Adding upstream version 1.2.3.

Signed-off-by: Daniel Baumann <daniel@debian.org>

verifying.go

@@ -0,0 +1,184 @@
+package httpsig
+
+import (
+	"crypto"
+	"encoding/base64"
+	"errors"
+	"fmt"
+	"net/http"
+	"strconv"
+	"strings"
+	"time"
+)
+
+var _ Verifier = &verifier{}
+
+type verifier struct {
+	header      http.Header
+	kId         string
+	signature   string
+	created     int64
+	expires     int64
+	headers     []string
+	sigStringFn func(http.Header, []string, int64, int64) (string, error)
+}
+
+func newVerifier(h http.Header, sigStringFn func(http.Header, []string, int64, int64) (string, error)) (*verifier, error) {
+	scheme, s, err := getSignatureScheme(h)
+	if err != nil {
+		return nil, err
+	}
+	kId, sig, headers, created, expires, err := getSignatureComponents(scheme, s)
+	if created != 0 {
+		//check if created is not in the future, we assume a maximum clock offset of 10 seconds
+		now := time.Now().Unix()
+		if created-now > 10 {
+			return nil, errors.New("created is in the future")
+		}
+	}
+	if expires != 0 {
+		//check if expires is in the past, we assume a maximum clock offset of 10 seconds
+		now := time.Now().Unix()
+		if now-expires > 10 {
+			return nil, errors.New("signature expired")
+		}
+	}
+	if err != nil {
+		return nil, err
+	}
+	return &verifier{
+		header:      h,
+		kId:         kId,
+		signature:   sig,
+		created:     created,
+		expires:     expires,
+		headers:     headers,
+		sigStringFn: sigStringFn,
+	}, nil
+}
+
+func (v *verifier) KeyId() string {
+	return v.kId
+}
+
+func (v *verifier) Verify(pKey crypto.PublicKey, algo Algorithm) error {
+	s, err := signerFromString(string(algo))
+	if err == nil {
+		return v.asymmVerify(s, pKey)
+	}
+	m, err := macerFromString(string(algo))
+	if err == nil {
+		return v.macVerify(m, pKey)
+	}
+	return fmt.Errorf("no crypto implementation available for %q: %s", algo, err)
+}
+
+func (v *verifier) macVerify(m macer, pKey crypto.PublicKey) error {
+	key, ok := pKey.([]byte)
+	if !ok {
+		return fmt.Errorf("public key for MAC verifying must be of type []byte")
+	}
+	signature, err := v.sigStringFn(v.header, v.headers, v.created, v.expires)
+	if err != nil {
+		return err
+	}
+	actualMAC, err := base64.StdEncoding.DecodeString(v.signature)
+	if err != nil {
+		return err
+	}
+	ok, err = m.Equal([]byte(signature), actualMAC, key)
+	if err != nil {
+		return err
+	} else if !ok {
+		return fmt.Errorf("invalid http signature")
+	}
+	return nil
+}
+
+func (v *verifier) asymmVerify(s signer, pKey crypto.PublicKey) error {
+	toHash, err := v.sigStringFn(v.header, v.headers, v.created, v.expires)
+	if err != nil {
+		return err
+	}
+	signature, err := base64.StdEncoding.DecodeString(v.signature)
+	if err != nil {
+		return err
+	}
+	err = s.Verify(pKey, []byte(toHash), signature)
+	if err != nil {
+		return err
+	}
+	return nil
+}
+
+func getSignatureScheme(h http.Header) (scheme SignatureScheme, val string, err error) {
+	s := h.Get(string(Signature))
+	sigHasAll := strings.Contains(s, keyIdParameter) ||
+		strings.Contains(s, headersParameter) ||
+		strings.Contains(s, signatureParameter)
+	a := h.Get(string(Authorization))
+	authHasAll := strings.Contains(a, keyIdParameter) ||
+		strings.Contains(a, headersParameter) ||
+		strings.Contains(a, signatureParameter)
+	if sigHasAll && authHasAll {
+		err = fmt.Errorf("both %q and %q have signature parameters", Signature, Authorization)
+		return
+	} else if !sigHasAll && !authHasAll {
+		err = fmt.Errorf("neither %q nor %q have signature parameters", Signature, Authorization)
+		return
+	} else if sigHasAll {
+		val = s
+		scheme = Signature
+		return
+	} else { // authHasAll
+		val = a
+		scheme = Authorization
+		return
+	}
+}
+
+func getSignatureComponents(scheme SignatureScheme, s string) (kId, sig string, headers []string, created int64, expires int64, err error) {
+	if as := scheme.authScheme(); len(as) > 0 {
+		s = strings.TrimPrefix(s, as+prefixSeparater)
+	}
+	params := strings.Split(s, parameterSeparater)
+	for _, p := range params {
+		kv := strings.SplitN(p, parameterKVSeparater, 2)
+		if len(kv) != 2 {
+			err = fmt.Errorf("malformed http signature parameter: %v", kv)
+			return
+		}
+		k := kv[0]
+		v := strings.Trim(kv[1], parameterValueDelimiter)
+		switch k {
+		case keyIdParameter:
+			kId = v
+		case createdKey:
+			created, err = strconv.ParseInt(v, 10, 64)
+			if err != nil {
+				return
+			}
+		case expiresKey:
+			expires, err = strconv.ParseInt(v, 10, 64)
+			if err != nil {
+				return
+			}
+		case algorithmParameter:
+			// Deprecated, ignore
+		case headersParameter:
+			headers = strings.Split(v, headerParameterValueDelim)
+		case signatureParameter:
+			sig = v
+		default:
+			// Ignore unrecognized parameters
+		}
+	}
+	if len(kId) == 0 {
+		err = fmt.Errorf("missing %q parameter in http signature", keyIdParameter)
+	} else if len(sig) == 0 {
+		err = fmt.Errorf("missing %q parameter in http signature", signatureParameter)
+	} else if len(headers) == 0 { // Optional
+		headers = defaultHeaders
+	}
+	return
+}