Re: [PATCH] Module for tpm2-abrmd

["Sugar, David" <dsugar@tresys.com>]

On 7/29/19 8:49 PM, Chris PeBenito wrote:
> On 7/25/19 10:43 AM, Sugar, David wrote:
>> Signed-off-by: Dave Sugar <dsugar@tresys.com>
>> ---
>>   policy/modules/services/tpm2_abrmd.fc |  3 ++
>>   policy/modules/services/tpm2_abrmd.if | 58 +++++++++++++++++++++++++++
>>   policy/modules/services/tpm2_abrmd.te | 29 ++++++++++++++
>>   3 files changed, 90 insertions(+)
>>   create mode 100644 policy/modules/services/tpm2_abrmd.fc
>>   create mode 100644 policy/modules/services/tpm2_abrmd.if
>>   create mode 100644 policy/modules/services/tpm2_abrmd.te
> 
> I think my only question is about the module name.  Why not tpm2?  I'm 
> not well versed on the Linux TPM stack, but isn't there other components 
> that potentially could need policy, like tss or totp?
> 
> 
I used this name because the only SELinux policy needed was for the 
daemon 'tpm2-abrmd'.  The processes that interact with the daemon to 
actually use the tpm are using default bin_t label and don't seem to 
need any additional permissions.  In my case I'm using /bin/tpm2_* and 
/bin/clevis.

I see a tss package but it is only adding libraries.  I don't see a 
package for totp.  I'm working on RHEL7.6 so there could be additional 
binaries on other distributions that will need labeling.

I'm happy to go either way here.  I don't have a strong feeling if other 
tpm2 related stuff should get grouped into a single module or if they 
should be separate.

I'm pretty sure anything using a tpm2 will need to use abrmd to access 
the TPM.  I just don't have enough insight to know if those other 
binaries will need labeling and policy.

If the decision is made to use tpm2.{fc,if,te} would any of the policy 
change?  I feel like the fc and te files are still correct.  Interface 
names might be changed slightly, but also might be OK as is.

Dave

> 
>> diff --git a/policy/modules/services/tpm2_abrmd.fc 
>> b/policy/modules/services/tpm2_abrmd.fc
>> new file mode 100644
>> index 00000000..4ccf2f25
>> --- /dev/null
>> +++ b/policy/modules/services/tpm2_abrmd.fc
>> @@ -0,0 +1,3 @@
>> +/usr/sbin/tpm2-abrmd                                --    
>> gen_context(system_u:object_r:tpm2_abrmd_exec_t,s0)
>> +
>> +/usr/lib/systemd/system/[^/]*tpm2-abrmd\.service    --    
>> gen_context(system_u:object_r:tpm2_abrmd_unit_t,s0)
>> diff --git a/policy/modules/services/tpm2_abrmd.if 
>> b/policy/modules/services/tpm2_abrmd.if
>> new file mode 100644
>> index 00000000..dabb4a65
>> --- /dev/null
>> +++ b/policy/modules/services/tpm2_abrmd.if
>> @@ -0,0 +1,58 @@
>> +## <summary>TPM2 Access Broker and Resource Management daemon.</summary>
>> +
>> +########################################
>> +## <summary>
>> +##    Allow specified domain to enable/disable tpm2-abrmd unit
>> +## </summary>
>> +## <param name="domain">
>> +##    <summary>
>> +##    Domain allowed access.
>> +##    </summary>
>> +## </param>
>> +#
>> +interface(`tpm2_abrmd_enabledisable',`
>> +    gen_require(`
>> +        type tpm2_abrmd_unit_t;
>> +        class service { enable disable };
>> +    ')
>> +
>> +    allow $1 tpm2_abrmd_unit_t:service { enable disable };
>> +')
>> +
>> +########################################
>> +## <summary>
>> +##    Allow specified domain to start/stop tpm2-abrmd unit
>> +## </summary>
>> +## <param name="domain">
>> +##    <summary>
>> +##    Domain allowed access.
>> +##    </summary>
>> +## </param>
>> +#
>> +interface(`tpm2_abrmd_startstop',`
>> +    gen_require(`
>> +        type tpm2_abrmd_unit_t;
>> +        class service { start stop };
>> +    ')
>> +
>> +    allow $1 tpm2_abrmd_unit_t:service { start stop };
>> +')
>> +
>> +########################################
>> +## <summary>
>> +##    Allow specified domain to get status of tpm2-abrmd unit
>> +## </summary>
>> +## <param name="domain">
>> +##    <summary>
>> +##    Domain allowed access.
>> +##    </summary>
>> +## </param>
>> +#
>> +interface(`tpm2_abrmd_status',`
>> +    gen_require(`
>> +        type tpm2_abrmd_unit_t;
>> +        class service status;
>> +    ')
>> +
>> +    allow $1 tpm2_abrmd_unit_t:service status;
>> +')
>> diff --git a/policy/modules/services/tpm2_abrmd.te 
>> b/policy/modules/services/tpm2_abrmd.te
>> new file mode 100644
>> index 00000000..8a8ba5f0
>> --- /dev/null
>> +++ b/policy/modules/services/tpm2_abrmd.te
>> @@ -0,0 +1,29 @@
>> +policy_module(tpm2_abrmd, 1.0.0)
>> +
>> +########################################
>> +#
>> +# Declarations
>> +#
>> +
>> +type tpm2_abrmd_t;
>> +type tpm2_abrmd_exec_t;
>> +init_daemon_domain(tpm2_abrmd_t, tpm2_abrmd_exec_t)
>> +
>> +type tpm2_abrmd_unit_t;
>> +init_unit_file(tpm2_abrmd_unit_t)
>> +
>> +########################################
>> +#
>> +# Local policy
>> +#
>> +
>> +allow tpm2_abrmd_t self:process signal;
>> +allow tpm2_abrmd_t self:unix_stream_socket create_socket_perms;
>> +
>> +dev_rw_tpm(tpm2_abrmd_t)
>> +
>> +kernel_read_crypto_sysctls(tpm2_abrmd_t)
>> +kernel_read_system_state(tpm2_abrmd_t)
>> +
>> +dbus_system_bus_client(tpm2_abrmd_t)
>> +dbus_connect_system_bus(tpm2_abrmd_t)
>>
> 
>