Messages in this thread Patch in this message | | | From | serue@us ... | Subject | [RFC PATCH 4/6] p9auth: add CAP_GRANT_ID to authorize use of /dev/caphash | Date | Tue, 5 Jan 2010 14:37:28 -0600 |
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From: Serge E. Hallyn <serue@us.ibm.com>
Granting userid capabilities to another task is a dangerous privilege. Don't just let file permissions authorize it. Define CAP_GRANT_ID as a new capability needed to write to /dev/caphash.
For one thing this lets us start a factotum server early on in init, then have init drop CAP_GRANT_ID from its bounding set so the rest of the system cannot regain it.
Signed-off-by: Serge E. Hallyn <serue@us.ibm.com> Cc: Greg KH <greg@kroah.com> cc: rsc@swtch.com Cc: Ashwin Ganti <ashwin.ganti@gmail.com> Cc: ericvh@gmail.com Cc: devel@linuxdriverproject.org Cc: linux-kernel@vger.kernel.org --- drivers/staging/p9auth/p9auth.c | 4 ++++ include/linux/capability.h | 6 +++++- 2 files changed, 9 insertions(+), 1 deletions(-)
diff --git a/drivers/staging/p9auth/p9auth.c b/drivers/staging/p9auth/p9auth.c index 8f70daa..fb27459 100644 --- a/drivers/staging/p9auth/p9auth.c +++ b/drivers/staging/p9auth/p9auth.c @@ -201,6 +201,10 @@ static ssize_t cap_write(struct file *filp, const char __user *buf, retval = -EINVAL; goto out; } + if (!capable(CAP_GRANT_ID)) { + retval = -EPERM; + goto out; + } printk(KERN_INFO "Capability being written to /dev/caphash : \n"); hexdump(user_buf, count); memcpy(node_ptr->data, user_buf, count); diff --git a/include/linux/capability.h b/include/linux/capability.h index 39e5ff5..ba2cbfe 100644 --- a/include/linux/capability.h +++ b/include/linux/capability.h @@ -355,7 +355,11 @@ struct cpu_vfs_cap_data { #define CAP_MAC_ADMIN 33 -#define CAP_LAST_CAP CAP_MAC_ADMIN +/* Allow granting setuid capabilities through p9auth /dev/caphash */ + +#define CAP_GRANT_ID 34 + +#define CAP_LAST_CAP CAP_GRANT_ID #define cap_valid(x) ((x) >= 0 && (x) <= CAP_LAST_CAP) -- 1.6.1
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