154 lines
3.3 KiB
Go
154 lines
3.3 KiB
Go
/*
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SSHSecure - a program to harden OpenSSH from defaults
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Copyright (C) 2020 Brent Saner
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This program is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <https://www.gnu.org/licenses/>.
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*/
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package moduli
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import (
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"bytes"
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"encoding/hex"
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"errors"
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"fmt"
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"net/http"
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"time"
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"github.com/Luzifer/go-dhparam"
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"golang.org/x/crypto/sha3"
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)
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// NewModuli returns a Moduli populated with Entry items.
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func NewModuli(usePreGen ...bool) (m *Moduli, err error) {
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var doPreGen bool
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m = new(Moduli)
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if usePreGen != nil {
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doPreGen = usePreGen[0]
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} else {
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doPreGen = false
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}
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if doPreGen {
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if err = GetPreGen(m); err != nil {
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return
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}
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// This may take a while.
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if err = m.Harden(); err != nil {
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return
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}
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} else {
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if err = Generate(m); err != nil {
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return
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}
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}
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return
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}
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// GetPreGen gets the pregenerated moduli from upstream mirror.
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func GetPreGen(m *Moduli) (err error) {
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var b []byte
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var goodCksum []byte
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var resp *http.Response
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// get the pregenerated moduli
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resp, err = http.Get(pregenURL)
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if err != nil {
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return
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}
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if resp.StatusCode != http.StatusOK {
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err = errors.New(fmt.Sprintf("returned status code %v: %v", resp.StatusCode, resp.Status))
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return
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}
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defer resp.Body.Close()
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b = make([]byte, resp.ContentLength)
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if _, err = resp.Body.Read(b); err != nil {
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return
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}
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// and compare the SHA3-512 (NIST) checksum.
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s := sha3.New512()
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if _, err = s.Write(b); err != nil {
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return
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}
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goodCksum, err = hex.DecodeString(pregenCksum)
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if err != nil {
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return
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}
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// We just compare the bytestrings.
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if bytes.Compare(s.Sum(nil), goodCksum) != 0 {
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err = errors.New("checksums do not match")
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return
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}
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if err := Unmarshal(b, m); err != nil {
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return
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}
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return
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}
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// Generate generates new moduli with Entry items. It's more secure than using GetPreGen (LogJam), but takes a *LOT* longer.
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func Generate(m *Moduli) (err error) {
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var dh *dhparam.DH
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for _, bitLen := range genBits {
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for _, generator := range genGenerators {
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var e Entry
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e = Entry{
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Time: time.Now(),
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Size: bitLen,
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Generator: uint8(generator),
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/*
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Type: 0,
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Tests: 0,
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Trials: 0,
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*/
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}
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if dh, err = dhparam.Generate(int(bitLen), generator, nil); err != nil {
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continue // TODO: log/print
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}
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// Check() applies big.Int.ProbablyPrime() (Miller-Rabin - 0x04 in ssh moduli - and Baillie-PSW test), so it's probably fine.
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if errs, ok := dh.Check(); !ok {
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_ = errs // TODO: log/print
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continue
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} else {
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e.Time = time.Now()
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// e.Type =
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// e.Tests =
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// e.Trials =
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e.Modulus = *dh.P
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// TODO: https://stackoverflow.com/questions/18499352/golang-concurrency-how-to-append-to-the-same-slice-from-different-goroutines
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m.Groups = append(m.Groups, e)
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}
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}
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}
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return
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}
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