79 lines
2.1 KiB
Go
79 lines
2.1 KiB
Go
// SPDX-FileCopyrightText: 2021 The NGI Pointer Secure-Scuttlebutt Team of 2020/2021
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//
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// SPDX-License-Identifier: MIT
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package signinwithssb
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import (
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"bytes"
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"crypto/rand"
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"encoding/base64"
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"fmt"
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"golang.org/x/crypto/ed25519"
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refs "github.com/ssbc/go-ssb-refs"
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)
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// sign-in with ssb uses 256-bit nonces
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const challengeLength = 32
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// DecodeChallengeString accepts base64 encoded strings and decodes them,
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// checks their length to be equal to challengeLength,
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// and returns the decoded bytes
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func DecodeChallengeString(c string) ([]byte, error) {
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challengeBytes, err := base64.URLEncoding.DecodeString(c)
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if err != nil {
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return nil, fmt.Errorf("invalid challenge encoding: %w", err)
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}
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if n := len(challengeBytes); n != challengeLength {
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return nil, fmt.Errorf("invalid challenge length: expected %d but got %d", challengeLength, n)
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}
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return challengeBytes, nil
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}
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// GenerateChallenge returs a base64 encoded string
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// with challangeLength bytes of random data
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func GenerateChallenge() string {
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buf := make([]byte, challengeLength)
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rand.Read(buf)
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return base64.URLEncoding.EncodeToString(buf)
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}
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// ClientPayload is used to create and verify solutions
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type ClientPayload struct {
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ClientID, ServerID refs.FeedRef
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ClientChallenge string
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ServerChallenge string
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}
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// recreate the signed message
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func (cr ClientPayload) createMessage() []byte {
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var msg bytes.Buffer
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msg.WriteString("=http-auth-sign-in:")
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msg.WriteString(cr.ServerID.String())
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msg.WriteString(":")
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msg.WriteString(cr.ClientID.String())
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msg.WriteString(":")
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msg.WriteString(cr.ServerChallenge)
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msg.WriteString(":")
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msg.WriteString(cr.ClientChallenge)
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return msg.Bytes()
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}
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// Sign returns the signature created with the passed privateKey
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func (cr ClientPayload) Sign(privateKey ed25519.PrivateKey) []byte {
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msg := cr.createMessage()
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return ed25519.Sign(privateKey, msg)
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}
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// Validate checks the signature by calling createMessage() and ed25519.Verify()
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// together with the ClientID public key.
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func (cr ClientPayload) Validate(signature []byte) bool {
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msg := cr.createMessage()
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return ed25519.Verify(cr.ClientID.PubKey(), msg, signature)
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}
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