[bug#48803] [PATCH] strongswan: provide a service definition and configuration interface.

[Domagoj Stolfa <ds815@gmx.com>]

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This commit adds a strongswan-service-type which allows the user to
start strongswan correctly on Guix. Without this, they would need to
manually write a strongswan.conf file and run it with

`STRONGSWAN_CONF=/path/to/strongswan.conf ipsec start`.

For now, we only support the legacy ipsec.conf/ipsec.secrets interface.
Because ipsec.conf depends on indentation and is a deprecated intreface,
we do not provide an EDSL to configure it, and we do not put the config
file in a Guile string (to avoid indentation issues). Similarly,
ipsec.secrets contains the users authentication token/passwords, and is
for security reasons transmitted separately from the configuration file.

This change allows the user to write something as follows in their
config:

```
    (service strongswan-service-type
	     (strongswan-configuration
	      (use-ipsec? #t)
	      (ipsec-conf "/config-files/ipsec.conf")
	      (ipsec-secrets "/config-files/ipsec.secrets")))
```

This will start the charon daemon and allow them to connect to their
VPNs configured in `/config-files/ipsec.conf`.
---
 gnu/services/vpn.scm | 128 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 128 insertions(+)

diff --git a/gnu/services/vpn.scm b/gnu/services/vpn.scm
index 2bcbf76727..e026f2aa58 100644
--- a/gnu/services/vpn.scm
+++ b/gnu/services/vpn.scm
@@ -4,6 +4,7 @@
 ;;; Copyright © 2017 Mathieu Othacehe <m.othacehe@gmail.com>
 ;;; Copyright © 2021 Guillaume Le Vaillant <glv@posteo.net>
 ;;; Copyright © 2021 Solene Rapenne <solene@perso.pw>
+;;; Copyright © 2021 Domagoj Stolfa <ds815@gmx.com>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -26,6 +27,7 @@
   #:use-module (gnu services shepherd)
   #:use-module (gnu system shadow)
   #:use-module (gnu packages admin)
+  #:use-module (gnu packages networking)
   #:use-module (gnu packages vpn)
   #:use-module (guix packages)
   #:use-module (guix records)
@@ -44,6 +46,9 @@
             generate-openvpn-client-documentation
             generate-openvpn-server-documentation
 
+            strongswan-configuration
+            strongswan-service-type
+
             wireguard-peer
             wireguard-peer?
             wireguard-peer-name
@@ -529,6 +534,129 @@ is truncated and rewritten every minute.")
      (openvpn-remote-configuration ,openvpn-remote-configuration-fields))
    'openvpn-client-configuration))
 
+;;;
+;;; Strongswan.
+;;;
+
+(define-record-type* <strongswan-configuration>
+  strongswan-configuration make-strongswan-configuration
+  strongswan-configuration?
+  (strongswan      strongswan-configuration-strongswan ;<package>
+                   (default strongswan))
+  (use-ipsec?      strongswan-configuration-use-ipsec? ;legacy interface
+                   (default #f))
+  (ipsec-conf      strongswan-configuration-ipsec-conf)
+  (ipsec-secrets   strongswan-configuration-ipsec-secrets))
+
+;; In the future, it might be worth implementing a record type to configure
+;; all of the plugins, but for *most* basic usecases, simply creating the
+;; files will be sufficient. Same is true of charon-plugins.
+(define strongswand-config-files
+  (list "charon" "charon-logging" "pki" "pool" "scepclient"
+        "swanctl" "tnc"))
+
+;; Plugins to load.
+(define charon-plugins
+  (list "aes" "aesni" "attr" "attr-sql" "chapoly" "cmac" "constraints"
+        "counters" "curl" "curve25519" "dhcp" "dnskey" "drbg" "eap-aka-3gpp"
+        "eap-aka" "eap-dynamic" "eap-identity" "eap-md5" "eap-mschapv2"
+        "eap-peap" "eap-radius" "eap-simaka-pseudonym" "eap-simaka-reauth"
+        "eap-simaka-sql" "eap-sim" "eap-sim-file" "eap-tls" "eap-tnc"
+        "eap-ttls" "ext-auth" "farp" "fips-prf" "gmp" "ha" "hmac"
+        "kernel-netlink" "led" "md4" "md5" "mgf1" "nonce" "openssl" "pem"
+        "pgp" "pkcs12" "pkcs1" "pkcs7" "pkcs8" "pubkey" "random" "rc2"
+        "resolve" "revocation" "sha1" "sha2" "socket-default" "soup" "sql"
+        "sqlite" "sshkey" "tnc-tnccs" "vici" "x509" "xauth-eap" "xauth-generic"
+        "xauth-noauth" "xauth-pam" "xcbc"))
+
+(define (strongswan-configuration-file config)
+  (match-record config <strongswan-configuration>
+    (strongswan use-ipsec? ipsec-conf ipsec-secrets)
+    (let* ((strongswan-dir
+            (computed-file
+             "strongswan.d"
+             #~(begin
+                 (mkdir #$output)
+                 ;; Create all of the configuration files in strongswan.d/*.conf
+                 (map (lambda (conf-file)
+                        (let* ((filename (string-append
+                                          #$output "/"
+                                          conf-file ".conf")))
+                          (call-with-output-file filename
+                            (lambda (port)
+                              (display
+                               "# Created by 'strongswan-service'\n"
+                               port)))))
+                      (list #$@strongswand-config-files))
+                 (mkdir (string-append #$output "/charon"))
+                 ;; And all of the strongswan.d/charon/*.conf files (plugins)
+                 (map (lambda (plugin)
+                        (let* ((filename (string-append
+                                          #$output "/charon/"
+                                          plugin ".conf")))
+                          (call-with-output-file filename
+                            (lambda (port)
+                              (format port "~a {
+  load = yes
+}"
+                                      plugin)))))
+                      (list #$@charon-plugins))))))
+      ;; Generate our strongswan.conf to reflect the user configuration.
+      (computed-file
+       "strongswan.conf"
+       #~(begin
+           (call-with-output-file #$output
+             (lambda (port)
+               (display "# Generated by 'strongswan-service'.\n" port)
+               (format port "charon {
+  load_modular = yes
+  plugins {
+    include ~a/charon/*.conf"
+                       #$strongswan-dir)
+               (if #$use-ipsec?
+                   (format port "
+    stroke {
+      load = yes
+      secrets_file = ~a
+    }
+  }
+}
+
+starter {
+  config_file = ~a
+}
+
+include ~a/*.conf"
+                           #$ipsec-secrets
+                           #$ipsec-conf
+                           #$strongswan-dir)
+                   (format port "
+  }
+}
+include ~a/*.conf"
+                           #$strongswan-dir)))))))))
+
+(define (strongswan-shepherd-service config)
+  (let* ((ipsec (file-append strongswan "/sbin/ipsec"))
+        (strongswan-conf-path (strongswan-configuration-file config)))
+    (list (shepherd-service
+           (requirement '(networking))
+           (provision '(strongswan))
+           (start #~(make-forkexec-constructor
+                     (list #$ipsec "start" "--nofork")
+                     #:environment-variables
+                     (list (string-append "STRONGSWAN_CONF="
+                                          #$strongswan-conf-path))))
+           (stop #~(make-kill-destructor))
+           (documentation "Start the charon daemon for IPsec VPN")))))
+
+(define strongswan-service-type
+  (service-type
+   (name 'strongswan)
+   (extensions
+    (list (service-extension shepherd-root-service-type
+                             strongswan-shepherd-service)))))
+
 ;;;
 ;;; Wireguard.
 ;;;
-- 
2.31.1


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