/
signatures.go
576 lines (545 loc) · 17.2 KB
/
signatures.go
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// Package httpsign signs HTTP requests and responses as defined in draft-ietf-httpbis-message-signatures.
// See https://www.ietf.org/archive/id/draft-ietf-httpbis-message-signatures-07.html.
//
// For client-side message signing and verification, use the Client wrapper.
// Alternatively, use SignRequest, VerifyResponse directly, but this is more complicated.
// For server-side operation,
// WrapHandler installs a wrapper around a normal HTTP message handler.
package httpsign
import (
"encoding/base64"
"fmt"
"github.com/dunglas/httpsfv"
"net/http"
"strings"
"time"
)
func signMessage(config SignConfig, signatureName string, signer Signer, parsedMessage parsedMessage,
fields Fields) (signatureInputHeader, signature, signatureInput string, err error) {
sigParams, err := generateSigParams(&config, signer.keyID, signer.alg, signer.foreignSigner, fields)
if err != nil {
return "", "", "", err
}
signatureInputHeader = fmt.Sprintf("%s=%s", signatureName, sigParams)
signatureInput, err = generateSignatureInput(parsedMessage, fields, sigParams)
if err != nil {
return "", "", "", err
}
signature, err = generateSignature(signatureName, signer, signatureInput)
if err != nil {
return "", "", "", err
}
return signatureInputHeader, signature, signatureInput, nil
}
func generateSignature(name string, signer Signer, input string) (string, error) {
raw, err := signer.sign([]byte(input))
if err != nil {
return "", err
}
return fmt.Sprintf("%s=%s", name, encodeBytes(raw)), nil
}
func encodeBytes(raw []byte) string {
return ":" + base64.StdEncoding.EncodeToString(raw) + ":"
}
func generateSignatureInput(message parsedMessage, fields Fields, params string) (string, error) {
inp := ""
for _, c := range fields.f {
f, err := c.asSignatureInput()
if err != nil {
return "", fmt.Errorf("could not marshal %v", f)
}
fieldValues, err := generateFieldValues(c, message)
if err != nil {
return "", err
}
for _, v := range fieldValues {
inp += fmt.Sprintf("%s: %s\n", f, v)
}
}
inp += fmt.Sprintf("\"%s\": %s", "@signature-params", params)
// log.Println("inp:", "\n"+inp)
return inp, nil
}
func generateFieldValues(f field, message parsedMessage) ([]string, error) {
if f.flagName == "" || f.flagName == "sf" {
if strings.HasPrefix(f.name, "@") { // derived component
vv, found := message.derived[f.name]
if !found {
return nil, fmt.Errorf("derived header %s not found", f.name)
}
return []string{vv}, nil
}
return message.getHeader(f.name, f.flagName == "sf")
}
if f.name == "@query-params" && f.flagName == "name" {
vals, found := message.qParams[f.flagValue]
if !found {
return nil, fmt.Errorf("query parameter %s not found", f.flagValue)
}
return vals, nil
}
if f.flagName == "key" { // dictionary header
return message.getDictHeader(f.name, f.flagValue)
}
return nil, fmt.Errorf("unrecognized field %s", f)
}
func (message *parsedMessage) getHeader(hdr string, structured bool) ([]string, error) {
vv, found := message.headers[hdr] // normal header, cannot use "Values" on lowercased header name
if !found {
return nil, fmt.Errorf("header %s not found", hdr)
}
if !structured {
return []string{foldFields(vv)}, nil
}
sfv, err := httpsfv.UnmarshalDictionary(vv)
if err != nil {
return nil, fmt.Errorf("could not unmarshal %s, possibly not a structured field: %w", hdr, err)
}
s, err := httpsfv.Marshal(sfv)
if err != nil {
return nil, fmt.Errorf("could not re-marshal %s", hdr)
}
return []string{s}, nil
}
func (message *parsedMessage) getDictHeader(hdr, member string) ([]string, error) {
vals, found := message.headers[hdr]
if !found {
return nil, fmt.Errorf("dictionary header %s not found", hdr)
}
dict, err := httpsfv.UnmarshalDictionary(vals)
if err != nil {
return nil, fmt.Errorf("cannot parse dictionary for %s: %w", hdr, err)
}
v, found := dict.Get(member)
if !found {
return nil, fmt.Errorf("cannot find member %s of dictionary %s", member, hdr)
}
switch v.(type) {
case httpsfv.Item:
vv, err := httpsfv.Marshal(v.(httpsfv.Item))
if err != nil {
return nil, fmt.Errorf("malformed dictionry member %s: %v", hdr, err)
}
return []string{vv}, nil
case httpsfv.InnerList:
vv, err := httpsfv.Marshal(v.(httpsfv.InnerList))
if err != nil {
return nil, fmt.Errorf("malformed dictionry member %s: %v", hdr, err)
}
return []string{vv}, nil
default:
return nil, fmt.Errorf("unexpected dictionary value")
}
}
func generateSigParams(config *SignConfig, keyID, alg string, foreignSigner interface{}, fields Fields) (string, error) {
p := httpsfv.NewParams()
var createdTime int64
if config.fakeCreated != 0 {
createdTime = config.fakeCreated
} else {
createdTime = time.Now().Unix()
}
if config.signCreated {
p.Add("created", createdTime)
}
if config.expires != 0 {
p.Add("expires", config.expires)
}
if config.nonce != "" {
p.Add("nonce", config.nonce)
}
if config.signAlg {
if foreignSigner != nil {
return "", fmt.Errorf("cannot use the alg parameter with a JWS signer")
}
p.Add("alg", alg)
}
p.Add("keyid", keyID)
return fields.asSignatureInput(p)
}
//
// SignRequest signs an HTTP request. Returns the Signature-Input and the Signature header values.
//
func SignRequest(signatureName string, signer Signer, req *http.Request) (signatureInputHeader, signature string, err error) {
signatureInputHeader, signature, signatureInput, err := signRequestDebug(signatureName, signer, req)
_ = signatureInput
return
}
// Same as SignRequest, but also returns the raw signature input string
func signRequestDebug(signatureName string, signer Signer, req *http.Request) (signatureInputHeader, signature, signatureInput string, err error) {
if req == nil {
return "", "", "", fmt.Errorf("nil request")
}
if signatureName == "" {
return "", "", "", fmt.Errorf("empty signature name")
}
if signer.config.requestResponse != nil {
return "", "", "", fmt.Errorf("use request-response only to sign responses")
}
parsedMessage, err := parseRequest(req)
if err != nil {
return "", "", "", err
}
return signMessage(*signer.config, signatureName, signer, *parsedMessage, signer.fields)
}
//
// SignResponse signs an HTTP response. Returns the Signature-Input and the Signature header values.
//
func SignResponse(signatureName string, signer Signer, res *http.Response) (signatureInput, signature string, err error) {
if res == nil {
return "", "", fmt.Errorf("nil response")
}
if signatureName == "" {
return "", "", fmt.Errorf("empty signature name")
}
parsedMessage, err := parseResponse(res)
if err != nil {
return "", "", err
}
extendedFields := addPseudoHeaders(parsedMessage, signer.config.requestResponse, signer.fields)
signatureInput, signature, _, err = signMessage(*signer.config, signatureName, signer, *parsedMessage, extendedFields)
return
}
// Handle the special header-like @request-response
func addPseudoHeaders(message *parsedMessage, rr *requestResponse, fields Fields) Fields {
if rr != nil {
rrfield := field{
name: "@request-response",
flagName: "key",
flagValue: rr.name,
}
message.headers.Add("@request-response", rr.name+"="+rr.signature)
fields.f = append(fields.f, rrfield)
return fields
}
return fields
}
//
// VerifyRequest verifies a signed HTTP request. Returns an error if verification failed for any reason, otherwise nil.
func VerifyRequest(signatureName string, verifier Verifier, req *http.Request) error {
_, err := verifyRequestDebug(signatureName, verifier, req)
return err
}
func verifyRequestDebug(signatureName string, verifier Verifier, req *http.Request) (signatureInput string, err error) {
if req == nil {
return "", fmt.Errorf("nil request")
}
if signatureName == "" {
return "", fmt.Errorf("empty signature name")
}
if verifier.config.requestResponse != nil {
return "", fmt.Errorf("use request-response only to verify responses")
}
parsedMessage, err := parseRequest(req)
if err != nil {
return "", err
}
return verifyMessage(*verifier.config, signatureName, verifier, *parsedMessage, verifier.fields)
}
// RequestDetails parses a signed request and returns the key ID and optionally the algorithm used in the given signature.
func RequestDetails(signatureName string, req *http.Request) (keyID, alg string, err error) {
if req == nil {
return "", "", fmt.Errorf("nil request")
}
if signatureName == "" {
return "", "", fmt.Errorf("empty signature name")
}
parsedMessage, err := parseRequest(req)
if err != nil {
return "", "", err
}
return messageKeyID(signatureName, *parsedMessage)
}
// ResponseDetails parses a signed response and returns the key ID and optionally the algorithm used in the given signature.
func ResponseDetails(signatureName string, res *http.Response) (keyID, alg string, err error) {
if res == nil {
return "", "", fmt.Errorf("nil response")
}
if signatureName == "" {
return "", "", fmt.Errorf("empty signature name")
}
parsedMessage, err := parseResponse(res)
if err != nil {
return "", "", err
}
return messageKeyID(signatureName, *parsedMessage)
}
// GetRequestSignature returns the base64-encoded signature, parsed from a signed request.
// This is useful for the request-response feature.
func GetRequestSignature(req *http.Request, signatureName string) (string, error) {
if req == nil {
return "", fmt.Errorf("nil request")
}
if signatureName == "" {
return "", fmt.Errorf("empty signature name")
}
parsedMessage, err := parseRequest(req)
if err != nil {
return "", err
}
ws, err := parsedMessage.getDictHeader("signature", signatureName)
if err != nil {
return "", fmt.Errorf("missing \"signature\" header for \"%s\"", signatureName)
}
if len(ws) > 1 {
return "", fmt.Errorf("more than one \"signature\" value for \"%s\"", signatureName)
}
sigHeader := ws[0]
sigRaw, err := parseWantSignature(sigHeader)
if err != nil {
return "", err
}
return encodeBytes(sigRaw), nil
}
func messageKeyID(signatureName string, parsedMessage parsedMessage) (keyID, alg string, err error) {
si, err := parsedMessage.getDictHeader("signature-input", signatureName)
if err != nil {
return "", "", fmt.Errorf("missing \"signature-input\" header, or cannot find \"%s\": %w", signatureName, err)
}
if len(si) > 1 {
return "", "", fmt.Errorf("more than one \"signature-input\" for %s", signatureName)
}
signatureInput := si[0]
psi, err := parseSignatureInput(signatureInput, signatureName)
if err != nil {
return
}
keyIDParam, ok := psi.params["keyid"]
if !ok {
return "", "", fmt.Errorf("missing \"keyid\" parameter")
}
keyID, ok = keyIDParam.(string)
if !ok {
return "", "", fmt.Errorf("malformed \"keyid\" parameter")
}
algParam, ok := psi.params["alg"] // "alg" is optional
if ok {
alg, ok = algParam.(string)
if !ok {
return "", "", fmt.Errorf("malformed \"alg\" parameter")
}
}
return keyID, alg, nil
}
//
// VerifyResponse verifies a signed HTTP response. Returns an error if verification failed for any reason, otherwise nil.
//
func VerifyResponse(signatureName string, verifier Verifier, res *http.Response) (err error) {
if res == nil {
return fmt.Errorf("nil response")
}
if signatureName == "" {
return fmt.Errorf("empty signature name")
}
parsedMessage, err := parseResponse(res)
if err != nil {
return err
}
extendedFields := addPseudoHeaders(parsedMessage, verifier.config.requestResponse, verifier.fields)
_, err = verifyMessage(*verifier.config, signatureName, verifier, *parsedMessage, extendedFields)
return err
}
func verifyMessage(config VerifyConfig, name string, verifier Verifier, message parsedMessage, fields Fields) (string, error) {
wsi, err := message.getDictHeader("signature-input", name)
if err != nil {
return "", fmt.Errorf("missing \"signature-input\" header, or cannot find signature \"%s\": %w", name, err)
}
if len(wsi) > 1 {
return "", fmt.Errorf("multiple \"signature-header\" values for %s", name)
}
wantSignatureInput := wsi[0]
ws, err := message.getDictHeader("signature", name)
if err != nil {
return "", fmt.Errorf("missing \"signature\" header")
}
if len(ws) > 1 {
return "", fmt.Errorf("multiple \"signature\" values for %s", name)
}
wantSignature := ws[0]
wantSigRaw, err := parseWantSignature(wantSignature)
if err != nil {
return "", err
}
psiSig, err := parseSignatureInput(wantSignatureInput, name)
if err != nil {
return "", err
}
if !(psiSig.fields.contains(&fields)) {
return "", fmt.Errorf("actual signature does not cover all required fields")
}
err = applyVerificationPolicy(verifier, psiSig, config)
if err != nil {
return "", err
}
signatureInput, err := generateSignatureInput(message, psiSig.fields, psiSig.origSigParams)
if err != nil {
return "", err
}
return signatureInput, verifySignature(verifier, signatureInput, wantSigRaw)
}
func applyVerificationPolicy(verifier Verifier, psi *psiSignature, config VerifyConfig) error {
err := applyPolicyCreated(psi, config)
if err != nil {
return err
}
err2 := applyPolicyAlgs(psi, config)
if err2 != nil {
return err2
}
err3 := applyPolicyExpired(psi, config)
if err3 != nil {
return err3
}
err4 := applyPolicyOthers(verifier, psi, config)
if err4 != nil {
return err4
}
return nil
}
func applyPolicyOthers(verifier Verifier, psi *psiSignature, config VerifyConfig) error {
if config.verifyKeyID {
keyidParam, ok := psi.params["keyid"]
if ok {
keyID, ok := keyidParam.(string)
if !ok {
return fmt.Errorf("malformed \"keyid\" parameter")
}
if keyID != verifier.keyID {
return fmt.Errorf("wrong keyid \"%s\"", keyID)
}
}
}
return nil
}
func applyPolicyExpired(psi *psiSignature, config VerifyConfig) error {
if config.rejectExpired {
now := time.Now()
expiresParam, ok := psi.params["expires"]
if ok {
expires, ok := expiresParam.(int64)
if !ok {
return fmt.Errorf("malformed \"expires\" parameter")
}
expiresTime := time.Unix(expires, 0)
if now.After(expiresTime) {
return fmt.Errorf("expired signature")
}
}
}
return nil
}
func applyPolicyAlgs(psi *psiSignature, config VerifyConfig) error {
if len(config.allowedAlgs) > 0 {
algParam, ok := psi.params["alg"]
if !ok {
return fmt.Errorf("missing \"alg\" parameter")
}
alg, ok := algParam.(string)
if !ok {
return fmt.Errorf("malformed \"alg\" parameter")
}
var algFound = false
for _, a := range config.allowedAlgs {
if a == alg {
algFound = true
}
}
if !algFound {
return fmt.Errorf("\"alg\" parameter not allowed by policy")
}
}
return nil
}
func applyPolicyCreated(psi *psiSignature, config VerifyConfig) error {
if config.verifyCreated {
now := time.Now()
createdParam, ok := psi.params["created"]
if !ok {
return fmt.Errorf("missing \"created\" parameter")
}
created, ok := createdParam.(int64)
if !ok {
return fmt.Errorf("malformed \"created\" parameter")
}
createdTime := time.Unix(created, 0)
if createdTime.After(now.Add(config.notNewerThan)) {
return fmt.Errorf("message appears to be too new, check for clock skew")
}
if createdTime.Add(config.notOlderThan).Before(now) {
return fmt.Errorf("message is too old, check for replay")
}
}
return nil
}
func verifySignature(verifier Verifier, input string, signature []byte) error {
verified, err := verifier.verify([]byte(input), signature)
if !verified && (err == nil) {
err = fmt.Errorf("bad signature, check key or signature value")
}
return err
}
type psiSignature struct {
signatureName string
origSigParams string
fields Fields
params map[string]interface{}
}
func parseSignatureInput(input string, sigName string) (*psiSignature, error) {
sigs, err := httpsfv.UnmarshalDictionary([]string{sigName + "=" + input}) // yes this is a hack, there is no UnmarshalInnerList
if err != nil {
return nil, fmt.Errorf("could not parse Signature-Input as dictionary: %w", err)
}
memberForName, _ := sigs.Get(sigName)
fieldsList, ok := memberForName.(httpsfv.InnerList)
osp, err := httpsfv.Marshal(fieldsList) // undocumented functionality
if err != nil {
return nil, fmt.Errorf("could not marshal inner list: %w", err)
}
if !ok {
return nil, fmt.Errorf("Signature-Input: signature %s does not have an inner list", sigName)
}
var f Fields
for _, ff := range fieldsList.Items {
fname, ok := ff.Value.(string)
if !ok {
return nil, fmt.Errorf("Signature-Input: value is not a string")
}
if ff.Params == nil || len(ff.Params.Names()) == 0 {
f.f = append(f.f, *fromHeaderName(fname))
} else {
if len(ff.Params.Names()) > 1 {
return nil, fmt.Errorf("more than one param for \"%s\"", fname)
}
flagNames := ff.Params.Names()
flagName := flagNames[0]
flagValue, _ := ff.Params.Get(flagName)
fv := flagValue.(string)
f.f = append(f.f, field{
name: fname,
flagName: flagName,
flagValue: fv,
})
}
}
params := map[string]interface{}{}
ps := fieldsList.Params
for _, p := range (*ps).Names() {
pp, ok := ps.Get(p)
if !ok {
return nil, fmt.Errorf("could not read param \"%s\"", p)
}
params[p] = pp
}
return &psiSignature{sigName, osp, f, params}, nil
}
func parseWantSignature(wantSignature string) ([]byte, error) {
wantSigItem, err := httpsfv.UnmarshalItem([]string{wantSignature})
if err != nil {
return nil, fmt.Errorf("unexpected value in signature field: %s", err)
}
wantSigRaw, ok := wantSigItem.Value.([]byte)
if !ok {
return nil, fmt.Errorf("could not parse raw signature")
}
return wantSigRaw, nil
}