Problem viewing smime encoded messages in gnus

[Alex Bennée]

Hi,

I'm not sure if this is a mu4e problem or a higher level issue with epg.
Someone sent me a message from a MS Exchange server which I can't open
properly. I get the following backtrace:

  Debugger entered--Lisp error: (wrong-type-argument epg-signature nil)
    mm-view-pkcs7-verify((#<buffer  *mm*-126284> ("application/pkcs7-mime" 
(name . "smime.p7m") (smime-type . "signed-data")) base64 nil ("attachment" 
(filename . "smime.p7m")) nil nil nil))
    mm-view-pkcs7((#<buffer  *mm*-126284> ("application/pkcs7-mime" (name . 
"smime.p7m") (smime-type . "signed-data")) base64 nil ("attachment" (filename . 
"smime.p7m")) nil nil nil) "redacted@email.addr")
    mm-possibly-verify-or-decrypt((#<buffer  *mm*-126284> 
("application/pkcs7-mime" (name . "smime.p7m") (smime-type . "signed-data")) 
base64 nil ("attachment" (filename . "smime.p7m")) nil nil nil) 
("application/pkcs7-mime" (name . "smime.p7m") (smime-type . "signed-data")) 
"redacted@email.addr")
    mm-dissect-buffer(nil t)
    gnus-display-mime(nil)
    #f(compiled-function (&optional ihandles) #<bytecode 0xc45d85df684117e>)()
    gnus-article-prepare-display()
    ...
    <identifying info redacted>
    ...

If I trace through epg-verify-string I end up with the following
messages:

  Result: #s(epg-context :protocol CMS :program "/usr/bin/gpgsm" 
:home-directory nil :armor nil :textmode nil :include-certs nil 
:cipher-algorithm nil :digest-algorithm nil :compress-algorithm nil 
:passphrase-callback (epa-passphrase-callback-function) :progress-callback nil 
:edit-callback nil :signers nil :sender nil :sig-notations nil :process 
#<process epg> :output-file "/tmp/epg-outputTXUCI2" :result nil :operation 
verify :pinentry-mode nil :error-output "" :error-buffer #<buffer  *epg-error*>)

  Result: "gpgsm: certificate not found\n"
  Continue...
  or: Wrong type argument: epg-signature, nil

So I can't work out is this a configuration problem with gpgsm or
something failing when extracting the message. The message has very
verbose headers but the message body is just a block of uuencoded data.
I don't think it's encrypted because gmail can display the message fine
although it did trip up on my Roundcube view as well.

Any clues how to further debug whats going on?

Running:
  Debian Buster (x86_64)
  "GNU Emacs 28.0.90 (build 4, x86_64-pc-linux-gnu, X toolkit, cairo version 
1.16.0, Xaw3d scroll bars) of 2021-12-13"
  mu+mu4e @ current HEAD (3001c78)

-- 
Alex Bennée