Re: [PATCH 5/7] Add support for gnupg < 1.4

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On Wed, Apr 5, 2017 at 3:04 PM, Tom G. Christensen <tgc@xxxxxxxxxxxxxxx> wrote:
> This adds an OLD_GNUPG define to the Makefile which when activated will
> ensure git does not use the --keyid-format argument when calling the
> 'gpg' program.
> This is consistent with how 'gpg' was used in git < 2.10.0 and slightly
> decreases security.

This changes the code Linus Torvalds added in b624a3e67f to mitigate
the evil32 project generating keys which looked the same for 32 bit
signatures.

I think this change makes sense, but the Makefile should have a
slightly scarier warning, something like:

"Define OLD_GNUPG if you need support for gnupg <1.4. Note that this
will cause git to only show the first 32 bits of PGP keys instead of
64, and there's a wide variety of brute-forced 32 bit keys in the wild
thanks to the evil32 project (https://evil32.com). Enabling this will
make GPG work old versions, but you might be fooled into accepting
malicious keys as a result".

> Signed-off-by: Tom G. Christensen <tgc@xxxxxxxxxxxxxxx>
> ---
>  Makefile        | 6 ++++++
>  gpg-interface.c | 2 ++
>  2 files changed, 8 insertions(+)
>
> diff --git a/Makefile b/Makefile
> index ca9f16d19..f8f585d21 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -386,6 +386,8 @@ all::
>  #
>  # to say "export LESS=FRX (and LV=-c) if the environment variable
>  # LESS (and LV) is not set, respectively".
> +#
> +# Define OLD_GNUPG if you need support for gnupg < 1.4.
>
>  GIT-VERSION-FILE: FORCE
>         @$(SHELL_PATH) ./GIT-VERSION-GEN
> @@ -1529,6 +1531,10 @@ ifndef PAGER_ENV
>  PAGER_ENV = LESS=FRX LV=-c
>  endif
>
> +ifdef OLD_GNUPG
> +       BASIC_CFLAGS += -DOLD_GNUPG
> +endif
> +
>  QUIET_SUBDIR0  = +$(MAKE) -C # space to separate -C and subdir
>  QUIET_SUBDIR1  =
>
> diff --git a/gpg-interface.c b/gpg-interface.c
> index e44cc27da..57f1ea792 100644
> --- a/gpg-interface.c
> +++ b/gpg-interface.c
> @@ -224,7 +224,9 @@ int verify_signed_buffer(const char *payload, size_t payload_size,
>         argv_array_pushl(&gpg.args,
>                          gpg_program,
>                          "--status-fd=1",
> +#ifndef OLD_GNUPG
>                          "--keyid-format=long",
> +#endif
>                          "--verify", temp.filename.buf, "-",
>                          NULL);
>
> --
> 2.12.2
>



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