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d2ea21d0d8
* use certmagic for more extensible/robust ACME cert handling * accept TOS based on config option Signed-off-by: Andrew Thornton <art27@cantab.net> Co-authored-by: zeripath <art27@cantab.net> Co-authored-by: Lauris BH <lauris@nix.lv>
264 lines
7.9 KiB
Go
Vendored
264 lines
7.9 KiB
Go
Vendored
// Copyright 2020 Matthew Holt
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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//
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// --- ORIGINAL LICENSE ---
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//
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// Copyright 2015 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the THIRD-PARTY file.
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//
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// (This file has been modified from its original contents.)
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// (And it has dragons. Don't wake the dragons.)
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package acme
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import (
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"crypto"
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"crypto/ecdsa"
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"crypto/hmac"
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"crypto/rand"
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"crypto/rsa"
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"crypto/sha256"
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_ "crypto/sha512" // need for EC keys
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"encoding/base64"
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"encoding/json"
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"fmt"
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"math/big"
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)
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var errUnsupportedKey = fmt.Errorf("unknown key type; only RSA and ECDSA are supported")
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// keyID is the account identity provided by a CA during registration.
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type keyID string
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// noKeyID indicates that jwsEncodeJSON should compute and use JWK instead of a KID.
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// See jwsEncodeJSON for details.
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const noKeyID = keyID("")
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// // noPayload indicates jwsEncodeJSON will encode zero-length octet string
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// // in a JWS request. This is called POST-as-GET in RFC 8555 and is used to make
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// // authenticated GET requests via POSTing with an empty payload.
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// // See https://tools.ietf.org/html/rfc8555#section-6.3 for more details.
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// const noPayload = ""
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// jwsEncodeEAB creates a JWS payload for External Account Binding according to RFC 8555 §7.3.4.
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func jwsEncodeEAB(accountKey crypto.PublicKey, hmacKey []byte, kid keyID, url string) ([]byte, error) {
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// §7.3.4: "The 'alg' field MUST indicate a MAC-based algorithm"
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alg, sha := "HS256", crypto.SHA256
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// §7.3.4: "The 'nonce' field MUST NOT be present"
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phead, err := jwsHead(alg, "", url, kid, nil)
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if err != nil {
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return nil, err
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}
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encodedKey, err := jwkEncode(accountKey)
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if err != nil {
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return nil, err
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}
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payload := base64.RawURLEncoding.EncodeToString([]byte(encodedKey))
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payloadToSign := []byte(phead + "." + payload)
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h := hmac.New(sha256.New, hmacKey)
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h.Write(payloadToSign)
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sig := h.Sum(nil)
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return jwsFinal(sha, sig, phead, payload)
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}
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// jwsEncodeJSON signs claimset using provided key and a nonce.
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// The result is serialized in JSON format containing either kid or jwk
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// fields based on the provided keyID value.
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//
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// If kid is non-empty, its quoted value is inserted in the protected head
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// as "kid" field value. Otherwise, JWK is computed using jwkEncode and inserted
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// as "jwk" field value. The "jwk" and "kid" fields are mutually exclusive.
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//
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// See https://tools.ietf.org/html/rfc7515#section-7.
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//
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// If nonce is empty, it will not be encoded into the header.
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func jwsEncodeJSON(claimset interface{}, key crypto.Signer, kid keyID, nonce, url string) ([]byte, error) {
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alg, sha := jwsHasher(key.Public())
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if alg == "" || !sha.Available() {
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return nil, errUnsupportedKey
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}
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phead, err := jwsHead(alg, nonce, url, kid, key)
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if err != nil {
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return nil, err
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}
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var payload string
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if claimset != nil {
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cs, err := json.Marshal(claimset)
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if err != nil {
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return nil, err
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}
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payload = base64.RawURLEncoding.EncodeToString(cs)
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}
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payloadToSign := []byte(phead + "." + payload)
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hash := sha.New()
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_, _ = hash.Write(payloadToSign)
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digest := hash.Sum(nil)
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sig, err := jwsSign(key, sha, digest)
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if err != nil {
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return nil, err
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}
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return jwsFinal(sha, sig, phead, payload)
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}
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// jwkEncode encodes public part of an RSA or ECDSA key into a JWK.
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// The result is also suitable for creating a JWK thumbprint.
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// https://tools.ietf.org/html/rfc7517
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func jwkEncode(pub crypto.PublicKey) (string, error) {
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switch pub := pub.(type) {
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case *rsa.PublicKey:
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// https://tools.ietf.org/html/rfc7518#section-6.3.1
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n := pub.N
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e := big.NewInt(int64(pub.E))
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// Field order is important.
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// See https://tools.ietf.org/html/rfc7638#section-3.3 for details.
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return fmt.Sprintf(`{"e":"%s","kty":"RSA","n":"%s"}`,
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base64.RawURLEncoding.EncodeToString(e.Bytes()),
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base64.RawURLEncoding.EncodeToString(n.Bytes()),
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), nil
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case *ecdsa.PublicKey:
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// https://tools.ietf.org/html/rfc7518#section-6.2.1
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p := pub.Curve.Params()
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n := p.BitSize / 8
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if p.BitSize%8 != 0 {
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n++
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}
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x := pub.X.Bytes()
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if n > len(x) {
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x = append(make([]byte, n-len(x)), x...)
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}
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y := pub.Y.Bytes()
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if n > len(y) {
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y = append(make([]byte, n-len(y)), y...)
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}
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// Field order is important.
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// See https://tools.ietf.org/html/rfc7638#section-3.3 for details.
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return fmt.Sprintf(`{"crv":"%s","kty":"EC","x":"%s","y":"%s"}`,
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p.Name,
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base64.RawURLEncoding.EncodeToString(x),
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base64.RawURLEncoding.EncodeToString(y),
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), nil
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}
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return "", errUnsupportedKey
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}
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// jwsHead constructs the protected JWS header for the given fields.
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// Since jwk and kid are mutually-exclusive, the jwk will be encoded
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// only if kid is empty. If nonce is empty, it will not be encoded.
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func jwsHead(alg, nonce, url string, kid keyID, key crypto.Signer) (string, error) {
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phead := fmt.Sprintf(`{"alg":%q`, alg)
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if kid == noKeyID {
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jwk, err := jwkEncode(key.Public())
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if err != nil {
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return "", err
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}
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phead += fmt.Sprintf(`,"jwk":%s`, jwk)
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} else {
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phead += fmt.Sprintf(`,"kid":%q`, kid)
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}
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if nonce != "" {
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phead += fmt.Sprintf(`,"nonce":%q`, nonce)
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}
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phead += fmt.Sprintf(`,"url":%q}`, url)
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phead = base64.RawURLEncoding.EncodeToString([]byte(phead))
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return phead, nil
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}
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// jwsFinal constructs the final JWS object.
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func jwsFinal(sha crypto.Hash, sig []byte, phead, payload string) ([]byte, error) {
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enc := struct {
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Protected string `json:"protected"`
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Payload string `json:"payload"`
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Sig string `json:"signature"`
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}{
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Protected: phead,
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Payload: payload,
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Sig: base64.RawURLEncoding.EncodeToString(sig),
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}
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result, err := json.Marshal(&enc)
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if err != nil {
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return nil, err
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}
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return result, nil
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}
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// jwsSign signs the digest using the given key.
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// The hash is unused for ECDSA keys.
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//
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// Note: non-stdlib crypto.Signer implementations are expected to return
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// the signature in the format as specified in RFC7518.
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// See https://tools.ietf.org/html/rfc7518 for more details.
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func jwsSign(key crypto.Signer, hash crypto.Hash, digest []byte) ([]byte, error) {
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if key, ok := key.(*ecdsa.PrivateKey); ok {
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// The key.Sign method of ecdsa returns ASN1-encoded signature.
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// So, we use the package Sign function instead
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// to get R and S values directly and format the result accordingly.
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r, s, err := ecdsa.Sign(rand.Reader, key, digest)
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if err != nil {
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return nil, err
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}
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rb, sb := r.Bytes(), s.Bytes()
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size := key.Params().BitSize / 8
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if size%8 > 0 {
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size++
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}
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sig := make([]byte, size*2)
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copy(sig[size-len(rb):], rb)
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copy(sig[size*2-len(sb):], sb)
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return sig, nil
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}
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return key.Sign(rand.Reader, digest, hash)
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}
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// jwsHasher indicates suitable JWS algorithm name and a hash function
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// to use for signing a digest with the provided key.
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// It returns ("", 0) if the key is not supported.
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func jwsHasher(pub crypto.PublicKey) (string, crypto.Hash) {
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switch pub := pub.(type) {
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case *rsa.PublicKey:
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return "RS256", crypto.SHA256
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case *ecdsa.PublicKey:
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switch pub.Params().Name {
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case "P-256":
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return "ES256", crypto.SHA256
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case "P-384":
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return "ES384", crypto.SHA384
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case "P-521":
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return "ES512", crypto.SHA512
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}
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}
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return "", 0
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}
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// jwkThumbprint creates a JWK thumbprint out of pub
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// as specified in https://tools.ietf.org/html/rfc7638.
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func jwkThumbprint(pub crypto.PublicKey) (string, error) {
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jwk, err := jwkEncode(pub)
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if err != nil {
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return "", err
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}
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b := sha256.Sum256([]byte(jwk))
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return base64.RawURLEncoding.EncodeToString(b[:]), nil
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}
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