Operating system name and version: CentOS Linux release 7.2.1511 (Core)
Version of smsd: smstools-3.1.15-12.el7
Smsd installed from: package repository
Name and model of a modem / phone: Nokia C5-00
Interface: USB

Problem: GNOKII can open /dev/ttyACM0 but smstools cannot.

All commands executed as root.

[root@server /]# uname -a Linux server 3.10.0-327.10.1.el7.x86_64 #1 SMP Tue Feb 16 17:03:50 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux

SELinux enabled
[root@server /]# service smsd restart Restarting smsd (via systemctl): [ OK ]

SELinux is not complaining...
[root@server /]# ausearch -m avc -ts recent <no matches>

SMS Server Tools has problem opening /dev/ttyACM0
[root@server /]# tail /var/log/smsd/smsd.log 2016-04-01 18:49:57,2, smsd: Smsd mainprocess is awaiting the termination of all modem handlers. PID: 13850. 2016-04-01 18:49:57,2, smsd: Smsd mainprocess terminated. PID 13850, was started 16-04-01 18:24:55. 2016-04-01 18:49:57,2, smsd: Smsd v3.1.15 started. 2016-04-01 18:49:57,2, smsd: Running as smstools:smstools. 2016-04-01 18:49:57,7, smsd: Running startup_check (shell): /var/spool/sms/incoming/smsd_script.kvK1Eb /tmp/smsd_data.ZOTUxs 2016-04-01 18:49:57,7, smsd: Done: startup_check (shell), execution time 0 sec., status: 0 (0) 2016-04-01 18:49:57,4, smsd: File mode creation mask: 022 (0644, rw-r--r--). 2016-04-01 18:49:57,5, smsd: Outgoing file checker has started. PID: 15416. 2016-04-01 18:49:57,7, smsd: All PID's: 15416,15417 2016-04-01 18:49:57,5, GSM1: Modem handler 0 has started. PID: 15417. 2016-04-01 18:49:57,3, GSM1: Couldn't open serial port /dev/ttyACM0, error: Permission denied, waiting 30 sec.

SELinux context of ACM0 device
[root@server /]# ls -Z /dev/ttyACM0 crw-rw----. root dialout system_u:object_r:tty_device_t:s0 /dev/ttyACM0

SELinux context of sms daemon
[root@server /]# ps axuwZ | grep sms system_u:system_r:smsd_t:s0 smstools 19026 0.0 0.1 9944 3744 ? Ss 18:50 0:00 /usr/sbin/smsd system_u:system_r:smsd_t:s0 smstools 19027 0.6 0.2 9980 3892 ? S 18:50 0:01 /usr/sbin/smsd

User smstools is member of dialout group
[root@server /]# id smstools uid=994(smstools) gid=992(smstools) groups=992(smstools),18(dialout)

ACM kernel module is loaded
[root@server /]# lsmod | grep cdc_acm cdc_acm 32971 0

GNOKII has no problems... (I also am able to send SMS using gnokii command)
]root@server]# gnokii --identify GNOKII Version 0.6.31 LOG: debug mask is 0x1 Config read from file /etc/gnokiirc. phone instance config: model = AT port = /dev/ttyACM0 connection = serial initlength = default serial_baudrate = 19200 serial_write_usleep = -1 handshake = software require_dcd = 0 smsc_timeout = 10 rfcomm_channel = 0 sm_retry = 0 Initializing AT capable mobile phone ... Serial device: opening device /dev/ttyACM0 Serial device: setting RTS to high and DTR to high -- cut out for brevity -- Received message type 06 IMEI : removed Manufacturer : Nokia Model : Nokia C5-00 Product name : Nokia C5-00 Revision : V ICPR82_11w16.3 Serial device: closing device

SELinux disabled
[root@server /]# setenforce 0

Now it seems that SMS Server Tools is able to open /dev/ttyACM0
[root@server /]# tail /var/log/smsd/smsd.log 2016-04-01 19:52:52,7, GSM1: -> AT+CMGF=0 2016-04-01 19:52:52,7, GSM1: Command is sent, waiting for the answer 2016-04-01 19:52:53,7, GSM1: <- OK 2016-04-01 19:52:53,6, GSM1: Checking memory size 2016-04-01 19:52:53,7, GSM1: -> AT+CPMS? 2016-04-01 19:52:53,7, GSM1: Command is sent, waiting for the answer 2016-04-01 19:52:53,7, GSM1: <- +CPMS: ,,,,,,,, OK 2016-04-01 19:52:53,6, GSM1: Reading of messages is not supported? 2016-04-01 19:52:53,6, GSM1: Command failed. 2016-04-01 19:52:53,6, GSM1: No SMS received (reading interrupted)

But it fails again
[root@server /]# /usr/bin/sendsms 123456789 'Hello, how are you' bash: /usr/bin/sendsms: Permission denied

GNOKII has no problem with sending SMS
[root@server /]# echo "This is a test message" | gnokii --sendsms 123456789 GNOKII Version 0.6.31 LOG: debug mask is 0x1 Config read from file /etc/gnokiirc. phone instance config: model = AT port = /dev/ttyACM0 connection = serial initlength = default serial_baudrate = 19200 -- cut out for brevity --- Received message type 21 Message sent (reference: 81) Send succeeded with reference 81! Serial device: closing device

Result: GNOKII is able to send SMS whether SELinux is enabled or not. SMS Server Tools is not able under any circumstances.

Note: somehow I was able to spot a problem with SMS Server Tools and SELinux, but it did not help a thing!
[root@server /]# grep smsd /var/log/audit/audit.log | audit2allow -M smstools [root@server /]# cat ./smstools.te module smstools 1.0; require { type tty_device_t; type smsd_t; class chr_file open; } #============= smsd_t ============== #!!!! This avc can be allowed using the boolean 'daemons_use_tty' allow smsd_t tty_device_t:chr_file open; [root@server /]# semodule -i smstools.pp

Finally it's working.

I had to disable SELinux because I was unable to find failing operations via ausearch command - SMS tools was still complaining about permission denied on /dev/ttyACM0.
And I had to use sendsms.sh from this site because the one which is packaged with RPM is interactive version.