanding of Open Redirect, and how it can be exploited."[42]

A patch was not immediately made available. Ori Eisen, founder, chairman and chief innovation officer at 41st Parameter told Sue Marquette Poremba, "In any distributed system, we are counting of the good nature of the participants to do the right thing. In cases like OAuth and OpenID, the distribution is so vast that it is unreasonable to expect each and every website to patch up in the near future".[43]

OpenID provides a cryptographic verification mechanism that prevents the attack below against users who misuse OAuth for authentication.

Note that the valet key does not describe the user in any way, it only provides limited access rights, to some house (which is not even necessarily the user's, they just had a key). Therefore if the key becomes compromised (the user is malicious and managed to steal the key to someone else's house), then the user can impersonate the house owner to the application who requested their authenticity. If the key is compromised by any point in the chain of trust, a malicious user may intercept it and use it to impersonate user X for any application relying on OAuth2 for pseudo authentication against the same OAuth authorization server. Conversely, the notarized letter contains the user's signature, which can be checked by the requesting application against the user, so this attack is not viable. [82]

The letter can use public-key cryptography to be authenticated.

• The requesting application provides its encryption public key to the user, which provides it to the authentication server.
• The authentication server encrypts a document containing an encryption key which corresponds to a one-way hash of a secret the user knows (e.g. passphrase) for challenge–response using the application's public key.
• The user passes the encrypted document back to the application, which decrypts it.
• The application encrypts a random phrase using the received encryption key, and asks that the user do the same, then compares the results, if they match, the user is authentic.