It is possible for a PKCS#7 message to have detached data. However, to verify
the signatures on a PKCS#7 message, we have to be able to digest the data.
Provide a function to supply that data. An error is given if the PKCS#7
message included embedded data.
This is used in a subsequent patch to supply the data to module signing where
the signature is in the form of a PKCS#7 message with detached data, whereby
the detached data is the module content that is signed.
Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
Tested-by: Vivek Goyal <vgoyal@xxxxxxxxxx>
---
crypto/asymmetric_keys/pkcs7_verify.c | 25 +++++++++++++++++++++++++
include/crypto/pkcs7.h | 3 +++
2 files changed, 28 insertions(+)
diff --git a/crypto/asymmetric_keys/pkcs7_verify.c b/crypto/asymmetric_keys/pkcs7_verify.c
index 42bfc9de0d79..404f89a0f852 100644
--- a/crypto/asymmetric_keys/pkcs7_verify.c
+++ b/crypto/asymmetric_keys/pkcs7_verify.c
@@ -382,3 +382,28 @@ int pkcs7_verify(struct pkcs7_message *pkcs7)
return enopkg;
}
EXPORT_SYMBOL_GPL(pkcs7_verify);
+
+/**
+ * pkcs7_supply_detached_data - Supply the data needed to verify a PKCS#7 message
+ * @pkcs7: The PKCS#7 message
+ * @data: The data to be verified
+ * @datalen: The amount of data
+ *
+ * Supply the detached data needed to verify a PKCS#7 message. Note that no
+ * attempt to retain/pin the data is made. That is left to the caller. The
+ * data will not be modified by pkcs7_verify() and will not be freed when the
+ * PKCS#7 message is freed.
+ *
+ * Returns -EINVAL if data is already supplied in the message, 0 otherwise.
+ */
+int pkcs7_supply_detached_data(struct pkcs7_message *pkcs7,
+ const void *data, size_t datalen)
+{
+ if (pkcs7->data) {
+ pr_debug("Data already supplied\n");
+ return -EINVAL;
+ }
+ pkcs7->data = data;
+ pkcs7->data_len = datalen;
+ return 0;
+}
diff --git a/include/crypto/pkcs7.h b/include/crypto/pkcs7.h
index 691c79172a26..e235ab4957ee 100644
--- a/include/crypto/pkcs7.h
+++ b/include/crypto/pkcs7.h
@@ -34,3 +34,6 @@ extern int pkcs7_validate_trust(struct pkcs7_message *pkcs7,
* pkcs7_verify.c
*/
extern int pkcs7_verify(struct pkcs7_message *pkcs7);
+
+extern int pkcs7_supply_detached_data(struct pkcs7_message *pkcs7,
+ const void *data, size_t datalen);
--
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