On Sun, 2018-10-21 at 08:57 +0900, Junio C Hamano wrote:
> Michał Górny <mgorny@xxxxxxxxxx> writes:
>
> > GnuPG supports creating signatures consisting of multiple signature
> > packets. If such a signature is verified, it outputs all the status
> > messages for each signature separately. However, git currently does not
> > account for such scenario and gets terribly confused over getting
> > multiple *SIG statuses.
> >
> > For example, if a malicious party alters a signed commit and appends
> > a new untrusted signature, git is going to ignore the original bad
> > signature and report untrusted commit instead. However, %GK and %GS
> > format strings may still expand to the data corresponding
> > to the original signature, potentially tricking the scripts into
> > trusting the malicious commit.
> >
> > Given that the use of multiple signatures is quite rare, git does not
> > support creating them without jumping through a few hoops, and finally
> > supporting them properly would require extensive API improvement, it
> > seems reasonable to just reject them at the moment.
> >
> > Signed-off-by: Michał Górny <mgorny@xxxxxxxxxx>
> > ---
> > gpg-interface.c | 90 +++++++++++++++++++++++++++-------------
> > t/t7510-signed-commit.sh | 26 ++++++++++++
> > 2 files changed, 87 insertions(+), 29 deletions(-)
> >
> > Changes in v4:
> > * switched to using skip_prefix(),
> > * renamed the variable to seen_exclusive_status,
> > * made the loop terminate early on first duplicate status seen.
>
> Thanks for sticking to the topic and polishing it further. Looks
> very good.
>
> Will replace.
>
> > + int seen_exclusive_status = 0;
> > +
> > + /* Iterate over all lines */
> > + for (line = buf; *line; line = strchrnul(line+1, '\n')) {
> > + while (*line == '\n')
> > + line++;
> > + /* Skip lines that don't start with GNUPG status */
> > + if (!skip_prefix(line, "[GNUPG:] ", &line))
> > + continue;
> > +
> > + /* Iterate over all search strings */
> > + for (i = 0; i < ARRAY_SIZE(sigcheck_gpg_status); i++) {
> > + if (skip_prefix(line, sigcheck_gpg_status[i].check, &line)) {
> > + if (sigcheck_gpg_status[i].flags & GPG_STATUS_EXCLUSIVE) {
> > + if (++seen_exclusive_status > 1)
> > + goto found_duplicate_status;
>
> Very minor point but by not using pre-increment, i.e.
>
> if (seen_exclusive_status++)
> goto found_duplicate_status;
>
> you can use the expression as a "have we already seen?" boolean,
> whic may probably be more idiomatic.
>
> The patch is good in the way written as-is, and this is so minor
> that it is not worth rerolling to only update this part.
>
Sure, thanks. For the record, I've been taught to use pre-increment
whenever possible to avoid copying the variable but I suppose it doesn't
really matter here. Just a habit.
I'll start working on my next ideas once this is merged and I rebase.
--
Best regards,
Michał Górny
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