added feature assert_devices

improved error messages
fixed cbor issues
added hmac example

Cargo.toml

@@ -1,11 +1,11 @@
 [package]
-name = "ctap"
-description = "A Rust implementation of the FIDO2 CTAP protocol"
-version = "0.1.0"
+name = "ctap_hmac"
+description = "A Rust implementation of the FIDO2 CTAP protocol, including the HMAC extension"
+version = "0.3.0"
 license = "Apache-2.0/MIT"
-homepage = "https://github.com/ArdaXi/ctap"
-repository = "https://github.com/ArdaXi/ctap"
-authors = ["Arda Xi <arda@ardaxi.com>"]
+homepage = "https://github.com/ArdaXi/ctap/pull/2"
+repository = "https://github.com/shimunn/ctap"
+authors = ["Arda Xi <arda@ardaxi.com>", "shimun <shimun@shimun.net>"]
 edition = "2018"
 
 [dependencies]
@@ -19,3 +19,12 @@ cbor-codec = "0.7"
 ring = "0.13"
 untrusted = "0.6"
 rust-crypto = "0.2"
+csv-core = "0.1.6"
+derive_builder = "0.9.0"
+crossbeam = { version = "0.7.3", optional = true }
+[dev-dependencies]
+crossbeam = "0.7.3"
+hex = "0.4.0"
+
+[features]
+assert_devices = ["crossbeam"]

README.md

@@ -13,28 +13,28 @@ ctap is a library implementing the [FIDO2 CTAP](https://fidoalliance.org/specs/f
 ## Usage example
 
 ```rust
-let devices = ctap::get_devices()?;
-let device_info = &devices[0];
-let mut device = ctap::FidoDevice::new(device_info)?;
+use ctap_hmac::*;
+let device_info = get_devices()?.next().expect("no device connected");
+let mut device = FidoDevice::new(&device_info)?;
 
 // This can be omitted if the FIDO device is not configured with a PIN.
 let pin = "test";
 device.unlock(pin)?;
 
 // In a real application these values would come from the requesting app.
-let rp_id = "rp_id";
-let user_id = [0];
-let user_name = "user_name";
-let client_data_hash = [0; 32];
-let cred = device.make_credential(
-    rp_id,
-    &user_id,
-    user_name,
-    &client_data_hash
-)?;
+let cred_request = FidoCredentialRequestBuilder::default()
+                    .rp_id("rp_id")
+                    .user_name("user_name")
+                    .build().unwrap();
 
+let cred = device.make_credential(&cred_request)?;
+let cred = &&cred;
+let assertion_request = FidoAssertionRequestBuilder::default()
+                            .rp_id("rp_id")
+                            .credential(&&cred)
+                            .build().unwrap();
 // In a real application the credential would be stored and used later.
-let result = device.get_assertion(&cred, &client_data_hash);
+let result = device.get_assertion(&assertion_request);
 ```
 
 ## Limitations

examples/hmac.rs

@@ -0,0 +1,50 @@
+extern crate ctap_hmac as ctap;
+
+use crypto::digest::Digest;
+use crypto::sha2::Sha256;
+use ctap::extensions::hmac::HmacExtension;
+use ctap::{FidoCredential, FidoCredentialRequestBuilder, AuthenticatorOptions};
+use hex;
+use std::env::args;
+use std::io::prelude::*;
+use std::io::stdin;
+use std::io::stdout;
+
+const RP_ID: &str = "ctap_demo";
+
+fn main() -> ctap::FidoResult<()> {
+    let mut devices = ctap::get_devices()?;
+    let device_info = &mut devices.next().expect("No authenticator found");
+    let mut device = ctap::FidoDevice::new(device_info)?;
+
+    let mut credential = match args().skip(1).next().map(|h| FidoCredential {
+        id: hex::decode(&h).expect("Invalid credential"),
+        public_key: None,
+    }) {
+        Some(cred) => cred,
+        _ => {
+            let req = FidoCredentialRequestBuilder::default().rp_id(RP_ID).rp_name("ctap_hmac crate").user_name("example").uv(false).build().unwrap();
+
+            println!("Authorize using your device");
+            let cred = device.make_hmac_credential(req).expect("Failed to request credential");
+            println!("Credential: {}\nNote: You can pass this credential as first argument in order to reproduce results", hex::encode(&cred.id));
+            cred
+        }
+    };
+    let credential = credential;
+    print!("Type in your message: ");
+    stdout().flush();
+    let mut message = String::new();
+    stdin()
+        .read_line(&mut message)
+        .expect("Couldn't get your message\nNote: this demo does not accept binary data");
+    println!("Authorize using your device");
+
+    let mut salt = [0u8; 32];
+    let mut digest = Sha256::new();
+    digest.input(&message.as_bytes());
+    digest.result(&mut salt);
+    let (cred, (hash1, _hash2)) = device.get_hmac_assertion(RP_ID, &[&credential], &salt, None, None)?;
+    println!("Hash: {}", hex::encode(&hash1));
+    Ok(())
+}

examples/multiple.rs

@@ -0,0 +1,58 @@
+extern crate ctap_hmac as ctap;
+
+use crossbeam::thread;
+use crypto::digest::Digest;
+use crypto::sha2::Sha256;
+use ctap::{
+    FidoAssertionRequestBuilder, FidoCredential, FidoCredentialRequestBuilder, FidoDevice,
+    FidoError, FidoResult,
+};
+use failure::_core::time::Duration;
+use hex;
+use std::env::args;
+use std::io::prelude::*;
+use std::io::stdin;
+use std::io::stdout;
+use std::sync::mpsc::channel;
+use std::sync::Mutex;
+
+const RP_ID: &str = "ctap_demo";
+
+fn run() -> ctap::FidoResult<()> {
+    let mut credentials = args()
+        .skip(1)
+        .map(|id| FidoCredential {
+            id: hex::decode(&id).expect("Invalid credential"),
+            public_key: None,
+        })
+        .collect::<Vec<_>>();
+    if credentials.len() == 0 {
+        credentials = ctap::get_devices()?
+            .map(|h| {
+                FidoDevice::new(&h).and_then(|mut dev| {
+                    FidoCredentialRequestBuilder::default()
+                        .rp_id(RP_ID)
+                        .build()
+                        .unwrap()
+                        .make_credential(&mut dev)
+                })
+            })
+            .collect::<FidoResult<Vec<FidoCredential>>>()?;
+    }
+    let credentials = credentials.iter().collect::<Vec<_>>();
+    let req = FidoAssertionRequestBuilder::default()
+        .rp_id(RP_ID)
+        .credentials(&credentials[..])
+        .build()
+        .unwrap();
+    let mut devices = ctap::get_devices()?
+        .map(|handle| FidoDevice::new(&handle))
+        .collect::<FidoResult<Vec<_>>>()?;
+    let (cred, _) = ctap::get_assertion_devices(&req, devices.iter_mut())?;
+    println!("Success, got assertion for: {}", hex::encode(&cred.id));
+    Ok(())
+}
+
+fn main() {
+    dbg!(run());
+}

src/cbor.rs

@@ -82,7 +82,11 @@ impl<'a> MakeCredentialRequest<'a> {
         let mut length = 4;
         length += !self.exclude_list.is_empty() as usize;
         length += !self.extensions.is_empty() as usize;
-        length += self.options.is_some() as usize;
+        length += self
+            .options
+            .as_ref()
+            .map(|opt| opt.encoded())
+            .unwrap_or(false) as usize;
         length += self.pin_auth.is_some() as usize;
         length += self.pin_protocol.is_some() as usize;
         encoder.object(length)?;
@@ -145,7 +149,7 @@ impl MakeCredentialResponse {
     pub fn decode<R: ReadBytesExt>(mut reader: R) -> FidoResult<Self> {
         let status = reader.read_u8().context(FidoErrorKind::CborDecode)?;
         if status != 0 {
-            Err(FidoErrorKind::CborError(status))?
+            Err(FidoErrorKind::CborError(CborErrorCode::from(status)))?
         }
         let mut decoder = Decoder::new(Config::default(), reader);
         let mut response = MakeCredentialResponse::default();
@@ -182,7 +186,11 @@ impl<'a> GetAssertionRequest<'a> {
         let mut length = 2;
         length += !self.allow_list.is_empty() as usize;
         length += !self.extensions.is_empty() as usize;
-        length += self.options.is_some() as usize;
+        length += self
+            .options
+            .as_ref()
+            .map(|opt| opt.encoded())
+            .unwrap_or(false) as usize;
         length += self.pin_auth.is_some() as usize;
         length += self.pin_protocol.is_some() as usize;
         encoder.object(length)?;
@@ -236,7 +244,7 @@ impl GetAssertionResponse {
     pub fn decode<R: ReadBytesExt>(mut reader: R) -> FidoResult<Self> {
         let status = reader.read_u8().context(FidoErrorKind::CborDecode)?;
         if status != 0 {
-            Err(FidoErrorKind::CborError(status))?
+            Err(FidoErrorKind::CborError(CborErrorCode::from(status)))?
         }
         let mut decoder = Decoder::new(Config::default(), reader);
         let mut response = GetAssertionResponse::default();
@@ -272,7 +280,7 @@ impl GetInfoResponse {
     pub fn decode<R: ReadBytesExt>(mut reader: R) -> FidoResult<Self> {
         let status = reader.read_u8().context(FidoErrorKind::CborDecode)?;
         if status != 0 {
-            Err(FidoErrorKind::CborError(status))?
+            Err(FidoErrorKind::CborError(CborErrorCode::from(status)))?
         }
         let mut decoder = Decoder::new(Config::default(), reader);
         let mut response = GetInfoResponse::default();
@@ -360,7 +368,7 @@ impl ClientPinResponse {
     pub fn decode<R: ReadBytesExt>(mut reader: R) -> FidoResult<Self> {
         let status = reader.read_u8().context(FidoErrorKind::CborDecode)?;
         if status != 0 {
-            Err(FidoErrorKind::CborError(status))?
+            Err(FidoErrorKind::CborError(CborErrorCode::from(status)))?
         }
         let mut decoder = Decoder::new(Config::default(), reader);
         let mut response = ClientPinResponse::default();
@@ -692,15 +700,16 @@ impl PublicKeyCredentialDescriptor {
 pub struct AuthenticatorOptions {
     pub rk: bool,
     pub uv: bool,
+    pub up: bool,
 }
 
 impl AuthenticatorOptions {
     pub fn encoded(&self) -> bool {
-        self.rk || self.uv
+        self.rk || self.uv || self.up
     }
 
     pub fn encode<W: WriteBytesExt>(&self, encoder: &mut Encoder<W>) -> FidoResult<()> {
-        let length = (self.rk as usize) + (self.uv as usize);
+        let length = (self.rk as usize) + (self.uv as usize) + (self.up as usize);
         encoder.object(length)?;
         if self.rk {
             encoder.text("rk")?;
@@ -710,6 +719,10 @@ impl AuthenticatorOptions {
             encoder.text("uv")?;
             encoder.bool(true)?;
         }
+        if self.up {
+            encoder.text("up")?;
+            encoder.bool(true)?;
+        }
         Ok(())
     }
 }

src/ctap_error_codes.csv

@@ -0,0 +1,49 @@
+Code,Name,Description
+0x00,"CTAP1_ERR_SUCCESS, CTAP2_OK",Indicates successful response.
+0x01,CTAP1_ERR_INVALID_COMMAND,The command is not a valid CTAP command.
+0x02,CTAP1_ERR_INVALID_PARAMETER,The command included an invalid parameter.
+0x03,CTAP1_ERR_INVALID_LENGTH,Invalid message or item length.
+0x04,CTAP1_ERR_INVALID_SEQ,Invalid message sequencing.
+0x05,CTAP1_ERR_TIMEOUT,Message timed out.
+0x06,CTAP1_ERR_CHANNEL_BUSY,Channel busy.
+0x0A,CTAP1_ERR_LOCK_REQUIRED,Command requires channel lock.
+0x0B,CTAP1_ERR_INVALID_CHANNEL,Command not allowed on this cid.
+0x11,CTAP2_ERR_CBOR_UNEXPECTED_TYPE,Invalid/unexpected CBOR error.
+0x12,CTAP2_ERR_INVALID_CBOR,Error when parsing CBOR.
+0x14,CTAP2_ERR_MISSING_PARAMETER,Missing non-optional parameter.
+0x15,CTAP2_ERR_LIMIT_EXCEEDED,Limit for number of items exceeded.
+0x16,CTAP2_ERR_UNSUPPORTED_EXTENSION,Unsupported extension.
+0x19,CTAP2_ERR_CREDENTIAL_EXCLUDED,Valid credential found in the exclude list.
+0x21,CTAP2_ERR_PROCESSING,Processing (Lengthy operation is in progress).
+0x22,CTAP2_ERR_INVALID_CREDENTIAL,Credential not valid for the authenticator.
+0x23,CTAP2_ERR_USER_ACTION_PENDING,Authentication is waiting for user interaction.
+0x24,CTAP2_ERR_OPERATION_PENDING,"Processing, lengthy operation is in progress."
+0x25,CTAP2_ERR_NO_OPERATIONS,No request is pending.
+0x26,CTAP2_ERR_UNSUPPORTED_ALGORITHM,Authenticator does not support requested algorithm.
+0x27,CTAP2_ERR_OPERATION_DENIED,Not authorized for requested operation.
+0x28,CTAP2_ERR_KEY_STORE_FULL,Internal key storage is full.
+0x29,CTAP2_ERR_NOT_BUSY,Authenticator cannot cancel as it is not busy.
+0x2A,CTAP2_ERR_NO_OPERATION_PENDING,No outstanding operations.
+0x2B,CTAP2_ERR_UNSUPPORTED_OPTION,Unsupported option.
+0x2C,CTAP2_ERR_INVALID_OPTION,Not a valid option for current operation.
+0x2D,CTAP2_ERR_KEEPALIVE_CANCEL,Pending keep alive was cancelled.
+0x2E,CTAP2_ERR_NO_CREDENTIALS,No valid credentials provided.
+0x2F,CTAP2_ERR_USER_ACTION_TIMEOUT,Timeout waiting for user interaction.
+0x30,CTAP2_ERR_NOT_ALLOWED,"Continuation command, such as, authenticatorGetNextAssertion not allowed."
+0x31,CTAP2_ERR_PIN_INVALID,PIN Invalid.
+0x32,CTAP2_ERR_PIN_BLOCKED,PIN Blocked.
+0x33,CTAP2_ERR_PIN_AUTH_INVALID,"PIN authentication, pinAuth, verification failed."
+0x34,CTAP2_ERR_PIN_AUTH_BLOCKED,"PIN authentication,pinAuth, blocked. Requires power recycle to reset."
+0x35,CTAP2_ERR_PIN_NOT_SET,No PIN has been set.
+0x36,CTAP2_ERR_PIN_REQUIRED,PIN is required for the selected operation.
+0x37,CTAP2_ERR_PIN_POLICY_VIOLATION,PIN policy violation. Currently only enforces minimum length.
+0x38,CTAP2_ERR_PIN_TOKEN_EXPIRED,pinToken expired on authenticator.
+0x39,CTAP2_ERR_REQUEST_TOO_LARGE,Authenticator cannot handle this request due to memory constraints.
+0x3A,CTAP2_ERR_ACTION_TIMEOUT,The current operation has timed out.
+0x3B,CTAP2_ERR_UP_REQUIRED,User presence is required for the requested operation.
+0x7F,CTAP1_ERR_OTHER,Other unspecified error.
+0xDF,CTAP2_ERR_SPEC_LAST,CTAP 2 spec last error.
+0xE0,CTAP2_ERR_EXTENSION_FIRST,Extension specific error.
+0xEF,CTAP2_ERR_EXTENSION_LAST,Extension specific error.
+0xF0,CTAP2_ERR_VENDOR_FIRST,Vendor specific error.
+0xFF,CTAP2_ERR_VENDOR_LAST,Vendor specific error.

src/error.rs

@@ -4,17 +4,21 @@
 // http://apache.org/licenses/LICENSE-2.0> or the MIT license <LICENSE-MIT or
 // http://opensource.org/licenses/MIT>, at your option. This file may not be
 // copied, modified, or distributed except according to those terms.
-use cbor_codec::{EncodeError, DecodeError};
-
+use cbor_codec::{DecodeError, EncodeError};
+use csv_core::{ReadFieldResult, Reader};
+use failure::_core::fmt::{Error, Formatter};
+use failure::{Backtrace, Context, Fail};
 use std::fmt;
 use std::fmt::Display;
-use failure::{Context, Backtrace, Fail};
 
 pub type FidoResult<T> = Result<T, FidoError>;
 
 #[derive(Debug)]
 pub struct FidoError(Context<FidoErrorKind>);
 
+#[derive(Debug, Copy, Clone, Fail, Eq, PartialEq)]
+pub struct CborErrorCode(u8);
+
 #[derive(Copy, Clone, Eq, PartialEq, Debug, Fail)]
 pub enum FidoErrorKind {
     #[fail(display = "Read/write error with device.")]
@@ -41,10 +45,12 @@ pub enum FidoErrorKind {
     EncryptPin,
     #[fail(display = "Failed to decrypt PIN.")]
     DecryptPin,
+    #[fail(display = "Failed to verify response signature.")]
+    VerifySignature,
     #[fail(display = "Supplied key has incorrect type.")]
     KeyType,
-    #[fail(display = "Device returned error: 0x{:x}", _0)]
-    CborError(u8),
+    #[fail(display = "Device returned error: {}", _0)]
+    CborError(CborErrorCode),
     #[fail(display = "Device does not support FIDO2")]
     DeviceUnsupported,
     #[fail(display = "This operating requires a PIN but none was provided.")]
@@ -52,7 +58,7 @@ pub enum FidoErrorKind {
 }
 
 impl Fail for FidoError {
-    fn cause(&self) -> Option<&Fail> {
+    fn cause(&self) -> Option<&dyn Fail> {
         self.0.cause()
     }
 
@@ -99,3 +105,67 @@ impl From<DecodeError> for FidoError {
         FidoError(err.context(FidoErrorKind::CborDecode))
     }
 }
+
+impl From<u8> for CborErrorCode {
+    fn from(code: u8) -> Self {
+        Self(code)
+    }
+}
+
+impl Display for CborErrorCode {
+    fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error> {
+        let messages = include_str!("ctap_error_codes.csv");
+        let mut rdr = Reader::new();
+        let mut bytes = messages.as_bytes();
+        let mut col: usize = 0;
+        let mut row: usize = 0;
+        let mut correct_row: bool = false;
+        let mut field = [0u8; 1024];
+        let mut name: Option<String> = None;
+        let mut desc: Option<String> = None;
+        loop {
+            let (result, nin, read) = rdr.read_field(&bytes, &mut field);
+            bytes = &bytes[nin..];
+            match result {
+                ReadFieldResult::InputEmpty => {}
+                ReadFieldResult::OutputFull => panic!("field too large"),
+                ReadFieldResult::Field { record_end } => {
+                    let text = String::from_utf8(field[..read].iter().cloned().collect()).unwrap();
+                    if row > 0 {
+                        match col {
+                            0 if i64::from_str_radix(&text[2..], 16)
+                                .expect("malformed ctap_error_codes.csv")
+                                == self.0 as i64 =>
+                            {
+                                correct_row = true
+                            }
+                            1 | 2 if correct_row => {
+                                if let Some(_) = name {
+                                    desc = Some(text);
+                                    break;
+                                } else {
+                                    name = Some(text);
+                                }
+                            }
+                            _ => (),
+                        }
+                    }
+                    col += 1;
+                    if record_end {
+                        col = 0;
+                        row += 1;
+                    }
+                }
+                ReadFieldResult::End => break,
+            }
+        }
+        if let Some((code, _name, desc)) =
+            name.and_then(|name| desc.map(|desc| (self.0, name, desc)))
+        {
+            write!(f, "CborError: 0x{:x?}: {}", code, desc)?;
+        } else {
+            write!(f, "CborError: 0x{:x?}", self.0)?;
+        }
+        Ok(())
+    }
+}

src/extensions/hmac.rs

@@ -1,4 +1,7 @@
-use crate::cbor;
+use crate::{
+    AuthenticatorOptions, FidoAssertionRequestBuilder,
+    FidoCredentialRequest,
+};
 use crate::{FidoCredential, FidoDevice, FidoErrorKind, FidoResult};
 use cbor_codec::value::{Bytes, Int, Key, Text, Value};
 use cbor_codec::Encoder;
@@ -10,31 +13,24 @@ use rust_crypto::mac::Mac;
 use rust_crypto::sha2::Sha256;
 use std::collections::BTreeMap;
 use std::io::Cursor;
-
-#[derive(Debug, Clone)]
-pub struct FidoHmacCredential {
-    pub id: Vec<u8>,
-    pub rp_id: String,
-}
-
-impl From<FidoCredential> for FidoHmacCredential {
-    fn from(cred: FidoCredential) -> Self {
-        FidoHmacCredential {
-            id: cred.id,
-            rp_id: cred.rp_id,
-        }
-    }
-}
+use std::iter::FromIterator;
 
 pub trait HmacExtension {
     fn extension_name() -> &'static str {
         "hmac-secret"
     }
 
+    fn extension_input() -> &'static Value {
+        &Value::Bool(true)
+    }
+
+    /// Generates data for the extension field as part of the assertion request
     fn get_dict(&mut self, salt: &[u8; 32], salt2: Option<&[u8; 32]>) -> FidoResult<Value> {
         let mut map = BTreeMap::new();
         map.insert(
-            Key::Text(Text::Text(Self::extension_name().to_owned())),
+            Key::Text(Text::Text(
+                <Self as HmacExtension>::extension_name().to_owned(),
+            )),
             self.get_data(salt, salt2)?,
         );
         Ok(Value::Map(map))
@@ -42,26 +38,50 @@ pub trait HmacExtension {
 
     fn get_data(&mut self, salt: &[u8; 32], salt2: Option<&[u8; 32]>) -> FidoResult<Value>;
 
-    fn make_hmac_credential(&mut self) -> FidoResult<FidoHmacCredential>;
+    /// Convenience function to create an credential which includes extension specific data
+    /// Use `FidoDevice::make_credential` if you need more control
+    fn make_hmac_credential(&mut self, request: FidoCredentialRequest) -> FidoResult<FidoCredential>;
 
-    fn get_hmac_assertion(
+
+    /// Request an assertion from the authenticator for a given credential and salt(s).
+    /// at least one `salt` must be provided, consider using a hashing function like SHA256
+    /// to ensure that your salt will fit 32 bytes.
+    /// Salt(s), credential and the authenticator internal secret will then be used to
+    /// generate a secret.
+    ///
+    /// This method will return the secret whether the assertion matches the credential
+    /// provided, and will fail if a PIN is required but not provided or if the
+    /// device returns malformed data.
+    ///
+    fn get_hmac_assertion<'a>(
         &mut self,
-        credential: &FidoHmacCredential,
+        rp_id: &str,
+        credentials: &'a [&'a FidoCredential],
         salt: &[u8; 32],
         salt2: Option<&[u8; 32]>,
-    ) -> FidoResult<([u8; 32], Option<[u8; 32]>)>;
+        options: Option<AuthenticatorOptions>,
+    ) -> FidoResult<(&'a FidoCredential, ([u8; 32], Option<[u8; 32]>))>;
 
+    /// Convenience function for `get_hmac_assertion` that will accept arbitrary
+    /// lenght input which will then be hashed and passed on
     fn hmac_challange(
         &mut self,
-        credential: &FidoHmacCredential,
+        rp_id: &str,
+        credential: &FidoCredential,
         input: &[u8],
     ) -> FidoResult<[u8; 32]> {
         let mut salt = [0u8; 32];
         let mut digest = Sha256::new();
         digest.input(input);
         digest.result(&mut salt);
-        self.get_hmac_assertion(credential, &salt, None)
-            .map(|secret| secret.0)
+        self.get_hmac_assertion(
+            rp_id,
+            &[credential],
+            &salt,
+            None,
+            Some(AuthenticatorOptions { uv: true, rk: true, up: false }),
+        )
+        .map(|(_cred, secret)| secret.0)
     }
 }
 
@@ -118,59 +138,48 @@ impl HmacExtension for FidoDevice {
         Ok(Value::Map(map))
     }
 
-    fn make_hmac_credential(&mut self) -> FidoResult<FidoHmacCredential> {
-        self.make_credential("hmac", &[0u8], "commandline", &[0u8; 32])
-            .map(|cred| cred.into())
+    fn make_hmac_credential(&mut self, request: FidoCredentialRequest) -> FidoResult<FidoCredential> {
+        let mut request = request;
+        request.rk = true;
+        request.extension_data.insert(<Self as HmacExtension>::extension_name(), <Self as HmacExtension>::extension_input());
+        self.make_credential(&request)
     }
 
-    fn get_hmac_assertion(
+    fn get_hmac_assertion<'a>(
         &mut self,
-        credential: &FidoHmacCredential,
+        rp_id: &str,
+        credentials: &'a [&'a FidoCredential],
         salt: &[u8; 32],
         salt2: Option<&[u8; 32]>,
-    ) -> FidoResult<([u8; 32], Option<[u8; 32]>)> {
-        let client_data_hash = [0u8; 32];
+        options: Option<AuthenticatorOptions>,
+    ) -> FidoResult<(&'a FidoCredential, ([u8; 32], Option<[u8; 32]>))> {
         while self.shared_secret.is_none() {
             self.init_shared_secret()?;
         }
-        if self.needs_pin && self.pin_token.is_none() {
-            Err(FidoErrorKind::PinRequired)?
+        let ext_data: Value = self.get_data(salt, salt2)?;
+
+        let ext_data: BTreeMap<&str, &Value> = BTreeMap::from_iter(
+            [(<Self as HmacExtension>::extension_name(), &ext_data)]
+                .iter()
+                .cloned(),
+        );
+
+        let mut builder = FidoAssertionRequestBuilder::default()
+            .credentials(credentials)
+            .rp_id(rp_id)
+            .extension_data(ext_data);
+
+        if let Some(opts) = options {
+            builder = builder.uv(opts.uv).up(opts.up);
         }
 
-        if client_data_hash.len() != 32 {
-            Err(FidoErrorKind::CborEncode)?
-        }
-        let pin_auth = self
-            .pin_token
-            .as_ref()
-            .map(|token| token.auth(&client_data_hash));
-        let ext_data: Value = self.get_data(salt, salt2)?;
-        let allow_list = [cbor::PublicKeyCredentialDescriptor {
-            cred_type: String::from("public-key"),
-            id: credential.id.clone(),
-        }];
-        let request = cbor::GetAssertionRequest {
-            rp_id: &credential.rp_id,
-            client_data_hash: &client_data_hash,
-            allow_list: &allow_list,
-            extensions: &[(<Self as HmacExtension>::extension_name(), &ext_data)],
-            options: Some(cbor::AuthenticatorOptions {
-                rk: false,
-                uv: true,
-            }),
-            pin_auth,
-            pin_protocol: pin_auth.and(Some(0x01)),
-        };
-        let response = match self.cbor(cbor::Request::GetAssertion(request))? {
-            cbor::Response::GetAssertion(resp) => resp,
-            _ => Err(FidoErrorKind::CborDecode)?,
-        };
+        let (cred, auth_data) =
+            self.get_assertion(&builder.build().unwrap())?;
         let shared_secret = self.shared_secret.as_ref().unwrap();
         let mut decryptor = shared_secret.decryptor();
         let mut hmac_secret_combined = [0u8; 64];
         let _output = RefWriteBuffer::new(&mut hmac_secret_combined);
-        let hmac_secret_enc = match response
-            .auth_data
+        let hmac_secret_enc = match auth_data
             .extensions
             .get(<Self as HmacExtension>::extension_name())
             .ok_or(FidoErrorKind::CborDecode)?
@@ -185,16 +194,19 @@ impl HmacExtension for FidoDevice {
             }),
             _ => Err(FidoErrorKind::CborDecode),
         }?;
-        let mut hmac_secret = ([0u8; 32], [0u8; 32]);
+        let mut hmac_secret = [0u8; 64];
         decryptor
             .decrypt(
                 &mut RefReadBuffer::new(&hmac_secret_enc),
-                &mut RefWriteBuffer::new(unsafe {
-                    std::mem::transmute::<_, &mut [u8; 64]>(&mut hmac_secret)
-                }),
+                &mut RefWriteBuffer::new(&mut hmac_secret),
                 true,
             )
-            .expect("failed to decrypt secret");
-        Ok((hmac_secret.0, salt2.map(|_| hmac_secret.1)))
+            .map_err(|_| FidoErrorKind::ReadPacket)?;
+        let mut hmac_secret_0 = [0u8; 32];
+        let mut hmac_secret_1 = [0u8; 32];
+        hmac_secret_0.copy_from_slice(&hmac_secret[0..32]);
+        hmac_secret_1.copy_from_slice(&hmac_secret[32..]);
+        let cred = credentials.into_iter().find(|c| c.id == cred.id).unwrap();
+        Ok((cred, (hmac_secret_0, salt2.and(Some(hmac_secret_1)))))
     }
 }

src/extensions/mod.rs

@@ -1 +1,2 @@
 pub mod hmac;
+pub use hmac::*;

src/hid_linux.rs

@@ -4,11 +4,11 @@
 // http://apache.org/licenses/LICENSE-2.0> or the MIT license <LICENSE-MIT or
 // http://opensource.org/licenses/MIT>, at your option. This file may not be
 // copied, modified, or distributed except according to those terms.
-use std::io;
-use std::fs;
-use std::path::PathBuf;
-use byteorder::{ByteOrder, LittleEndian};
 pub use super::hid_common::*;
+use byteorder::{ByteOrder, LittleEndian};
+use std::fs;
+use std::io;
+use std::path::PathBuf;
 
 static REPORT_DESCRIPTOR_KEY_MASK: u8 = 0xfc;
 static LONG_ITEM_ENCODING: u8 = 0xfe;
@@ -18,9 +18,9 @@ static REPORT_SIZE: u8 = 0x74;
 
 pub fn enumerate() -> io::Result<impl Iterator<Item = DeviceInfo>> {
     fs::read_dir("/sys/class/hidraw").map(|entries| {
-        entries.filter_map(|entry| entry.ok()).filter_map(|entry| {
-            path_to_device(&entry.path()).ok()
-        })
+        entries
+            .filter_map(|entry| entry.ok())
+            .filter_map(|entry| path_to_device(&entry.path()).ok())
     })
 }
 

src/lib.rs

@@ -9,67 +9,76 @@
 //! # Example
 //!
 //! ```
-//! # fn do_fido() -> ctap::FidoResult<()> {
-//! let mut devices = ctap::get_devices()?;
-//! let device_info = &devices.next().unwrap();
-//! let mut device = ctap::FidoDevice::new(device_info)?;
+//! # use ctap_hmac::*;
+//! # fn do_fido() -> FidoResult<()> {
 //!
-//! // This can be omitted if the FIDO device is not configured with a PIN.
-//! let pin = "test";
-//! device.unlock(pin)?;
+//!use ctap_hmac::*;
+//!let device_info = get_devices()?.next().expect("no device connected");
+//!let mut device = FidoDevice::new(&device_info)?;
 //!
-//! // In a real application these values would come from the requesting app.
-//! let rp_id = "rp_id";
-//! let user_id = [0];
-//! let user_name = "user_name";
-//! let client_data_hash = [0; 32];
-//! let cred = device.make_credential(
-//!     rp_id,
-//!     &user_id,
-//!     user_name,
-//!     &client_data_hash
-//! )?;
+//!// This can be omitted if the FIDO device is not configured with a PIN.
+//!let pin = "test";
+//!device.unlock(pin)?;
+//!
+//!// In a real application these values would come from the requesting app.
+//!let cred_request = FidoCredentialRequestBuilder::default()
+//!     .rp_id("rp_id")
+//!     .user_name("user_name")
+//!     .build().unwrap();
+//!let cred = device.make_credential(&cred_request)?;
+//!let cred = &&cred;
+//!let assertion_request = FidoAssertionRequestBuilder::default()
+//!     .rp_id("rp_id")
+//!     .credential(cred)
+//!     .build().unwrap();
+//!// In a real application the credential would be stored and used later.
+//!let result = device.get_assertion(&assertion_request);
 //!
-//! // In a real application the credential would be stored and used later.
-//! let result = device.get_assertion(&cred, &client_data_hash);
 //! # Ok(())
 //! # }
 
 #![allow(dead_code)]
 
-extern crate rand;
 extern crate failure;
+extern crate rand;
 #[macro_use]
 extern crate failure_derive;
 #[macro_use]
 extern crate num_derive;
-extern crate num_traits;
+#[macro_use]
+extern crate derive_builder;
 extern crate byteorder;
 extern crate cbor as cbor_codec;
+extern crate crypto as rust_crypto;
+extern crate num_traits;
 extern crate ring;
 extern crate untrusted;
-extern crate crypto as rust_crypto;
 
-mod packet;
+mod cbor;
+mod crypto;
+mod error;
+pub mod extensions;
 mod hid_common;
 mod hid_linux;
-mod error;
-mod crypto;
-mod cbor;
-pub mod extensions;
+mod packet;
+mod util;
 
 use std::cmp;
-use std::u8;
-use std::u16;
 use std::fs;
-use std::io::{Write, Cursor};
+use std::io::{Cursor, Write};
+use std::u16;
+use std::u8;
 
-use failure::{Fail, ResultExt};
-use rand::prelude::*;
-use num_traits::FromPrimitive;
+use self::cbor::{AuthenticatorOptions, PublicKeyCredentialDescriptor};
+pub use self::error::*;
 use self::hid_linux as hid;
 use self::packet::CtapCommand;
-pub use self::error::*;
+pub use self::util::*;
+use crate::cbor::{AuthenticatorData, GetAssertionRequest};
+use failure::{Fail, ResultExt};
+use num_traits::FromPrimitive;
+use rand::prelude::*;
+use std::collections::BTreeMap;
 
 static BROADCAST_CID: [u8; 4] = [0xff, 0xff, 0xff, 0xff];
 
@@ -77,23 +86,18 @@ static BROADCAST_CID: [u8; 4] = [0xff, 0xff, 0xff, 0xff];
 pub fn get_devices() -> FidoResult<impl Iterator<Item = hid::DeviceInfo>> {
     hid::enumerate()
         .context(FidoErrorKind::Io)
-        .map(|devices| {
-            devices.filter(|dev| dev.usage_page == 0xf1d0 && dev.usage == 0x21)
-        })
+        .map(|devices| devices.filter(|dev| dev.usage_page == 0xf1d0 && dev.usage == 0x21))
         .map_err(From::from)
 }
 
 /// A credential created by a FIDO2 authenticator.
-#[derive(Debug)]
+#[derive(Debug, Clone)]
 pub struct FidoCredential {
     /// The ID provided by the authenticator.
     pub id: Vec<u8>,
     /// The public key provided by the authenticator, in uncompressed form.
-    pub public_key: Vec<u8>,
-    /// The Relying Party ID provided by the platform when this key was generated.
-    pub rp_id: String,
+    pub public_key: Option<Vec<u8>>,
 }
-
 /// An opened FIDO authenticator.
 pub struct FidoDevice {
     device: fs::File,
@@ -105,6 +109,145 @@ pub struct FidoDevice {
     aaguid: [u8; 16],
 }
 
+pub struct FidoCancelHandle {
+    device: fs::File,
+    packet_size: u16,
+    channel_id: [u8; 4],
+}
+
+impl FidoCancelHandle {
+    pub fn cancel(&mut self) -> FidoResult<()> {
+        let payload = &[1u8];
+        let to_send = payload.len() as u16;
+        let max_payload = (self.packet_size - 7) as usize;
+        let (frame, payload) = payload.split_at(cmp::min(payload.len(), max_payload));
+        packet::write_init_packet(
+            &mut self.device,
+            64,
+            &self.channel_id,
+            &CtapCommand::Cancel,
+            to_send,
+            frame,
+        )?;
+        if payload.is_empty() {
+            return Ok(());
+        }
+        let max_payload = (self.packet_size - 5) as usize;
+        for (seq, frame) in (0..u8::MAX).zip(payload.chunks(max_payload)) {
+            packet::write_cont_packet(&mut self.device, 64, &self.channel_id, seq, frame)?;
+        }
+        self.device.flush().context(FidoErrorKind::WritePacket)?;
+        Ok(())
+    }
+
+    pub fn cancel_after<T>(&mut self, body: impl Fn(()) -> T) -> FidoResult<T> {
+        let res = body(());
+        match self.cancel() {
+            Ok(_) => Ok(res),
+            Err(e) => Err(e),
+        }
+    }
+}
+
+/// Request a new credential from the authenticator. The `rp_id` should be
+/// a stable string used to identify the party for whom the credential is
+/// created, for convenience it will be returned with the credential.
+/// `user_id` and `user_name` are not required when requesting attestations
+/// but they MAY be displayed to the user and MAY be stored on the device
+/// to be returned with an attestation if the device supports this.
+/// `client_data_hash` SHOULD be a SHA256 hash of provided `client_data`,
+/// this is only used to verify the attestation provided by the
+/// authenticator. When not implementing WebAuthN this can be any random
+/// 32-byte array.
+///
+/// This method will fail if a PIN is required but the device is not
+/// unlocked or if the device returns malformed data.
+#[derive(Clone, Debug, Builder)]
+#[builder(setter(into))]
+#[builder(pattern = "owned")]
+pub struct FidoCredentialRequest<'a> {
+    /// create resident key
+    #[builder(default)]
+    rk: bool,
+    /// user verification
+    #[builder(default)]
+    uv: bool,
+    /// relying party id
+    rp_id: &'a str,
+    /// relying party id
+    #[builder(default)]
+    rp_name: Option<&'a str>,
+    /// relying party icon url
+    #[builder(default)]
+    rp_icon_url: Option<&'a str>,
+    /// user id
+    #[builder(default = "&[0u8]")]
+    user_id: &'a [u8],
+    /// user name
+    #[builder(default)]
+    user_name: Option<&'a str>,
+    /// user icon url
+    #[builder(default)]
+    user_icon_url: Option<&'a str>,
+    /// user display name
+    #[builder(default)]
+    user_display_name: Option<&'a str>,
+    #[builder(default = "&[]")]
+    exclude_list: &'a [&'a FidoCredential],
+    #[builder(default = "&[0u8; 32]")]
+    client_data_hash: &'a [u8],
+    #[builder(default)]
+    extension_data: BTreeMap<&'a str, &'a cbor_codec::value::Value>,
+}
+
+impl<'a> FidoCredentialRequest<'a> {
+    pub fn make_credential(&self, device: &mut FidoDevice) -> FidoResult<FidoCredential> {
+        device.make_credential(&self)
+    }
+}
+
+/// Request an assertion from the authenticator for a given credential.
+/// `client_data_hash` SHOULD be a SHA256 hash of provided `client_data`,
+/// this is signed and verified as part of the attestation. When not
+/// implementing WebAuthN this can be any random 32-byte array.
+///
+/// This method will return whether the assertion matches the credential
+/// provided, and will fail if a PIN is required but not provided or if the
+/// device returns malformed data.
+#[derive(Clone, Debug, Builder)]
+#[builder(setter(into))]
+#[builder(pattern = "owned")]
+pub struct FidoAssertionRequest<'a> {
+    #[builder(default)]
+    up: bool,
+    #[builder(default)]
+    rk: bool,
+    #[builder(default)]
+    uv: bool,
+    /// The Relying Party ID provided by the platform when this key was generated.
+    rp_id: &'a str,
+    credentials: &'a [&'a FidoCredential],
+    #[builder(default = "&[]")]
+    exclude_list: &'a [&'a FidoCredential],
+    #[builder(default = "&[0u8; 32]")]
+    client_data_hash: &'a [u8],
+    #[builder(default)]
+    extension_data: BTreeMap<&'a str, &'a cbor_codec::value::Value>,
+}
+
+impl<'a> FidoAssertionRequest<'a> {
+    pub fn get_assertion(&self, device: &mut FidoDevice) -> FidoResult<&'a FidoCredential> {
+        device.get_assertion(self).map(|res| res.0)
+    }
+}
+
+impl<'a> FidoAssertionRequestBuilder<'a> {
+    pub fn credential(mut self, credential: &'a &'a FidoCredential) -> Self {
+        self.credentials = Some(std::slice::from_ref(credential));
+        self
+    }
+}
+
 impl FidoDevice {
     /// Open and initialize a given device. DeviceInfo is provided by the `get_devices`
     /// function. This method will allocate a channel for this application, verify that
@@ -147,7 +290,12 @@ impl FidoDevice {
         if !response.versions.iter().any(|ver| ver == "FIDO_2_0") {
             Err(FidoErrorKind::DeviceUnsupported)?
         }
-        if !response.pin_protocols.iter().any(|ver| *ver == 1) {
+        // Require pin protocol version 1, only if pin-protocol is supported at all
+        if !response
+            .pin_protocols
+            .iter()
+            .fold(true, |supported, ver| *ver == 1 && supported)
+        {
             Err(FidoErrorKind::DeviceUnsupported)?
         }
         self.needs_pin = response.options.client_pin == Some(true);
@@ -209,6 +357,93 @@ impl FidoDevice {
         }
     }
 
+    pub fn cancel_handle(&mut self) -> FidoResult<FidoCancelHandle> {
+        Ok(self
+            .device
+            .try_clone()
+            .map(|device| FidoCancelHandle {
+                device,
+                packet_size: self.packet_size,
+                channel_id: self.channel_id,
+            })
+            .context(FidoErrorKind::Io)?)
+    }
+
+    pub fn make_credential(
+        &mut self,
+        request: &FidoCredentialRequest<'_>,
+    ) -> FidoResult<FidoCredential> {
+        let rp = cbor::PublicKeyCredentialRpEntity {
+            id: request.rp_id,
+            name: request.rp_name,
+            icon: request.rp_icon_url,
+        };
+        let user = cbor::PublicKeyCredentialUserEntity {
+            id: request.user_id,
+            name: request.user_name.unwrap_or(""),
+            icon: request.user_icon_url,
+            display_name: request.user_display_name,
+        };
+
+        let options = Some(AuthenticatorOptions {
+            up: false,
+            uv: request.uv,
+            rk: request.rk,
+        });
+        if self.needs_pin && self.pin_token.is_none() {
+            Err(FidoErrorKind::PinRequired)?
+        }
+        if request.client_data_hash.len() != 32 {
+            Err(FidoErrorKind::CborEncode)?
+        }
+        while self.shared_secret.is_none() {
+            self.init_shared_secret()?;
+        }
+        let pub_key_cred_params = [("public-key", -7)];
+        let pin_auth = self
+            .pin_token
+            .as_ref()
+            .map(|token| token.auth(&request.client_data_hash));
+        let request = cbor::MakeCredentialRequest {
+            client_data_hash: request.client_data_hash,
+            rp,
+            user,
+            pub_key_cred_params: &pub_key_cred_params,
+            exclude_list: &request
+                .exclude_list
+                .iter()
+                .map(|cred| PublicKeyCredentialDescriptor {
+                    cred_type: "public-key".into(),
+                    id: cred.id.clone(),
+                })
+                .collect::<Vec<_>>()[..],
+            extensions: &request
+                .extension_data
+                .iter()
+                .map(|(name, data)| (*name, *data))
+                .collect::<Vec<_>>()[..],
+            options,
+            pin_auth,
+            pin_protocol: pin_auth.and(Some(0x01)),
+        };
+
+        let response = match self.cbor(cbor::Request::MakeCredential(request))? {
+            cbor::Response::MakeCredential(resp) => resp,
+            _ => Err(FidoErrorKind::CborDecode)?,
+        };
+        let public_key = cbor::P256Key::from_cose(
+            &response
+                .auth_data
+                .attested_credential_data
+                .credential_public_key,
+        )?
+        .bytes();
+        Ok(FidoCredential {
+            id: response.auth_data.attested_credential_data.credential_id,
+            public_key: Some(Vec::from(&public_key[..])),
+        })
+    }
+
     /// Request a new credential from the authenticator. The `rp_id` should be
     /// a stable string used to identify the party for whom the credential is
     /// created, for convenience it will be returned with the credential.
@@ -222,121 +457,93 @@ impl FidoDevice {
     ///
     /// This method will fail if a PIN is required but the device is not
     /// unlocked or if the device returns malformed data.
-    pub fn make_credential(
-        &mut self,
-        rp_id: &str,
-        user_id: &[u8],
-        user_name: &str,
-        client_data_hash: &[u8],
-    ) -> FidoResult<FidoCredential> {
-        if self.needs_pin && self.pin_token.is_none() {
-            Err(FidoErrorKind::PinRequired)?
-        }
-        if client_data_hash.len() != 32 {
-            Err(FidoErrorKind::CborEncode)?
-        }
-        let pin_auth = self.pin_token.as_ref().map(
-            |token| token.auth(&client_data_hash),
-        );
-        let rp = cbor::PublicKeyCredentialRpEntity {
-            id: rp_id,
-            name: None,
-            icon: None,
-        };
-        let user = cbor::PublicKeyCredentialUserEntity {
-            id: user_id,
-            name: user_name,
-            icon: None,
-            display_name: None,
-        };
-        let pub_key_cred_params = [("public-key", -7)];
-        let request = cbor::MakeCredentialRequest {
-            client_data_hash,
-            rp,
-            user,
-            pub_key_cred_params: &pub_key_cred_params,
-            exclude_list: Default::default(),
-            extensions: Default::default(),
-            options: Some(cbor::AuthenticatorOptions {
-                rk: false,
-                uv: true,
-            }),
-            pin_auth,
-            pin_protocol: pin_auth.and(Some(0x01)),
-        };
-        let response = match self.cbor(cbor::Request::MakeCredential(request))? {
-            cbor::Response::MakeCredential(resp) => resp,
-            _ => Err(FidoErrorKind::CborDecode)?,
-        };
-        let public_key = cbor::P256Key::from_cose(
-            &response
-                .auth_data
-                .attested_credential_data
-                .credential_public_key,
-        )?
-            .bytes();
-        Ok(FidoCredential {
-            id: response.auth_data.attested_credential_data.credential_id,
-            rp_id: String::from(rp_id),
-            public_key: Vec::from(&public_key[..]),
-        })
-    }
 
-    /// Request an assertion from the authenticator for a given credential.
-    /// `client_data_hash` SHOULD be a SHA256 hash of provided `client_data`,
-    /// this is signed and verified as part of the attestation. When not
-    /// implementing WebAuthN this can be any random 32-byte array.
-    ///
-    /// This method will return whether the assertion matches the credential
-    /// provided, and will fail if a PIN is required but not provided or if the
-    /// device returns malformed data.
-    pub fn get_assertion(
+    pub fn get_assertion<'a>(
         &mut self,
-        credential: &FidoCredential,
-        client_data_hash: &[u8],
-    ) -> FidoResult<bool> {
+        assertion: &FidoAssertionRequest<'a>,
+    ) -> FidoResult<(&'a FidoCredential, AuthenticatorData)> {
+        while self.shared_secret.is_none() {
+            self.init_shared_secret()?;
+        }
         if self.needs_pin && self.pin_token.is_none() {
             Err(FidoErrorKind::PinRequired)?
         }
-        if client_data_hash.len() != 32 {
+        if assertion.client_data_hash.len() != 32 {
             Err(FidoErrorKind::CborEncode)?
         }
-        let pin_auth = self.pin_token.as_ref().map(
-            |token| token.auth(&client_data_hash),
-        );
-        let allow_list = [
-            cbor::PublicKeyCredentialDescriptor {
-                cred_type: String::from("public-key"),
-                id: credential.id.clone(),
-            },
-        ];
-        let request = cbor::GetAssertionRequest {
-            rp_id: &credential.rp_id,
-            client_data_hash: client_data_hash,
-            allow_list: &allow_list,
-            extensions: Default::default(),
-            options: Some(cbor::AuthenticatorOptions {
-                rk: false,
-                uv: true,
+        let pin_auth = self
+            .pin_token
+            .as_ref()
+            .map(|token| token.auth(&assertion.client_data_hash));
+        let request = GetAssertionRequest {
+            rp_id: assertion.rp_id,
+            client_data_hash: assertion.client_data_hash,
+            allow_list: &assertion
+                .credentials
+                .iter()
+                .map(|cred| PublicKeyCredentialDescriptor {
+                    cred_type: "public-key".into(),
+                    id: cred.id.clone(),
+                })
+                .collect::<Vec<_>>()[..],
+            extensions: &assertion
+                .extension_data
+                .iter()
+                .map(|(name, data)| (*name, *data))
+                .collect::<Vec<_>>()[..],
+            options: Some(AuthenticatorOptions {
+                rk: assertion.rk,
+                uv: assertion.uv,
+                up: assertion.up,
             }),
-            pin_auth,
+            pin_auth: pin_auth,
             pin_protocol: pin_auth.and(Some(0x01)),
         };
         let response = match self.cbor(cbor::Request::GetAssertion(request))? {
             cbor::Response::GetAssertion(resp) => resp,
             _ => Err(FidoErrorKind::CborDecode)?,
         };
-        Ok(crypto::verify_signature(
-            &credential.public_key,
-            &client_data_hash,
-            &response.auth_data_bytes,
-            &response.signature,
-        ))
+        let credential = assertion
+            .credentials
+            .iter()
+            .flat_map(|cred| {
+                response
+                    .credential
+                    .as_ref()
+                    .filter(|rcred| rcred.id == cred.id)
+                    .map(|_| *cred)
+            })
+            .next();
+
+        credential
+            .and_then(|cred| {
+                if cred
+                    .public_key
+                    .as_ref()
+                    .map(|public_key| {
+                        crypto::verify_signature(
+                            &public_key,
+                            &assertion.client_data_hash,
+                            &response.auth_data_bytes,
+                            &response.signature,
+                        )
+                    })
+                    .unwrap_or(true)
+                {
+                    Some(cred)
+                } else {
+                    None
+                }
+            })
+            .ok_or(FidoError::from(FidoErrorKind::VerifySignature))
+            .map(|cred| (cred, response.auth_data))
     }
 
     fn cbor(&mut self, request: cbor::Request) -> FidoResult<cbor::Response> {
         let mut buf = Cursor::new(Vec::new());
-        request.encode(&mut buf).context(FidoErrorKind::CborEncode)?;
+        request
+            .encode(&mut buf)
+            .context(FidoErrorKind::CborEncode)?;
         let response = self.exchange(CtapCommand::Cbor, &buf.into_inner())?;
         request
             .decode(Cursor::new(response))
@@ -373,11 +580,9 @@ impl FidoDevice {
         while first_packet.is_none() {
             let packet = packet::InitPacket::from_reader(&mut self.device, 64)?;
             if packet.cmd == CtapCommand::Error {
-                Err(
-                    packet::CtapError::from_u8(packet.payload[0])
-                        .unwrap_or(packet::CtapError::Other)
-                        .context(FidoErrorKind::ParseCtap),
-                )?
+                Err(packet::CtapError::from_u8(packet.payload[0])
+                    .unwrap_or(packet::CtapError::Other)
+                    .context(FidoErrorKind::ParseCtap))?
             }
             if packet.cid == self.channel_id && &packet.cmd == cmd {
                 first_packet = Some(packet);

src/packet.rs

@@ -4,9 +4,9 @@
 // http://apache.org/licenses/LICENSE-2.0> or the MIT license <LICENSE-MIT or
 // http://opensource.org/licenses/MIT>, at your option. This file may not be
 // copied, modified, or distributed except according to those terms.
-use num_traits::{FromPrimitive, ToPrimitive};
-use failure::ResultExt;
 use super::error::*;
+use failure::ResultExt;
+use num_traits::{FromPrimitive, ToPrimitive};
 
 use std::io::{Read, Write};
 
@@ -81,9 +81,9 @@ pub fn write_init_packet<W: Write>(
         Err(FidoErrorKind::WritePacket)?
     }
     packet.resize(report_size + 1, 0);
-    writer.write_all(&packet).context(
-        FidoErrorKind::WritePacket,
-    )?;
+    writer
+        .write_all(&packet)
+        .context(FidoErrorKind::WritePacket)?;
     Ok(())
 }
 
@@ -98,9 +98,9 @@ impl InitPacket {
     pub fn from_reader<R: Read>(mut reader: R, report_size: usize) -> FidoResult<InitPacket> {
         let mut buf = Vec::with_capacity(report_size);
         buf.resize(report_size, 0);
-        reader.read_exact(&mut buf[0..report_size]).context(
-            FidoErrorKind::ReadPacket,
-        )?;
+        reader
+            .read_exact(&mut buf[0..report_size])
+            .context(FidoErrorKind::ReadPacket)?;
         let mut cid = [0; 4];
         cid.copy_from_slice(&buf[0..4]);
         let cmd = match CtapCommand::from_u8(buf[4] ^ FRAME_INIT) {
@@ -142,9 +142,9 @@ pub fn write_cont_packet<W: Write>(
         Err(FidoErrorKind::WritePacket)?
     }
     packet.resize(report_size + 1, 0);
-    writer.write_all(&packet).context(
-        FidoErrorKind::WritePacket,
-    )?;
+    writer
+        .write_all(&packet)
+        .context(FidoErrorKind::WritePacket)?;
     Ok(())
 }
 
@@ -162,9 +162,9 @@ impl ContPacket {
     ) -> FidoResult<ContPacket> {
         let mut buf = Vec::with_capacity(report_size);
         buf.resize(report_size, 0);
-        reader.read_exact(&mut buf[0..report_size]).context(
-            FidoErrorKind::ReadPacket,
-        )?;
+        reader
+            .read_exact(&mut buf[0..report_size])
+            .context(FidoErrorKind::ReadPacket)?;
         let mut cid = [0; 4];
         cid.copy_from_slice(&buf[0..4]);
         let seq = buf[4];

src/util.rs

@@ -0,0 +1,44 @@
+use crate::cbor::AuthenticatorData;
+use crate::{FidoAssertionRequest, FidoCredential, FidoDevice, FidoErrorKind, FidoResult};
+use std::sync::mpsc::channel;
+#[cfg(feature = "assert_devices")]
+use crossbeam::thread;
+
+/// Will send the `assertion` to all supplied `devices` and return either the first successful assertion or the last error
+#[cfg(feature = "assert_devices")]
+pub fn get_assertion_devices<'a>(
+    assertion: &'a FidoAssertionRequest,
+    devices: impl Iterator<Item = &'a mut FidoDevice>,
+) -> FidoResult<(&'a FidoCredential, AuthenticatorData)> {
+    thread::scope(
+        |scope| -> FidoResult<(&'a FidoCredential, AuthenticatorData)> {
+            let (tx, rx) = channel();
+            let handles = devices
+                .map(|device| {
+                    let cancel = device.cancel_handle()?;
+                    let tx = tx.clone();
+                    let thread_handle =
+                        scope.spawn(move |_| tx.send(device.get_assertion(assertion)));
+                    Ok((cancel, thread_handle))
+                })
+                .collect::<FidoResult<Vec<_>>>()?;
+
+            let mut err = None;
+            for res in rx.iter().take(handles.len()) {
+                match res {
+                    Ok(_) => {
+                        for (mut cancel, join) in handles {
+                            // Canceling out of courtesy don't care if it fails
+                            let _ = cancel.cancel();
+                            let _ = join.join();
+                        }
+                        return res;
+                    }
+                    e => err = Some(e),
+                }
+            }
+            err.unwrap_or(Err(FidoErrorKind::DeviceUnsupported.into()))
+        },
+    )
+    .unwrap()
+}