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(define-module (email-key-rotation dkim)
#:use-module ((email-key-rotation openssl) #:prefix openssl:)
#:use-module ((email-key-rotation dns) #:prefix dns:)
#:use-module (web uri)
#:use-module (web request)
#:use-module (web response)
#:use-module (web client)
#:use-module (json)
#:use-module (ice-9 exceptions)
#:use-module (ice-9 match)
#:use-module (ice-9 rdelim)
#:use-module (ice-9 i18n)
#:use-module (srfi srfi-9 gnu)
#:use-module (sxml match)
#:export (<key>
make-key
key?
current-selector
current-private-key
expired-private-key
sxml->key
key->sxml
initialize
rotate
write-private-key
write-current-selector
dns-records)
#:declarative? #t)
(define (G_ msg) (gettext msg "email-key-rotation"))
(define-immutable-record-type <key>
(make-key current-selector next-selectors current-private-key expired-private-key)
key?
(current-selector current-selector set-current-selector)
(next-selectors next-selectors set-next-selectors)
(current-private-key current-private-key set-current-private-key)
(expired-private-key expired-private-key set-expired-private-key))
(define (sxml->key sxml)
(with-exception-handler
(lambda (exn)
(raise-exception
(make-exception
(make-error)
(make-exception-with-origin 'sxml->key)
(make-exception-with-irritants (list sxml))
(make-exception-with-message
(G_ "cannot read the XML fragment as a key."))
exn)))
(lambda ()
(sxml-match
sxml
;; Guile removes newlines in attributes, so we preserve them by
;; saving the keys as uri-encoded strings.
((https://planete-kraus.eu/ns/email-key-rotation:key
(@ (current-selector ,current-selector)
(current-private-key ,current-private-key-encoded)
(expired-private-key ,expired-private-key-encoded))
(https://planete-kraus.eu/ns/email-key-rotation:next-selector
(@ (name ,next-selectors))) ...)
(make-key (string->symbol current-selector)
(map string->symbol next-selectors)
(uri-decode current-private-key-encoded)
(uri-decode expired-private-key-encoded)))
((https://planete-kraus.eu/ns/email-key-rotation:key
(@ (current-selector ,current-selector)
(current-private-key ,current-private-key-encoded))
(https://planete-kraus.eu/ns/email-key-rotation:next-selector
(@ (name ,next-selectors))) ...)
(make-key (string->symbol current-selector)
(map string->symbol next-selectors)
(uri-decode current-private-key-encoded)
#f))))))
(define (key->sxml key)
(with-exception-handler
(lambda (exn)
(raise-exception
(make-exception
(make-exception-with-origin 'key->sxml)
(make-exception-with-irritants (list key))
(make-exception-with-message
(G_ "when converting a DKIM key to SXML:"))
exn)))
(lambda ()
(match key
(($ <key> current-selector next-selectors current-private-key expired-private-key)
(let ((current-selector (symbol->string current-selector))
(next-selectors
(map
(lambda (s)
`(next-selector (@ (name ,(symbol->string s)))))
next-selectors)))
`(key (@ (current-selector ,current-selector)
(current-private-key
,(uri-encode current-private-key))
,@(if expired-private-key
`((expired-private-key
,(uri-encode expired-private-key)))
'()))
,@next-selectors)))))))
(define (initialize selectors)
(with-exception-handler
(lambda (exn)
(raise-exception
(make-exception
(make-exception-with-origin 'initialize)
(make-exception-with-irritants (list selectors))
(make-exception-with-message
(G_ "when initializing a new DKIM key:"))
exn)))
(lambda ()
(make-key (car selectors)
(cdr selectors)
(openssl:generate-key 2048)
#f))))
(define (rotate key)
(with-exception-handler
(lambda (exn)
(raise-exception
(make-exception
(make-exception-with-origin 'rotate)
(make-exception-with-irritants (list key))
(make-exception-with-message
(G_ "when rotating a DKIM key:"))
exn)))
(lambda ()
(match key
(($ <key> current-selector next-selectors current-private-key expired-private-key)
(make-key (car next-selectors)
`(,@(cdr next-selectors) ,current-selector)
(openssl:generate-key 2048)
current-private-key))))))
(define* (write-current-selector key #:optional (port (current-output-port)))
(with-exception-handler
(lambda (exn)
(raise-exception
(make-exception
(make-exception-with-origin 'write-current-selector)
(make-exception-with-irritants (list key port))
(make-exception-with-message
(G_ "when writing the DKIM selector to file:"))
exn)))
(lambda ()
(seek port 0 SEEK_SET)
(format port "~a\n" (current-selector key))
(truncate-file port))))
(define* (write-private-key key #:optional (port (current-output-port)))
(with-exception-handler
(lambda (exn)
(raise-exception
(make-exception
(make-exception-with-origin 'write-private-key)
(make-exception-with-irritants (list key port))
(make-exception-with-message
(G_ "when saving a private DKIM key:"))
exn)))
(lambda ()
(unless (port? port)
(raise-exception
(make-exception
(make-error)
(make-exception-with-message
(G_ "the port to write must be a port object.")))))
(when (file-port? port)
(chmod port #o600))
(seek port 0 SEEK_SET)
(match key
(($ <key> _ _ key _)
(begin
(display key port)
(truncate-file port)))))))
(define (public-key->dkim-record public-key)
;; Discard the first and last lines and remove newlines
(call-with-output-string
(lambda (out)
(format out "v=DKIM1; k=rsa; t=s; p=")
(call-with-input-string public-key
(lambda (port)
(let collect-lines ((carry #f)
(first? #t))
(let ((next (read-line port)))
(unless (eof-object? next)
(when carry
(display carry out))
(collect-lines (if first? #f next)
#f)))))))))
(define (private-key->dkim-record key)
(public-key->dkim-record
(openssl:private-key->public-key key)))
(define optional-private-key->dkim-record
(match-lambda
(#f "v=DKIM1; k=rsa; t=s; p=deleted")
(key
(private-key->dkim-record key))))
(define (dns-records key)
(with-exception-handler
(lambda (exn)
(raise-exception
(make-exception
(make-exception-with-origin 'dns-records)
(make-exception-with-irritants (list key))
(make-exception-with-message
(G_ "when computing the DKIM DNS records:"))
exn)))
(lambda ()
(match key
(($ <key>
(= symbol->string current-record)
(= reverse
(= car
(= symbol->string previous-record)))
(= private-key->dkim-record current)
(= optional-private-key->dkim-record expired))
(list
(dns:make-dns-record
(string-append current-record "._domainkey")
"TXT"
current)
(dns:make-dns-record
(string-append previous-record "._domainkey")
"TXT"
expired)))))))
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