Bug 878

Summary:	sudo segfaults when "Defaults mailerpath" is set in sudoers
Product:	Sudo	Reporter:	Kim Scarborough <kim>
Component:	Sudo	Assignee:	Todd C. Miller <Todd.Miller>
Status:	RESOLVED FIXED
Severity:	normal
Priority:	low
Version:	1.8.27
Hardware:	PC
OS:	Linux

Description Kim Scarborough 2019-04-18 12:31:33 MDT

I'm on Arch Linux. My sudoers include these lines:

Defaults mail_always
Defaults mailerpath=/usr/bin/sendmail

Whenever I execute a sudo command, it runs fine but no e-mail is sent. These lines appear in the system journal:

Apr 18 13:19:02 plankton kernel: sudo[590]: segfault at 0 ip 00007ff2c77b36e5 sp 00007ffc664bb8c8 error 4 in libc-2.28.so[7ff2c7676000+14b000]
Apr 18 13:19:02 plankton kernel: Code: 00 00 0f 1f 00 31 c0 c5 f8 77 c3 66 2e 0f 1f 84 00 00 00 00 00 f3 0f 1e fa 89 f9 48 89 fa c5 f9 ef c0 83 e1 3f 83 f9 20 77 2b <c5> fd 74 0f c5 fd d7 c1 85 c0 0f 85 eb 00 00 00 48 83 c7 20 83 e1

Please let me know what further information you need from me.

Comment 1 Kim Scarborough 2019-04-18 12:35:58 MDT

Possibly related: Arch upgraded glibc 2.28 last week. But I hadn't been running this configuration before today, so I can't tell you if it worked before. I tried downgrading glibc and sudo but I still get the error.

Comment 2 Todd C. Miller 2019-04-18 12:43:42 MDT

Do you have mailerflags set in sudoers as well?

Comment 3 Kim Scarborough 2019-04-18 12:47:16 MDT

No other mail-related commands in my sudoers. I can post the whole thing if you like, it's only a few lines.

Also, I tried changing the mailerpath to a script that just records the arguments to see how it was invoking sendmail. The script didn't execute at all, so it looks like this segfault is happening before the invocation.

Comment 4 Todd C. Miller 2019-04-19 10:02:11 MDT

Thanks, that is helpful.  I haven't been able to reproduce this on other Linux systems so I installed arch linux in a VM and can reproduce it there.  However, if I rebuild sudo from source the crash no longer occurs.

Comment 5 Todd C. Miller 2019-04-19 10:14:58 MDT

I see the problem.  Since sendmail was not detected during build, mailerflags was not set.  You can work around this by adding:

Defaults mailerflags="-t"

to sudoers.

I have committed a fix for the issue:
https://www.sudo.ws/repos/sudo/rev/6c57f5ddca54

Comment 6 Todd C. Miller 2019-10-14 10:35:21 MDT

Fixed in sudo 1.8.28