[PATCH] crypto: rsa-pkcs1pad: export rsa1_asn_lookup()

[Jarkko Sakkinen]

ASN.1 template is required for TPM2 asymmetric keys, as it needs to be
piggy-packed with the input data before applying TPM2_RSA_Decrypt. This
patch prepares crypto subsystem for the addition of those keys.

Later rsa_lookup_asn1() can be enabled in crypto/asymmetric_keys/Kconfig
by:

        depends on CRYPTO_RSA >= <TPM2 asymmetric keys>

Cc: James Prestwood <prest...@gmail.com>
Signed-off-by: Jarkko Sakkinen <jar...@kernel.org>
---
 crypto/rsa-pkcs1pad.c         | 10 +++++++++-
 include/crypto/rsa-pkcs1pad.h | 11 +++++++++++
 2 files changed, 20 insertions(+), 1 deletion(-)
 create mode 100644 include/crypto/rsa-pkcs1pad.h

diff --git a/crypto/rsa-pkcs1pad.c b/crypto/rsa-pkcs1pad.c
index cd501195f34a..a07ccf179f56 100644
--- a/crypto/rsa-pkcs1pad.c
+++ b/crypto/rsa-pkcs1pad.c
@@ -7,6 +7,7 @@
 
 #include <crypto/algapi.h>
 #include <crypto/akcipher.h>
+#include <crypto/rsa-pkcs1pad.h>
 #include <crypto/internal/akcipher.h>
 #include <crypto/internal/rsa.h>
 #include <linux/err.h>
@@ -101,7 +102,13 @@ static const struct rsa_asn1_template {
        { NULL }
 };
 
-static const struct rsa_asn1_template *rsa_lookup_asn1(const char *name)
+/**
+ * rsa_lookup_asn1() - Lookup the ASN.1 digest info given the hash
+ * name:       hash algorithm name
+ *
+ * Returns theu ASN.1 digest info on success, and NULL on failure.
+ */
+const struct rsa_asn1_template *rsa_lookup_asn1(const char *name)
 {
        const struct rsa_asn1_template *p;
 
@@ -110,6 +117,7 @@ static const struct rsa_asn1_template 
*rsa_lookup_asn1(const char *name)
                        return p;
        return NULL;
 }
+EXPORT_SYMBOL_GPL(rsa_lookup_asn1);
 
 struct pkcs1pad_ctx {
        struct crypto_akcipher *child;
diff --git a/include/crypto/rsa-pkcs1pad.h b/include/crypto/rsa-pkcs1pad.h
new file mode 100644
index 000000000000..9881fa23d0dd
--- /dev/null
+++ b/include/crypto/rsa-pkcs1pad.h
@@ -0,0 +1,11 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * RSA padding templates.
+ */
+
+#ifndef _CRYPTO_RSA_PKCS1PAD_H
+#define _CRYPTO_RSA_PKCS1PAD_H
+
+const struct rsa_asn1_template *rsa_lookup_asn1(const char *name);
+
+#endif /* _CRYPTO_RSA_PKCS1PAD_H */
-- 
2.45.0