Feature/remove credentials

authorizer.go

@@ -34,8 +34,8 @@ type Authorizers[R any] []Authorizer[R]
 // Append tacks on one or more authorizers to this collection.  The possibly
 // new Authorizers instance is returned.  The semantics of this method are
 // the same as the built-in append.
-func (as Authorizers[R]) Append(a ...Authorizer[R]) Authorizers[R] {
-	return append(as, a...)
+func (as Authorizers[R]) Append(more ...Authorizer[R]) Authorizers[R] {
+	return append(as, more...)
 }
 
 // Authorize requires all authorizers in this sequence to allow access.  This

basculehttp/authorization.go

@@ -0,0 +1,128 @@
+// SPDX-FileCopyrightText: 2024 Comcast Cable Communications Management, LLC
+// SPDX-License-Identifier: Apache-2.0
+
+package basculehttp
+
+import (
+	"context"
+	"errors"
+	"net/http"
+	"strings"
+
+	"github.com/xmidt-org/bascule/v1"
+)
+
+const (
+	// DefaultAuthorizationHeader is the default HTTP header used for authorization
+	// tokens in an HTTP request.
+	DefaultAuthorizationHeader = "Authorization"
+)
+
+var (
+	// ErrInvalidAuthorization indicates an authorization header value did not
+	// correspond to the standard.
+	ErrInvalidAuthorization = errors.New("invalidation authorization")
+
+	// ErrMissingAuthorization indicates that no authorization header was
+	// present in the source HTTP request.
+	ErrMissingAuthorization = errors.New("missing authorization")
+)
+
+// fastIsSpace tests an ASCII byte to see if it's whitespace.
+// HTTP headers are restricted to US-ASCII, so we don't need
+// the full unicode stack.
+func fastIsSpace(b byte) bool {
+	return b == ' ' || b == '\t' || b == '\n' || b == '\r' || b == '\v' || b == '\f'
+}
+
+// ParseAuthorization parses an authorization value typically passed in
+// the Authorization HTTP header.
+//
+// The required format is <scheme><single space><credential value>.  This function
+// is strict:  it requires no leading or trailing space and exactly (1) space as
+// a separator.  If the raw value does not adhere to this format, ErrInvalidAuthorization
+// is returned.
+func ParseAuthorization(raw string) (s Scheme, v string, err error) {
+	var scheme string
+	var found bool
+	scheme, v, found = strings.Cut(raw, " ")
+	if found && len(scheme) > 0 && !fastIsSpace(v[0]) && !fastIsSpace(v[len(v)-1]) {
+		s = Scheme(scheme)
+	} else {
+		err = ErrInvalidAuthorization
+	}
+
+	return
+}
+
+type AuthorizationParserOption interface {
+	apply(*AuthorizationParser) error
+}
+
+type authorizationParserOptionFunc func(*AuthorizationParser) error
+
+func (apof authorizationParserOptionFunc) apply(ap *AuthorizationParser) error { return apof(ap) }
+
+func WithAuthorizationHeader(header string) AuthorizationParserOption {
+	return authorizationParserOptionFunc(func(ap *AuthorizationParser) error {
+		ap.header = header
+		return nil
+	})
+}
+
+func WithScheme(scheme Scheme, parser bascule.TokenParser[string]) AuthorizationParserOption {
+	return authorizationParserOptionFunc(func(ap *AuthorizationParser) error {
+		// we want case-insensitive matches, so lowercase everything
+		ap.parsers[scheme.lower()] = parser
+		return nil
+	})
+}
+
+type AuthorizationParser struct {
+	header  string
+	parsers map[Scheme]bascule.TokenParser[string]
+}
+
+func NewAuthorizationParser(opts ...AuthorizationParserOption) (*AuthorizationParser, error) {
+	ap := &AuthorizationParser{
+		parsers: make(map[Scheme]bascule.TokenParser[string]),
+	}
+
+	for _, o := range opts {
+		if err := o.apply(ap); err != nil {
+			return nil, err
+		}
+	}
+
+	if len(ap.header) == 0 {
+		ap.header = DefaultAuthorizationHeader
+	}
+
+	return ap, nil
+}
+
+// Parse extracts the appropriate header, Authorization by default, and parses the
+// scheme and value.  Schemes are case-insensitive, e.g. BASIC and Basic are the same scheme.
+//
+// If a token parser is registered for the given scheme, that token parser is invoked.
+// Otherwise, UnsupportedSchemeError is returned, indicating the scheme in question.
+func (ap *AuthorizationParser) Parse(ctx context.Context, source *http.Request) (bascule.Token, error) {
+	authValue := source.Header.Get(ap.header)
+	if len(authValue) == 0 {
+		return nil, bascule.ErrMissingCredentials
+	}
+
+	scheme, value, err := ParseAuthorization(authValue)
+	if err != nil {
+		return nil, err
+	}
+
+	p, registered := ap.parsers[scheme.lower()]
+	if !registered {
+		return nil, &UnsupportedSchemeError{
+			Scheme: scheme,
+		}
+	}
+
+	return p.Parse(ctx, value)
+}

basculehttp/basic.go

@@ -6,55 +6,62 @@
 import (
 	"context"
 	"encoding/base64"
-	"net/http"
 	"strings"
 
 	"github.com/xmidt-org/bascule/v1"
 )
 
-// InvalidBasicAuthError indicates that the Basic credentials were improperly
-// encoded, either due to base64 issues or formatting.
-type InvalidBasicAuthError struct {
-	// Cause represents the lower level error that occurred, e.g. a base64
-	// encoding error.
-	Cause error
+// BasicToken is the interface that Basic Auth tokens implement.
+type BasicToken interface {
+	UserName() string
+	Password() string
 }
 
-func (err *InvalidBasicAuthError) Unwrap() error { return err.Cause }
+// basicToken is the internal basic token struct that results from
+// parsing a Basic Authorization header value.
+type basicToken struct {
+	userName string
+	password string
+}
 
-func (err *InvalidBasicAuthError) Error() string {
-	var o strings.Builder
-	o.WriteString("Basic auth string not encoded properly")
+func (bt basicToken) Principal() string {
+	return bt.userName
+}
 
-	if err.Cause != nil {
-		o.WriteString(": ")
-		o.WriteString(err.Cause.Error())
-	}
+func (bt basicToken) UserName() string {
+	return bt.userName
+}
 
-	return o.String()
+func (bt basicToken) Password() string {
+	return bt.password
 }
 
-type basicTokenParser struct{}
+// BasicTokenParser is a string-based bascule.TokenParser that produces
+// BasicToken instances from strings.
+//
+// An instance of this parser may be passed to WithScheme in order to
+// configure an AuthorizationParser.
+type BasicTokenParser struct{}
 
-func (btp basicTokenParser) Parse(_ context.Context, _ *http.Request, c bascule.Credentials) (t bascule.Token, err error) {
-	var decoded []byte
-	decoded, err = base64.StdEncoding.DecodeString(c.Value)
+// Parse assumes that value is of the format required by https://datatracker.ietf.org/doc/html/rfc7617.
+// The returned Token will return the basic auth username from its Principal() method.
+// The returned Token will also implement BasicToken.
+func (BasicTokenParser) Parse(_ context.Context, value string) (bascule.Token, error) {
+	// this mimics what the stdlib does at net/http.Request.BasicAuth()
+	raw, err := base64.StdEncoding.DecodeString(value)
 	if err != nil {
-		err = &InvalidBasicAuthError{
-			Cause: err,
-		}
-
-		return
+		return nil, bascule.ErrInvalidCredentials
 	}
 
-	username, _, found := strings.Cut(string(decoded), ":")
-	if found {
-		t = &Token{
-			principal: username,
-		}
-	} else {
-		err = &InvalidBasicAuthError{}
+	var (
+		bt basicToken
+		ok bool
+	)
+
+	bt.userName, bt.password, ok = strings.Cut(string(raw), ":")
+	if ok {
+		return bt, nil
 	}
 
-	return
+	return nil, bascule.ErrInvalidCredentials
 }

basculehttp/challenge.go

@@ -6,17 +6,9 @@
 import (
 	"net/http"
 	"strings"
-
-	"github.com/xmidt-org/bascule/v1"
 )
 
 const (
-	// BasicScheme is the name of the basic HTTP authentication scheme.
-	BasicScheme bascule.Scheme = "Basic"
-
-	// BearerScheme is the name of the bearer HTTP authentication scheme.
-	BearerScheme bascule.Scheme = "Bearer"
-
 	// WwwAuthenticateHeaderName is the HTTP header used for StatusUnauthorized challenges.
 	WwwAuthenticateHeaderName = "WWW-Authenticate"
 
@@ -63,7 +55,7 @@
 type BasicChallenge struct {
 	// Scheme is the name of scheme supplied in the challenge.  If this
 	// field is unset, BasicScheme is used.
-	Scheme bascule.Scheme
+	Scheme Scheme
 
 	// Realm is the name of the realm for the challenge.  If this field
 	// is unset, DefaultBasicRealm is used.
@@ -81,7 +73,7 @@
 	if len(bc.Scheme) > 0 {
 		o.WriteString(string(bc.Scheme))
 	} else {
-		o.WriteString(string(BasicScheme))
+		o.WriteString(string(SchemeBasic))
 	}
 
 	o.WriteString(` realm="`)
@@ -100,7 +92,7 @@
 type BearerChallenge struct {
 	// Scheme is the name of scheme supplied in the challenge.  If this
 	// field is unset, BearerScheme is used.
-	Scheme bascule.Scheme
+	Scheme Scheme
 
 	// Realm is the name of the realm for the challenge.  If this field
 	// is unset, DefaultBearerRealm is used.
@@ -114,7 +106,7 @@
 	if len(bc.Scheme) > 0 {
 		o.WriteString(string(bc.Scheme))
 	} else {
-		o.WriteString(string(BasicScheme))
+		o.WriteString(string(SchemeBearer))
 	}
 
 	o.WriteString(` realm="`)