Re: [PATCH 01/13] LSM: Add the lsmblob data structure.

[Georgia Garcia <georgia.garcia@canonical.com>]

Hi Casey,

On Sun, 2024-08-25 at 12:00 -0700, Casey Schaufler wrote:
> When more than one security module is exporting data to audit and
> networking sub-systems a single 32 bit integer is no longer
> sufficient to represent the data. Add a structure to be used instead.
> 
> The lsmblob structure definition is intended to keep the LSM
> specific information private to the individual security modules.
> The module specific information is included in a new set of
> header files under include/lsm. Each security module is allowed
> to define the information included for its use in the lsmblob.
> SELinux includes a u32 secid. Smack includes a pointer into its
> global label list. The conditional compilation based on feature
> inclusion is contained in the include/lsm files.
> 
> Suggested-by: Paul Moore <paul@paul-moore.com>
> Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
> ---
>  include/linux/lsm/apparmor.h | 17 +++++++++++++++++
>  include/linux/lsm/bpf.h      | 16 ++++++++++++++++
>  include/linux/lsm/selinux.h  | 16 ++++++++++++++++
>  include/linux/lsm/smack.h    | 17 +++++++++++++++++
>  include/linux/security.h     | 20 ++++++++++++++++++++
>  5 files changed, 86 insertions(+)
>  create mode 100644 include/linux/lsm/apparmor.h
>  create mode 100644 include/linux/lsm/bpf.h
>  create mode 100644 include/linux/lsm/selinux.h
>  create mode 100644 include/linux/lsm/smack.h
> 
> diff --git a/include/linux/lsm/apparmor.h b/include/linux/lsm/apparmor.h
> new file mode 100644
> index 000000000000..8ff1cd899a20
> --- /dev/null
> +++ b/include/linux/lsm/apparmor.h
> @@ -0,0 +1,17 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * Linux Security Module interface to other subsystems.
> + * AppArmor presents a single u32 value which is known as a secid.

Just a small nitpick: this comment doesn't match the code since it's
using aa_label instead of a u32 secid.

> + */
> +#ifndef __LINUX_LSM_APPARMOR_H
> +#define __LINUX_LSM_APPARMOR_H
> +
> +struct aa_label;
> +
> +struct lsmblob_apparmor {
> +#ifdef CONFIG_SECURITY_APPARMOR
> +	struct aa_label *label;
> +#endif
> +};
> +
> +#endif /* ! __LINUX_LSM_APPARMOR_H */
> diff --git a/include/linux/lsm/bpf.h b/include/linux/lsm/bpf.h
> new file mode 100644
> index 000000000000..48abdcd82ded
> --- /dev/null
> +++ b/include/linux/lsm/bpf.h
> @@ -0,0 +1,16 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * Linux Security Module interface to other subsystems.
> + * BPF may present a single u32 value.
> + */
> +#ifndef __LINUX_LSM_BPF_H
> +#define __LINUX_LSM_BPF_H
> +#include <linux/types.h>
> +
> +struct lsmblob_bpf {
> +#ifdef CONFIG_BPF_LSM
> +	u32 secid;
> +#endif
> +};
> +
> +#endif /* ! __LINUX_LSM_BPF_H */
> diff --git a/include/linux/lsm/selinux.h b/include/linux/lsm/selinux.h
> new file mode 100644
> index 000000000000..fd16456b36ac
> --- /dev/null
> +++ b/include/linux/lsm/selinux.h
> @@ -0,0 +1,16 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * Linux Security Module interface to other subsystems.
> + * SELinux presents a single u32 value which is known as a secid.
> + */
> +#ifndef __LINUX_LSM_SELINUX_H
> +#define __LINUX_LSM_SELINUX_H
> +#include <linux/types.h>
> +
> +struct lsmblob_selinux {
> +#ifdef CONFIG_SECURITY_SELINUX
> +	u32 secid;
> +#endif
> +};
> +
> +#endif /* ! __LINUX_LSM_SELINUX_H */
> diff --git a/include/linux/lsm/smack.h b/include/linux/lsm/smack.h
> new file mode 100644
> index 000000000000..2018f288302f
> --- /dev/null
> +++ b/include/linux/lsm/smack.h
> @@ -0,0 +1,17 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * Linux Security Module interface to other subsystems.
> + * Smack presents a pointer into the global Smack label list.
> + */
> +#ifndef __LINUX_LSM_SMACK_H
> +#define __LINUX_LSM_SMACK_H
> +
> +struct smack_known;
> +
> +struct lsmblob_smack {
> +#ifdef CONFIG_SECURITY_SMACK
> +	struct smack_known *skp;
> +#endif
> +};
> +
> +#endif /* ! __LINUX_LSM_SMACK_H */
> diff --git a/include/linux/security.h b/include/linux/security.h
> index 1390f1efb4f0..0057a22137e8 100644
> --- a/include/linux/security.h
> +++ b/include/linux/security.h
> @@ -34,6 +34,10 @@
>  #include <linux/sockptr.h>
>  #include <linux/bpf.h>
>  #include <uapi/linux/lsm.h>
> +#include <linux/lsm/selinux.h>
> +#include <linux/lsm/smack.h>
> +#include <linux/lsm/apparmor.h>
> +#include <linux/lsm/bpf.h>
>  
>  struct linux_binprm;
>  struct cred;
> @@ -140,6 +144,22 @@ enum lockdown_reason {
>  	LOCKDOWN_CONFIDENTIALITY_MAX,
>  };
>  
> +/* scaffolding */
> +struct lsmblob_scaffold {
> +	u32 secid;
> +};
> +
> +/*
> + * Data exported by the security modules
> + */
> +struct lsmblob {
> +	struct lsmblob_selinux selinux;
> +	struct lsmblob_smack smack;
> +	struct lsmblob_apparmor apparmor;
> +	struct lsmblob_bpf bpf;
> +	struct lsmblob_scaffold scaffold;
> +};
> +
>  extern const char *const lockdown_reasons[LOCKDOWN_CONFIDENTIALITY_MAX+1];
>  extern u32 lsm_active_cnt;
>  extern const struct lsm_id *lsm_idlist[];