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// Copyright 2024 OpenPubkey
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
// SPDX-License-Identifier: Apache-2.0
package pktoken
import (
"bytes"
"fmt"
"github.com/openpubkey/openpubkey/oidc"
)
// CompactPKToken creates a compact representation of a PK Token from a list of tokens
func CompactPKToken(tokens [][]byte, freshIDToken []byte) ([]byte, error) {
if len(tokens) == 0 {
return nil, fmt.Errorf("no tokens provided")
}
compact := [][]byte{}
var payload []byte
for _, tok := range tokens {
tokProtected, tokPayload, tokSig, err := oidc.SplitCompact(tok)
if err != nil {
return nil, err
}
if payload != nil {
if !bytes.Equal(payload, tokPayload) {
return nil, fmt.Errorf("payloads in tokens are not the same got %s and %s", payload, tokPayload)
}
} else {
payload = tokPayload
}
compact = append(compact, tokProtected, tokSig)
}
// prepend the payload to the front
compact = append([][]byte{payload}, compact...)
pktCom := bytes.Join(compact, []byte(":"))
// If we have a refreshed ID Token, append it to the compact representation using "."
if freshIDToken != nil {
if len(bytes.Split(freshIDToken, []byte("."))) != 3 {
// Compact ID Token should be reformated as Base64(protected)"."Base64(payload)"."Base64(signature)
return nil, fmt.Errorf("invalid refreshed ID Token")
}
pktCom = bytes.Join([][]byte{pktCom, freshIDToken}, []byte("."))
}
return pktCom, nil
}
// SplitCompactPKToken breaks a compact representation of a PK Token into its constituent tokens
func SplitCompactPKToken(pktCom []byte) ([][]byte, []byte, error) {
tokensBytes, freshIDToken, _ := bytes.Cut(pktCom, []byte("."))
tokensParts := bytes.Split(tokensBytes, []byte(":"))
if freshIDToken != nil && len(bytes.Split(freshIDToken, []byte("."))) != 3 {
// Compact ID Token should be reformated as Base64(protected)"."Base64(payload)"."Base64(signature)
return nil, nil, fmt.Errorf("invalid refreshed ID Token")
}
// Compact PK Token with refreshed ID Token should have at least 3 parts and should be:
// Base64(payload)":"Base64(protected1)":"Base64(signature1)"...":"Base64(protectedN)":"Base64(signatureN)"
if len(tokensParts) < 3 || len(tokensParts)%2 != 1 {
return nil, nil, fmt.Errorf("invalid number of segments, got %d", len(tokensParts))
}
tokens := [][]byte{}
payload := tokensParts[0]
for i := 1; i < len(tokensParts); i += 2 {
// We return each token in JWT compact format (Base64(protected)"."Base64(payload)"."Base64(signature))
token := bytes.Join([][]byte{tokensParts[i], payload, tokensParts[i+1]}, []byte("."))
tokens = append(tokens, token)
}
return tokens, freshIDToken, nil
}
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