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Subject[PATCH 10/10] keys: Add capability-checking keyctl function [ver #3]
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Date
Add a keyctl function that requests a set of capability bits to find out
what features are supported.

Signed-off-by: David Howells <dhowells@redhat.com>
---

include/uapi/linux/keyctl.h | 14 ++++++++++++++
security/keys/compat.c | 3 +++
security/keys/internal.h | 2 ++
security/keys/keyctl.c | 35 +++++++++++++++++++++++++++++++++++
4 files changed, 54 insertions(+)

diff --git a/include/uapi/linux/keyctl.h b/include/uapi/linux/keyctl.h
index fd9fb11b312b..551b5814f53e 100644
--- a/include/uapi/linux/keyctl.h
+++ b/include/uapi/linux/keyctl.h
@@ -68,6 +68,7 @@
#define KEYCTL_PKEY_VERIFY 28 /* Verify a public key signature */
#define KEYCTL_RESTRICT_KEYRING 29 /* Restrict keys allowed to link to a keyring */
#define KEYCTL_MOVE 30 /* Move keys between keyrings */
+#define KEYCTL_CAPABILITIES 31 /* Find capabilities of keyrings subsystem */

/* keyctl structures */
struct keyctl_dh_params {
@@ -115,4 +116,17 @@ struct keyctl_pkey_params {

#define KEYCTL_MOVE_EXCL 0x00000001 /* Do not displace from the to-keyring */

+/*
+ * Capabilities flags. The capabilities list is an array of 8-bit integers;
+ * each integer can carry up to 8 flags.
+ */
+#define KEYCTL_CAPS0_CAPABILITIES 0x01 /* KEYCTL_CAPABILITIES supported */
+#define KEYCTL_CAPS0_PERSISTENT_KEYRINGS 0x02 /* Persistent keyrings enabled */
+#define KEYCTL_CAPS0_DIFFIE_HELLMAN 0x04 /* Diffie-Hellman computation enabled */
+#define KEYCTL_CAPS0_PUBLIC_KEY 0x08 /* Public key ops enabled */
+#define KEYCTL_CAPS0_BIG_KEY 0x10 /* big_key-type enabled */
+#define KEYCTL_CAPS0_INVALIDATE 0x20 /* KEYCTL_INVALIDATE supported */
+#define KEYCTL_CAPS0_RESTRICT_KEYRING 0x40 /* KEYCTL_RESTRICT_KEYRING supported */
+#define KEYCTL_CAPS0_MOVE 0x80 /* KEYCTL_MOVE supported */
+
#endif /* _LINUX_KEYCTL_H */
diff --git a/security/keys/compat.c b/security/keys/compat.c
index b326bc4f84d7..a53e30da20c5 100644
--- a/security/keys/compat.c
+++ b/security/keys/compat.c
@@ -162,6 +162,9 @@ COMPAT_SYSCALL_DEFINE5(keyctl, u32, option,
case KEYCTL_MOVE:
return keyctl_keyring_move(arg2, arg3, arg4, arg5);

+ case KEYCTL_CAPABILITIES:
+ return keyctl_capabilities(compat_ptr(arg2), arg3);
+
default:
return -EOPNOTSUPP;
}
diff --git a/security/keys/internal.h b/security/keys/internal.h
index b54a58c025ae..d04bff631227 100644
--- a/security/keys/internal.h
+++ b/security/keys/internal.h
@@ -329,6 +329,8 @@ static inline long keyctl_pkey_e_d_s(int op,
}
#endif

+extern long keyctl_capabilities(unsigned char __user *_buffer, size_t buflen);
+
/*
* Debugging key validation
*/
diff --git a/security/keys/keyctl.c b/security/keys/keyctl.c
index bbfe7d92d41c..9f418e66f067 100644
--- a/security/keys/keyctl.c
+++ b/security/keys/keyctl.c
@@ -30,6 +30,18 @@

#define KEY_MAX_DESC_SIZE 4096

+static const unsigned char keyrings_capabilities[1] = {
+ [0] = (KEYCTL_CAPS0_CAPABILITIES |
+ (IS_ENABLED(CONFIG_PERSISTENT_KEYRINGS) ? KEYCTL_CAPS0_PERSISTENT_KEYRINGS : 0) |
+ (IS_ENABLED(CONFIG_KEY_DH_OPERATIONS) ? KEYCTL_CAPS0_DIFFIE_HELLMAN : 0) |
+ (IS_ENABLED(CONFIG_ASYMMETRIC_KEY_TYPE) ? KEYCTL_CAPS0_PUBLIC_KEY : 0) |
+ (IS_ENABLED(CONFIG_BIG_KEYS) ? KEYCTL_CAPS0_BIG_KEY : 0) |
+ KEYCTL_CAPS0_INVALIDATE |
+ KEYCTL_CAPS0_RESTRICT_KEYRING |
+ KEYCTL_CAPS0_MOVE
+ ),
+};
+
static int key_get_type_from_user(char *type,
const char __user *_type,
unsigned len)
@@ -1678,6 +1690,26 @@ long keyctl_restrict_keyring(key_serial_t id, const char __user *_type,
return ret;
}

+/*
+ * Get keyrings subsystem capabilities.
+ */
+long keyctl_capabilities(unsigned char __user *_buffer, size_t buflen)
+{
+ size_t size = buflen;
+
+ if (size > 0) {
+ if (size > sizeof(keyrings_capabilities))
+ size = sizeof(keyrings_capabilities);
+ if (copy_to_user(_buffer, keyrings_capabilities, size) != 0)
+ return -EFAULT;
+ if (size < buflen &&
+ clear_user(_buffer + size, buflen - size) != 0)
+ return -EFAULT;
+ }
+
+ return sizeof(keyrings_capabilities);
+}
+
/*
* The key control system call
*/
@@ -1824,6 +1856,9 @@ SYSCALL_DEFINE5(keyctl, int, option, unsigned long, arg2, unsigned long, arg3,
(key_serial_t)arg4,
(unsigned int)arg5);

+ case KEYCTL_CAPABILITIES:
+ return keyctl_capabilities((unsigned char __user *)arg2, (size_t)arg3);
+
default:
return -EOPNOTSUPP;
}
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