The values computed during Diffie-Hellman key exchange are often used
in combination with key derivation functions to create cryptographic
keys. Add an interface to configure a key derivation function that
will transform the Diffie-Hellman result returned by the
KEYCTL_DH_COMPUTE command.
Signed-off-by: Mat Martineau <mathew.j.martineau@xxxxxxxxxxxxxxx>
---
Documentation/security/keys.txt | 9 ++++++++-
include/uapi/linux/keyctl.h | 5 +++++
security/keys/compat.c | 2 +-
security/keys/dh.c | 8 +++++++-
security/keys/internal.h | 5 +++--
security/keys/keyctl.c | 4 ++--
6 files changed, 26 insertions(+), 7 deletions(-)
diff --git a/Documentation/security/keys.txt b/Documentation/security/keys.txt
index 20d0571..47470a6 100644
--- 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,
+ struct keyctl_kdf_params *kdf);
The params struct contains serial numbers for three keys:
@@ -843,6 +844,12 @@ The keyctl syscall functions are:
public key. If the base is the remote public key, the result is
the shared secret.
+ When kdf is NULL, the raw computed value is written to the
+ buffer. If valid kdf parameters are provided, the result of the
+ DH computation is transformed according to the requested key
+ derivation function and the transformed value is written to the
+ buffer.
+
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/include/uapi/linux/keyctl.h b/include/uapi/linux/keyctl.h
index 86eddd6..d55cf53 100644
--- a/include/uapi/linux/keyctl.h
+++ b/include/uapi/linux/keyctl.h
@@ -68,4 +68,9 @@ struct keyctl_dh_params {
__s32 base;
};
+struct keyctl_kdf_params {
+ char *name;
+ __u8 reserved[32]; /* Reserved for future use, must be 0 */
+};
+
#endif /* _LINUX_KEYCTL_H */
diff --git a/security/keys/compat.c b/security/keys/compat.c
index c8783b3..36c80bf 100644
--- 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..e415d4c 100644
--- 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,
+ struct keyctl_kdf_params __user *kdf)
{
long ret;
MPI base, private, prime, result;
@@ -97,6 +98,11 @@ long keyctl_dh_compute(struct keyctl_dh_params __user *params,
goto out;
}
+ if (kdf) {
+ 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..1b7aaaa22 100644
--- 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, struct keyctl_kdf_params __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,
+ struct keyctl_kdf_params __user *kdf)
{
return -EOPNOTSUPP;
}
diff --git a/security/keys/keyctl.c b/security/keys/keyctl.c
index 3b135a0..b106898 100644
--- 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,
+ (struct keyctl_kdf_params __user *) arg5);
default:
return -EOPNOTSUPP;
--
2.8.3
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