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Message-Id: <1192544299.8702.78.camel@moss-spartans.epoch.ncsc.mil>
Date: Tue, 16 Oct 2007 10:18:19 -0400
From: Stephen Smalley <sds@...ho.nsa.gov>
To: "Serge E. Hallyn" <serue@...ibm.com>
Cc: linux-security-module@...r.kernel.org,
Andrew Morton <akpm@...l.org>,
Andrew Morgan <morgan@...nel.org>,
Chris Wright <chrisw@...s-sol.org>,
lkml <linux-kernel@...r.kernel.org>,
KaiGai Kohei <kaigai@...gai.gr.jp>,
Casey Schaufler <casey@...aufler-ca.com>
Subject: Re: [RFC] [PATCH 2/2] capabilities: implement 64-bit capabilities
On Mon, 2007-10-15 at 21:31 -0500, Serge E. Hallyn wrote:
> >From 7dd503c612afcb86b3165602ab264e2e9493b4bf Mon Sep 17 00:00:00 2001
> From: Serge E. Hallyn <serue@...ibm.com>
> Date: Mon, 15 Oct 2007 20:57:52 -0400
> Subject: [RFC] [PATCH 2/2] capabilities: implement 64-bit capabilities
>
> We are out of capabilities in the 32-bit capability fields, and
> several users could make use of additional capabilities.
> Convert the capabilities to 64-bits, change the capability
> version number accordingly, and convert the file capability
> code to handle both 32-bit and 64-bit file capability xattrs.
>
> It might seem desirable to also implement back-compatibility
> to read 32-bit caps from userspace, but that becomes
> problematic with capget, as capget could return valid info
> for processes not using high bits, but would have to return
> -EINVAL for those which were.
>
> So with this patch, libcap would need to be updated to make
> use of capset/capget.
>
> Signed-off-by: Serge E. Hallyn <serue@...ibm.com>
> ---
> fs/proc/array.c | 6 +++---
> include/linux/capability.h | 29 ++++++++++++++++++++---------
> security/commoncap.c | 37 +++++++++++++++++++++++++++++--------
> 3 files changed, 52 insertions(+), 20 deletions(-)
>
> diff --git a/fs/proc/array.c b/fs/proc/array.c
> index 3f4d824..c8ea46d 100644
> --- a/fs/proc/array.c
> +++ b/fs/proc/array.c
> @@ -288,9 +288,9 @@ static inline char *task_sig(struct task_struct *p, char *buffer)
>
> static inline char *task_cap(struct task_struct *p, char *buffer)
> {
> - return buffer + sprintf(buffer, "CapInh:\t%016x\n"
> - "CapPrm:\t%016x\n"
> - "CapEff:\t%016x\n",
> + return buffer + sprintf(buffer, "CapInh:\t%016lx\n"
> + "CapPrm:\t%016lx\n"
> + "CapEff:\t%016lx\n",
> cap_t(p->cap_inheritable),
> cap_t(p->cap_permitted),
> cap_t(p->cap_effective));
> diff --git a/include/linux/capability.h b/include/linux/capability.h
> index bb017ed..a3da4b9 100644
> --- a/include/linux/capability.h
> +++ b/include/linux/capability.h
> @@ -29,7 +29,7 @@ struct task_struct;
> library since the draft standard requires the use of malloc/free
> etc.. */
>
> -#define _LINUX_CAPABILITY_VERSION 0x19980330
> +#define _LINUX_CAPABILITY_VERSION 0x20071015
>
> typedef struct __user_cap_header_struct {
> __u32 version;
> @@ -37,29 +37,40 @@ typedef struct __user_cap_header_struct {
> } __user *cap_user_header_t;
>
> typedef struct __user_cap_data_struct {
> - __u32 effective;
> - __u32 permitted;
> - __u32 inheritable;
> + __u64 effective;
> + __u64 permitted;
> + __u64 inheritable;
> } __user *cap_user_data_t;
>
> #define XATTR_CAPS_SUFFIX "capability"
> #define XATTR_NAME_CAPS XATTR_SECURITY_PREFIX XATTR_CAPS_SUFFIX
>
> -#define XATTR_CAPS_SZ (3*sizeof(__le32))
> +#define XATTR_CAPS_SZ_1 (3*sizeof(__le32))
> +#define XATTR_CAPS_SZ_2 (2*sizeof(__le64) + sizeof(__le32))
> #define VFS_CAP_REVISION_MASK 0xFF000000
> #define VFS_CAP_REVISION_1 0x01000000
> +#define VFS_CAP_REVISION_2 0x02000000
>
> -#define VFS_CAP_REVISION VFS_CAP_REVISION_1
> +#define VFS_CAP_REVISION VFS_CAP_REVISION_2
> +#define XATTR_CAPS_SZ XATTR_CAPS_SZ_2
>
> #define VFS_CAP_FLAGS_MASK ~VFS_CAP_REVISION_MASK
> #define VFS_CAP_FLAGS_EFFECTIVE 0x000001
>
> -struct vfs_cap_data {
> +struct vfs_cap_data_v1 {
> __u32 magic_etc; /* Little endian */
> __u32 permitted; /* Little endian */
> __u32 inheritable; /* Little endian */
> };
>
> +struct vfs_cap_data_v2 {
> + __u32 magic_etc; /* Little endian */
> + __u64 permitted; /* Little endian */
> + __u64 inheritable; /* Little endian */
> +};
> +
> +typedef struct vfs_cap_data_v2 vfs_cap_data;
> +
> #ifdef __KERNEL__
>
> /* #define STRICT_CAP_T_TYPECHECKS */
> @@ -67,12 +78,12 @@ struct vfs_cap_data {
> #ifdef STRICT_CAP_T_TYPECHECKS
>
> typedef struct kernel_cap_struct {
> - __u32 cap;
> + __u64 cap;
> } kernel_cap_t;
>
> #else
>
> -typedef __u32 kernel_cap_t;
> +typedef __u64 kernel_cap_t;
>
> #endif
Don't you need to update CAP_TO_MASK() too?
And, of course, SELinux task_has_capability() will then need to deal
with higher capabilities differently, most likely by mapping them to
permissions in a new class and access vector.
> diff --git a/security/commoncap.c b/security/commoncap.c
> index 542bbe9..2cca843 100644
> --- a/security/commoncap.c
> +++ b/security/commoncap.c
> @@ -190,25 +190,46 @@ int cap_inode_killpriv(struct dentry *dentry)
> return inode->i_op->removexattr(dentry, XATTR_NAME_CAPS);
> }
>
> -static inline int cap_from_disk(struct vfs_cap_data *caps,
> +union vfs_cap_union {
> + struct vfs_cap_data_v1 v1;
> + struct vfs_cap_data_v2 v2;
> +};
> +
> +static inline int cap_from_disk(union vfs_cap_union *caps,
> struct linux_binprm *bprm,
> int size)
> {
> __u32 magic_etc;
>
> - if (size != XATTR_CAPS_SZ)
> + if (size != XATTR_CAPS_SZ_1 && size != XATTR_CAPS_SZ_2)
> return -EINVAL;
>
> - magic_etc = le32_to_cpu(caps->magic_etc);
> + magic_etc = le32_to_cpu(caps->v1.magic_etc);
>
> switch ((magic_etc & VFS_CAP_REVISION_MASK)) {
> - case VFS_CAP_REVISION:
> + case VFS_CAP_REVISION_1:
> + if (size != XATTR_CAPS_SZ_1)
> + return -EINVAL;
> + if (magic_etc & VFS_CAP_FLAGS_EFFECTIVE)
> + bprm->cap_effective = true;
> + else
> + bprm->cap_effective = false;
> + bprm->cap_permitted = to_cap_t(
> + (__u64) le32_to_cpu(caps->v1.permitted) );
> + bprm->cap_inheritable = to_cap_t(
> + (__u64) le32_to_cpu(caps->v1.inheritable) );
> + return 0;
> + case VFS_CAP_REVISION_2:
> + if (size != XATTR_CAPS_SZ_2)
> + return -EINVAL;
> if (magic_etc & VFS_CAP_FLAGS_EFFECTIVE)
> bprm->cap_effective = true;
> else
> bprm->cap_effective = false;
> - bprm->cap_permitted = to_cap_t( le32_to_cpu(caps->permitted) );
> - bprm->cap_inheritable = to_cap_t( le32_to_cpu(caps->inheritable) );
> + bprm->cap_permitted = to_cap_t(
> + le64_to_cpu(caps->v2.permitted) );
> + bprm->cap_inheritable = to_cap_t(
> + le64_to_cpu(caps->v2.inheritable) );
> return 0;
> default:
> return -EINVAL;
> @@ -220,7 +241,7 @@ static int get_file_caps(struct linux_binprm *bprm)
> {
> struct dentry *dentry;
> int rc = 0;
> - struct vfs_cap_data incaps;
> + union vfs_cap_union incaps;
> struct inode *inode;
>
> if (bprm->file->f_vfsmnt->mnt_flags & MNT_NOSUID) {
> @@ -235,7 +256,7 @@ static int get_file_caps(struct linux_binprm *bprm)
>
> rc = inode->i_op->getxattr(dentry, XATTR_NAME_CAPS, NULL, 0);
> if (rc > 0) {
> - if (rc == XATTR_CAPS_SZ)
> + if (rc == XATTR_CAPS_SZ_2 || rc == XATTR_CAPS_SZ_1)
> rc = inode->i_op->getxattr(dentry, XATTR_NAME_CAPS,
> &incaps, XATTR_CAPS_SZ);
> else
--
Stephen Smalley
National Security Agency
-
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