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|
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
}
|
