Troubleshooting "git send-email" problemsEdit

While git send-email itself is a fairly simple, conservatively-written program, it is written in Perl and depends on a number of CPAN modules and that in turn makes it fairly brittle and sensitive to changes in the system. In particular, if you move outside of the most basic usage patterns and start wanting to use things like SMTP authentication and SSL then you’re more likely to run into problems. For example, see "Installing Net::SMTP::SSL for sending patches with Git over secure SMTP", which describes the problems I had when first trying to get it to work.

It’s been a while since I submitted any patches via git send-email, and since then Git itself has gone through many updates, as has my operating system (Mac OS X) and the CPAN has been in constant churn. After an initial, successful invocation using the --dry-run switch, I tried the real thing, and I guess it’s not surprising that it didn’t work:

...
(body) Adding cc: Wincent Colaiuta <win@wincent.com> from line 'Signed-off-by: Wincent Colaiuta <win@wincent.com>'
Use of uninitialized value in concatenation (.) or string at /System/Library/Perl/5.8.8/darwin-thread-multi-2level/Scalar/Util.pm line 30.
 is only avaliable with the XS version at /Library/Perl/5.8.8/IO/Socket/SSL.pm line 30
BEGIN failed--compilation aborted at /Library/Perl/5.8.8/IO/Socket/SSL.pm line 30.
Compilation failed in require at /Library/Perl/5.8.8/Net/SMTP/SSL.pm line 8.
BEGIN failed--compilation aborted at /Library/Perl/5.8.8/Net/SMTP/SSL.pm line 8.
Compilation failed in require at /usr/local/libexec/git-core/git-send-email line 859.

My first trouble-shooting technique was seeing if CPAN updates – chosen based on Google searches and module names appearing in error messages – would fix the problem, and fairly consistently with my previous experience with CPAN, it proved to be a broken, brittle, wonky stack of teetering shards:

  • cpan Net::SMTP::SSL: "Net::SMTP::SSL is up to date (1.01)."
  • cpan CPAN: fails.
  • cpan Scalar::Util: "Scalar::Util is up to date (1.19)."
  • cpan IO:Socket::SSL: fails.
  • cpan ExtUtils::F77: fails.
  • cpan ExtUtils::XSBuilder: works.
  • cpan Scalar::List::Utils: not found.
  • cpan Archive::Zip: fails.
  • cpan Compress::Zlib: fails.
  • cpan List::Utils: not found.

In the end, the only thing that would make git send-email work was to manually install Scalar::List::Utils after grabbing it manually from http://search.cpan.org/dist/Scalar-List-Utils/:

wget http://search.cpan.org/CPAN/authors/id/G/GB/GBARR/Scalar-List-Utils-1.19.tar.gz
tar xzvf Scalar-List-Utils-1.19.tar.gz
cd Scalar-List-Utils-1.19
perl Makefile.PL
make
make test
make install

That mostly fixed the problem:

...
(body) Adding cc: Wincent Colaiuta <win@wincent.com> from line 'Signed-off-by: Wincent Colaiuta <win@wincent.com>'
5.7.0 authentication failed

So at this point it looks like the breakage wasn’t caused by any changes to git send-email itself, nor by any manual manipulation of installed CPAN modules on my system (I explicitly avoid touching that wobbly house of cards unless really forced to). My prime suspect here is breakage in the Apple-provided Scalar::Util module installed at /System/Library/Perl/5.8.8/darwin-thread-multi-2level/Scalar/Util.pm.

The next step was to find out why authentication was failing. Before getting into true debug mode, I decided to have some more "fun" with CPAN:

  • cpan IO:Socket::SSL: still fails.
  • cpan Net::SSLeay: works.
  • cpan IO:Socket::SSL: still fails.
  • cpan IO::Socket::INET: works.
  • cpan Net::IDN::Encode: not available.
  • cpan Net::LibIDN: fails.
  • cpan IO:Socket::SSL: still fails.

So time to see what’s going on using a debugging script:

#!/usr/bin/env perl
use warnings;
use strict;
use Net::SMTP::SSL;
$IO::Socket::SSL::DEBUG = 1;
my $smtp = Net::SMTP::SSL->new('wincent.com', Port => 465, Debug => 1,) or die "didn't work";
my $auth = $smtp->auth('username', 'passphrase') or die $smtp->message;

Here is the relevant snippet of the output:

Net::SMTP::SSL>>> Net::SMTP::SSL(1.01)
Net::SMTP::SSL>>>   IO::Socket::SSL(1.12)
Net::SMTP::SSL>>>     IO::Socket::INET(1.31)
Net::SMTP::SSL>>>       IO::Socket(1.30)
Net::SMTP::SSL>>>         IO::Handle(1.27)
Net::SMTP::SSL>>>           Exporter(5.58)
Net::SMTP::SSL>>>   Net::Cmd(2.29)
Net::SMTP::SSL=GLOB(0x8a0110)<<< 220 wincent1.inetu.net ESMTP Sendmail 8.13.8/8.13.8; Wed, 25 Mar 2009 14:08:48 -0400
Net::SMTP::SSL=GLOB(0x8a0110)>>> EHLO localhost.localdomain
Net::SMTP::SSL=GLOB(0x8a0110)<<< 250-wincent1.inetu.net Hello 179.pool85-53-16.dynamic.orange.es [85.53.16.179], pleased to meet you
Net::SMTP::SSL=GLOB(0x8a0110)<<< 250-ENHANCEDSTATUSCODES
Net::SMTP::SSL=GLOB(0x8a0110)<<< 250-PIPELINING
Net::SMTP::SSL=GLOB(0x8a0110)<<< 250-8BITMIME
Net::SMTP::SSL=GLOB(0x8a0110)<<< 250-SIZE
Net::SMTP::SSL=GLOB(0x8a0110)<<< 250-DSN
Net::SMTP::SSL=GLOB(0x8a0110)<<< 250-ETRN
Net::SMTP::SSL=GLOB(0x8a0110)<<< 250-AUTH DIGEST-MD5 CRAM-MD5 LOGIN PLAIN
Net::SMTP::SSL=GLOB(0x8a0110)<<< 250-DELIVERBY
Net::SMTP::SSL=GLOB(0x8a0110)<<< 250 HELP
Net::SMTP::SSL=GLOB(0x8a0110)>>> AUTH DIGEST-MD5

So here we see it’s choosing the DIGEST-MD5 authentication method. A quick(?) Google search reveals the likely cause of the problem:

If you want to use DIGEST-MD5 or CRAM-MD5 and it doesn’t work despite the previous check, make sure that sasldb actually contains passwords for those mechanism. This can be done by looking at its content (using strings or od -c) and checking that the names of those mechanisms appear in the file.

Quickly disable those authentication methods with a quick cd /etc/mail && vim sendmail.mc && make && service sendmail restart, and sure enough, the debugging script works and so does git send-email.

The page I’ve already linked to above contains instructions on how to set up the sasldb or sasldb2 password file if you want to offer the DIGEST-MD5 and CRAM-MD5 methods.

See also