archive: Add '--generate-key'.

* guix/pk-crypto.scm (error-source, error-string): New procedures.
* guix/pki.scm (%private-key-file): New variable.
* guix/scripts/archive.scm (show-help): Document '--generate-key'.
  (%options): Add "generate-key".
  (generate-key-pair): New procedure.
  (guix-archive): Call 'generate-key' when OPTS contains a
  'generate-key' pair.
* doc/guix.texi (Setting Up the Daemon): Suggest generating a key pair.
  (Invoking guix archive): Document '--generate-key'.

1 files changed, 18 insertions, 0 deletions

diff --git a/guix/pk-crypto.scm b/guix/pk-crypto.scm
index d5b3eeb350..50f709418c 100644
--- a/guix/pk-crypto.scm
+++ b/guix/pk-crypto.scm
@@ -25,6 +25,8 @@
   #:use-module (rnrs bytevectors)
   #:use-module (ice-9 match)
   #:export (canonical-sexp?
+            error-source
+            error-string
             string->canonical-sexp
             canonical-sexp->string
             number->canonical-sexp
@@ -98,6 +100,22 @@
       (set-pointer-finalizer! ptr finalize-canonical-sexp!))
     sexp))
 
+(define error-source
+  (let* ((ptr  (libgcrypt-func "gcry_strsource"))
+         (proc (pointer->procedure '* ptr (list int))))
+    (lambda (err)
+      "Return the error source (a string) for ERR, an error code as thrown
+along with 'gcry-error'."
+      (pointer->string (proc err)))))
+
+(define error-string
+  (let* ((ptr  (libgcrypt-func "gcry_strerror"))
+         (proc (pointer->procedure '* ptr (list int))))
+    (lambda (err)
+      "Return the error description (a string) for ERR, an error code as
+thrown along with 'gcry-error'."
+      (pointer->string (proc err)))))
+
 (define string->canonical-sexp
   (let* ((ptr  (libgcrypt-func "gcry_sexp_new"))
          (proc (pointer->procedure int ptr `(* * ,size_t ,int))))