[PATCH v2 3/4] crypto: s390/phmac - Refuse clear key material by default

[Harald Freudenberger <freude@linux.ibm.com>]

This patch exploits the new xflag PKEY_XFLAG_NOCLEARKEY from the pkey
layer. So now by default the phmac refuses the use of clear key
material ("clear key tokens") in the setkey function with
-EINVAL.

With a new kernel module parameter "clrkey" this behavior can be
controlled. By default clrkey is 'N' but for testing purpose on module
load a true value (1, 'Y') may be given to accept clear key tokens.

Note that during selftest clear keys are always used and thus the
xflag PKEY_XFLAG_NOCLEARKEY is NOT set as long as the algorithm is in
a larval state indicated by crypto_ahash_tested() returning false.

Signed-off-by: Harald Freudenberger <freude@linux.ibm.com>
Reviewed-by: Holger Dengler <dengler@linux.ibm.com>
Reviewed-by: Ingo Franzki <ifranzki@linux.ibm.com>
---
 arch/s390/crypto/phmac_s390.c | 29 ++++++++++++++++++++---------
 1 file changed, 20 insertions(+), 9 deletions(-)

diff --git a/arch/s390/crypto/phmac_s390.c b/arch/s390/crypto/phmac_s390.c
index 88342bd4c37a..03ca33ffe6cc 100644
--- a/arch/s390/crypto/phmac_s390.c
+++ b/arch/s390/crypto/phmac_s390.c
@@ -23,6 +23,10 @@
 static struct crypto_engine *phmac_crypto_engine;
 #define MAX_QLEN 10
 
+static bool pkey_clrkey_allowed;
+module_param_named(clrkey, pkey_clrkey_allowed, bool, 0444);
+MODULE_PARM_DESC(clrkey, "Allow clear key material (default N)");
+
 /*
  * A simple hash walk helper
  */
@@ -311,10 +315,14 @@ static inline int phmac_tfm_ctx_setkey(struct phmac_tfm_ctx *tfm_ctx,
  * This function may sleep - don't call in non-sleeping context.
  */
 static inline int convert_key(const u8 *key, unsigned int keylen,
-			      struct phmac_protkey *pk)
+			      struct phmac_protkey *pk, bool tested)
 {
+	u32 xflags = PKEY_XFLAG_NOMEMALLOC;
 	int rc, i;
 
+	if (tested && !pkey_clrkey_allowed)
+		xflags |= PKEY_XFLAG_NOCLEARKEY;
+
 	pk->len = sizeof(pk->protkey);
 
 	/*
@@ -328,7 +336,7 @@ static inline int convert_key(const u8 *key, unsigned int keylen,
 		}
 		rc = pkey_key2protkey(key, keylen,
 				      pk->protkey, &pk->len, &pk->type,
-				      PKEY_XFLAG_NOMEMALLOC);
+				      xflags);
 	}
 
 out:
@@ -350,7 +358,7 @@ static inline int convert_key(const u8 *key, unsigned int keylen,
  * unnecessary additional conversion but never to invalid data on the
  * hash operation.
  */
-static int phmac_convert_key(struct phmac_tfm_ctx *tfm_ctx)
+static int phmac_convert_key(struct phmac_tfm_ctx *tfm_ctx, bool tested)
 {
 	struct phmac_protkey pk;
 	int rc;
@@ -359,7 +367,7 @@ static int phmac_convert_key(struct phmac_tfm_ctx *tfm_ctx)
 	tfm_ctx->pk_state = PK_STATE_CONVERT_IN_PROGRESS;
 	spin_unlock_bh(&tfm_ctx->pk_lock);
 
-	rc = convert_key(tfm_ctx->keybuf, tfm_ctx->keylen, &pk);
+	rc = convert_key(tfm_ctx->keybuf, tfm_ctx->keylen, &pk, tested);
 
 	/* update context */
 	spin_lock_bh(&tfm_ctx->pk_lock);
@@ -404,6 +412,7 @@ static int phmac_kmac_update(struct ahash_request *req, bool maysleep)
 	struct kmac_sha2_ctx *ctx = &req_ctx->kmac_ctx;
 	struct hash_walk_helper *hwh = &req_ctx->hwh;
 	unsigned int bs = crypto_ahash_blocksize(tfm);
+	bool tested = crypto_ahash_tested(tfm);
 	unsigned int offset, k, n;
 	int rc = 0;
 
@@ -444,7 +453,7 @@ static int phmac_kmac_update(struct ahash_request *req, bool maysleep)
 					rc = -EKEYEXPIRED;
 					goto out;
 				}
-				rc = phmac_convert_key(tfm_ctx);
+				rc = phmac_convert_key(tfm_ctx, tested);
 				if (rc)
 					goto out;
 				spin_lock_bh(&tfm_ctx->pk_lock);
@@ -480,7 +489,7 @@ static int phmac_kmac_update(struct ahash_request *req, bool maysleep)
 					rc = -EKEYEXPIRED;
 					goto out;
 				}
-				rc = phmac_convert_key(tfm_ctx);
+				rc = phmac_convert_key(tfm_ctx, tested);
 				if (rc)
 					goto out;
 				spin_lock_bh(&tfm_ctx->pk_lock);
@@ -517,6 +526,7 @@ static int phmac_kmac_final(struct ahash_request *req, bool maysleep)
 	struct kmac_sha2_ctx *ctx = &req_ctx->kmac_ctx;
 	unsigned int ds = crypto_ahash_digestsize(tfm);
 	unsigned int bs = crypto_ahash_blocksize(tfm);
+	bool tested = crypto_ahash_tested(tfm);
 	unsigned int k, n;
 	int rc = 0;
 
@@ -537,7 +547,7 @@ static int phmac_kmac_final(struct ahash_request *req, bool maysleep)
 			rc = -EKEYEXPIRED;
 			goto out;
 		}
-		rc = phmac_convert_key(tfm_ctx);
+		rc = phmac_convert_key(tfm_ctx, tested);
 		if (rc)
 			goto out;
 		spin_lock_bh(&tfm_ctx->pk_lock);
@@ -741,11 +751,12 @@ static int phmac_setkey(struct crypto_ahash *tfm,
 	struct phmac_tfm_ctx *tfm_ctx = crypto_ahash_ctx(tfm);
 	unsigned int ds = crypto_ahash_digestsize(tfm);
 	unsigned int bs = crypto_ahash_blocksize(tfm);
+	bool tested = crypto_ahash_tested(tfm);
 	unsigned int tmpkeylen;
 	u8 *tmpkey = NULL;
 	int rc = 0;
 
-	if (!crypto_ahash_tested(tfm)) {
+	if (!tested) {
 		/*
 		 * selftest running: key is a raw hmac clear key and needs
 		 * to get embedded into a 'clear key token' in order to have
@@ -770,7 +781,7 @@ static int phmac_setkey(struct crypto_ahash *tfm,
 		goto out;
 
 	/* convert raw key into protected key */
-	rc = phmac_convert_key(tfm_ctx);
+	rc = phmac_convert_key(tfm_ctx, tested);
 	if (rc)
 		goto out;
 
-- 
2.43.0