On Wed, May 24, 2017 at 04:11:44PM -0400, Stephen Smalley wrote: > On Wed, 2017-05-24 at 14:08 +0200, Dominick Grift wrote: > > I was looking again at ioctl whitelisting, and excuse me if I > > overlooked some documentation, but I am having a hard time > > implementing this. > > what I did was I just wanted to basically test blacklisting a single > > ioctl (no particular one) > > > > So i looked into androids sepolicy and just picked a semi-random > > ioctl from their "https://android.googlesource.com/platform/system/se > > policy/+/master/public/ioctl_defines" > > > > for example: PHONE_CAPABILITIES_CHECK 0x40087182 > > > > However the xpermissions statement only allows 0x0000 to 0xFFFF when > > i tried: (xpermission alg_socket_ioctl (ioctl alg_socket (not > > (0x40087182)))) > > > > My question is how do i convert these to something i can use with the > > xpermission statement in CIL, and why can seandroid sepolicy get away > > with using 0x12345678 where i have to use 0x1234? I could not find > > any scripts that converts these in the android tree. > > FWIW, I added a simple test of ioctl whitelisting to the selinux- > testsuite, although that was done in source policy and depends on the > binary module format support for xperms. > > With regard to your question though, only the low 16 bits of the ioctl > value (the type/driver and number/function fields) are actually used; > the upper 16 bits encode the direction (read/write) and size of any > argument to the ioctl and are therefore not relevant for whitelisting. > So you can just use 0x7182. checkpolicy just ignores the upper bits, > which I guess is convenient so that they can use ioctl macro lists > generated from kernel header definitions, and Android builds by using > checkpolicy -C to convert policy.conf to CIL.
Thanks. I considered that but then I thought I saw various different ioctls with the same last 16 bits so that got me confused -- Key fingerprint = 5F4D 3CDB D3F8 3652 FBD8 02D5 3B6C 5F1D 2C7B 6B02 https://sks-keyservers.net/pks/lookup?op=get&search=0x3B6C5F1D2C7B6B02 Dominick Grift
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