Re: [PATCH 02/14] LSM/SELinux: inode_{get,set,notify}secctx hooks to access LSM security context information.

["Serge E. Hallyn" <serue@us.ibm.com>]

Quoting David P. Quigley (dpquigl@tycho.nsa.gov):
> This patch introduces three new hooks. The inode_getsecctx hook is used to get
> all relevant information from an LSM about an inode. The inode_setsecctx is
> used to set both the in-core and on-disk state for the inode based on a context
> derived from inode_getsecctx.The final hook inode_notifysecctx will notify the
> LSM of a change for the in-core state of the inode in question. These hooks are
> for use in the labeled NFS code and addresses concerns of how to set security
> on an inode in a multi-xattr LSM. For historical reasons Stephen Smalley's
> explanation of the reason for these hooks is pasted below.
> 
> Quote Stephen Smalley
> 
> inode_setsecctx:  Change the security context of an inode.  Updates the
> in core security context managed by the security module and invokes the
> fs code as needed (via __vfs_setxattr_noperm) to update any backing
> xattrs that represent the context.  Example usage:  NFS server invokes
> this hook to change the security context in its incore inode and on the
> backing file system to a value provided by the client on a SETATTR
> operation.
> 
> inode_notifysecctx:  Notify the security module of what the security
> context of an inode should be.  Initializes the incore security context
> managed by the security module for this inode.  Example usage:  NFS
> client invokes this hook to initialize the security context in its
> incore inode to the value provided by the server for the file when the
> server returned the file's attributes to the client.
> 
> Signed-off-by: Matthew N. Dodd <Matthew.Dodd@sparta.com>
> Signed-off-by: David P. Quigley <dpquigl@tycho.nsa.gov>

Hmm, sorry, for all of these new hooks which you introduce, you do not
define empty cap_* versions and assign them when need in
security_fixup_ops().  But you unconditionally call them if
CONFIG_SECURITY=y.  So if you compile a kernel with CONFIG_SECURITY=y
but CONFIG_SECURITY_SELINUX=n, don't you hose your box?

> ---
>  include/linux/security.h |   50 ++++++++++++++++++++++++++++++++++++++++++++++
>  security/security.c      |   18 ++++++++++++++++
>  security/selinux/hooks.c |   25 +++++++++++++++++++++++
>  3 files changed, 93 insertions(+), 0 deletions(-)
> 
> diff --git a/include/linux/security.h b/include/linux/security.h
> index 80c4d00..8b5b041 100644
> --- a/include/linux/security.h
> +++ b/include/linux/security.h
> @@ -1289,6 +1289,36 @@ static inline void security_free_mnt_opts(struct security_mnt_opts *opts)
>   *	audit_rule_init.
>   *	@rule contains the allocated rule
>   *
> + * @inode_notifysecctx:
> + *	Notify the security module of what the security context of an inode
> + *	should be.  Initializes the incore security context managed by the
> + *	security module for this inode.  Example usage:  NFS client invokes
> + *	this hook to initialize the security context in its incore inode to the
> + *	value provided by the server for the file when the server returned the
> + *	file's attributes to the client.
> + *
> + * 	@inode we wish to set the security context of.
> + * 	@ctx contains the string which we wish to set in the inode.
> + * 	@ctxlen contains the length of @ctx.
> + *
> + * @inode_setsecctx:
> + * 	Change the security context of an inode.  Updates the
> + * 	incore security context managed by the security module and invokes the
> + * 	fs code as needed (via __vfs_setxattr_noperm) to update any backing
> + * 	xattrs that represent the context.  Example usage:  NFS server invokes
> + * 	this hook to change the security context in its incore inode and on the
> + * 	backing filesystem to a value provided by the client on a SETATTR
> + * 	operation.
> + *
> + * 	@dentry contains the inode we wish to set the security context of.
> + * 	@ctx contains the string which we wish to set in the inode.
> + * 	@ctxlen contains the length of @ctx.
> + *
> + * @inode_getsecctx:
> + * 	Returns a string containing all relavent security context information
> + * 	@inode we wish to set the security context of.
> + *	@ctx is a pointer to place the allocated security context should be placed.
> + *	@ctxlen points to the place to put the length of @ctx.
>   * This is the main security structure.
>   */
>  struct security_operations {
> @@ -1479,6 +1509,10 @@ struct security_operations {
>  	int (*secctx_to_secid) (const char *secdata, u32 seclen, u32 *secid);
>  	void (*release_secctx) (char *secdata, u32 seclen);
> 
> +	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_SECURITY_NETWORK
>  	int (*unix_stream_connect) (struct socket *sock,
>  				    struct socket *other, struct sock *newsk);
> @@ -1727,6 +1761,9 @@ int security_secid_to_secctx(u32 secid, char **secdata, u32 *seclen);
>  int security_secctx_to_secid(const char *secdata, u32 seclen, u32 *secid);
>  void security_release_secctx(char *secdata, u32 seclen);
> 
> +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);
>  #else /* CONFIG_SECURITY */
>  struct security_mnt_opts {
>  };
> @@ -2458,6 +2495,19 @@ static inline int security_secctx_to_secid(const char *secdata,
>  static inline void security_release_secctx(char *secdata, u32 seclen)
>  {
>  }
> +
> +static inline int security_inode_notifysecctx(struct inode *inode, void *ctx, u32 ctxlen)
> +{
> +	return -EOPNOTSUPP;
> +}
> +static inline int security_inode_setsecctx(struct dentry *dentry, void *ctx, u32 ctxlen)
> +{
> +	return -EOPNOTSUPP;
> +}
> +static inline int security_inode_getsecctx(struct inode *inode, void **ctx, u32 *ctxlen)
> +{
> +	return -EOPNOTSUPP;
> +}
>  #endif	/* CONFIG_SECURITY */
> 
>  #ifdef CONFIG_SECURITY_NETWORK
> diff --git a/security/security.c b/security/security.c
> index 3a4b4f5..d0fd42a 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -869,6 +869,24 @@ void security_release_secctx(char *secdata, u32 seclen)
>  }
>  EXPORT_SYMBOL(security_release_secctx);
> 
> +int security_inode_notifysecctx(struct inode *inode, void *ctx, u32 ctxlen)
> +{
> +	return security_ops->inode_notifysecctx(inode, ctx, ctxlen);
> +}
> +EXPORT_SYMBOL(security_inode_notifysecctx);
> +
> +int security_inode_setsecctx(struct dentry *dentry, void *ctx, u32 ctxlen)
> +{
> +	return security_ops->inode_setsecctx(dentry, ctx, ctxlen);
> +}
> +EXPORT_SYMBOL(security_inode_setsecctx);
> +
> +int security_inode_getsecctx(struct inode *inode, void **ctx, u32 *ctxlen)
> +{
> +	return security_ops->inode_getsecctx(inode, ctx, ctxlen);
> +}
> +EXPORT_SYMBOL(security_inode_getsecctx);
> +
>  #ifdef CONFIG_SECURITY_NETWORK
> 
>  int security_unix_stream_connect(struct socket *sock, struct socket *other,
> diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
> index 03fc6a8..b07871b 100644
> --- a/security/selinux/hooks.c
> +++ b/security/selinux/hooks.c
> @@ -5285,6 +5285,28 @@ static void selinux_release_secctx(char *secdata, u32 seclen)
>  	kfree(secdata);
>  }
> 
> +/*
> + *	This hook requires that the inode i_mutex be locked
> + */
> +static int selinux_inode_notifysecctx(struct inode *inode, void *ctx, u32 ctxlen)
> +{
> +	return selinux_inode_setsecurity(inode, XATTR_SELINUX_SUFFIX, ctx, ctxlen, 0);
> +}
> +
> +/*
> + *	This hook requires that the inode i_mutex be locked
> + */
> +static int selinux_inode_setsecctx(struct dentry *dentry, void *ctx, u32 ctxlen)
> +{
> +	return __vfs_setxattr_noperm(dentry, XATTR_NAME_SELINUX, ctx, ctxlen, 0);
> +}
> +
> +static int selinux_inode_getsecctx(struct inode *inode, void **ctx, u32 *ctxlen)
> +{
> +	*ctxlen = selinux_inode_getsecurity(inode, XATTR_SELINUX_SUFFIX,
> +						ctx, true);
> +	return *ctxlen;
> +}
>  #ifdef CONFIG_KEYS
> 
>  static int selinux_key_alloc(struct key *k, struct task_struct *tsk,
> @@ -5491,6 +5513,9 @@ static struct security_operations selinux_ops = {
>  	.secid_to_secctx =		selinux_secid_to_secctx,
>  	.secctx_to_secid =		selinux_secctx_to_secid,
>  	.release_secctx =		selinux_release_secctx,
> +	.inode_notifysecctx =		selinux_inode_notifysecctx,
> +	.inode_setsecctx =		selinux_inode_setsecctx,
> +	.inode_getsecctx =		selinux_inode_getsecctx,
> 
>  	.unix_stream_connect =		selinux_socket_unix_stream_connect,
>  	.unix_may_send =		selinux_socket_unix_may_send,
> -- 
> 1.5.5.1
> 
> 
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