Add Nix flake for mciasctl and mciasgrpcctl

Vendor dependencies and expose control program binaries via
nix build. Uses nixpkgs-unstable for Go 1.26 support.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

vendor/github.com/go-webauthn/webauthn/protocol/assertion.go

@@ -0,0 +1,199 @@
+package protocol
+
+import (
+	"crypto/sha256"
+	"encoding/base64"
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+
+	"github.com/go-webauthn/webauthn/protocol/webauthncose"
+)
+
+// The CredentialAssertionResponse is the raw response returned to the Relying Party from an authenticator when we request a
+// credential for login/assertion.
+type CredentialAssertionResponse struct {
+	PublicKeyCredential
+
+	AssertionResponse AuthenticatorAssertionResponse `json:"response"`
+}
+
+// The ParsedCredentialAssertionData is the parsed [CredentialAssertionResponse] that has been marshalled into a format
+// that allows us to verify the client and authenticator data inside the response.
+type ParsedCredentialAssertionData struct {
+	ParsedPublicKeyCredential
+
+	Response ParsedAssertionResponse
+	Raw      CredentialAssertionResponse
+}
+
+// The AuthenticatorAssertionResponse contains the raw authenticator assertion data and is parsed into
+// [ParsedAssertionResponse].
+type AuthenticatorAssertionResponse struct {
+	AuthenticatorResponse
+
+	AuthenticatorData URLEncodedBase64 `json:"authenticatorData"`
+	Signature         URLEncodedBase64 `json:"signature"`
+	UserHandle        URLEncodedBase64 `json:"userHandle,omitempty"`
+}
+
+// ParsedAssertionResponse is the parsed form of [AuthenticatorAssertionResponse].
+type ParsedAssertionResponse struct {
+	CollectedClientData CollectedClientData
+	AuthenticatorData   AuthenticatorData
+	Signature           []byte
+	UserHandle          []byte
+}
+
+// ParseCredentialRequestResponse parses the credential request response into a format that is either required by the
+// specification or makes the assertion verification steps easier to complete. This takes a [*http.Request] that contains
+// the assertion response data in a raw, mostly base64 encoded format, and parses the data into manageable structures.
+func ParseCredentialRequestResponse(response *http.Request) (*ParsedCredentialAssertionData, error) {
+	if response == nil || response.Body == nil {
+		return nil, ErrBadRequest.WithDetails("No response given")
+	}
+
+	defer func(request *http.Request) {
+		_, _ = io.Copy(io.Discard, request.Body)
+		_ = request.Body.Close()
+	}(response)
+
+	return ParseCredentialRequestResponseBody(response.Body)
+}
+
+// ParseCredentialRequestResponseBody parses the credential request response into a format that is either required by
+// the specification or makes the assertion verification steps easier to complete. This takes an [io.Reader] that contains
+// the assertion response data in a raw, mostly base64 encoded format, and parses the data into manageable structures.
+func ParseCredentialRequestResponseBody(body io.Reader) (par *ParsedCredentialAssertionData, err error) {
+	var car CredentialAssertionResponse
+
+	if err = decodeBody(body, &car); err != nil {
+		return nil, ErrBadRequest.WithDetails("Parse error for Assertion").WithInfo(err.Error()).WithError(err)
+	}
+
+	return car.Parse()
+}
+
+// ParseCredentialRequestResponseBytes is an alternative version of [ParseCredentialRequestResponseBody] that just takes
+// a byte slice.
+func ParseCredentialRequestResponseBytes(data []byte) (par *ParsedCredentialAssertionData, err error) {
+	var car CredentialAssertionResponse
+
+	if err = decodeBytes(data, &car); err != nil {
+		return nil, ErrBadRequest.WithDetails("Parse error for Assertion").WithInfo(err.Error()).WithError(err)
+	}
+
+	return car.Parse()
+}
+
+// Parse validates and parses the [CredentialAssertionResponse] into a [ParseCredentialCreationResponseBody]. This receiver
+// is unlikely to be expressly guaranteed under the versioning policy. Users looking for this guarantee should see
+// [ParseCredentialRequestResponseBody] instead, and this receiver should only be used if that function is inadequate
+// for their use case.
+func (car CredentialAssertionResponse) Parse() (par *ParsedCredentialAssertionData, err error) {
+	if car.ID == "" {
+		return nil, ErrBadRequest.WithDetails("CredentialAssertionResponse with ID missing")
+	}
+
+	if _, err = base64.RawURLEncoding.DecodeString(car.ID); err != nil {
+		return nil, ErrBadRequest.WithDetails("CredentialAssertionResponse with ID not base64url encoded").WithError(err)
+	}
+
+	if car.Type != string(PublicKeyCredentialType) {
+		return nil, ErrBadRequest.WithDetails("CredentialAssertionResponse with bad type")
+	}
+
+	var attachment AuthenticatorAttachment
+
+	switch att := AuthenticatorAttachment(car.AuthenticatorAttachment); att {
+	case Platform, CrossPlatform:
+		attachment = att
+	}
+
+	par = &ParsedCredentialAssertionData{
+		ParsedPublicKeyCredential{
+			ParsedCredential{car.ID, car.Type}, car.RawID, car.ClientExtensionResults, attachment,
+		},
+		ParsedAssertionResponse{
+			Signature:  car.AssertionResponse.Signature,
+			UserHandle: car.AssertionResponse.UserHandle,
+		},
+		car,
+	}
+
+	// Step 5. Let JSONtext be the result of running UTF-8 decode on the value of cData.
+	// We don't call it cData but this is Step 5 in the spec.
+	if err = json.Unmarshal(car.AssertionResponse.ClientDataJSON, &par.Response.CollectedClientData); err != nil {
+		return nil, err
+	}
+
+	if err = par.Response.AuthenticatorData.Unmarshal(car.AssertionResponse.AuthenticatorData); err != nil {
+		return nil, ErrParsingData.WithDetails("Error unmarshalling auth data").WithError(err)
+	}
+
+	return par, nil
+}
+
+// Verify the remaining elements of the assertion data by following the steps outlined in the referenced specification
+// documentation. It's important to note that the credentialBytes field is the CBOR representation of the credential.
+//
+// Specification: §7.2 Verifying an Authentication Assertion (https://www.w3.org/TR/webauthn/#sctn-verifying-assertion)
+func (p *ParsedCredentialAssertionData) Verify(storedChallenge string, relyingPartyID string, rpOrigins, rpTopOrigins []string, rpTopOriginsVerify TopOriginVerificationMode, appID string, verifyUser bool, verifyUserPresence bool, credentialBytes []byte) error {
+	// Steps 4 through 6 in verifying the assertion data (https://www.w3.org/TR/webauthn/#verifying-assertion) are
+	// "assertive" steps, i.e. "Let JSONtext be the result of running UTF-8 decode on the value of cData."
+	// We handle these steps in part as we verify but also beforehand
+	//
+	// Handle steps 7 through 10 of assertion by verifying stored data against the Collected Client Data
+	// returned by the authenticator.
+	validError := p.Response.CollectedClientData.Verify(storedChallenge, AssertCeremony, rpOrigins, rpTopOrigins, rpTopOriginsVerify)
+	if validError != nil {
+		return validError
+	}
+
+	// Begin Step 11. Verify that the rpIdHash in authData is the SHA-256 hash of the RP ID expected by the RP.
+	rpIDHash := sha256.Sum256([]byte(relyingPartyID))
+
+	var appIDHash [32]byte
+	if appID != "" {
+		appIDHash = sha256.Sum256([]byte(appID))
+	}
+
+	// Handle steps 11 through 14, verifying the authenticator data.
+	validError = p.Response.AuthenticatorData.Verify(rpIDHash[:], appIDHash[:], verifyUser, verifyUserPresence)
+	if validError != nil {
+		return validError
+	}
+
+	// Step 15. Let hash be the result of computing a hash over the cData using SHA-256.
+	clientDataHash := sha256.Sum256(p.Raw.AssertionResponse.ClientDataJSON)
+
+	// Step 16. Using the credential public key looked up in step 3, verify that sig is
+	// a valid signature over the binary concatenation of authData and hash.
+
+	sigData := append(p.Raw.AssertionResponse.AuthenticatorData, clientDataHash[:]...) //nolint:gocritic // This is intentional.
+
+	var (
+		key any
+		err error
+	)
+
+	// If the Session Data does not contain the appID extension or it wasn't reported as used by the Client/RP then we
+	// use the standard CTAP2 public key parser.
+	if appID == "" {
+		key, err = webauthncose.ParsePublicKey(credentialBytes)
+	} else {
+		key, err = webauthncose.ParseFIDOPublicKey(credentialBytes)
+	}
+
+	if err != nil {
+		return ErrAssertionSignature.WithDetails(fmt.Sprintf("Error parsing the assertion public key: %+v", err)).WithError(err)
+	}
+
+	valid, err := webauthncose.VerifySignature(key, sigData, p.Response.Signature)
+	if !valid || err != nil {
+		return ErrAssertionSignature.WithDetails(fmt.Sprintf("Error validating the assertion signature: %+v", err)).WithError(err)
+	}
+
+	return nil
+}