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97 lines
2.9 KiB
97 lines
2.9 KiB
// Copyright 2018 by David A. Golden. All rights reserved. |
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// |
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// Licensed under the Apache License, Version 2.0 (the "License"); you may |
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// not use this file except in compliance with the License. You may obtain |
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// a copy of the License at http://www.apache.org/licenses/LICENSE-2.0 |
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package scram |
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import ( |
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"crypto/hmac" |
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"crypto/rand" |
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"encoding/base64" |
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"strings" |
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) |
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// NonceGeneratorFcn defines a function that returns a string of high-quality |
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// random printable ASCII characters EXCLUDING the comma (',') character. The |
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// default nonce generator provides Base64 encoding of 24 bytes from |
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// crypto/rand. |
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type NonceGeneratorFcn func() string |
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// derivedKeys collects the three cryptographically derived values |
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// into one struct for caching. |
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type derivedKeys struct { |
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ClientKey []byte |
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StoredKey []byte |
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ServerKey []byte |
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} |
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// KeyFactors represent the two server-provided factors needed to compute |
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// client credentials for authentication. Salt is decoded bytes (i.e. not |
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// base64), but in string form so that KeyFactors can be used as a map key for |
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// cached credentials. |
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type KeyFactors struct { |
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Salt string |
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Iters int |
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} |
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// StoredCredentials are the values that a server must store for a given |
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// username to allow authentication. They include the salt and iteration |
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// count, plus the derived values to authenticate a client and for the server |
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// to authenticate itself back to the client. |
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// |
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// NOTE: these are specific to a given hash function. To allow a user to |
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// authenticate with either SCRAM-SHA-1 or SCRAM-SHA-256, two sets of |
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// StoredCredentials must be created and stored, one for each hash function. |
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type StoredCredentials struct { |
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KeyFactors |
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StoredKey []byte |
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ServerKey []byte |
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} |
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// CredentialLookup is a callback to provide StoredCredentials for a given |
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// username. This is used to configure Server objects. |
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// |
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// NOTE: these are specific to a given hash function. The callback provided |
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// to a Server with a given hash function must provide the corresponding |
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// StoredCredentials. |
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type CredentialLookup func(string) (StoredCredentials, error) |
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func defaultNonceGenerator() string { |
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raw := make([]byte, 24) |
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nonce := make([]byte, base64.StdEncoding.EncodedLen(len(raw))) |
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rand.Read(raw) |
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base64.StdEncoding.Encode(nonce, raw) |
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return string(nonce) |
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} |
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func encodeName(s string) string { |
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return strings.Replace(strings.Replace(s, "=", "=3D", -1), ",", "=2C", -1) |
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} |
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func decodeName(s string) (string, error) { |
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// TODO Check for = not followed by 2C or 3D |
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return strings.Replace(strings.Replace(s, "=2C", ",", -1), "=3D", "=", -1), nil |
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} |
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func computeHash(hg HashGeneratorFcn, b []byte) []byte { |
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h := hg() |
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h.Write(b) |
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return h.Sum(nil) |
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} |
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func computeHMAC(hg HashGeneratorFcn, key, data []byte) []byte { |
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mac := hmac.New(hg, key) |
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mac.Write(data) |
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return mac.Sum(nil) |
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} |
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func xorBytes(a, b []byte) []byte { |
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// TODO check a & b are same length, or just xor to smallest |
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xor := make([]byte, len(a)) |
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for i := range a { |
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xor[i] = a[i] ^ b[i] |
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} |
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return xor |
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}
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