PKCS#7: Allow detached data to be supplied for signature checking purposes
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@redhat.com>
Tested-by: Vivek Goyal <vgoyal@redhat.com>
diff --git a/crypto/asymmetric_keys/pkcs7_verify.c b/crypto/asymmetric_keys/pkcs7_verify.c
index 42bfc9d..404f89a 100644
--- a/crypto/asymmetric_keys/pkcs7_verify.c
+++ b/crypto/asymmetric_keys/pkcs7_verify.c
@@ -382,3 +382,28 @@
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;
+}