pkcs7: move common functions to PKCS7 helper

Move pkcs7_get_content_data as a helper function that can be
shared by legacy crypto lib and MbedTLS implementation.

Signed-off-by: Raymond Mao <raymond.mao@linaro.org>
Reviewed-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>

1 files changed, 37 insertions, 0 deletions

diff --git a/lib/crypto/pkcs7_helper.c b/lib/crypto/pkcs7_helper.c
new file mode 100644
index 00000000000..bb3b9d1354f
--- /dev/null
+++ b/lib/crypto/pkcs7_helper.c
@@ -0,0 +1,37 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * PKCS7 helper functions
+ *
+ * Copyright (c) 2012 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ */
+#include <linux/kernel.h>
+#include <linux/err.h>
+#include <crypto/pkcs7_parser.h>
+
+/**
+ * pkcs7_get_content_data - Get access to the PKCS#7 content
+ * @pkcs7: The preparsed PKCS#7 message to access
+ * @_data: Place to return a pointer to the data
+ * @_data_len: Place to return the data length
+ * @_headerlen: Size of ASN.1 header not included in _data
+ *
+ * Get access to the data content of the PKCS#7 message.  The size of the
+ * header of the ASN.1 object that contains it is also provided and can be used
+ * to adjust *_data and *_data_len to get the entire object.
+ *
+ * Returns -ENODATA if the data object was missing from the message.
+ */
+int pkcs7_get_content_data(const struct pkcs7_message *pkcs7,
+			   const void **_data, size_t *_data_len,
+			   size_t *_headerlen)
+{
+	if (!pkcs7->data)
+		return -ENODATA;
+
+	*_data = pkcs7->data;
+	*_data_len = pkcs7->data_len;
+	if (_headerlen)
+		*_headerlen = pkcs7->data_hdrlen;
+	return 0;
+}