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This document defines all the strings and constants reserved by UAF protocols. The values defined in this document are referenced by various UAF specifications.
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THIS FIDO ALLIANCE SPECIFICATION IS PROVIDED “AS IS” AND WITHOUT ANY WARRANTY OF ANY KIND, INCLUDING, WITHOUT LIMITATION, ANY EXPRESS OR IMPLIED WARRANTY OF NON-INFRINGEMENT, MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Type names, attribute names and element names are written as code.
String literals are enclosed in “”, e.g. “UAF-TLV”.
In formulas we use “|” to denote byte wise concatenation operations.
UAF specific terminology used in this document is defined in [FIDOGlossary].
All diagrams, examples, notes in this specification are non-normative.
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].
This section is non-normative.
This document defines the registry of UAF-specific constants that are used and referenced in various UAF specifications. It is expected that, over time, new constants will be added to this registry. For example new authentication algorithms and new types of authenticator characteristics will require new constants to be defined for use within the specifications.
This section is normative.
The USER_VERIFY constants are flags in a bitfield represented
as a 32 bit long integer. They describe
the methods and capabilities of an UAF authenticator for locally verifying
a user. The operational details of
these methods are opaque to the server. These constants are used in the
authoritative metadata for an authenticator,
reported and queried through the UAF Discovery APIs, and used to form authenticator
policies in UAF protocol messages.
All user verification methods must be performed locally by the authenticator in order to meet FIDO privacy principles.
USER_VERIFY_PRESENCE 0x01USER_VERIFY_FINGERPRINT 0x02USER_VERIFY_PASSCODE 0x04USER_VERIFY_VOICEPRINT 0x08USER_VERIFY_FACEPRINT 0x10USER_VERIFY_LOCATION 0x20USER_VERIFY_EYEPRINT 0x40USER_VERIFY_PATTERN 0x80USER_VERIFY_HANDPRINT 0x100USER_VERIFY_NONE 0x200USER_VERIFY_ALL 0x400The KEY_PROTECTION constants are flags in a bit field
represented as a 16 bit long integer. They describe the method an
authenticator uses to protect the private key material for FIDO registrations.
Refer to [UAFAuthnrCommands] for more details on the relevance of keys and
key protection. These constants are used in the authoritative metadata for an
authenticator, reported and queried through the UAF Discovery APIs, and used to
form authenticator policies in UAF protocol messages.
When used in metadata describing an authenticator, several of these flags are exclusive of
others (i.e. can not be combined) - the certified metadata may have
at most one of the mutually exclusive bits set to 1. When used in authenticator
policy, any bit may be set to 1, e.g. to indicate that a server is
willing to accept authenticators using either KEY_PROTECTION_SOFTWARE or
KEY_PROTECTION_HARDWARE.
These flags must be set according to the effective security of the
keys, in order to follow the assumptions made in [FIDOSecRef]. For example, if a key
is stored in a secure element but software running on the FIDO User Device
could call a function in the secure element to export the key either in the clear or using
an arbitrary wrapping key, then the effective security is KEY_PROTECTION_SOFTWARE and
not KEY_PROTECTION_SECURE_ELEMENT.
KEY_PROTECTION_SOFTWARE 0x01KEY_PROTECTION_HARDWARE, KEY_PROTECTION_TEE,
KEY_PROTECTION_SECURE_ELEMENT
KEY_PROTECTION_HARDWARE 0x02KEY_PROTECTION_SOFTWARE
KEY_PROTECTION_TEE 0x04KEY_PROTECTION_HARDWARE.
Exclusive in authenticator metadata with
KEY_PROTECTION_SOFTWARE, KEY_PROTECTION_SECURE_ELEMENT
KEY_PROTECTION_SECURE_ELEMENT 0x08KEY_PROTECTION_HARDWARE.
Exclusive in authenticator metadata with
KEY_PROTECTION_TEE, KEY_PROTECTION_SOFTWARE
KEY_PROTECTION_REMOTE_HANDLE 0x10KEY_PROTECTION
flags to indicate how the local key handle wrapping key and operations are protected.
Servers MAY unset this flag in authenticator policy if they are not prepared to store and return
key handles, for example, if they have a requirement to respond
indistinguishably to authentication attempts against userIDs that do and
do not exist. Refer to [UAFProtocol] for more details.The MATCHER_PROTECTION constants are flags in a bit field
represented as a 16 bit long integer.
They describe the method an authenticator uses to protect the matcher
that performs user verification.
These constants are used in the authoritative metadata for an authenticator,
reported and queried through
the UAF Discovery APIs, and used to form authenticator policies in
UAF protocol messages. Refer to [UAFAuthnrCommands]
for more details on the matcher component.
These flags must be set according to the effective security of the
matcher, in order to follow the assumptions made in [FIDOSecRef]. For example, if a passcode based
matcher is implemented in a secure element, but the passcode is expected to be
provided as unauthenticated parameter, then the effective security
is MATCHER_PROTECTION_SOFTWARE and
not MATCHER_PROTECTION_ON_CHIP.
MATCHER_PROTECTION_SOFTWARE 0x01MATCHER_PROTECTION_TEE,
MATCHER_PROTECTION_ON_CHIP
MATCHER_PROTECTION_TEE 0x02MATCHER_PROTECTION_SOFTWARE,
MATCHER_PROTECTION_ON_CHIP
MATCHER_PROTECTION_ON_CHIP 0x04MATCHER_PROTECTION_TEE,
MATCHER_PROTECTION_SOFTWARE
The ATTACHMENT_HINT constants are flags in a bit field
represented as a 32 bit long. They describe the method an
authenticator uses to communicate with the FIDO User Device. These constants are reported and
queried through the UAF Discovery APIs [UAFAppAPIAndTransport], and used to form Authenticator
policies in UAF protocol messages. Because the connection
state and topology of an authenticator may be transient, these values are
only hints that can be used by server-supplied policy
to guide the user experience, e.g. to prefer a device that is connected and
ready for authenticating or confirming a low-value transaction,
rather than one that is more secure but requires more user effort.
These flags are not a mandatory part of authenticator metadata and, when present, only indicate possible states that may be reported during authenticator discovery.
ATTACHMENT_HINT_INTERNAL 0x01A device such as a smartphone may have authenticator functionality that is able to be used both locally and remotely. In such a case, the FIDO client MUST filter and exclusively report only the relevant bit during Discovery and when performing policy matching.
This flag cannot be combined with any other ATTACHMENT_HINT flags.
ATTACHMENT_HINT_EXTERNAL 0x02A device such as a smartphone may have authenticator functionality that is able to be used both locally and remotely. In such a case, the FIDO UAF Client MUST filter and exclusively report only the relevant bit during discovery and when performing policy matching.
ATTACHMENT_HINT_WIRED 0x04ATTACHMENT_HINT_WIRELESS 0x08ATTACHMENT_HINT_NFC 0x10ATTACHMENT_HINT_WIRELESS flag SHOULD also be set as well.ATTACHMENT_HINT_BLUETOOTH 0x20ATTACHMENT_HINT_WIRELESS flag SHOULD also be set.ATTACHMENT_HINT_NETWORK 0x40ATTACHMENT_HINT_READY 0x80Generally this should indicate that the device is immediately available to perform user verification without additional actions such as connecting the device or creating a new biometric profile enrollment, but the exact meaning may vary for different types of devices. For example, a USB authenticator may only report itself as ready when it is plugged in, or a Bluetooth authenticator when it is paired and connected, but an NFC-based authenticator may always report itself as ready.
ATTACHMENT_HINT_WIFI_DIRECT 0x100ATTACHMENT_HINT_WIRELESS flag SHOULD also be set.The TRANSACTION_CONFIRMATION_DISPLAY constants are flags
in a bit field represented as a 16 bit long
integer. They describe the availability and implementation of a
transaction confirmation display capability required
for the transaction confirmation operation. These constants are
used in the authoritative metadata for an authenticator,
reported and queried through the UAF Discovery APIs, and used to
form authenticator policies in UAF protocol messages.
Refer to [UAFAuthnrCommands] for more details on the security aspects
of TransactionConfirmation Display.
TRANSACTION_CONFIRMATION_DISPLAY_ANY 0x01TRANSACTION_CONFIRMATION_DISPLAY_PRIVILEGED_SOFTWARE
0x02A FIDO client that is capable of providing this
capability MAY set this bit for all authenticators of type
ATTACHMENT_HINT_INTERNAL, even if the authoritative metadata for the
authenticator does not indicate this capability.
Software based transaction confirmation displays might be implemented within the boundaries of the ASM rather than by the authenticator itself [UAFASM].
TRANSACTION_CONFIRMATION_DISPLAY_TEE 0x04TRANSACTION_CONFIRMATION_DISPLAY_HARDWARE 0x08TRANSACTION_CONFIRMATION_DISPLAY_REMOTE 0x10Names of assertion schemes are strings with a length of 8 characters.
UAF TLV based assertion scheme “UAFV1TLV”UAF_ALG). This assertion scheme is using a compact
Tag Length Value (TLV) encoding for the KRD and SignData messages generated
by the authenticators. This is the default assertion scheme for the UAF protocol.This section is normative.
The internal structure of UAF authenticator commands is a “Tag-Length-Value” (TLV) sequence. The tag is a 2-byte unique unsigned value describing the type of field the data represents, the length is a 2-byte unsigned value indicating the size of the value in bytes, and the value is the variable-sized series of bytes which contain data for this item in the sequence.
Although 2 bytes are allotted for the tag, only the first 14 bits (values up to 0x3FFF) should be used to accommodate the limitations of some hardware platforms.
A tag that has the 14th bit (0x2000) set indicates that it is critical and a receiver must abort processing the entire message if it cannot process that tag.
A tag that has the 13th bit (0x1000) set indicates a composite tag that can be parsed by recursive descent.