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Wed, 19 Jun 2019 17:00:26 +0000 Received: from c-73-223-4-185.hsd1.ca.comcast.net (EHLO [192.168.0.103]) ([73.223.4.185]) by smtp431.mail.gq1.yahoo.com (Oath Hermes SMTP Server) with ESMTPA ID 2e2cec29b67b10fdc4f09eb213618ef2; Wed, 19 Jun 2019 17:00:25 +0000 (UTC) Subject: Re: [PATCH v2 15/25] LSM: Specify which LSM to display To: Kees Cook Cc: casey.schaufler@intel.com, jmorris@namei.org, linux-security-module@vger.kernel.org, selinux@vger.kernel.org, john.johansen@canonical.com, penguin-kernel@i-love.sakura.ne.jp, paul@paul-moore.com, sds@tycho.nsa.gov, casey@schaufler-ca.com References: <20190618230551.7475-1-casey@schaufler-ca.com> <20190618230551.7475-16-casey@schaufler-ca.com> <201906182221.8E3938600D@keescook> From: Casey Schaufler Openpgp: preference=signencrypt Autocrypt: addr=casey@schaufler-ca.com; keydata= mQINBFzV9HABEAC/mmv3jeJyF7lR7QhILYg1+PeBLIMZv7KCzBSc/4ZZipoWdmr77Lel/RxQ 1PrNx0UaM5r6Hj9lJmJ9eg4s/TUBSP67mTx+tsZ1RhG78/WFf9aBe8MSXxY5cu7IUwo0J/CG vdSqACKyYPV5eoTJmnMxalu8/oVUHyPnKF3eMGgE0mKOFBUMsb2pLS/enE4QyxhcZ26jeeS6 3BaqDl1aTXGowM5BHyn7s9LEU38x/y2ffdqBjd3au2YOlvZ+XUkzoclSVfSR29bomZVVyhMB h1jTmX4Ac9QjpwsxihT8KNGvOM5CeCjQyWcW/g8LfWTzOVF9lzbx6IfEZDDoDem4+ZiPsAXC SWKBKil3npdbgb8MARPes2DpuhVm8yfkJEQQmuLYv8GPiJbwHQVLZGQAPBZSAc7IidD2zbf9 XAw1/SJGe1poxOMfuSBsfKxv9ba2i8hUR+PH7gWwkMQaQ97B1yXYxVEkpG8Y4MfE5Vd3bjJU kvQ/tOBUCw5zwyIRC9+7zr1zYi/3hk+OG8OryZ5kpILBNCo+aePeAJ44znrySarUqS69tuXd a3lMPHUJJpUpIwSKQ5UuYYkWlWwENEWSefpakFAIwY4YIBkzoJ/t+XJHE1HTaJnRk6SWpeDf CreF3+LouP4njyeLEjVIMzaEpwROsw++BX5i5vTXJB+4UApTAQARAQABtChDYXNleSBTY2hh dWZsZXIgPGNhc2V5QHNjaGF1Zmxlci1jYS5jb20+iQJUBBMBCAA+FiEEC+9tH1YyUwIQzUIe OKUVfIxDyBEFAlzV9HACGwMFCRLMAwAFCwkIBwIGFQoJCAsCBBYCAwECHgECF4AACgkQOKUV fIxDyBG6ag/6AiRl8yof47YOEVHlrmewbpnlBTaYNfJ5cZflNRKRX6t4bp1B2YV1whlDTpiL vNOwFkh+ZE0eI5M4x8Gw2Oiok+4Q5liA9PHTozQYF+Ia+qdL5EehfbLGoEBqklpGvG3h8JsO 7SvONJuFDgvab/U/UriDYycJwzwKZuhVtK9EMpnTtUDyP3DY+Q8h7MWsniNBLVXnh4yBIEJg SSgDn3COpZoFTPGKE+rIzioo/GJe8CTa2g+ZggJiY/myWTS3quG0FMvwvNYvZ4I2g6uxSl7n bZVqAZgqwoTAv1HSXIAn9muwZUJL03qo25PFi2gQmX15BgJKQcV5RL0GHFHRThDS3IyadOgK P2j78P8SddTN73EmsG5OoyzwZAxXfck9A512BfVESqapHurRu2qvMoUkQaW/2yCeRQwGTsFj /rr0lnOBkyC6wCmPSKXe3dT2mnD5KnCkjn7KxLqexKt4itGjJz4/ynD/qh+gL7IPbifrQtVH JI7cr0fI6Tl8V6efurk5RjtELsAlSR6fKV7hClfeDEgLpigHXGyVOsynXLr59uE+g/+InVic jKueTq7LzFd0BiduXGO5HbGyRKw4MG5DNQvC//85EWmFUnDlD3WHz7Hicg95D+2IjD2ZVXJy x3LTfKWdC8bU8am1fi+d6tVEFAe/KbUfe+stXkgmfB7pxqW5Ag0EXNX0cAEQAPIEYtPebJzT wHpKLu1/j4jQcke06Kmu5RNuj1pEje7kX5IKzQSs+CPH0NbSNGvrA4dNGcuDUTNHgb5Be9hF zVqRCEvF2j7BFbrGe9jqMBWHuWheQM8RRoa2UMwQ704mRvKr4sNPh01nKT52ASbWpBPYG3/t WbYaqfgtRmCxBnqdOx5mBJIBh9Q38i63DjQgdNcsTx2qS7HFuFyNef5LCf3jogcbmZGxG/b7 yF4OwmGsVc8ufvlKo5A9Wm+tnRjLr/9Mn9vl5Xa/tQDoPxz26+aWz7j1in7UFzAarcvqzsdM Em6S7uT+qy5jcqyuipuenDKYF/yNOVSNnsiFyQTFqCPCpFihOnuaWqfmdeUOQHCSo8fD4aRF emsuxqcsq0Jp2ODq73DOTsdFxX2ESXYoFt3Oy7QmIxeEgiHBzdKU2bruIB5OVaZ4zWF+jusM Uh+jh+44w9DZkDNjxRAA5CxPlmBIn1OOYt1tsphrHg1cH1fDLK/pDjsJZkiH8EIjhckOtGSb aoUUMMJ85nVhN1EbU/A3DkWCVFEA//Vu1+BckbSbJKE7Hl6WdW19BXOZ7v3jo1q6lWwcFYth esJfk3ZPPJXuBokrFH8kqnEQ9W2QgrjDX3et2WwZFLOoOCItWxT0/1QO4ikcef/E7HXQf/ij Dxf9HG2o5hOlMIAkJq/uLNMvABEBAAGJAjwEGAEIACYWIQQL720fVjJTAhDNQh44pRV8jEPI EQUCXNX0cAIbDAUJEswDAAAKCRA4pRV8jEPIEWkzEACKFUnpp+wIVHpckMfBqN8BE5dUbWJc GyQ7wXWajLtlPdw1nNw0Wrv+ob2RCT7qQlUo6GRLcvj9Fn5tR4hBvR6D3m8aR0AGHbcC62cq I7LjaSDP5j/em4oVL2SMgNTrXgE2w33JMGjAx9oBzkxmKUqprhJomPwmfDHMJ0t7y39Da724 oLPTkQDpJL1kuraM9TC5NyLe1+MyIxqM/8NujoJbWeQUgGjn9uxQAil7o/xSCjrWCP3kZDID vd5ZaHpdl8e1mTExQoKr4EWgaMjmD/a3hZ/j3KfTVNpM2cLfD/QwTMaC2fkK8ExMsz+rUl1H icmcmpptCwOSgwSpPY1Zfio6HvEJp7gmDwMgozMfwQuT9oxyFTxn1X3rn1IoYQF3P8gsziY5 qtTxy2RrgqQFm/hr8gM78RhP54UPltIE96VywviFzDZehMvuwzW//fxysIoK97Y/KBZZOQs+ /T+Bw80Pwk/dqQ8UmIt2ffHEgwCTbkSm711BejapWCfklxkMZDp16mkxSt2qZovboVjXnfuq wQ1QL4o4t1hviM7LyoflsCLnQFJh6RSBhBpKQinMJl/z0A6NYDkQi6vEGMDBWX/M2vk9Jvwa v0cEBfY3Z5oFgkh7BUORsu1V+Hn0fR/Lqq/Pyq+nTR26WzGDkolLsDr3IH0TiAVH5ZuPxyz6 abzjfg== Message-ID: Date: Wed, 19 Jun 2019 10:00:24 -0700 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.7.1 MIME-Version: 1.0 In-Reply-To: <201906182221.8E3938600D@keescook> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Content-Language: en-US Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: On 6/18/2019 10:28 PM, Kees Cook wrote: > On Tue, Jun 18, 2019 at 04:05:41PM -0700, Casey Schaufler wrote: >> Create a new entry "display" in /proc/.../attr for controlling >> which LSM security information is displayed for a process. >> The name of an active LSM that supplies hooks for human readable >> data may be written to "display" to set the value. The name of >> the LSM currently in use can be read from "display". >> At this point there can only be one LSM capable of display >> active. >> >> This affects /proc/.../attr/current and SO_PEERSEC. >> >> Signed-off-by: Casey Schaufler >> --- >> fs/proc/base.c | 1 + >> security/security.c | 108 +++++++++++++++++++++++++++++++++++--------= - >> 2 files changed, 88 insertions(+), 21 deletions(-) >> >> diff --git a/fs/proc/base.c b/fs/proc/base.c >> index ddef482f1334..7bf70e041315 100644 >> --- a/fs/proc/base.c >> +++ b/fs/proc/base.c >> @@ -2618,6 +2618,7 @@ static const struct pid_entry attr_dir_stuff[] =3D= { >> ATTR(NULL, "fscreate", 0666), >> ATTR(NULL, "keycreate", 0666), >> ATTR(NULL, "sockcreate", 0666), >> + ATTR(NULL, "display", 0666), >> #ifdef CONFIG_SECURITY_SMACK >> DIR("smack", 0555, >> proc_smack_attr_dir_inode_ops, proc_smack_attr_dir_ops), >> diff --git a/security/security.c b/security/security.c >> index 46f6cf21d33c..9cfdc664239e 100644 >> --- a/security/security.c >> +++ b/security/security.c >> @@ -46,7 +46,9 @@ static struct kmem_cache *lsm_file_cache; >> static struct kmem_cache *lsm_inode_cache; >> =20 >> char *lsm_names; >> -static struct lsm_blob_sizes blob_sizes __lsm_ro_after_init; >> +static struct lsm_blob_sizes blob_sizes __lsm_ro_after_init =3D { >> + .lbs_task =3D sizeof(int), >> +}; > This needs some comments. I know what's happening here only because I > understand very well how the blob sizing works. :) Perhaps: > > .lbs_task =3D sizeof(int), /* storage for selected "display" LSM */ Point. >> =20 >> /* Boot-time LSM user choice */ >> static __initdata const char *chosen_lsm_order; >> @@ -578,6 +580,8 @@ int lsm_inode_alloc(struct inode *inode) >> */ >> static int lsm_task_alloc(struct task_struct *task) >> { >> + int *display; >> + >> if (blob_sizes.lbs_task =3D=3D 0) { >> task->security =3D NULL; >> return 0; >> @@ -586,6 +590,10 @@ static int lsm_task_alloc(struct task_struct *tas= k) >> task->security =3D kzalloc(blob_sizes.lbs_task, GFP_KERNEL); >> if (task->security =3D=3D NULL) >> return -ENOMEM; >> + >> + display =3D task->security; >> + *display =3D LSMDATA_INVALID; > Similarly I think a comment here would be nice. "Initialize currently > selected "display" LSM to unselected" or something. Point. > Also: "int" is okay here for now, but if the LSM infrastructure wants t= o > do more like this we'll want to convert to a struct of some kind at the= > start of the lbs_task. We could go whole hog and include a lsm_info pointer (once the slot number moves there) instead of an int, but I think it best to leave it as is for now. I don't see a case where more information would be required, and it would not be a hard change to make later. >> + >> return 0; >> } >> =20 >> @@ -1574,14 +1582,27 @@ int security_file_open(struct file *file) >> =20 >> int security_task_alloc(struct task_struct *task, unsigned long clone= _flags) >> { >> + int *odisplay =3D current->security; >> + int *ndisplay; >> int rc =3D lsm_task_alloc(task); >> =20 >> - if (rc) >> + if (unlikely(rc)) >> return rc; >> + >> rc =3D call_int_hook(task_alloc, 0, task, clone_flags); >> - if (unlikely(rc)) >> + if (unlikely(rc)) { >> security_task_free(task); >> - return rc; >> + return rc; >> + } >> + >> + ndisplay =3D task->security; >> + if (ndisplay =3D=3D NULL) >> + return 0; >> + >> + if (odisplay !=3D NULL) > Perhaps merge these into "if (ndisplay && odisplay)" to drop the early > return 0 check? Sure. The logic took a few iterations before it got to what you see here. >> + *ndisplay =3D *odisplay; >> + >> + return 0; >> } >> =20 >> void security_task_free(struct task_struct *task) >> @@ -1967,10 +1988,28 @@ int security_getprocattr(struct task_struct *p= , const char *lsm, char *name, >> char **value) >> { >> struct security_hook_list *hp; >> + int *display =3D current->security; >> + >> + if (!strcmp(name, "display")) { >> + hlist_for_each_entry(hp, &security_hook_heads.secid_to_secctx, >> + list) { >> + if (*display =3D=3D LSMDATA_INVALID || >> + hp->slot =3D=3D *display) { >> + *value =3D kstrdup(hp->lsm, GFP_KERNEL); >> + if (*value) >> + return strlen(hp->lsm); >> + return -ENOMEM; >> + } >> + } >> + return -EINVAL; >> + } >> =20 >> hlist_for_each_entry(hp, &security_hook_heads.getprocattr, list) { >> if (lsm !=3D NULL && strcmp(lsm, hp->lsm)) >> continue; >> + if (lsm =3D=3D NULL && *display !=3D LSMDATA_INVALID && >> + *display !=3D hp->slot) >> + continue; >> return hp->hook.getprocattr(p, name, value); >> } >> return -EINVAL; >> @@ -1980,10 +2019,27 @@ int security_setprocattr(const char *lsm, cons= t char *name, void *value, >> size_t size) >> { >> struct security_hook_list *hp; >> + int *display =3D current->security; >> + int len; >> + >> + if (!strcmp(name, "display")) { >> + hlist_for_each_entry(hp, &security_hook_heads.secid_to_secctx, >> + list) { >> + len =3D strlen(hp->lsm); >> + if (size >=3D len && !strncmp(value, hp->lsm, len)) { >> + *display =3D hp->slot; >> + return size; >> + } >> + } >> + return -EINVAL; >> + } >> =20 >> hlist_for_each_entry(hp, &security_hook_heads.setprocattr, list) { >> if (lsm !=3D NULL && strcmp(lsm, hp->lsm)) >> continue; >> + if (lsm =3D=3D NULL && *display !=3D LSMDATA_INVALID && >> + *display !=3D hp->slot) >> + continue; >> return hp->hook.setprocattr(name, value, size); >> } >> return -EINVAL; >> @@ -2002,38 +2058,41 @@ EXPORT_SYMBOL(security_ismaclabel); >> =20 >> int security_secid_to_secctx(struct lsmblob *l, char **secdata, u32 *= seclen) >> { >> + int *display =3D current->security; >> struct security_hook_list *hp; >> - int rc; >> =20 >> - hlist_for_each_entry(hp, &security_hook_heads.secid_to_secctx, list)= { >> - rc =3D hp->hook.secid_to_secctx(l->secid[hp->slot], >> - secdata, seclen); >> - if (rc !=3D 0) >> - return rc; >> - } >> + hlist_for_each_entry(hp, &security_hook_heads.secid_to_secctx, list)= >> + if (*display =3D=3D LSMDATA_INVALID || *display =3D=3D hp->slot) >> + return hp->hook.secid_to_secctx(l->secid[hp->slot], >> + secdata, seclen); >> return 0; >> } >> EXPORT_SYMBOL(security_secid_to_secctx); >> =20 >> int security_secctx_to_secid(const char *secdata, u32 seclen, struct = lsmblob *l) >> { >> + int *display =3D current->security; >> struct security_hook_list *hp; >> - int rc; >> =20 >> lsmblob_init(l, 0); >> - hlist_for_each_entry(hp, &security_hook_heads.secctx_to_secid, list)= { >> - rc =3D hp->hook.secctx_to_secid(secdata, seclen, >> - &l->secid[hp->slot]); >> - if (rc !=3D 0) >> - return rc; >> - } >> + hlist_for_each_entry(hp, &security_hook_heads.secctx_to_secid, list)= >> + if (*display =3D=3D LSMDATA_INVALID || *display =3D=3D hp->slot) >> + return hp->hook.secctx_to_secid(secdata, seclen, >> + &l->secid[hp->slot]); >> return 0; >> } >> EXPORT_SYMBOL(security_secctx_to_secid); >> =20 >> void security_release_secctx(char *secdata, u32 seclen) >> { >> - call_void_hook(release_secctx, secdata, seclen); >> + int *display =3D current->security; >> + struct security_hook_list *hp; >> + >> + hlist_for_each_entry(hp, &security_hook_heads.release_secctx, list) >> + if (*display =3D=3D LSMDATA_INVALID || *display =3D=3D hp->slot) { >> + hp->hook.release_secctx(secdata, seclen); >> + return; >> + } >> } >> EXPORT_SYMBOL(security_release_secctx); >> =20 >> @@ -2158,8 +2217,15 @@ EXPORT_SYMBOL(security_sock_rcv_skb); >> int security_socket_getpeersec_stream(struct socket *sock, char __use= r *optval, >> int __user *optlen, unsigned len) >> { >> - return call_int_hook(socket_getpeersec_stream, -ENOPROTOOPT, sock, >> - optval, optlen, len); >> + int *display =3D current->security; >> + struct security_hook_list *hp; >> + >> + hlist_for_each_entry(hp, &security_hook_heads.socket_getpeersec_stre= am, >> + list) >> + if (*display =3D=3D LSMDATA_INVALID || *display =3D=3D hp->slot) >> + return hp->hook.socket_getpeersec_stream(sock, optval, >> + optlen, len); >> + return -ENOPROTOOPT; >> } >> =20 >> int security_socket_getpeersec_dgram(struct socket *sock, struct sk_b= uff *skb, >> --=20 >> 2.20.1 >>