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Date: Mon, 8 Jul 2019 14:46:11 -0400
From: Stephen Smalley <sds@...ho.nsa.gov>
To: David Howells <dhowells@...hat.com>, viro@...iv.linux.org.uk
Cc: Casey Schaufler <casey@...aufler-ca.com>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
nicolas.dichtel@...nd.com, raven@...maw.net,
Christian Brauner <christian@...uner.io>,
keyrings@...r.kernel.org, linux-usb@...r.kernel.org,
linux-security-module@...r.kernel.org,
linux-fsdevel@...r.kernel.org, linux-api@...r.kernel.org,
linux-block@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/9] security: Add hooks to rule on setting a watch [ver
#5]
On 6/28/19 11:48 AM, David Howells wrote:
> Add security hooks that will allow an LSM to rule on whether or not a watch
> may be set. More than one hook is required as the watches watch different
> types of object.
>
> Signed-off-by: David Howells <dhowells@...hat.com>
> cc: Casey Schaufler <casey@...aufler-ca.com>
> cc: Stephen Smalley <sds@...ho.nsa.gov>
> cc: linux-security-module@...r.kernel.org
> ---
>
> include/linux/lsm_hooks.h | 22 ++++++++++++++++++++++
> include/linux/security.h | 15 +++++++++++++++
> security/security.c | 13 +++++++++++++
> 3 files changed, 50 insertions(+)
>
> diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
> index 47f58cfb6a19..f9d31f6445e4 100644
> --- a/include/linux/lsm_hooks.h
> +++ b/include/linux/lsm_hooks.h
> @@ -1413,6 +1413,20 @@
> * @ctx is a pointer in which to place the allocated security context.
> * @ctxlen points to the place to put the length of @ctx.
> *
> + * Security hooks for the general notification queue:
> + *
> + * @watch_key:
> + * Check to see if a process is allowed to watch for event notifications
> + * from a key or keyring.
> + * @watch: The watch object
> + * @key: The key to watch.
> + *
> + * @watch_devices:
> + * Check to see if a process is allowed to watch for event notifications
> + * from devices (as a global set).
> + * @watch: The watch object
It is difficult to evaluate these without at least one implementation of
each hook. I am unclear as to how any security module would use the
watch argument, since it has no security field/blob and does not appear
to contain any information that would be relevant to deciding whether or
not to permit the watch to be set.
> + *
> + *
> * Security hooks for using the eBPF maps and programs functionalities through
> * eBPF syscalls.
> *
> @@ -1688,6 +1702,10 @@ union security_list_options {
> int (*inode_notifysecctx)(struct inode *inode, void *ctx, u32 ctxlen);
> int (*inode_setsecctx)(struct dentry *dentry, void *ctx, u32 ctxlen);
> int (*inode_getsecctx)(struct inode *inode, void **ctx, u32 *ctxlen);
> +#ifdef CONFIG_WATCH_QUEUE
> + int (*watch_key)(struct watch *watch, struct key *key);
> + int (*watch_devices)(struct watch *watch);
> +#endif /* CONFIG_WATCH_QUEUE */
>
> #ifdef CONFIG_SECURITY_NETWORK
> int (*unix_stream_connect)(struct sock *sock, struct sock *other,
> @@ -1964,6 +1982,10 @@ struct security_hook_heads {
> struct hlist_head inode_notifysecctx;
> struct hlist_head inode_setsecctx;
> struct hlist_head inode_getsecctx;
> +#ifdef CONFIG_WATCH_QUEUE
> + struct hlist_head watch_key;
> + struct hlist_head watch_devices;
> +#endif /* CONFIG_WATCH_QUEUE */
> #ifdef CONFIG_SECURITY_NETWORK
> struct hlist_head unix_stream_connect;
> struct hlist_head unix_may_send;
> diff --git a/include/linux/security.h b/include/linux/security.h
> index 659071c2e57c..540863678355 100644
> --- a/include/linux/security.h
> +++ b/include/linux/security.h
> @@ -57,6 +57,7 @@ struct mm_struct;
> struct fs_context;
> struct fs_parameter;
> enum fs_value_type;
> +struct watch;
>
> /* Default (no) options for the capable function */
> #define CAP_OPT_NONE 0x0
> @@ -392,6 +393,10 @@ void security_inode_invalidate_secctx(struct inode *inode);
> int security_inode_notifysecctx(struct inode *inode, void *ctx, u32 ctxlen);
> int security_inode_setsecctx(struct dentry *dentry, void *ctx, u32 ctxlen);
> int security_inode_getsecctx(struct inode *inode, void **ctx, u32 *ctxlen);
> +#ifdef CONFIG_WATCH_QUEUE
> +int security_watch_key(struct watch *watch, struct key *key);
> +int security_watch_devices(struct watch *watch);
> +#endif /* CONFIG_WATCH_QUEUE */
> #else /* CONFIG_SECURITY */
>
> static inline int call_lsm_notifier(enum lsm_event event, void *data)
> @@ -1204,6 +1209,16 @@ static inline int security_inode_getsecctx(struct inode *inode, void **ctx, u32
> {
> return -EOPNOTSUPP;
> }
> +#ifdef CONFIG_WATCH_QUEUE
> +static inline int security_watch_key(struct watch *watch, struct key *key)
> +{
> + return 0;
> +}
> +static inline int security_watch_devices(struct watch *watch)
> +{
> + return 0;
> +}
> +#endif /* CONFIG_WATCH_QUEUE */
> #endif /* CONFIG_SECURITY */
>
> #ifdef CONFIG_SECURITY_NETWORK
> diff --git a/security/security.c b/security/security.c
> index 613a5c00e602..2c9919226ad1 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -1917,6 +1917,19 @@ int security_inode_getsecctx(struct inode *inode, void **ctx, u32 *ctxlen)
> }
> EXPORT_SYMBOL(security_inode_getsecctx);
>
> +#ifdef CONFIG_WATCH_QUEUE
> +int security_watch_key(struct watch *watch, struct key *key)
> +{
> + return call_int_hook(watch_key, 0, watch, key);
> +}
> +
> +int security_watch_devices(struct watch *watch)
> +{
> + return call_int_hook(watch_devices, 0, watch);
> +}
> +
> +#endif /* CONFIG_WATCH_QUEUE */
> +
> #ifdef CONFIG_SECURITY_NETWORK
>
> int security_unix_stream_connect(struct sock *sock, struct sock *other, struct sock *newsk)
>
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