On Wed, 2007-12-05 at 12:12 -0800, Casey Schaufler wrote:
> --- David Howells <[email protected]> wrote:
>
> > Add a keyctl() function to get the security label of a key.
> >
> > The following is added to Documentation/keys.txt:
> >
> > (*) Get the LSM security context attached to a key.
> >
> > long keyctl(KEYCTL_GET_SECURITY, key_serial_t key, char *buffer,
> > size_t buflen)
> >
> > This function returns a string that represents the LSM security context
> > attached to a key in the buffer provided.
> >
> > Unless there's an error, it always returns the amount of data it could
> > produce, even if that's too big for the buffer, but it won't copy more
> > than requested to userspace. If the buffer pointer is NULL then no copy
> > will take place.
> >
> > A NUL character is included at the end of the string if the buffer is
> > sufficiently big. This is included in the returned count. If no LSM is
> > in force then an empty string will be returned.
> >
> > A process must have view permission on the key for this function to be
> > successful.
> >
> > Signed-off-by: David Howells <[email protected]>
> > ---
> >
> > Documentation/keys.txt | 21 +++++++++++++++
> > include/linux/keyctl.h | 1 +
> > include/linux/security.h | 20 +++++++++++++-
> > security/dummy.c | 8 ++++++
> > security/keys/compat.c | 3 ++
> > security/keys/keyctl.c | 66
> > ++++++++++++++++++++++++++++++++++++++++++++++
> > security/security.c | 5 +++
> > security/selinux/hooks.c | 21 +++++++++++++--
> > 8 files changed, 141 insertions(+), 4 deletions(-)
> >
> > diff --git a/Documentation/keys.txt b/Documentation/keys.txt
> > index b82d38d..be424b0 100644
> > --- a/Documentation/keys.txt
> > +++ b/Documentation/keys.txt
> > @@ -711,6 +711,27 @@ The keyctl syscall functions are:
> > The assumed authoritative key is inherited across fork and exec.
> >
> >
> > + (*) Get the LSM security context attached to a key.
> > +
> > + long keyctl(KEYCTL_GET_SECURITY, key_serial_t key, char *buffer,
> > + size_t buflen)
> > +
> > + This function returns a string that represents the LSM security context
> > + attached to a key in the buffer provided.
> > +
> > + Unless there's an error, it always returns the amount of data it could
> > + produce, even if that's too big for the buffer, but it won't copy more
> > + than requested to userspace. If the buffer pointer is NULL then no copy
> > + will take place.
> > +
> > + A NUL character is included at the end of the string if the buffer is
> > + sufficiently big. This is included in the returned count. If no LSM
> > is
> > + in force then an empty string will be returned.
> > +
> > + A process must have view permission on the key for this function to be
> > + successful.
> > +
> > +
> > ===============
> > KERNEL SERVICES
> > ===============
> > diff --git a/include/linux/keyctl.h b/include/linux/keyctl.h
> > index 3365945..656ee6b 100644
> > --- a/include/linux/keyctl.h
> > +++ b/include/linux/keyctl.h
> > @@ -49,5 +49,6 @@
> > #define KEYCTL_SET_REQKEY_KEYRING 14 /* set default request-key keyring */
> > #define KEYCTL_SET_TIMEOUT 15 /* set key timeout */
> > #define KEYCTL_ASSUME_AUTHORITY 16 /* assume request_key() authorisation */
> > +#define KEYCTL_GET_SECURITY 17 /* get key security label */
> >
> > #endif /* _LINUX_KEYCTL_H */
> > diff --git a/include/linux/security.h b/include/linux/security.h
> > index ac05083..8d9e946 100644
> > --- a/include/linux/security.h
> > +++ b/include/linux/security.h
> > @@ -959,6 +959,17 @@ struct request_sock;
> > * @perm describes the combination of permissions required of this key.
> > * Return 1 if permission granted, 0 if permission denied and -ve it the
> > * normal permissions model should be effected.
> > + * @key_getsecurity:
>
> If I contradict what I said last time around, well, I've seen
> more of what's going on since then. (insert smiley here)
>
> I think that this should be key_getsecctx(). That would get you
> what you need from SELinux and Smack. Unfortunately, there is no
> precedent for interfaces that return the secctx, while the are
> places in networking and audit (audit needs to be converted off
> of SELinux calls to LSM calls) that call getsecid() interfaces
> and later use security_secid_to_secctx() to get the "printable"
> version. So, key_getsecid() is the interface to introduce if you
> want to be consistant, and pass the result to
> security_secid_to_secctx() to get the data you're looking for.
inode_getsecurity and getprocattr directly return the strings.
Admittedly, the whole interface could be cleaned up and made far more
consistent, but I don't think he necessarily has to go through the
getsecid + secid_to_secctx sequence if he only wants the secctx.
> > + * Get a textual representation of the security context attached to a key
> > + * for the purposes of honouring KEYCTL_GETSECURITY. This function
> > + * allocates the storage for the NUL-terminated string and the caller
> > + * should free it.
> > + * @key points to the key to be queried.
> > + * @_buffer points to a pointer that should be set to point to the
> > + * resulting string (if no label or an error occurs).
> > + * Return the length of the string (including terminating NUL) or -ve if
> > + * an error.
> > + * May also return 0 (and a NULL buffer pointer) if there is no label.
> > *
> > * Security hooks affecting all System V IPC operations.
> > *
> > @@ -1437,7 +1448,7 @@ struct security_operations {
> > int (*key_permission)(key_ref_t key_ref,
> > struct task_struct *context,
> > key_perm_t perm);
> > -
> > + int (*key_getsecurity)(struct key *key, char **_buffer);
> > #endif /* CONFIG_KEYS */
> >
> > };
> > @@ -2567,6 +2578,7 @@ int security_key_alloc(struct key *key, struct
> > task_struct *tsk, unsigned long f
> > void security_key_free(struct key *key);
> > int security_key_permission(key_ref_t key_ref,
> > struct task_struct *context, key_perm_t perm);
> > +int security_key_getsecurity(struct key *key, char **_buffer);
> >
> > #else
> >
> > @@ -2588,6 +2600,12 @@ static inline int security_key_permission(key_ref_t
> > key_ref,
> > return 0;
> > }
> >
> > +static inline int security_key_getsecurity(struct key *key, char **_buffer)
> > +{
> > + *_buffer = NULL;
> > + return 0;
> > +}
> > +
> > #endif
> > #endif /* CONFIG_KEYS */
> >
> > diff --git a/security/dummy.c b/security/dummy.c
> > index 6d895ad..7993b30 100644
> > --- a/security/dummy.c
> > +++ b/security/dummy.c
> > @@ -949,6 +949,13 @@ static inline int dummy_key_permission(key_ref_t
> > key_ref,
> > {
> > return 0;
> > }
> > +
> > +static int dummy_key_getsecurity(struct key *key, char **_buffer)
> > +{
> > + *_buffer = NULL;
> > + return 0;
> > +}
> > +
> > #endif /* CONFIG_KEYS */
> >
> > struct security_operations dummy_security_ops;
> > @@ -1133,6 +1140,7 @@ void security_fixup_ops (struct security_operations
> > *ops)
> > set_to_dummy_if_null(ops, key_alloc);
> > set_to_dummy_if_null(ops, key_free);
> > set_to_dummy_if_null(ops, key_permission);
> > + set_to_dummy_if_null(ops, key_getsecurity);
> > #endif /* CONFIG_KEYS */
> >
> > }
> > diff --git a/security/keys/compat.c b/security/keys/compat.c
> > index e10ec99..c766c68 100644
> > --- a/security/keys/compat.c
> > +++ b/security/keys/compat.c
> > @@ -79,6 +79,9 @@ asmlinkage long compat_sys_keyctl(u32 option,
> > case KEYCTL_ASSUME_AUTHORITY:
> > return keyctl_assume_authority(arg2);
> >
> > + case KEYCTL_GET_SECURITY:
> > + return keyctl_get_security(arg2, compat_ptr(arg3), arg4);
> > +
> > default:
> > return -EOPNOTSUPP;
> > }
> > diff --git a/security/keys/keyctl.c b/security/keys/keyctl.c
> > index 1698bf9..56e963b 100644
> > --- a/security/keys/keyctl.c
> > +++ b/security/keys/keyctl.c
> > @@ -20,6 +20,7 @@
> > #include <linux/string.h>
> > #include <linux/err.h>
> > #include <linux/vmalloc.h>
> > +#include <linux/security.h>
> > #include <asm/uaccess.h>
> > #include "internal.h"
> >
> > @@ -1080,6 +1081,66 @@ error:
> >
> > } /* end keyctl_assume_authority() */
> >
> > +/*
> > + * get the security label of a key
> > + * - the key must grant us view permission
> > + * - if there's a buffer, we place up to buflen bytes of data into it
> > + * - unless there's an error, we return the amount of information available,
> > + * irrespective of how much we may have copied (including the terminal
> > NUL)
> > + * - implements keyctl(KEYCTL_GET_SECURITY)
> > + */
> > +long keyctl_get_security(key_serial_t keyid,
> > + char __user *buffer,
> > + size_t buflen)
> > +{
> > + struct key *key, *instkey;
> > + key_ref_t key_ref;
> > + char *context;
> > + long ret;
> > +
> > + key_ref = lookup_user_key(NULL, keyid, 0, 1, KEY_VIEW);
> > + if (IS_ERR(key_ref)) {
> > + if (PTR_ERR(key_ref) != -EACCES)
> > + return PTR_ERR(key_ref);
> > +
> > + /* viewing a key under construction is also permitted if we
> > + * have the authorisation token handy */
> > + instkey = key_get_instantiation_authkey(keyid);
> > + if (IS_ERR(instkey))
> > + return PTR_ERR(key_ref);
> > + key_put(instkey);
> > +
> > + key_ref = lookup_user_key(NULL, keyid, 0, 1, 0);
> > + if (IS_ERR(key_ref))
> > + return PTR_ERR(key_ref);
> > + }
> > +
> > + key = key_ref_to_ptr(key_ref);
> > + ret = security_key_getsecurity(key, &context);
> > + if (ret == 0) {
> > + /* if no information was returned, give userspace an empty
> > + * string */
> > + ret = 1;
> > + if (buffer && buflen > 0 &&
> > + copy_to_user(buffer, "", 1) != 0)
> > + ret = -EFAULT;
> > + } else if (ret > 0) {
> > + /* return as much data as there's room for */
> > + if (buffer && buflen > 0) {
> > + if (buflen > ret)
> > + buflen = ret;
> > +
> > + if (copy_to_user(buffer, context, buflen) != 0)
> > + ret = -EFAULT;
> > + }
> > +
> > + kfree(context);
> > + }
> > +
> > + key_ref_put(key_ref);
> > + return ret;
> > +}
> > +
> >
> >
> /*****************************************************************************/
> > /*
> > * the key control system call
> > @@ -1160,6 +1221,11 @@ asmlinkage long sys_keyctl(int option, unsigned long
> > arg2, unsigned long arg3,
> > case KEYCTL_ASSUME_AUTHORITY:
> > return keyctl_assume_authority((key_serial_t) arg2);
> >
> > + case KEYCTL_GET_SECURITY:
> > + return keyctl_get_security((key_serial_t) arg2,
> > + (char *) arg3,
> > + (size_t) arg4);
> > +
> > default:
> > return -EOPNOTSUPP;
> > }
> > diff --git a/security/security.c b/security/security.c
> > index 0e1f1f1..16213e3 100644
> > --- a/security/security.c
> > +++ b/security/security.c
> > @@ -1079,4 +1079,9 @@ int security_key_permission(key_ref_t key_ref,
> > return security_ops->key_permission(key_ref, context, perm);
> > }
> >
> > +int security_key_getsecurity(struct key *key, char **_buffer)
> > +{
> > + return security_ops->key_getsecurity(key, _buffer);
> > +}
> > +
> > #endif /* CONFIG_KEYS */
> > diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
> > index 9f3124b..bd4cfab 100644
> > --- a/security/selinux/hooks.c
> > +++ b/security/selinux/hooks.c
> > @@ -4768,6 +4768,20 @@ static int selinux_key_permission(key_ref_t key_ref,
> > SECCLASS_KEY, perm, NULL);
> > }
> >
> > +static int selinux_key_getsecurity(struct key *key, char **_buffer)
> > +{
> > + struct key_security_struct *ksec = key->security;
> > + char *context = NULL;
> > + unsigned len;
> > + int rc;
> > +
> > + rc = security_sid_to_context(ksec->sid, &context, &len);
> > + if (!rc)
> > + rc = len;
> > + *_buffer = context;
> > + return rc;
> > +}
> > +
> > #endif
> >
> > static struct security_operations selinux_ops = {
> > @@ -4943,9 +4957,10 @@ static struct security_operations selinux_ops = {
> > #endif
> >
> > #ifdef CONFIG_KEYS
> > - .key_alloc = selinux_key_alloc,
> > - .key_free = selinux_key_free,
> > - .key_permission = selinux_key_permission,
> > + .key_alloc = selinux_key_alloc,
> > + .key_free = selinux_key_free,
> > + .key_permission = selinux_key_permission,
> > + .key_getsecurity = selinux_key_getsecurity,
> > #endif
> > };
> >
> >
> >
> >
>
>
> Casey Schaufler
> [email protected]
>
> --
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--
Stephen Smalley
National Security Agency
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