[PATCH v3] send-email: auth plain/login fix

git send-email was not authenticating properly when communicating over
TLS with a server supporting only AUTH PLAIN and AUTH LOGIN. This is
e.g. the standard server setup under debian with exim4 and probably
everywhere where system accounts are used.

The problem (only?) exists when libauthen-sasl-cyrus-perl
(Authen::SASL::Cyrus) is installed. Importing Authen::SASL::Perl
makes Authen::SASL use the perl implementation which works
better.

The solution is based on this forum thread:
http://www.perlmonks.org/?node_id=904354.

This patch is tested by sending it :)

Before:
Net::SMTP>>> Net::SMTP(2.31)
Net::SMTP>>>   Net::Cmd(2.29)
Net::SMTP>>>     Exporter(5.64_01)
Net::SMTP>>>   IO::Socket::INET(1.31)
Net::SMTP>>>     IO::Socket(1.31)
Net::SMTP>>>       IO::Handle(1.28)
...
Net::SMTP=GLOB(0x238f668)>>> STARTTLS
Net::SMTP=GLOB(0x238f668)<<< 220 2.0.0 Ready to start TLS
Net::SMTP::SSL=GLOB(0x238f668)>>> EHLO localhost.localdomain
Net::SMTP::SSL=GLOB(0x238f668)<<< 250-yyy.yyy.yyy Hello xxx.xxx [xxx.xxx.xxx.xxx], pleased to meet you
Net::SMTP::SSL=GLOB(0x238f668)<<< 250-ENHANCEDSTATUSCODES
Net::SMTP::SSL=GLOB(0x238f668)<<< 250-PIPELINING
Net::SMTP::SSL=GLOB(0x238f668)<<< 250-8BITMIME
Net::SMTP::SSL=GLOB(0x238f668)<<< 250-SIZE 80000000
Net::SMTP::SSL=GLOB(0x238f668)<<< 250-DSN
Net::SMTP::SSL=GLOB(0x238f668)<<< 250-AUTH=LOGIN PLAIN
Net::SMTP::SSL=GLOB(0x238f668)<<< 250-AUTH LOGIN PLAIN
Net::SMTP::SSL=GLOB(0x238f668)<<< 250-DELIVERBY
Net::SMTP::SSL=GLOB(0x238f668)<<< 250 HELP
Password:
Net::SMTP::SSL=GLOB(0x238f668)>>> AUTH
Net::SMTP::SSL=GLOB(0x238f668)<<< 501 5.5.2 AUTH mechanism must be specified
5.5.2 AUTH mechanism must be specified

After:
Net::SMTP=GLOB(0x1ac4a60)>>> STARTTLS
Net::SMTP=GLOB(0x1ac4a60)<<< 220 2.0.0 Ready to start TLS
Net::SMTP::SSL=GLOB(0x1ac4a60)>>> EHLO localhost.localdomain
Net::SMTP::SSL=GLOB(0x1ac4a60)<<< 250-yyy.yyy.yyy Hello xxx.xxx [xxx.xxx.xxx.xxx], pleased to meet you
Net::SMTP::SSL=GLOB(0x1ac4a60)<<< 250-ENHANCEDSTATUSCODES
Net::SMTP::SSL=GLOB(0x1ac4a60)<<< 250-PIPELINING
Net::SMTP::SSL=GLOB(0x1ac4a60)<<< 250-8BITMIME
Net::SMTP::SSL=GLOB(0x1ac4a60)<<< 250-SIZE 80000000
Net::SMTP::SSL=GLOB(0x1ac4a60)<<< 250-DSN
Net::SMTP::SSL=GLOB(0x1ac4a60)<<< 250-AUTH=LOGIN PLAIN
Net::SMTP::SSL=GLOB(0x1ac4a60)<<< 250-AUTH LOGIN PLAIN
Net::SMTP::SSL=GLOB(0x1ac4a60)<<< 250-DELIVERBY
Net::SMTP::SSL=GLOB(0x1ac4a60)<<< 250 HELP
Password:
Net::SMTP::SSL=GLOB(0x1ac4a60)>>> AUTH LOGIN
Net::SMTP::SSL=GLOB(0x1ac4a60)<<< 334 VXNlcm5hbWU6
Net::SMTP::SSL=GLOB(0x1ac4a60)>>> emJ5c3plaw==
Net::SMTP::SSL=GLOB(0x1ac4a60)<<< 334 UGFzc3dvcmQ6
Net::SMTP::SSL=GLOB(0x1ac4a60)>>> dGVzdA==
Net::SMTP::SSL=GLOB(0x1ac4a60)<<< 535 5.7.0 authentication failed
5.7.0 authentication failed

The password is incorrect in this snippet, but the protocol works correctly.

Signed-off-by: Zbigniew Jędrzejewski-Szmek <redacted>
---
v3:  - the import is performed only if it will be used, and failure is ignored

 git-send-email.perl |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)

diff --git a/git-send-email.perl b/git-send-email.perl
index 37dfbe7..dbc435a 100755
--- a/git-send-email.perl
+++ b/git-send-email.perl

@@ -1098,6 +1098,10 @@ X-Mailer: git-send-email $gitversion
 		}
 
 		if (defined $smtp_authuser) {
+			eval {
+				require Authen::SASL;
+				Authen::SASL->import(qw(Perl));
+			};
 
 			if (!defined $smtp_authpass) {
 

-- 
1.7.6