all the directives are copied in with their types. working on validators now.

2020-09-27 03:23:58 -04:00 · 2020-09-27 03:23:58 -04:00 · 4b912a8dae
commit 4b912a8dae
parent c22786204a
21 changed files with 859 additions and 131 deletions
--- a/README.md
+++ b/README.md
@ -54,7 +54,8 @@ no identifying information other than the fact that you are using SSHSecure.
 It will create backups of any file(s) it replaces and automatically rolls back `sshd` 
 configuration changes if it does not pass the syntax check (`sshd -t`) to avoid 
 accidentally locking you out.
- 
+
+<!--
 The first time you run it, it will quite possibly take a **very** long time. This is 
 because it's generating fresh DH parameters, which is a very time-consuming process. 
 Subsequent runs will not take as long, however, as checks are put in place to determine
@ -62,6 +63,7 @@ if custom DH parameters have been generated or not yet. If it's running on a GNU
 system and you have [`haveged`](http://www.issihosts.com/haveged/) installed, that will 
 significantly speed up the process (SSHSecure will start it automatically if it isn't
 running already).
+-->

 ## FAQ

--- a/29
+++ b/29
@ -1,27 +1,24 @@
-sshkeys (see ref/<type>/parse_poc_<keytype>.go for POC)
--hostkeys (https://security.stackexchange.com/questions/211106/what-is-the-difference-between-host-and-client-ssh-key-generation)?
-moduli dhparams generation (dh.c? moduli.c?)
--ssh-keygen.c, ~L3565
-
 - General/common
-- Locking?
-- Constants for common file dests
-- Func to write to dest, backing up dest if exists first
-- Test ssh config (sshd -t) and rollback if fail
+-- HALF-DONE: Locking?
+-- DONE: Constants for common file dests
+-- DONE: Func to write to dest, backing up dest if exists first
+-- DONE: Test ssh config (sshd -t) and rollback if fail
+-- When completely done, go.mod

 - Key generation
 -- DONE: Generate priv/pubkeys
-- Build key structure
+-- DONE: Build key structure
 -- write out base64 with headers to files

 - SSH Moduli
-- Do DH param gen in goroutine so we can do other things while it spawns and runs
-- Check if haveged is running. If not and installed, start it.
-- Generate moduli
-- Render to /etc/ssh/moduli format
--- custom moduli marshaler/unmarshaler? (e.g. https://stackoverflow.com/a/50211222)
+-- NOT NEEDED?: Do DH param gen in goroutine so we can do other things while it spawns and runs
+--- Check if haveged is running. If not and installed, start it.
+--- Generate moduli
+-- DONE: Render to /etc/ssh/moduli format
+--- DONE: custom moduli marshaler/unmarshaler? (e.g. https://stackoverflow.com/a/50211222)
 -- Write to dest

 - Config
 -- Need to merge in changes
-- Track options in struct?
+-- Track options in struct?
+--- add subtype structs
--- a/config/const.go
+++ b/config/const.go
@ -0,0 +1,268 @@
+/*
+   SSHSecure - a program to harden OpenSSH from defaults
+   Copyright (C) 2020  Brent Saner
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation, either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
+package config
+
+const (
+	// To check if this release of SSHSecure is up-to-date with the default values.
+	// upstreamSshdURL   string = "https://anongit.mindrot.org/openssh.git/plain/sshd_config"
+	upstreamSshdURL   string = "https://raw.githubusercontent.com/openssh/openssh-portable/master/sshd_config"
+	upstreamSshdCksum string = "952C844D7B36C54B03E2ADFB24860405" +
+		"1A702620A0ADC0738A8C30DC83D42A75" +
+		"27F5B3C184E779B1430168950F7695A1" +
+		"AA249F7CC719DEC1631ACFDDC2E8B653"
+	// upstreamSshURL   string = "https://anongit.mindrot.org/openssh.git/plain/ssh_config"
+	upstreamSshURL   string = "https://raw.githubusercontent.com/openssh/openssh-portable/master/ssh_config"
+	upstreamSshCksum string = "FF2D600465CC5D9CFBB57346491CCAF2" +
+		"C917E2F0C7B4D4EF6B851940948B55BD" +
+		"88205AC8153210ECA6C6BEA38E800F33" +
+		"7562C0190AE760220417A5DC2E00A5E1"
+)
+
+// These are items that this program modifies.
+var (
+	// sshdModify are values we modify.
+	sshdModify = [...]string{
+		"HostKey",
+		"PermitRootLogin",
+		"StrictModes",
+		"PubkeyAuthentication",
+		"PasswordAuthentication",
+		"PermitEmptyPasswords",
+		"ChallengeResponseAuthentication",
+		"KexAlgorithms",
+		"Protocol",
+		"Ciphers",
+		"MACs",
+	}
+
+	// sshModify are values we modify.
+	sshModify = [...]string{""}
+)
+
+// These are collections of long lists of valid values.
+var (
+	// sshdMulti are values that can be specified multiple times (multiple lines).
+	sshdMulti = [...]string{
+		"",
+	}
+
+	// authMethods are authentication methods that openssh supports.
+	authMethods = []string{
+		"any",
+		"keyboard-interactive",
+		"keyboard-interactive:bsdauth",
+		"keyboard-interactive:pam",
+		"gssapi-with-mic",
+		"hostbased",
+		"none",
+		"password",
+		"publickey",
+	}
+
+	// ciphers are cipher algorithms that openssh supports.
+	ciphers = []string{
+		"3des-cbc",
+		"aes128-cbc",
+		"aes192-cbc",
+		"aes256-cbc",
+		"aes128-ctr",
+		"aes192-ctr",
+		"aes256-ctr",
+		"aes128-gcm@openssh.com",
+		"aes256-gcm@openssh.com",
+		"chacha20-poly1305@openssh.com",
+	}
+
+	// forwardAllows are shared values used by forwarding access control.
+	forwardAllows = []string{"yes", "all", "no", "local", "remote"}
+
+	// hostkeyTypes are algorithms/types used for host keys.
+	// The following should generate the same list.
+	// ssh -Q HostKeyAlgorithms | sed -re 's/^/"/g' -e 's/$/",/g'
+	// ssh -Q HostbasedAcceptedKeyTypes | sed -re 's/^/"/g' -e 's/$/",/g'
+	hostkeyTypes = []string{
+		"ssh-ed25519",
+		"ssh-ed25519-cert-v01@openssh.com",
+		"sk-ssh-ed25519@openssh.com",
+		"sk-ssh-ed25519-cert-v01@openssh.com",
+		"ssh-rsa",
+		"rsa-sha2-256",
+		"rsa-sha2-512",
+		"ssh-dss",
+		"ecdsa-sha2-nistp256",
+		"ecdsa-sha2-nistp384",
+		"ecdsa-sha2-nistp521",
+		"sk-ecdsa-sha2-nistp256@openssh.com",
+		"ssh-rsa-cert-v01@openssh.com",
+		"rsa-sha2-256-cert-v01@openssh.com",
+		"rsa-sha2-512-cert-v01@openssh.com",
+		"ssh-dss-cert-v01@openssh.com",
+		"ecdsa-sha2-nistp256-cert-v01@openssh.com",
+		"ecdsa-sha2-nistp384-cert-v01@openssh.com",
+		"ecdsa-sha2-nistp521-cert-v01@openssh.com",
+		"sk-ecdsa-sha2-nistp256-cert-v01@openssh.com",
+	}
+
+	// ipQoS is a list of valid QoS profiles.
+	ipQoS = []string{
+		// This also supports a "numeric value" per sshd_config(5),
+		// but I have no idea what those values are, their range, etc.
+		// So strings only. Makes for more readable configs anyways.
+		// TODO: is this specified in the source anywhere?
+		"af11",
+		"af12",
+		"af13",
+		"af21",
+		"af22",
+		"af23",
+		"af31",
+		"af32",
+		"af33",
+		"af41",
+		"af42",
+		"af43",
+		"cs0",
+		"cs1",
+		"cs2",
+		"cs3",
+		"cs4",
+		"cs5",
+		"cs6",
+		"cs7",
+		"ef",
+		"le",
+		"lowdelay",
+		"throughput",
+		"reliability",
+		"none",
+	}
+
+	// kexAlgos is a lost of valid kex ("KEy eXchange") algorithms.
+	// ssh -Q kex | sed -re 's/^/"/g' -e 's/$/",/g'
+	kexAlgos = []string{
+		"diffie-hellman-group1-sha1",
+		"diffie-hellman-group14-sha1",
+		"diffie-hellman-group14-sha256",
+		"diffie-hellman-group16-sha512",
+		"diffie-hellman-group18-sha512",
+		"diffie-hellman-group-exchange-sha1",
+		"diffie-hellman-group-exchange-sha256",
+		"ecdh-sha2-nistp256",
+		"ecdh-sha2-nistp384",
+		"ecdh-sha2-nistp521",
+		"curve25519-sha256",
+		"curve25519-sha256@libssh.org",
+		"sntrup4591761x25519-sha512@tinyssh.org",
+	}
+
+	// sigAlgos is a list of valid algorithms for CA signatures.
+	sigAlgos = []string{
+		// These are the defaults. TODO: are any others valid?
+		"ecdsa-sha2-nistp256",
+		"ecdsa-sha2-nistp384",
+		"ecdsa-sha2-nistp521",
+		"ssh-ed25519",
+		"rsa-sha2-512",
+		"rsa-sha2-256",
+		"ssh-rsa",
+	}
+
+	// logLevels is a list of valid LogLevel levels.
+	logLevels = []string{
+		"QUIET",
+		"FATAL",
+		"ERROR",
+		"INFO", // default
+		"VERBOSE",
+		"DEBUG",  // same as DEBUG1
+		"DEBUG1", // same as DEBUG
+		"DEBUG2",
+		"DEBUG3",
+	}
+
+	// macAlgos is a list of valid MAC (Message Authentication Code) values. "-etm" algos are recommended by upstream.
+	// ssh -Q mac | sed -re 's/^/"/g' -e 's/$/",/g'
+	macAlgos = []string{
+		"hmac-sha1",
+		"hmac-sha1-96",
+		"hmac-sha2-256",
+		"hmac-sha2-512",
+		"hmac-md5",
+		"hmac-md5-96",
+		"umac-64@openssh.com",
+		"umac-128@openssh.com",
+		"hmac-sha1-etm@openssh.com",
+		"hmac-sha1-96-etm@openssh.com",
+		"hmac-sha2-256-etm@openssh.com",
+		"hmac-sha2-512-etm@openssh.com",
+		"hmac-md5-etm@openssh.com",
+		"hmac-md5-96-etm@openssh.com",
+		"umac-64-etm@openssh.com",
+		"umac-128-etm@openssh.com",
+	}
+)
+
+// This is a collection related to Match blocks.
+var (
+	// sshdMatchCriteria is a list of valid criteria that can be used in a Match block.
+	// Valid keys for sshdMatchCriteria are tracked via field names in SshdMatchRule.
+	// Multiple criteria can be specified by e.g. "Match User foo, Host bar.tld"
+	sshdMatchCriteria = []string{
+		"All",
+		"User",
+		"Group",
+		"Host",
+		"LocalAddress",
+		"LocalPort",
+		"RDomain",
+		"Address",
+	}
+)
+
+// The following are validator maps.
+var (
+	// These directives can also begin with "+", "-", or "^", so they need to be stripped off.
+	// TODO: How to do this non-destructively?
+	sshdStripPre = []string{
+		"HostbasedAcceptedKeyTypes",
+		"KexAlgorithms",
+	}
+	// validSshdSingleVals are values that can accept a single string value from a static list.
+	validSshdSingleVals = map[string][]string{
+		"AddressFamily":              {"any", "inet", "inet6"},
+		"AllowStreamLocalForwarding": forwardAllows,
+		"AllowTcpForwarding":         forwardAllows,
+		"Compression":                {"yes", "delayed", "no"}, // "delayed" is legacy, same as "yes".
+		"FingerprintHash":            {"sha256", "md5"},
+		"GatewayPorts":               {"yes", "no", "clientspecified"},
+		"IgnoreRHosts":               {"yes", "shosts-only", "no"},
+		"LogLevel":                   logLevels,
+	}
+
+	// validSshdMultiVals are values that can accept multiple values from a static list.
+	validSshdMultiVals = map[string][]string{
+		"AuthenticationMethods":     authMethods,
+		"CASignatureAlgorithms":     sigAlgos,
+		"Ciphers":                   ciphers,
+		"HostbasedAcceptedKeyTypes": hostkeyTypes, // NOTE: Can also begin with "+", "-", or "^"
+		"HostKeyAlgorithms":         hostkeyTypes,
+		"KexAlgorithms":             kexAlgos, // NOTE: Can also begin with "+", "-", or "^"
+		"MACs":                      macAlgos,
+	}
+)
--- a/config/func.go
+++ b/config/func.go
@ -0,0 +1,81 @@
+/*
+   SSHSecure - a program to harden OpenSSH from defaults
+   Copyright (C) 2020  Brent Saner
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation, either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
+package config
+
+import (
+	"bytes"
+	"fmt"
+	"io/ioutil"
+	"os"
+	"os/exec"
+	"path"
+
+	"github.com/pkg/errors"
+	"r00t2.io/sysutils/exec_extra"
+	"r00t2.io/sysutils/paths"
+)
+
+func TestConfig(config *[]byte) (bool, error) {
+	var sysPaths []string
+	var binPath string
+	var tmpConf *os.File
+	var err error
+	var stdout, stderr bytes.Buffer
+	// sshd *requires* to be invoked with an absolute path.
+	sysPaths, err = paths.GetPathEnv()
+	if err != nil {
+		return false, err
+	}
+	for _, p := range sysPaths {
+		fpath := path.Join(p, "sshd")
+		if exists, err := paths.RealPathExists(&fpath); err != nil {
+			return false, err
+		} else if !exists {
+			continue
+		}
+		binPath = fpath
+		break
+	}
+	tmpConf, err = ioutil.TempFile("/tmp", ".test.sshconf.")
+	if err != nil {
+		return false, err
+	}
+	defer os.Remove(tmpConf.Name())
+	if err = tmpConf.Chmod(0600); err != nil {
+		return false, err
+	}
+	if _, err = tmpConf.Write(*config); err != nil {
+		return false, err
+	}
+	cmd := exec.Command(binPath,
+		"-T", fmt.Sprintf("-f %v",
+			tmpConf.Name()))
+	cmd.Stdout = &stdout
+	cmd.Stderr = &stderr
+	exitStatus, err := exec_extra.ExecCmdReturn(cmd)
+	if err != nil {
+		return false, err
+	}
+	if exitStatus != 0 {
+		// TODO: also handle non-empty stderr?
+		e := fmt.Sprintf("returned status/exit code %d", exitStatus)
+		return false, errors.New(e)
+	}
+	return true, nil
+}
--- a/config/struct.go
+++ b/config/struct.go
@ -0,0 +1,150 @@
+/*
+   SSHSecure - a program to harden OpenSSH from defaults
+   Copyright (C) 2020  Brent Saner
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation, either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
+package config
+
+/*
+	NOTATION KEY:
+		.: Exists in default upstream config (but usually they're commented out)
+		+: These values are/may be modified by this program.
+		*: These values are not in the upstream config but are allowed via the man page (sshd_config(5) and ssh_config(5)).
+*/
+
+// More or less a subset of SshdConf. These are valid keywords for Match blocks in sshd_config.
+type SshdMatchRule struct {
+	AcceptEnv                       []string // *
+	AllowAgentForwarding            sshBool  // .
+	AllowGroups                     []string // *
+	AllowStreamLocalForwarding      string   // *
+	AllowTcpForwarding              string   // .
+	AllowUsers                      []string // *
+	AuthenticationMethods           []string // +*
+	AuthorizedKeysCommand           string   // .
+	AuthorizedKeysCommandUser       string   // .
+	AuthorizedKeysFile              string   // .
+	AuthorizedPrincipalsCommand     string   // *
+	AuthorizedPrincipalsCommandUser string   // *
+	AuthorizedPrincipalsFile        string   // .
+	Banner                          string   // .
+	ChrootDirectory                 string   // .
+	ClientAliveCountMax             int      // .
+	ClientAliveInterval             int      // .
+	DenyGroups                      []string // *
+	DenyUsers                       []string // *
+	ForceCommand                    string   // *
+	GatewayPorts                    string   // .
+	GSSAPIAuthentication            sshBool  // .
+	HostbasedAcceptedKeyTypes       []string // *
+	HostbasedAuthentication         sshBool  // .
+	HostbasedUsesNameFromPacketOnly sshBool  // *
+	IgnoreRhosts                    string   // .
+	// Do we handle includes? Or just let sshd -T handle it?
+	Include string // *
+	// Accepts one or two. If two, first is interactive and second is non-interactive.
+	IPQoS                        [2]string         // *
+	KbdInteractiveAuthentication sshBool           // *
+	KerberosAuthentication       sshBool           // .
+	LogLevel                     string            // .
+	MaxAuthTries                 int               // .
+	MaxSessions                  int               // .
+	PasswordAuthentication       sshBool           // .+
+	PermitEmptyPasswords         sshBool           // +
+	PermitListen                 string            // *
+	PermitOpen                   string            // *
+	PermitRootLogin              string            // .+
+	PermitTTY                    sshBool           // .
+	PermitTunnel                 string            // .
+	PermitUserRC                 sshBool           // *
+	PubkeyAcceptedKeyTypes       []string          // *
+	PubkeyAuthentication         sshBool           // .+
+	RekeyLimit                   string            // .
+	RevokedKeys                  string            // *
+	RDomain                      string            // *
+	SetEnv                       map[string]string // *
+	// max is 4095, it goes in the config as an octal.
+	StreamLocalBindMask   uint16  // *
+	StreamLocalBindUnlink sshBool // *
+	TrustedUserCAKeys     string  // *
+	X11DisplayOffset      int     // .
+	X11Forwarding         sshBool // .
+}
+
+// SshdConf represents an /etc/ssh/sshd_config file's directives/values.
+// Values in SshdMatchRule are not reproduced here.
+type SshdConf struct {
+	SshdMatchRule
+	AddressFamily                   string            // .
+	CASignatureAlgorithms           []string          // *
+	ChallengeResponseAuthentication sshBool           // .+
+	Ciphers                         []string          // +*
+	Compression                     string            // .
+	DisableForwarding               sshBool           // *
+	ExposeAuthInfo                  sshBool           // *
+	FingerprintHash                 string            // *
+	GSSAPICleanupCredentials        sshBool           // .
+	GSSAPIStrictAcceptorCheck       sshBool           // *
+	HostCertificate                 string            // *
+	HostKeyAgent                    string            // *
+	HostKeyAlgorithms               []string          // +*
+	HostKey                         []string          // .
+	IgnoreUserKnownHosts            sshBool           // .
+	KerberosGetAFSToken             sshBool           // .
+	KerberosOrLocalPasswd           sshBool           // .
+	KerberosTicketCleanup           sshBool           // .
+	KexAlgorithms                   string            // +*
+	ListenAddress                   ListenAddr        // .
+	LoginGraceTime                  string            // .
+	MACs                            []string          // +*
+	Match                           map[string]string // .
+	MaxStartups                     string            // .
+	PermitUserEnvironment           sshBool           // .
+	PidFile                         string            // .
+	Port                            uint16            // .
+	PrintLastLog                    sshBool           // .+
+	PrintMotd                       sshBool           // .
+	Protocol                        int               // +*
+	PubkeyAuthOptions               string            // *
+	SecurityKeyProvider             string            // *
+	StrictModes                     sshBool           // .+
+	Subsystem                       string            // .
+	SyslogFacility                  string            // .
+	TCPKeepAlive                    sshBool           // .
+	UseDNS                          sshBool           // .
+	UsePAM                          sshBool           // .
+	VersionAddendum                 string            // .
+	X11UseLocalhost                 sshBool           // .
+	XAuthLocation                   string            // *
+}
+
+// SshConf represents an /etc/ssh/ssh_config (or ~/.ssh/config) file
+type SshConf struct {
+	// These are in the default upstream sshd_config so we don't touch them. (Most, if not all, are commented out.)
+	// We just have them here to parse them.
+	Host map[string]string
+}
+
+type ListenAddr struct {
+	Addr    string // hostname|address, hostname:port, IPv4_address:port, or [hostname|address]:port in conf string.
+	Port    uint16
+	RDomain string
+}
+
+type MatchSshd struct {
+	Criteria map[string]string
+	Rules    []SshdMatchRule
+}
--- a/config/type.go
+++ b/config/type.go
@ -0,0 +1,10 @@
+package config
+
+type sshBool bool
+
+func (b sshBool) Str() string {
+	if b {
+		return "yes"
+	}
+	return "no"
+}
--- a/config/validator.go
+++ b/config/validator.go
@ -0,0 +1,34 @@
+package config
+
+import (
+	"fmt"
+
+	"github.com/oleiade/reflections"
+	"github.com/pkg/errors"
+)
+
+var err error
+
+func (c *SshdConf) Validate() (bool, error) {
+	for k, v := range validSshdSingleVals {
+		realV, err := reflections.GetField(c, k)
+		if err != nil {
+			return false, err
+		}
+		valid := false
+		for _, i := range v {
+			if i == realV {
+				valid = true
+				break
+			}
+		}
+		if !valid {
+			e := fmt.Sprintf(
+				"field %v value %v is not allowed",
+				k, realV)
+			return false, errors.New(e)
+		}
+	}
+
+	return true, nil
+}
--- a/go.mod
+++ b/go.mod
@ -1,9 +0,0 @@
-module r00t2.io/sshsecure
-
-go 1.15
-
-require (
-	github.com/dchest/bcrypt_pbkdf v0.0.0-20150205184540-83f37f9c154a
-	github.com/go-restruct/restruct v1.2.0-alpha
-	golang.org/x/crypto v0.0.0-20200820211705-5c72a883971a // indirect
-)
--- a/go.sum
+++ b/go.sum
@ -1,24 +0,0 @@
-github.com/davecgh/go-spew v1.1.0 h1:ZDRjVQ15GmhC3fiQ8ni8+OwkZQO4DARzQgrnXU1Liz8=
-github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
-github.com/dchest/bcrypt_pbkdf v0.0.0-20150205184540-83f37f9c154a h1:saTgr5tMLFnmy/yg3qDTft4rE5DY2uJ/cCxCe3q0XTU=
-github.com/dchest/bcrypt_pbkdf v0.0.0-20150205184540-83f37f9c154a/go.mod h1:Bw9BbhOJVNR+t0jCqx2GC6zv0TGBsShs56Y3gfSCvl0=
-github.com/go-restruct/restruct v1.2.0-alpha h1:2Lp474S/9660+SJjpVxoKuWX09JsXHSrdV7Nv3/gkvc=
-github.com/go-restruct/restruct v1.2.0-alpha/go.mod h1:KqrpKpn4M8OLznErihXTGLlsXFGeLxHUrLRRI/1YjGk=
-github.com/pkg/errors v0.8.1 h1:iURUrRGxPUNPdy5/HRSm+Yj6okJ6UtLINN0Q9M4+h3I=
-github.com/pkg/errors v0.8.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
-github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
-github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
-github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
-github.com/stretchr/testify v1.4.0 h1:2E4SXV/wtOkTonXsotYi4li6zVWxYlZuYNCXe9XRJyk=
-github.com/stretchr/testify v1.4.0/go.mod h1:j7eGeouHqKxXV5pUuKE4zz7dFj8WfuZ+81PSLYec5m4=
-golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
-golang.org/x/crypto v0.0.0-20200820211705-5c72a883971a h1:vclmkQCjlDX5OydZ9wv8rBCcS0QyQY66Mpf/7BZbInM=
-golang.org/x/crypto v0.0.0-20200820211705-5c72a883971a/go.mod h1:LzIPMQfyMNhhGPhUkYOs5KpL4U8rLKemX1yGLhDgUto=
-golang.org/x/net v0.0.0-20190404232315-eb5bcb51f2a3/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
-golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
-golang.org/x/sys v0.0.0-20190412213103-97732733099d/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
-golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
-gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
-gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
-gopkg.in/yaml.v2 v2.2.2 h1:ZCJp+EgiOT7lHqUV2J862kp8Qj64Jo6az82+3Td9dZw=
-gopkg.in/yaml.v2 v2.2.2/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
--- a/moduli/const.go
+++ b/moduli/const.go
@ -27,7 +27,8 @@ import (
 // Misc
 const (
 	// Where to find an up-to-date copy of the upstream moduli and its SHA3-512 (NIST) checksum.
-	pregenURL string = "https://anongit.mindrot.org/openssh.git/tree/moduli"
+	// pregenURL string = "https://anongit.mindrot.org/openssh.git/plain/moduli"
+	pregenURL string = "https://raw.githubusercontent.com/openssh/openssh-portable/master/moduli"
 	// This is the best way I could think of to verify integrity, since the file itself doesn't have a signature or anything like that.
 	pregenCksum string = "106EDB19A936608D065D2E8E81F7BDE7" +
 		"434AF80EF81102E9440B99ACB98FBEF8" +
@ -37,7 +38,8 @@ const (
 	parseTag string = "sshmoduli"
 	// The recommended minimum moduli to have available.
 	recMinMod int = 400
-	// The
+	// The minimum bits for filtering. It's generally bits - 1
+	minBits uint8 = 4095
 )

 // The header line on the /etc/ssh/moduli file.
@ -55,7 +57,8 @@ const (
 	timeFormat string = "20060102150405" // %Y%m%d%H%M%S
 )

-// For validation
+// For validation. Currently unused.
+/*
 var (
 	validTypes = []uint8{
 		0, // Unknown, not tested
@ -69,3 +72,4 @@ var (
 		0x04, // Probabilistic Miller-Rabin primality tests.
 	}
 )
+*/
--- a/moduli/func.go
+++ b/moduli/func.go
@ -28,33 +28,38 @@ import (
 	"golang.org/x/crypto/sha3"
 )

-func getPregen() ([]byte, error) {
+// getPregen gets the pregenerated moduli from upstream mirror.
+func getPregen() (Moduli, error) {
+	m := Moduli{}
 	// get the pregenerated moduli
 	resp, err := http.Get(pregenURL)
 	if err != nil {
-		return nil, err
+		return m, err
 	}
 	if resp.StatusCode != http.StatusOK {
-		return nil, errors.New(fmt.Sprintf("returned status code %v: %v", resp.StatusCode, resp.Status))
+		return m, errors.New(fmt.Sprintf("returned status code %v: %v", resp.StatusCode, resp.Status))
 	}
 	defer resp.Body.Close()
 	b := make([]byte, resp.ContentLength)
 	if _, err = resp.Body.Read(b); err != nil {
-		return nil, err
+		return m, err
 	}
 	// and compare the SHA3-512 (NIST) checksum.
 	s := sha3.New512()
 	if _, err = s.Write(b); err != nil {
 		// TODO: return nil instead of b?
-		return b, err
+		return m, err
 	}
 	goodCksum, err := hex.DecodeString(pregenCksum)
 	if err != nil {
-		return nil, err
+		return m, err
 	}
 	// We just compare the bytestrings.
 	if bytes.Compare(s.Sum(nil), goodCksum) != 0 {
-		return nil, errors.New("checksums do not match")
+		return m, errors.New("checksums do not match")
 	}
-	return b, nil
+	if err := Unmarshal(b, m); err != nil {
+		return m, err
+	}
+	return m, nil
 }
--- a/moduli/main.go
+++ b/moduli/main.go
@ -1,23 +0,0 @@
-/*
-   SSHSecure - a program to harden OpenSSH from defaults
-   Copyright (C) 2020  Brent Saner
-
-   This program is free software: you can redistribute it and/or modify
-   it under the terms of the GNU General Public License as published by
-   the Free Software Foundation, either version 3 of the License, or
-   (at your option) any later version.
-
-   This program is distributed in the hope that it will be useful,
-   but WITHOUT ANY WARRANTY; without even the implied warranty of
-   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-   GNU General Public License for more details.
-
-   You should have received a copy of the GNU General Public License
-   along with this program.  If not, see <https://www.gnu.org/licenses/>.
-*/
-
-package moduli
-
-func main() {
-
-}
--- a/moduli/parser.go
+++ b/moduli/parser.go
@ -50,7 +50,7 @@ func (m *Moduli) Marshal() ([]byte, error) {
 }

 // marshalEntry is used to parse a specific DH entry into the moduli.
-func (m *ModuliEntry) marshalEntry() ([]byte, error) {
+func (m *Entry) marshalEntry() ([]byte, error) {
 	mod := hex.EncodeToString(m.Modulus.Bytes())
 	s := fmt.Sprintf(
 		"%v %v %v %v %v %v %v\n",
@ -68,10 +68,10 @@ func (m *ModuliEntry) marshalEntry() ([]byte, error) {
 // Unmarshal writes the Moduli format into m from the /etc/ssh/moduli format in data.
 func Unmarshal(data []byte, m Moduli) error {
 	var lines []string
-	var entries []ModuliEntry
+	var entries []Entry
 	lines = strings.Split(string(data), "\n")
 	for _, line := range lines {
-		e := ModuliEntry{}
+		e := Entry{}
 		if reSkipLine.MatchString(line) {
 			continue
 		}
@ -85,7 +85,8 @@ func Unmarshal(data []byte, m Moduli) error {
 	return nil
 }

-func unmarshalEntry(line []string, m ModuliEntry) error {
+func unmarshalEntry(line []string, m Entry) error {
+	var err error
 	if len(line) != 7 {
 		return errors.New("field count mismatch")
 	}
@ -117,3 +118,19 @@ func unmarshalEntry(line []string, m ModuliEntry) error {
 	m.Modulus.SetBytes(modb)
 	return nil
 }
+
+func (m *Moduli) Harden() error {
+	var entries []Entry
+	for _, e := range m.Params {
+		if e.Size >= minBits {
+			entries = append(entries, e)
+		}
+	}
+	m.Params = entries
+	if len(m.Params) < recMinMod {
+		return errors.New("does not meet recommended minimum moduli")
+	}
+	return nil
+}
+
+// TODO: find way of testing/sieving primes
--- a/moduli/struct.go
+++ b/moduli/struct.go
@ -26,11 +26,11 @@ import (
 // Moduli contains all data needed for generated /etc/ssh/moduli. of ModuliEntry entries.
 type Moduli struct {
 	Header string
-	Params []ModuliEntry
+	Params []Entry
 }

 // Moduli is a struct reflecting the format of a single /etc/ssh/moduli entry. See moduli(5) for details.
-type ModuliEntry struct {
+type Entry struct {
 	Time time.Time // YYYYMMDDHHSS
 	/*
 		// man 5 moduli:
--- a/sharedconsts/const.go
+++ b/sharedconsts/const.go
@ -1,3 +1,21 @@
+/*
+   SSHSecure - a program to harden OpenSSH from defaults
+   Copyright (C) 2020  Brent Saner
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation, either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
 package sharedconsts

 import (
@ -11,3 +29,22 @@ const (
 )

 var IDCmnt = string(fmt.Sprintf("Autogenerated by %v (%v)", projName, projUrl))
+
+// Common file/directory paths.
+const (
+	// System-wide files.
+	LockFile      string = "/tmp/.sshsecure.lck"
+	SysSshConfDir string = "/etc/ssh"
+	// The following are joined with SysSshConfDir.
+	SshdConfFile    string = "sshd_config"
+	SshConfFile     string = "ssh_config"
+	HostEd25519File string = "ssh_host_ed25519_key"
+	HostRsaFile     string = "ssh_host_rsa_key"
+	ModuliFile      string = "moduli"
+	// Invoking user's files.
+	UserSshConfDir string = "~/.ssh"
+	// The following are joined with userSshConfDir.
+	UserSshConfFile string = "config"
+	UserEd25519File string = "id_ed25519"
+	UserRsaFile     string = "id_rsa"
+)
--- a/sshkeys/const.go
+++ b/sshkeys/const.go
@ -43,7 +43,7 @@ const (
 	CipherAes256Ctr string = "aes256-ctr"
 )

-var allowed_ciphers = [...]string{CipherNull, CipherAes256Ctr}
+var allowedCiphers = [...]string{CipherNull, CipherAes256Ctr}

 // Key types.
 const (
@ -51,7 +51,7 @@ const (
 	KeyRsa     string = "ssh-rsa"
 )

-var allowed_keytypes = [...]string{KeyEd25519, KeyRsa}
+var allowedKeytypes = [...]string{KeyEd25519, KeyRsa}

 // KDF names. I believe only bcrypt is supported upstream currently.
 const (
@ -59,7 +59,7 @@ const (
 	KdfBcrypt string = "bcrypt"
 )

-var allowed_kdfnames = [...]string{KdfNull, KdfBcrypt}
+var allowedKdfnames = [...]string{KdfNull, KdfBcrypt}

 // Key lengths.
 const (
--- a/sshkeys/crypt.go
+++ b/sshkeys/crypt.go
@ -1,12 +1,30 @@
+/*
+   SSHSecure - a program to harden OpenSSH from defaults
+   Copyright (C) 2020  Brent Saner
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation, either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
 package sshkeys

 import (
-	`crypto/aes`
-	`crypto/cipher`
-	`errors`
+	"crypto/aes"
+	"crypto/cipher"
+	"errors"

 	// `golang.org/x/crypto/ssh/internal/bcrypt_pbkdf` Golang doesn't let you import "internal" libs. Fine. Lame language.
-	`github.com/dchest/bcrypt_pbkdf`
+	"github.com/dchest/bcrypt_pbkdf"
 )

 func (k *EncryptedSSHKeyV1) setCrypt() error {
@ -22,6 +40,7 @@ func (k *EncryptedSSHKeyV1) setCrypt() error {
 }

 func (k *EncryptedSSHKeyV1) setCipher() error {
+	var err error
 	switch k.CipherName {
 	case CipherAes256Ctr:
 		if k.Crypt.Cipher, err = aes.NewCipher(k.Crypt.PrivateKey); err != nil {
@ -37,14 +56,15 @@ func (k *EncryptedSSHKeyV1) setCipher() error {
 }

 func (k *EncryptedSSHKeyV1) setKDF() error {
+	var err error
 	// Upstream only currently supports bcrypt_pbkdf ("bcrypt").
 	// This should always eval to true, but is here for future planning in case other KDF are implemented.
 	switch k.KDFName {
 	case KdfBcrypt:
 		if k.Crypt.CryptKey, err = bcrypt_pbkdf.Key(k.Passphrase,
-													k.KDFOpts.Salt,
-													int(k.KDFOpts.Rounds),
-													kdfKeyLen + len(k.KDFOpts.Salt),
+			k.KDFOpts.Salt,
+			int(k.KDFOpts.Rounds),
+			kdfKeyLen+len(k.KDFOpts.Salt),
 		); err != nil {
 			return err
 		} else {
@ -54,4 +74,5 @@ func (k *EncryptedSSHKeyV1) setKDF() error {
 	default:
 		return errors.New("could not find KDF")
 	}
-}
+	return nil
+}
--- a/sshkeys/func.go
+++ b/sshkeys/func.go
@ -22,7 +22,6 @@ import (
 	"bytes"
 	"crypto/rand"
 	"errors"
-	"fmt"

 	"r00t2.io/sshsecure/sharedconsts"
 )
@ -34,19 +33,19 @@ func (k *EncryptedSSHKeyV1) validate() error {
 	var validCipher bool
 	var validKDF bool
 	var validKT bool
-	for _, v := range allowed_ciphers {
+	for _, v := range allowedCiphers {
 		if v == k.CipherName {
 			validCipher = true
 			break
 		}
 	}
-	for _, v := range allowed_kdfnames {
+	for _, v := range allowedKdfnames {
 		if v == k.KDFName {
 			validKDF = true
 			break
 		}
 	}
-	for _, v := range allowed_keytypes {
+	for _, v := range allowedKeytypes {
 		if v == k.DefKeyType {
 			validKT = true
 		}
@ -107,7 +106,7 @@ func (k *EncryptedSSHKeyV1) Generate(force bool) error {
 		return errors.New("unknown key type; could not generate private/public keypair")
 	}
 	k.Keys = append(k.Keys, pk)
-	// We also need an encrypter/decrypter since this is an encrypted key.
+	// We also need an encryptor/decryptor since this is an encrypted key.
 	if err := k.setCrypt(); err != nil {
 		return err
 	}
@ -120,7 +119,7 @@ func (k *EncryptedSSHKeyV1) Generate(force bool) error {

 func (k *SSHKeyV1) validate() error {
 	var validKT bool
-	for _, v := range allowed_keytypes {
+	for _, v := range allowedKeytypes {
 		if v == k.DefKeyType {
 			validKT = true
 		}
@ -143,7 +142,7 @@ func (k *SSHKeyV1) Generate(force bool) error {
 	// Currently, OpenSSH has an option for multiple private keys. However, it is hardcoded to 1.
 	// If multiple key support is added in the future, will need to re-tool how I do this, perhaps, in the future. TODO.
 	pk := SSHPrivKey{
-		Comment: fmt.Sprintf("Autogenerated via SSHSecure (%v)", projUrl),
+		Comment: sharedconsts.IDCmnt,
 	}
 	pk.Checksum = make([]byte, 4)
 	if _, err := rand.Read(pk.Checksum); err != nil {
--- a/sshkeys/main.go
+++ b/sshkeys/main.go
@ -1,23 +0,0 @@
-/*
-   SSHSecure - a program to harden OpenSSH from defaults
-   Copyright (C) 2020  Brent Saner
-
-   This program is free software: you can redistribute it and/or modify
-   it under the terms of the GNU General Public License as published by
-   the Free Software Foundation, either version 3 of the License, or
-   (at your option) any later version.
-
-   This program is distributed in the hope that it will be useful,
-   but WITHOUT ANY WARRANTY; without even the implied warranty of
-   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-   GNU General Public License for more details.
-
-   You should have received a copy of the GNU General Public License
-   along with this program.  If not, see <https://www.gnu.org/licenses/>.
-*/
-
-package sshkeys
-
-func main() {
-
-}
--- a/utils/files.go
+++ b/utils/files.go
@ -0,0 +1,172 @@
+/*
+   SSHSecure - a program to harden OpenSSH from defaults
+   Copyright (C) 2020  Brent Saner
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation, either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
+package utils
+
+import (
+	"encoding/gob"
+	"errors"
+	"fmt"
+	"os"
+	gopath "path"
+	"path/filepath"
+	"time"
+
+	"r00t2.io/sysutils/paths"
+
+	"r00t2.io/sshsecure/sharedconsts"
+)
+
+func backupWrite(path string, data []byte, system bool, force bool) error {
+	var err error
+	var uid int
+	var gid int
+	var running bool
+	var runningInfo runInfo
+	var curInfo runInfo
+	uid, gid, err = getPerms(system)
+	if err != nil {
+		return err
+	}
+	if err = paths.RealPath(&path); err != nil {
+		return err
+	}
+	curInfo = getInfo()
+	parent := filepath.Dir(path)
+	parentExists, err := paths.RealPathExists(&parent)
+	infoFile := gopath.Join(
+		parent,
+		fmt.Sprintf(".%v.gob",
+			filepath.Base(path),
+		))
+	if err = paths.MakeDirIfNotExist(&parent); err != nil {
+		return err
+	}
+	exists, err := paths.RealPathExists(&path)
+	if err != nil {
+		return err
+	} else if !parentExists {
+		// It exists *now*, but it's a new dir. We set perms thusly.
+		os.Chmod(parent, 0700)
+	}
+	if gobExists, err := paths.RealPathExists(&infoFile); err != nil {
+		return err
+	} else if gobExists && !force {
+		return nil // Don't go any further; the file was already generated.
+	}
+	running, runningInfo, err = isRunning()
+	if err != nil {
+		return err
+	}
+	if exists && running {
+		e := fmt.Sprintf(
+			"refusing to write to %v; another instance of program is currently running with PID %v started at %v",
+			path, runningInfo.Pid, runningInfo.TimeStarted)
+		return errors.New(e)
+	} else if exists && !running {
+		newName := fmt.Sprintf("%v.bak.%d", path, curInfo.TimeStarted.Unix())
+		if err = os.Rename(path, newName); err != nil {
+			return err
+		}
+	}
+	// FINALLY. The business end.
+	w, err := os.Create(path)
+	if err != nil {
+		return err
+	}
+	gobFile, err := os.Create(infoFile)
+	if err != nil {
+		return err
+	}
+	g := gob.NewEncoder(gobFile)
+	defer w.Close()
+	defer gobFile.Close()
+	if err = w.Chmod(0600); err != nil {
+		return err
+	}
+	if err = w.Chown(uid, gid); err != nil {
+		return err
+	}
+	if _, err = w.Write(data); err != nil {
+		return err
+	}
+	if err = gobFile.Chmod(0600); err != nil {
+		return err
+	}
+	if err = gobFile.Chown(uid, gid); err != nil {
+		return err
+	}
+	if err = g.Encode(curInfo); err != nil {
+		return err
+	}
+	return nil
+}
+
+func getInfo() runInfo {
+	curInfo := runInfo{
+		TimeStarted: getTime(),
+		Pid:         getPid(),
+	}
+	return curInfo
+}
+
+func getPid() int {
+	return os.Getpid()
+}
+
+func getPerms(system bool) (int, int, error) {
+	var uid int
+	var gid int
+	if system {
+		if os.Geteuid() != 0 {
+			return 0, 0, errors.New("cannot create system file without root permissions")
+		}
+		uid = 0
+		gid = 0
+	} else {
+		uid = os.Geteuid()
+		gid = os.Getegid()
+	}
+	return uid, gid, nil
+}
+
+func getTime() time.Time {
+	return time.Now()
+}
+
+func isRunning() (bool, runInfo, error) {
+	curInfo := getInfo()
+	var fileInfo runInfo
+	lckFile := sharedconsts.LockFile
+	exists, _ := paths.RealPathExists(&lckFile)
+	if !exists {
+		// This should never happen. If it does, I goofed the locking (or it's not invoked from a shell).
+		return false, fileInfo, errors.New("*grabs shotgun* computer's haunted")
+	}
+	reader, err := os.Open(lckFile)
+	if err != nil {
+		return false, fileInfo, err
+	}
+	defer reader.Close()
+	gobDecoder := gob.NewDecoder(reader)
+	gobDecoder.Decode(&fileInfo)
+	if fileInfo != curInfo {
+		return true, fileInfo, nil
+	}
+	return false, fileInfo, nil
+}
--- a/utils/struct.go
+++ b/utils/struct.go
@ -0,0 +1,10 @@
+package utils
+
+import (
+	"time"
+)
+
+type runInfo struct {
+	TimeStarted time.Time
+	Pid         int
+}