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authorDavid Howells <dhowells@redhat.com>2009-09-02 09:14:21 +0100
committerJames Morris <jmorris@namei.org>2009-09-02 21:29:22 +1000
commitee18d64c1f632043a02e6f5ba5e045bb26a5465f (patch)
tree80b5a4d530ec7d5fd69799920f0db7b78aba6b9d /include/linux/security.h
parentKEYS: Extend TIF_NOTIFY_RESUME to (almost) all architectures [try #6] (diff)
downloadlinux-dev-ee18d64c1f632043a02e6f5ba5e045bb26a5465f.tar.xz
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KEYS: Add a keyctl to install a process's session keyring on its parent [try #6]
Add a keyctl to install a process's session keyring onto its parent. This replaces the parent's session keyring. Because the COW credential code does not permit one process to change another process's credentials directly, the change is deferred until userspace next starts executing again. Normally this will be after a wait*() syscall. To support this, three new security hooks have been provided: cred_alloc_blank() to allocate unset security creds, cred_transfer() to fill in the blank security creds and key_session_to_parent() - which asks the LSM if the process may replace its parent's session keyring. The replacement may only happen if the process has the same ownership details as its parent, and the process has LINK permission on the session keyring, and the session keyring is owned by the process, and the LSM permits it. Note that this requires alteration to each architecture's notify_resume path. This has been done for all arches barring blackfin, m68k* and xtensa, all of which need assembly alteration to support TIF_NOTIFY_RESUME. This allows the replacement to be performed at the point the parent process resumes userspace execution. This allows the userspace AFS pioctl emulation to fully emulate newpag() and the VIOCSETTOK and VIOCSETTOK2 pioctls, all of which require the ability to alter the parent process's PAG membership. However, since kAFS doesn't use PAGs per se, but rather dumps the keys into the session keyring, the session keyring of the parent must be replaced if, for example, VIOCSETTOK is passed the newpag flag. This can be tested with the following program: #include <stdio.h> #include <stdlib.h> #include <keyutils.h> #define KEYCTL_SESSION_TO_PARENT 18 #define OSERROR(X, S) do { if ((long)(X) == -1) { perror(S); exit(1); } } while(0) int main(int argc, char **argv) { key_serial_t keyring, key; long ret; keyring = keyctl_join_session_keyring(argv[1]); OSERROR(keyring, "keyctl_join_session_keyring"); key = add_key("user", "a", "b", 1, keyring); OSERROR(key, "add_key"); ret = keyctl(KEYCTL_SESSION_TO_PARENT); OSERROR(ret, "KEYCTL_SESSION_TO_PARENT"); return 0; } Compiled and linked with -lkeyutils, you should see something like: [dhowells@andromeda ~]$ keyctl show Session Keyring -3 --alswrv 4043 4043 keyring: _ses 355907932 --alswrv 4043 -1 \_ keyring: _uid.4043 [dhowells@andromeda ~]$ /tmp/newpag [dhowells@andromeda ~]$ keyctl show Session Keyring -3 --alswrv 4043 4043 keyring: _ses 1055658746 --alswrv 4043 4043 \_ user: a [dhowells@andromeda ~]$ /tmp/newpag hello [dhowells@andromeda ~]$ keyctl show Session Keyring -3 --alswrv 4043 4043 keyring: hello 340417692 --alswrv 4043 4043 \_ user: a Where the test program creates a new session keyring, sticks a user key named 'a' into it and then installs it on its parent. Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: James Morris <jmorris@namei.org>
Diffstat (limited to '')
-rw-r--r--include/linux/security.h38
1 files changed, 38 insertions, 0 deletions
diff --git a/include/linux/security.h b/include/linux/security.h
index 40ba39ea68ce..97de3fe3dd0d 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -653,6 +653,11 @@ static inline void security_free_mnt_opts(struct security_mnt_opts *opts)
* manual page for definitions of the @clone_flags.
* @clone_flags contains the flags indicating what should be shared.
* Return 0 if permission is granted.
+ * @cred_alloc_blank:
+ * @cred points to the credentials.
+ * @gfp indicates the atomicity of any memory allocations.
+ * Only allocate sufficient memory and attach to @cred such that
+ * cred_transfer() will not get ENOMEM.
* @cred_free:
* @cred points to the credentials.
* Deallocate and clear the cred->security field in a set of credentials.
@@ -665,6 +670,10 @@ static inline void security_free_mnt_opts(struct security_mnt_opts *opts)
* @new points to the new credentials.
* @old points to the original credentials.
* Install a new set of credentials.
+ * @cred_transfer:
+ * @new points to the new credentials.
+ * @old points to the original credentials.
+ * Transfer data from original creds to new creds
* @kernel_act_as:
* Set the credentials for a kernel service to act as (subjective context).
* @new points to the credentials to be modified.
@@ -1103,6 +1112,13 @@ static inline void security_free_mnt_opts(struct security_mnt_opts *opts)
* 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.
+ * @key_session_to_parent:
+ * Forcibly assign the session keyring from a process to its parent
+ * process.
+ * @cred: Pointer to process's credentials
+ * @parent_cred: Pointer to parent process's credentials
+ * @keyring: Proposed new session keyring
+ * Return 0 if permission is granted, -ve error otherwise.
*
* Security hooks affecting all System V IPC operations.
*
@@ -1498,10 +1514,12 @@ struct security_operations {
int (*dentry_open) (struct file *file, const struct cred *cred);
int (*task_create) (unsigned long clone_flags);
+ int (*cred_alloc_blank) (struct cred *cred, gfp_t gfp);
void (*cred_free) (struct cred *cred);
int (*cred_prepare)(struct cred *new, const struct cred *old,
gfp_t gfp);
void (*cred_commit)(struct cred *new, const struct cred *old);
+ void (*cred_transfer)(struct cred *new, const struct cred *old);
int (*kernel_act_as)(struct cred *new, u32 secid);
int (*kernel_create_files_as)(struct cred *new, struct inode *inode);
int (*kernel_module_request)(void);
@@ -1639,6 +1657,9 @@ struct security_operations {
const struct cred *cred,
key_perm_t perm);
int (*key_getsecurity)(struct key *key, char **_buffer);
+ int (*key_session_to_parent)(const struct cred *cred,
+ const struct cred *parent_cred,
+ struct key *key);
#endif /* CONFIG_KEYS */
#ifdef CONFIG_AUDIT
@@ -1755,9 +1776,11 @@ int security_file_send_sigiotask(struct task_struct *tsk,
int security_file_receive(struct file *file);
int security_dentry_open(struct file *file, const struct cred *cred);
int security_task_create(unsigned long clone_flags);
+int security_cred_alloc_blank(struct cred *cred, gfp_t gfp);
void security_cred_free(struct cred *cred);
int security_prepare_creds(struct cred *new, const struct cred *old, gfp_t gfp);
void security_commit_creds(struct cred *new, const struct cred *old);
+void security_transfer_creds(struct cred *new, const struct cred *old);
int security_kernel_act_as(struct cred *new, u32 secid);
int security_kernel_create_files_as(struct cred *new, struct inode *inode);
int security_kernel_module_request(void);
@@ -2286,6 +2309,9 @@ static inline int security_task_create(unsigned long clone_flags)
return 0;
}
+static inline void security_cred_alloc_blank(struct cred *cred, gfp_t gfp)
+{ }
+
static inline void security_cred_free(struct cred *cred)
{ }
@@ -2301,6 +2327,11 @@ static inline void security_commit_creds(struct cred *new,
{
}
+static inline void security_transfer_creds(struct cred *new,
+ const struct cred *old)
+{
+}
+
static inline int security_kernel_act_as(struct cred *cred, u32 secid)
{
return 0;
@@ -2923,6 +2954,9 @@ void security_key_free(struct key *key);
int security_key_permission(key_ref_t key_ref,
const struct cred *cred, key_perm_t perm);
int security_key_getsecurity(struct key *key, char **_buffer);
+int security_key_session_to_parent(const struct cred *cred,
+ const struct cred *parent_cred,
+ struct key *key);
#else
@@ -2950,6 +2984,10 @@ static inline int security_key_getsecurity(struct key *key, char **_buffer)
return 0;
}
+static inline int security_key_session_to_parent(const struct cred *cred,
+ const struct cred *parent_cred,
+ struct key *key);
+
#endif
#endif /* CONFIG_KEYS */