From 4693fc734d675c5518ea9bd4c9623db45bc37402 Mon Sep 17 00:00:00 2001 From: Stephan Mueller Date: Thu, 26 May 2016 23:38:12 +0200 Subject: [PATCH] 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 Signed-off-by: Stephan Mueller Signed-off-by: David Howells Signed-off-by: James Morris --- Documentation/security/keys.txt | 5 ++++- security/keys/compat.c | 2 +- security/keys/dh.c | 8 +++++++- security/keys/internal.h | 5 +++-- security/keys/keyctl.c | 4 ++-- 5 files changed, 17 insertions(+), 7 deletions(-) diff --git a/Documentation/security/keys.txt b/Documentation/security/keys.txt index 20d0571..3849814 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, + 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 --- 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 --- 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 --- 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 --- 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; -- 2.7.4