Re: [PATCH] Filesystem capabilities support

Jesper Juhl
2005-07-15T03:46:01Z

On 7/16/05, Nicholas Hans Simmonds <nhstux@gmail.com> wrote:

While I'm not qualified to comment on the implementation I do have a
few small codingstyle comments :-)

> diff --git a/fs/read_write.c b/fs/read_write.c
> --- a/fs/read_write.c
> +++ b/fs/read_write.c
> @@ -14,6 +14,7 @@
> #include <linux/security.h>
> #include <linux/module.h>
> #include <linux/syscalls.h>
> +#include <linux/xattr.h>
>
> #include <asm/uaccess.h>
> #include <asm/unistd.h>
> @@ -303,6 +304,16 @@ ssize_t vfs_write(struct file *file, con
> else
> ret = do_sync_write(file, buf, count, pos);
> if (ret > 0) {
> +#ifdef CONFIG_SECURITY_FS_CAPABILITIES
> + struct dentry *d = file->f_dentry;
> + if(d->d_inode->i_op && d->d_inode->i_op->

if (d->d_inode->i_op ...

> + removexattr) {
> + down(&d->d_inode->i_sem);
> + d->d_inode->i_op->removexattr(d,
> + XATTR_CAP_SET);
> + up(&d->d_inode->i_sem);
> + }
> +#endif /* CONFIG_SECURITY_FS_CAPABILITIES */
> fsnotify_modify(file->f_dentry);
> current->wchar += ret;
> }
> diff --git a/include/linux/capability.h b/include/linux/capability.h
> --- a/include/linux/capability.h
> +++ b/include/linux/capability.h
> @@ -39,7 +39,19 @@ typedef struct __user_cap_data_struct {
> __u32 permitted;
> __u32 inheritable;
> } __user *cap_user_data_t;
> -
> +
> +struct cap_xattr_data {
> + __u32 version;
> + __u32 mask_effective;
> + __u32 effective;
> + __u32 mask_permitted;
> + __u32 permitted;
> + __u32 mask_inheritable;
> + __u32 inheritable;
> +};
> +
> +#define XATTR_CAP_SET XATTR_SECURITY_PREFIX "cap_set"
> +
> #ifdef __KERNEL__
>
> #include <linux/spinlock.h>
> diff --git a/security/Kconfig b/security/Kconfig
> --- a/security/Kconfig
> +++ b/security/Kconfig
> @@ -60,6 +60,13 @@ config SECURITY_CAPABILITIES
> This enables the "default" Linux capabilities functionality.
> If you are unsure how to answer this question, answer Y.
>
> +config SECURITY_FS_CAPABILITIES
> + bool "Filesystem Capabilities (EXPERIMENTAL)"
> + depends on SECURITY && EXPERIMENTAL
> + help
> + This permits a process' capabilities to be set by an extended
> + attribute in the security namespace (security.cap_set).
> +
> config SECURITY_ROOTPLUG
> tristate "Root Plug Support"
> depends on USB && SECURITY
> diff --git a/security/commoncap.c b/security/commoncap.c
> --- a/security/commoncap.c
> +++ b/security/commoncap.c
> @@ -111,9 +111,15 @@ void cap_capset_set (struct task_struct
>
> int cap_bprm_set_security (struct linux_binprm *bprm)
> {
> +#ifdef CONFIG_SECURITY_FS_CAPABILITIES
> + ssize_t (*bprm_getxattr)(struct dentry *,const char *,void *,size_t);
> + struct dentry *bprm_dentry;
> + ssize_t ret;
> + struct cap_xattr_data caps;
> +#endif /* CONFIG_SECURITY_FS_CAPABILITIES */
> +
> /* Copied from fs/exec.c:prepare_binprm. */
>
> - /* We don't have VFS support for capabilities yet */
> cap_clear (bprm->cap_inheritable);
> cap_clear (bprm->cap_permitted);
> cap_clear (bprm->cap_effective);
> @@ -134,6 +140,44 @@ int cap_bprm_set_security (struct linux_
> if (bprm->e_uid == 0)
> cap_set_full (bprm->cap_effective);
> }
> +
> +#ifdef CONFIG_SECURITY_FS_CAPABILITIES
> + /* Locate any VFS capabilities: */
> +
> + bprm_dentry = bprm->file->f_dentry;
> + if(!(bprm_dentry->d_inode->i_op &&

if (!(bprm_dentry->d_inode->i_op ...

> + bprm_dentry->d_inode->i_op->getxattr))
> + return 0;
> + bprm_getxattr = bprm_dentry->d_inode->i_op->getxattr;
> +
> + down(&bprm_dentry->d_inode->i_sem);
> + ret = bprm_getxattr(bprm_dentry,XATTR_CAP_SET,&caps,sizeof(caps));
> + up(&bprm_dentry->d_inode->i_sem);
> + if(ret == sizeof(caps)) {

if (ret == sizeof(caps)) {

> + be32_to_cpus(&caps.version);
> + be32_to_cpus(&caps.effective);
> + be32_to_cpus(&caps.mask_effective);
> + be32_to_cpus(&caps.permitted);
> + be32_to_cpus(&caps.mask_permitted);
> + be32_to_cpus(&caps.inheritable);
> + be32_to_cpus(&caps.mask_inheritable);
> + if(caps.version == _LINUX_CAPABILITY_VERSION) {

if (caps.version ...

> + cap_t(bprm->cap_effective) &= caps.mask_effective;
> + cap_t(bprm->cap_effective) |= caps.effective;
> +
> + cap_t(bprm->cap_permitted) &= caps.mask_permitted;
> + cap_t(bprm->cap_permitted) |= caps.permitted;
> +
> + cap_t(bprm->cap_inheritable) &= caps.mask_inheritable;
> + cap_t(bprm->cap_inheritable) |= caps.inheritable;
> + } else
> + printk(KERN_WARNING "Warning: %s capability set has "
> + "incorrect version %08X. Correct version "
> + "is %08X.\n",bprm->filename,caps.version,
> + _LINUX_CAPABILITY_VERSION);
> + }
> +#endif /* CONFIG_SECURITY_FS_CAPABILITIES */
> +
> return 0;
> }
>

--
Jesper Juhl <jesper.juhl@gmail.com>
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