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96 lines
2.6 KiB
Go
96 lines
2.6 KiB
Go
// Copyright (c) 2019 Shivaram Lingamneni
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package cloaks
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import (
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"fmt"
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"net"
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"golang.org/x/crypto/sha3"
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"github.com/ergochat/ergo/irc/utils"
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)
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type CloakConfig struct {
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Enabled bool
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EnabledForAlwaysOn bool `yaml:"enabled-for-always-on"`
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Netname string
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CidrLenIPv4 int `yaml:"cidr-len-ipv4"`
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CidrLenIPv6 int `yaml:"cidr-len-ipv6"`
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NumBits int `yaml:"num-bits"`
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LegacySecretValue string `yaml:"secret"`
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secret string
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numBytes int
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ipv4Mask net.IPMask
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ipv6Mask net.IPMask
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}
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func (cloakConfig *CloakConfig) Initialize() {
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// sanity checks:
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numBits := cloakConfig.NumBits
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if 0 == numBits {
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numBits = 64
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} else if 256 < numBits {
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numBits = 256
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}
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// derived values:
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cloakConfig.numBytes = numBits / 8
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// round up to the nearest byte
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if numBits%8 != 0 {
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cloakConfig.numBytes += 1
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}
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cloakConfig.ipv4Mask = net.CIDRMask(cloakConfig.CidrLenIPv4, 32)
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cloakConfig.ipv6Mask = net.CIDRMask(cloakConfig.CidrLenIPv6, 128)
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}
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func (cloakConfig *CloakConfig) SetSecret(secret string) {
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cloakConfig.secret = secret
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}
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// simple cloaking algorithm: normalize the IP to its CIDR,
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// then hash the resulting bytes with a secret key,
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// then truncate to the desired length, b32encode, and append the fake TLD.
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func (config *CloakConfig) ComputeCloak(ip net.IP) string {
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if !config.Enabled {
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return ""
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} else if config.NumBits == 0 || config.secret == "" {
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return config.Netname
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}
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var masked net.IP
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v4ip := ip.To4()
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if v4ip != nil {
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masked = v4ip.Mask(config.ipv4Mask)
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} else {
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masked = ip.Mask(config.ipv6Mask)
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}
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return config.macAndCompose(masked)
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}
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func (config *CloakConfig) macAndCompose(b []byte) string {
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// SHA3(K || M):
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// https://crypto.stackexchange.com/questions/17735/is-hmac-needed-for-a-sha-3-based-mac
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input := make([]byte, len(config.secret)+len(b))
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copy(input, config.secret[:])
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copy(input[len(config.secret):], b)
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digest := sha3.Sum512(input)
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b32digest := utils.B32Encoder.EncodeToString(digest[:config.numBytes])
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return fmt.Sprintf("%s.%s", b32digest, config.Netname)
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}
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func (config *CloakConfig) ComputeAccountCloak(accountName string) string {
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// XXX don't bother checking EnabledForAlwaysOn, since if it's disabled,
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// we need to use the server name which we don't have
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if config.NumBits == 0 || config.secret == "" {
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return config.Netname
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}
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// pad with 16 initial bytes of zeroes, avoiding any possibility of collision
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// with a masked IP that could be an input to ComputeCloak:
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paddedAccountName := make([]byte, 16+len(accountName))
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copy(paddedAccountName[16:], accountName[:])
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return config.macAndCompose(paddedAccountName)
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}
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