SUNRPC: Parametrize the key length passed to context_v2_alloc_cipher()

Although the Kerberos specs have always listed separate subkey
lengths, the Linux kernel's SunRPC GSS Kerberos enctype profiles
assume the base key and the derived keys have identical lengths.

The aes256-cts-hmac-sha384-192 enctype specifies the length of its
checksum and integrity subkeys as 192 bits, but the length of its
encryption subkey (Ke) as 256 bits.

To support that enctype, parametrize context_v2_alloc_cipher() so
that each of its call sites can pass in its desired key length. For
now it will be the same length as before (gk5e->keylength), but a
subsequent patch will change this.
Tested-by: Scott Mayhew <smayhew@redhat.com>
Reviewed-by: Simo Sorce <simo@redhat.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

net/sunrpc/auth_gss/gss_krb5_mech.c

@@ -341,26 +341,6 @@ gss_import_v1_context(const void *p, const void *end, struct krb5_ctx *ctx)
 	return PTR_ERR(p);
 }
 
-static inline struct crypto_sync_skcipher *
-context_v2_alloc_cipher(struct krb5_ctx *ctx, const char *cname, u8 *key)
-{
-	struct crypto_sync_skcipher *cp;
-
-	cp = crypto_alloc_sync_skcipher(cname, 0, 0);
-	if (IS_ERR(cp)) {
-		dprintk("gss_kerberos_mech: unable to initialize "
-			"crypto algorithm %s\n", cname);
-		return NULL;
-	}
-	if (crypto_sync_skcipher_setkey(cp, key, ctx->gk5e->keylength)) {
-		dprintk("gss_kerberos_mech: error setting key for "
-			"crypto algorithm %s\n", cname);
-		crypto_free_sync_skcipher(cp);
-		return NULL;
-	}
-	return cp;
-}
-
 #if defined(CONFIG_RPCSEC_GSS_KRB5_SIMPLIFIED)
 static int
 gss_krb5_import_ctx_des(struct krb5_ctx *ctx, gfp_t gfp_mask)
@@ -403,6 +383,21 @@ gss_krb5_import_ctx_v1(struct krb5_ctx *ctx, gfp_t gfp_mask)
 
 #if defined(CONFIG_RPCSEC_GSS_KRB5_CRYPTOSYSTEM)
 
+static struct crypto_sync_skcipher *
+gss_krb5_alloc_cipher_v2(const char *cname, const struct xdr_netobj *key)
+{
+	struct crypto_sync_skcipher *tfm;
+
+	tfm = crypto_alloc_sync_skcipher(cname, 0, 0);
+	if (IS_ERR(tfm))
+		return NULL;
+	if (crypto_sync_skcipher_setkey(tfm, key->data, key->len)) {
+		crypto_free_sync_skcipher(tfm);
+		return NULL;
+	}
+	return tfm;
+}
+
 static struct crypto_ahash *
 gss_krb5_alloc_hash_v2(struct krb5_ctx *kctx, const struct xdr_netobj *key)
 {
@@ -427,27 +422,24 @@ gss_krb5_import_ctx_v2(struct krb5_ctx *ctx, gfp_t gfp_mask)
 	};
 	struct xdr_netobj keyout;
 	int ret = -EINVAL;
-	void *subkey;
 
-	subkey = kmalloc(ctx->gk5e->keylength, gfp_mask);
-	if (!subkey)
+	keyout.data = kmalloc(ctx->gk5e->keylength, gfp_mask);
+	if (!keyout.data)
 		return -ENOMEM;
 	keyout.len = ctx->gk5e->keylength;
-	keyout.data = subkey;
 
 	/* initiator seal encryption */
 	if (krb5_derive_key(ctx, &keyin, &keyout, KG_USAGE_INITIATOR_SEAL,
 			    KEY_USAGE_SEED_ENCRYPTION, gfp_mask))
 		goto out;
-	ctx->initiator_enc = context_v2_alloc_cipher(ctx,
-						     ctx->gk5e->encrypt_name,
-						     subkey);
+	ctx->initiator_enc = gss_krb5_alloc_cipher_v2(ctx->gk5e->encrypt_name,
+						      &keyout);
 	if (ctx->initiator_enc == NULL)
 		goto out;
 	if (ctx->gk5e->aux_cipher) {
 		ctx->initiator_enc_aux =
-			context_v2_alloc_cipher(ctx, ctx->gk5e->aux_cipher,
-						subkey);
+			gss_krb5_alloc_cipher_v2(ctx->gk5e->aux_cipher,
+						 &keyout);
 		if (ctx->initiator_enc_aux == NULL)
 			goto out_free;
 	}
@@ -456,15 +448,14 @@ gss_krb5_import_ctx_v2(struct krb5_ctx *ctx, gfp_t gfp_mask)
 	if (krb5_derive_key(ctx, &keyin, &keyout, KG_USAGE_ACCEPTOR_SEAL,
 			    KEY_USAGE_SEED_ENCRYPTION, gfp_mask))
 		goto out_free;
-	ctx->acceptor_enc = context_v2_alloc_cipher(ctx,
-						    ctx->gk5e->encrypt_name,
-						    subkey);
+	ctx->acceptor_enc = gss_krb5_alloc_cipher_v2(ctx->gk5e->encrypt_name,
+						     &keyout);
 	if (ctx->acceptor_enc == NULL)
 		goto out_free;
 	if (ctx->gk5e->aux_cipher) {
 		ctx->acceptor_enc_aux =
-			context_v2_alloc_cipher(ctx, ctx->gk5e->aux_cipher,
-						subkey);
+			gss_krb5_alloc_cipher_v2(ctx->gk5e->aux_cipher,
+						 &keyout);
 		if (ctx->acceptor_enc_aux == NULL)
 			goto out_free;
 	}
@@ -503,7 +494,7 @@ gss_krb5_import_ctx_v2(struct krb5_ctx *ctx, gfp_t gfp_mask)
 
 	ret = 0;
 out:
-	kfree_sensitive(subkey);
+	kfree_sensitive(keyout.data);
 	return ret;
 
 out_free: