On 6/21/19 11:52 AM, 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.
>
> Signed-off-by: Casey Schaufler <casey@xxxxxxxxxxxxxxxx>
there is small issue, see below
Also I want to get rid of the list search for the display lsm
but that can come as a separate patch later
> ---
> fs/proc/base.c | 1 +
> security/security.c | 110 +++++++++++++++++++++++++++++++++++---------
> 2 files changed, 90 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[] = {
> 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 aa8e1c73a062..92c5aa427b53 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;
>
> 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 = {
> + .lbs_task = sizeof(int), /* slot number for the "display" LSM */
> +};
>
> /* Boot-time LSM user choice */
> static __initdata const char *chosen_lsm_order;
> @@ -583,6 +585,8 @@ int lsm_inode_alloc(struct inode *inode)
> */
> static int lsm_task_alloc(struct task_struct *task)
> {
> + int *display;
> +
> if (blob_sizes.lbs_task == 0) {
> task->security = NULL;
> return 0;
> @@ -591,6 +595,15 @@ static int lsm_task_alloc(struct task_struct *task)
> task->security = kzalloc(blob_sizes.lbs_task, GFP_KERNEL);
> if (task->security == NULL)
> return -ENOMEM;
> +
> + /*
> + * The start of the task blob contains the "display" LSM slot number.
> + * Start with it set to the invalid slot number, indicating that the
> + * default first registered LSM be displayed.
> + */
> + display = task->security;
> + *display = LSMBLOB_INVALID;
> +
> return 0;
> }
>
> @@ -1579,14 +1592,24 @@ int security_file_open(struct file *file)
>
> int security_task_alloc(struct task_struct *task, unsigned long clone_flags)
> {
> + int *odisplay = current->security;
> + int *ndisplay;
> int rc = lsm_task_alloc(task);
>
> - if (rc)
> + if (unlikely(rc))
> return rc;
> +
> rc = call_int_hook(task_alloc, 0, task, clone_flags);
> - if (unlikely(rc))
> + if (unlikely(rc)) {
> security_task_free(task);
> - return rc;
> + return rc;
> + }
> +
> + ndisplay = task->security;
> + if (ndisplay && odisplay)
> + *ndisplay = *odisplay;
> +
> + return 0;
> }
>
> void security_task_free(struct task_struct *task)
> @@ -1972,10 +1995,28 @@ int security_getprocattr(struct task_struct *p, const char *lsm, char *name,
> char **value)
> {
> struct security_hook_list *hp;
> + int *display = current->security;
> +
> + if (!strcmp(name, "display")) {
> + hlist_for_each_entry(hp, &security_hook_heads.secid_to_secctx,
> + list) {
> + if (*display == LSMBLOB_INVALID ||
> + hp->slot == *display) {
> + *value = kstrdup(hp->lsm, GFP_KERNEL);
> + if (*value)
> + return strlen(hp->lsm);
> + return -ENOMEM;
> + }
> + }
> + return -EINVAL;
> + }
>
> hlist_for_each_entry(hp, &security_hook_heads.getprocattr, list) {
> if (lsm != NULL && strcmp(lsm, hp->lsm))
> continue;
> + if (lsm == NULL && *display != LSMBLOB_INVALID &&
> + *display != hp->slot)
> + continue;
> return hp->hook.getprocattr(p, name, value);
> }
> return -EINVAL;
> @@ -1985,10 +2026,27 @@ int security_setprocattr(const char *lsm, const char *name, void *value,
> size_t size)
> {
> struct security_hook_list *hp;
> + int *display = current->security;
> + int len;
> +
> + if (!strcmp(name, "display")) {
> + hlist_for_each_entry(hp, &security_hook_heads.secid_to_secctx,
> + list) {
> + len = strlen(hp->lsm);
> + if (size >= len && !strncmp(value, hp->lsm, len)) {
This isn't quite right. It allows a value that contains a prefix of an lsm to match. That
is
selinux2
etc would match to selinux. While it isn't a real problem atm. Its not something I
want as part of the user space API which would make it so we can't fix it.
> + *display = hp->slot;
> + return size;
> + }
> + }
> + return -EINVAL;
> + }
>
> hlist_for_each_entry(hp, &security_hook_heads.setprocattr, list) {
> if (lsm != NULL && strcmp(lsm, hp->lsm))
> continue;
> + if (lsm == NULL && *display != LSMBLOB_INVALID &&
> + *display != hp->slot)
> + continue;
> return hp->hook.setprocattr(name, value, size);
> }
> return -EINVAL;
> @@ -2008,14 +2066,12 @@ EXPORT_SYMBOL(security_ismaclabel);
> int security_secid_to_secctx(struct lsmblob *blob, char **secdata, u32 *seclen)
> {
> struct security_hook_list *hp;
> - int rc;
> + int *display = current->security;
>
> - hlist_for_each_entry(hp, &security_hook_heads.secid_to_secctx, list) {
> - rc = hp->hook.secid_to_secctx(blob->secid[hp->slot],
> - secdata, seclen);
> - if (rc != 0)
> - return rc;
> - }
> + hlist_for_each_entry(hp, &security_hook_heads.secid_to_secctx, list)
> + if (*display == LSMBLOB_INVALID || *display == hp->slot)
> + return hp->hook.secid_to_secctx(blob->secid[hp->slot],
> + secdata, seclen);
> return 0;
> }
> EXPORT_SYMBOL(security_secid_to_secctx);
> @@ -2024,22 +2080,27 @@ int security_secctx_to_secid(const char *secdata, u32 seclen,
> struct lsmblob *blob)
> {
> struct security_hook_list *hp;
> - int rc;
> + int *display = current->security;
>
> lsmblob_init(blob, 0);
> - hlist_for_each_entry(hp, &security_hook_heads.secctx_to_secid, list) {
> - rc = hp->hook.secctx_to_secid(secdata, seclen,
> - &blob->secid[hp->slot]);
> - if (rc != 0)
> - return rc;
> - }
> + hlist_for_each_entry(hp, &security_hook_heads.secctx_to_secid, list)
> + if (*display == LSMBLOB_INVALID || *display == hp->slot)
> + return hp->hook.secctx_to_secid(secdata, seclen,
> + &blob->secid[hp->slot]);
> return 0;
> }
> EXPORT_SYMBOL(security_secctx_to_secid);
>
> void security_release_secctx(char *secdata, u32 seclen)
> {
> - call_void_hook(release_secctx, secdata, seclen);
> + struct security_hook_list *hp;
> + int *display = current->security;
> +
> + hlist_for_each_entry(hp, &security_hook_heads.release_secctx, list)
> + if (*display == LSMBLOB_INVALID || *display == hp->slot) {
> + hp->hook.release_secctx(secdata, seclen);
> + return;
> + }
> }
> EXPORT_SYMBOL(security_release_secctx);
>
> @@ -2164,8 +2225,15 @@ EXPORT_SYMBOL(security_sock_rcv_skb);
> int security_socket_getpeersec_stream(struct socket *sock, char __user *optval,
> int __user *optlen, unsigned len)
> {
> - return call_int_hook(socket_getpeersec_stream, -ENOPROTOOPT, sock,
> - optval, optlen, len);
> + int *display = current->security;
> + struct security_hook_list *hp;
> +
> + hlist_for_each_entry(hp, &security_hook_heads.socket_getpeersec_stream,
> + list)
> + if (*display == LSMBLOB_INVALID || *display == hp->slot)
> + return hp->hook.socket_getpeersec_stream(sock, optval,
> + optlen, len);
> + return -ENOPROTOOPT;
> }
>
> int security_socket_getpeersec_dgram(struct socket *sock, struct sk_buff *skb,
>
