KEYS: Add placeholder for KDF usage with DH

The values computed during Diffie-Hellman key exchange are often used
in combination with key derivation functions to create cryptographic
keys.  Add a placeholder for a later implementation to configure a
key derivation function that will transform the Diffie-Hellman
result returned by the KEYCTL_DH_COMPUTE command.

[This patch was stripped down from a patch produced by Mat Martineau that
 had a bug in the compat code - so for the moment Stephan's patch simply
 requires that the placeholder argument must be NULL]

Original-signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: Stephan Mueller <smueller@chronox.de>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: James Morris <james.l.morris@oracle.com>

diff --git a/Documentation/security/keys.txt b/Documentation/security/keys.txt
index 20d0571..3849814 100644 (file)
--- a/Documentation/security/keys.txt
+++ b/Documentation/security/keys.txt
@@ -826,7 +826,8 @@ The keyctl syscall functions are:
  (*) Compute a Diffie-Hellman shared secret or public key
 
        long keyctl(KEYCTL_DH_COMPUTE, struct keyctl_dh_params *params,
-                  char *buffer, size_t buflen);
+                  char *buffer, size_t buflen,
+                  void *reserved);
 
      The params struct contains serial numbers for three keys:
 
@@ -843,6 +844,8 @@ The keyctl syscall functions are:
      public key.  If the base is the remote public key, the result is
      the shared secret.
 
+     The reserved argument must be set to NULL.
+
      The buffer length must be at least the length of the prime, or zero.
 
      If the buffer length is nonzero, the length of the result is

diff --git a/security/keys/compat.c b/security/keys/compat.c
index c8783b3..36c80bf 100644 (file)
--- a/security/keys/compat.c
+++ b/security/keys/compat.c
@@ -134,7 +134,7 @@ COMPAT_SYSCALL_DEFINE5(keyctl, u32, option,
 
        case KEYCTL_DH_COMPUTE:
                return keyctl_dh_compute(compat_ptr(arg2), compat_ptr(arg3),
-                                        arg4);
+                                        arg4, compat_ptr(arg5));
 
        default:
                return -EOPNOTSUPP;

diff --git a/security/keys/dh.c b/security/keys/dh.c
index 880505a..531ed2e 100644 (file)
--- a/security/keys/dh.c
+++ b/security/keys/dh.c
@@ -78,7 +78,8 @@ error:
 }
 
 long keyctl_dh_compute(struct keyctl_dh_params __user *params,
-                      char __user *buffer, size_t buflen)
+                      char __user *buffer, size_t buflen,
+                      void __user *reserved)
 {
        long ret;
        MPI base, private, prime, result;
@@ -97,6 +98,11 @@ long keyctl_dh_compute(struct keyctl_dh_params __user *params,
                goto out;
        }
 
+       if (reserved) {
+               ret = -EINVAL;
+               goto out;
+       }
+
        keylen = mpi_from_key(pcopy.prime, buflen, &prime);
        if (keylen < 0 || !prime) {
                /* buflen == 0 may be used to query the required buffer size,

diff --git a/security/keys/internal.h b/security/keys/internal.h
index 8ec7a52..a705a7d 100644 (file)
--- a/security/keys/internal.h
+++ b/security/keys/internal.h
@@ -260,10 +260,11 @@ static inline long keyctl_get_persistent(uid_t uid, key_serial_t destring)
 
 #ifdef CONFIG_KEY_DH_OPERATIONS
 extern long keyctl_dh_compute(struct keyctl_dh_params __user *, char __user *,
-                             size_t);
+                             size_t, void __user *);
 #else
 static inline long keyctl_dh_compute(struct keyctl_dh_params __user *params,
-                                    char __user *buffer, size_t buflen)
+                                    char __user *buffer, size_t buflen,
+                                    void __user *reserved)
 {
        return -EOPNOTSUPP;
 }

diff --git a/security/keys/keyctl.c b/security/keys/keyctl.c
index 3b135a0..d580ad0 100644 (file)
--- a/security/keys/keyctl.c
+++ b/security/keys/keyctl.c
@@ -1688,8 +1688,8 @@ SYSCALL_DEFINE5(keyctl, int, option, unsigned long, arg2, unsigned long, arg3,
 
        case KEYCTL_DH_COMPUTE:
                return keyctl_dh_compute((struct keyctl_dh_params __user *) arg2,
-                                        (char __user *) arg3,
-                                        (size_t) arg4);
+                                        (char __user *) arg3, (size_t) arg4,
+                                        (void __user *) arg5);
 
        default:
                return -EOPNOTSUPP;