[pkg-gnupg-maint] Bug#847380: gnupg: gpg unusable with pipe -- 'Inappropriate ioctl for device'

[David Buckley]

Package: gnupg
Version: 2.1.16-2
Severity: important

Dear Maintainer,

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$ gpg -a -d < FILENAME
gpg: encrypted with 2048-bit ELG key, ID <SNIPPED>
gpg: public key decryption failed: Inappropriate ioctl for device
gpg: decryption failed: No secret key
$

This seems to be something to do with gpg-agent trying to use pinentry
and this conflicting with stdin being a pipe. If I force pinentry-curses
and pass a filename directly, I get a curses prompt for my password.

After entering the password, I can use a pipe as normal. I think older
gpg did whatever it is 'less' does in order to get terminal I/O without
trying to read it from stdin.

At the least, the error message is completely unhelpful.

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-- System Information:
Debian Release: stretch/sid
  APT prefers testing
  APT policy: (1000, 'testing'), (1, 'experimental')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 4.8.0-1-amd64 (SMP w/4 CPU cores)
Locale: LANG=en_GB.UTF-8, LC_CTYPE=en_GB.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)

Versions of packages gnupg depends on:
ii  gnupg-agent    2.1.16-2
ii  libassuan0     2.4.3-2
ii  libbz2-1.0     1.0.6-8
ii  libc6          2.24-7
ii  libgcrypt20    1.7.3-2
ii  libgpg-error0  1.25-1
ii  libksba8       1.3.5-2
ii  libreadline7   7.0-1
ii  libsqlite3-0   3.15.2-1
ii  zlib1g         1:1.2.8.dfsg-2+b3

Versions of packages gnupg recommends:
ii  dirmngr     2.1.16-2
ii  gnupg-l10n  2.1.16-2

Versions of packages gnupg suggests:
pn  parcimonie  <none>
pn  xloadimage  <none>

-- no debconf information