gnu: Add pep-engine.

* gnu/packages/pep.scm (fdik-libetpan, sequoia4pEp, pep-engine): New
  variables.

gnu/packages/pep.scm

@@ -19,9 +19,19 @@
 (define-module (gnu packages pep)
   #:use-module ((guix licenses) #:prefix license:)
   #:use-module (guix packages)
+  #:use-module (guix git-download)
   #:use-module (guix hg-download)
+  #:use-module (guix build-system gnu)
   #:use-module (guix build-system python)
   #:use-module (gnu packages)
+  #:use-module (gnu packages base)
+  #:use-module (gnu packages linux)
+  #:use-module (gnu packages mail) ; for libetpan
+  #:use-module (gnu packages nettle)
+  #:use-module (gnu packages pkg-config)
+  #:use-module (gnu packages sequoia)
+  #:use-module (gnu packages sqlite)
+  #:use-module (gnu packages tls)
   #:use-module (gnu packages xml))
 
 (define-public yml2
@@ -47,3 +57,99 @@ (define-public yml2
 your script and outputs to stdout, that usually is the terminal.  Your
 shell provides options to redirect the output into a pipe or a file.")
     (license license:gpl2)))
+
+(define fdik-libetpan
+  ;; pEp Engine requires libetpan with a set of patches that have not been
+  ;; upstreamed yet.
+  (let ((commit "210ba2b3b310b8b7a6ee4a4e35e50f7fa379643f") ; 2020-06-03
+        (checksum "00000nij3ray7nssvq0lzb352wmnab8ffzk7dgff2c68mvjbh1l6")
+        (revision "5"))
+   (package
+    (inherit libetpan)
+    (name "fdik-libetpan")
+    (version (string-append "1.6-" revision "." (string-take commit 8)))
+    (source
+     (origin
+       (inherit (package-source libetpan))
+       (method git-fetch)
+       (uri (git-reference
+             (url "https://github.com/fdik/libetpan")
+             (commit commit)))
+       (file-name (string-append name "-" version))
+       (sha256 (base32 checksum)))))))
+
+(define sequoia4pEp
+  ;; Currently pEp Engine requires sequoia in not-so-current version
+  (package/inherit sequoia
+    (name "sequoia")
+    (version "0.15.0-pEp")
+    (source
+     (origin
+       (method git-fetch)
+       (uri (git-reference
+             (url "https://gitlab.com/sequoia-pgp/sequoia.git")
+             (commit "0eb1b6cd846ea8c36b3dfdf01ec88383fc64f2fe")))
+       (sha256
+        (base32 "06dqs9whwp9lfibwp8dqm0aw4nm3s3v4jp2n4fz51zcvsld40nfh"))
+       (file-name (git-file-name name version))))))
+
+(define-public pep-engine
+  (package
+    (name "pep-engine")
+    (version "2.0.6")
+    (source
+     (origin
+       (method hg-fetch)
+       (uri (hg-reference
+             (url "https://pep.foundation/dev/repos/pEpEngine")
+             (changeset "ebb62ba262dd"))) ;; r4721
+       (file-name (string-append name "-" version "-checkout"))
+       (sha256
+        (base32 "0ljf79j4ng7l8w6pbdcrfzb4yk51zslypvq0n72ib1d7grqvnagi"))))
+    (build-system gnu-build-system)
+    (arguments
+     '(#:parallel-build? #f
+       #:phases
+       (modify-phases %standard-phases
+         (replace 'configure
+           ;; pEpEngie does not use autotools and configure,
+           ;; but a local.conf. We need to tweak the values there.
+           (lambda* (#:key inputs outputs #:allow-other-keys)
+             (let ((out (assoc-ref outputs "out"))
+                   (yml2 (assoc-ref inputs "yml2")))
+               (with-output-to-file "local.conf"
+                 (lambda ()
+                   (format #t "
+PREFIX=~a
+PER_MACHINE_DIRECTORY=${PREFIX}/share/pEp
+SYSTEM_DB=~a/share/pEp/system.db
+ASN1C=~a
+YML2_PATH=~a
+OPENPGP=SEQUOIA
+"
+                           out out (which "asn1c")
+                           (string-append yml2 "/bin"))))
+               #t)))
+         (delete 'check)
+         (add-after 'install 'install-db
+           (lambda _
+             (invoke "make" "-C" "db" "install"))))))
+    (native-inputs
+     `(("asn1c" ,asn1c) ; >= 0.9.27
+       ("pkg-config" ,pkg-config)
+       ("yml2" ,yml2)))
+    (inputs
+     `(("libetpan" ,fdik-libetpan)
+       ("libiconv" ,libiconv)
+       ("nettle" ,nettle)
+       ("openssl" ,openssl)
+       ("sequoia" ,sequoia4pEp)
+       ("sqlite3" ,sqlite)
+       ("util-linux" ,util-linux "lib"))) ;; uuid.h
+    (home-page "https://pep.foundation/")
+    (synopsis "Library for automatic key management and encryption of
+messages")
+    (description "The p≡p engine is the core part of p≡p (pretty Easy
+privacy).")
+    (license ;; code: GPL 3, docs: CC-BY-SA
+     (list license:gpl3 license:cc-by-sa3.0))))