pefile: Parse the "Microsoft individual code signing" data blob

The PKCS#7 certificate should contain a "Microsoft individual code signing"
data blob as its signed content.  This blob contains a digest of the signed
content of the PE binary and the OID of the digest algorithm used (typically
SHA256).

Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Reviewed-by: Kees Cook <keescook@chromium.org>

crypto/asymmetric_keys/verify_pefile.h

@@ -35,3 +35,8 @@ struct pefile_context {
 	pr_devel("==> %s("FMT")\n", __func__, ##__VA_ARGS__)
 #define kleave(FMT, ...) \
 	pr_devel("<== %s()"FMT"\n", __func__, ##__VA_ARGS__)
+
+/*
+ * mscode_parser.c
+ */
+extern int mscode_parse(struct pefile_context *ctx);