[PATCH v2 11/18] crypto: Scaffolding for RSA-PSS signature style

[Varad Gautam]

Add a crypto_template for rsa-psspad, hidden behind
CONFIG_CRYPTO_RSASSA_PSS. Set the sign/verify/encrypt/decrypt
operations to return -EOPNOTSUPP, to be implemented in the future

Signed-off-by: Varad Gautam <varad.gautam@xxxxxxxx>
---
 crypto/Kconfig                |  6 ++++++
 crypto/Makefile               |  1 +
 crypto/rsa-psspad.c           | 39 +++++++++++++++++++++++++++++++++++
 crypto/rsa.c                  | 20 +++++++++++++++---
 include/crypto/internal/rsa.h |  3 +++
 5 files changed, 66 insertions(+), 3 deletions(-)
 create mode 100644 crypto/rsa-psspad.c

diff --git a/crypto/Kconfig b/crypto/Kconfig
index 5809cc198fa7c..3aedb40aa08f1 100644
--- a/crypto/Kconfig
+++ b/crypto/Kconfig
@@ -224,6 +224,12 @@ config CRYPTO_RSA
 	help
 	  Generic implementation of the RSA public key algorithm.
 
+config CRYPTO_RSASSA_PSS
+	bool "RSASSA-PSS algorithm"
+	select CRYPTO_RSA
+	help
+	  RSASSA-PSS signature verification scheme.
+
 config CRYPTO_DH
 	tristate "Diffie-Hellman algorithm"
 	select CRYPTO_KPP
diff --git a/crypto/Makefile b/crypto/Makefile
index 57a85b2b3429b..88be24b9bcb24 100644
--- a/crypto/Makefile
+++ b/crypto/Makefile
@@ -42,6 +42,7 @@ rsa_generic-y += rsa_helper.o
 rsa_generic-y += rsa-common.o
 rsa_generic-y += rsa-pkcs1pad.o
 obj-$(CONFIG_CRYPTO_RSA) += rsa_generic.o
+obj-$(CONFIG_CRYPTO_RSASSA_PSS) += rsa-psspad.o
 
 $(obj)/sm2signature.asn1.o: $(obj)/sm2signature.asn1.c $(obj)/sm2signature.asn1.h
 $(obj)/sm2.o: $(obj)/sm2signature.asn1.h
diff --git a/crypto/rsa-psspad.c b/crypto/rsa-psspad.c
new file mode 100644
index 0000000000000..0e5422b05c081
--- /dev/null
+++ b/crypto/rsa-psspad.c
@@ -0,0 +1,39 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * RSASSA-PSS signature scheme.
+ *
+ * Copyright (C) 2021, SUSE
+ * Authors: Varad Gautam <varad.gautam@xxxxxxxx>
+ */
+
+#include <crypto/internal/akcipher.h>
+#include <crypto/internal/rsa-common.h>
+
+static int psspad_s_v_e_d(struct akcipher_request *req)
+{
+	return -EOPNOTSUPP;
+}
+
+static struct akcipher_alg psspad_alg = {
+	.init = rsapad_akcipher_init_tfm,
+	.exit = rsapad_akcipher_exit_tfm,
+
+	.encrypt = psspad_s_v_e_d,
+	.decrypt = psspad_s_v_e_d,
+	.sign = psspad_s_v_e_d,
+	.verify = psspad_s_v_e_d,
+	.set_pub_key = rsapad_set_pub_key,
+	.set_priv_key = rsapad_set_priv_key,
+	.max_size = rsapad_get_max_size
+};
+
+static int psspad_create(struct crypto_template *tmpl, struct rtattr **tb)
+{
+	return rsapad_akcipher_create(tmpl, tb, &psspad_alg);
+}
+
+struct crypto_template rsa_psspad_tmpl = {
+	.name = "psspad",
+	.create = psspad_create,
+	.module = THIS_MODULE,
+};
diff --git a/crypto/rsa.c b/crypto/rsa.c
index 5c4eece5b8028..de4ad34f9cd95 100644
--- a/crypto/rsa.c
+++ b/crypto/rsa.c
@@ -258,17 +258,31 @@ static int rsa_init(void)
 		return err;
 
 	err = crypto_register_template(&rsa_pkcs1pad_tmpl);
+	if (err)
+		goto out_err;
+
+#ifdef CONFIG_CRYPTO_RSASSA_PSS
+	err = crypto_register_template(&rsa_psspad_tmpl);
 	if (err) {
-		crypto_unregister_akcipher(&rsa);
-		return err;
+		crypto_unregister_template(&rsa_pkcs1pad_tmpl);
+		goto out_err;
 	}
+#endif
 
-	return 0;
+	goto out;
+
+out_err:
+	crypto_unregister_akcipher(&rsa);
+out:
+	return err;
 }
 
 static void rsa_exit(void)
 {
 	crypto_unregister_template(&rsa_pkcs1pad_tmpl);
+#ifdef CONFIG_CRYPTO_RSASSA_PSS
+	crypto_unregister_template(&rsa_psspad_tmpl);
+#endif
 	crypto_unregister_akcipher(&rsa);
 }
 
diff --git a/include/crypto/internal/rsa.h b/include/crypto/internal/rsa.h
index e73c61f788e68..4c168ea2f050a 100644
--- a/include/crypto/internal/rsa.h
+++ b/include/crypto/internal/rsa.h
@@ -61,4 +61,7 @@ struct rsa_mpi_key {
 };
 
 extern struct crypto_template rsa_pkcs1pad_tmpl;
+#ifdef CONFIG_CRYPTO_RSASSA_PSS
+extern struct crypto_template rsa_psspad_tmpl;
+#endif /* CONFIG_CRYPTO_RSASSA_PSS */
 #endif
-- 
2.30.2