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ASN1_ITEM_SIGN(3)		    OpenSSL		     ASN1_ITEM_SIGN(3)

NAME
       ASN1_item_sign, ASN1_item_sign_ex, ASN1_item_sign_ctx,
       ASN1_item_verify, ASN1_item_verify_ex, ASN1_item_verify_ctx - ASN1 sign
       and verify

SYNOPSIS
	#include <openssl/x509.h>

	int ASN1_item_sign_ex(const ASN1_ITEM *it, X509_ALGOR *algor1,
			      X509_ALGOR *algor2, ASN1_BIT_STRING *signature,
			      const void *data,	const ASN1_OCTET_STRING	*id,
			      EVP_PKEY *pkey, const EVP_MD *md,	OSSL_LIB_CTX *libctx,
			      const char *propq);

	int ASN1_item_sign(const ASN1_ITEM *it,	X509_ALGOR *algor1, X509_ALGOR *algor2,
			   ASN1_BIT_STRING *signature, const void *data,
			   EVP_PKEY *pkey, const EVP_MD	*md);

	int ASN1_item_sign_ctx(const ASN1_ITEM *it, X509_ALGOR *algor1,
			       X509_ALGOR *algor2, ASN1_BIT_STRING *signature,
			       const void *data, EVP_MD_CTX *ctx);

	int ASN1_item_verify_ex(const ASN1_ITEM	*it, const X509_ALGOR *alg,
				const ASN1_BIT_STRING *signature, const	void *data,
				const ASN1_OCTET_STRING	*id, EVP_PKEY *pkey,
				OSSL_LIB_CTX *libctx, const char *propq);

	int ASN1_item_verify(const ASN1_ITEM *it, const	X509_ALGOR *alg,
			     const ASN1_BIT_STRING *signature, const void *data,
			     EVP_PKEY *pkey);

	int ASN1_item_verify_ctx(const ASN1_ITEM *it, const X509_ALGOR *alg,
				 const ASN1_BIT_STRING *signature, const void *data,
				 EVP_MD_CTX *ctx);

DESCRIPTION
       ASN1_item_sign_ex() is used to sign arbitrary ASN1 data using a data
       object data, the	ASN.1 structure	it, private key	pkey and message
       digest md.  The data that is signed is formed by	taking the data	object
       in data and converting it to der	format using the ASN.1 structure it.
       The data	that will be signed, and a structure containing	the signature
       may both	have a copy of the X509_ALGOR. The ASN1_item_sign_ex()
       function	will write the correct X509_ALGOR to the structs based on the
       algorithms and parameters that have been	set up.	If one of algor1 or
       algor2 points to	the X509_ALGOR of the data to be signed, then that
       X509_ALGOR will first be	written	before the signature is	generated.
       Examples	of valid values	that can be used by the	ASN.1 structure	it are
       ASN1_ITEM_rptr(X509_CINF), ASN1_ITEM_rptr(X509_REQ_INFO)	and
       ASN1_ITEM_rptr(X509_CRL_INFO).  The OSSL_LIB_CTX	specified in libctx
       and the property	query string specified in props	are used when
       searching for algorithms	in providers.  The generated signature is set
       into signature.	The optional parameter id can be NULL, but can be set
       for special key types.  See EVP_PKEY_CTX_set1_id() for further info.
       The output parameters <algor1> and algor2 are ignored if	they are NULL.

       ASN1_item_sign()	is similar to ASN1_item_sign_ex() but uses default
       values of NULL for the id, libctx and propq.

       ASN1_item_sign_ctx() is similiar	to ASN1_item_sign() but	uses the
       parameters contained in digest context ctx.

       ASN1_item_verify_ex() is	used to	verify the signature signature of
       internal	data data using	the public key pkey and	algorithm identifier
       alg.  The data that is verified is formed by taking the data object in
       data and	converting it to der format using the ASN.1 structure it.  The
       OSSL_LIB_CTX specified in libctx	and the	property query string
       specified in props are used when	searching for algorithms in providers.
       The optional parameter id can be	NULL, but can be set for special key
       types.  See EVP_PKEY_CTX_set1_id() for further info.

       ASN1_item_verify() is similar to	ASN1_item_verify_ex() but uses default
       values of NULL for the id, libctx and propq.

       ASN1_item_verify_ctx() is similiar to ASN1_item_verify()	but uses the
       parameters contained in digest context ctx.

RETURN VALUES
       All sign	functions return the size of the signature in bytes for
       success and zero	for failure.

       All verify functions return 1 if	the signature is valid and 0 if	the
       signature check fails. If the signature could not be checked at all
       because it was ill-formed or some other error occurred then -1 is
       returned.

EXAMPLES
       In the following	example	a 'MyObject' object is signed using the	key
       contained in an EVP_MD_CTX. The signature is written to
       MyObject.signature. The object is then output in	DER format and then
       loaded back in and verified.

	#include <openssl/x509.h>
	#include <openssl/asn1t.h>

	/* An object used to store the ASN1 data fields	that will be signed */
	typedef	struct MySignInfoObject_st
	{
	    ASN1_INTEGER *version;
	    X509_ALGOR sig_alg;
	} MySignInfoObject;

	DECLARE_ASN1_FUNCTIONS(MySignInfoObject)
	/*
	 * A higher level object containing the	ASN1 fields, signature alg and
	 * output signature.
	 */
	typedef	struct MyObject_st
	{
	    MySignInfoObject info;
	    X509_ALGOR sig_alg;
	    ASN1_BIT_STRING *signature;
	} MyObject;

	DECLARE_ASN1_FUNCTIONS(MyObject)

	/* The ASN1 definition of MySignInfoObject */
	ASN1_SEQUENCE_cb(MySignInfoObject, NULL) = {
	    ASN1_SIMPLE(MySignInfoObject, version, ASN1_INTEGER)
	    ASN1_EMBED(MySignInfoObject, sig_alg, X509_ALGOR),
	} ASN1_SEQUENCE_END_cb(MySignInfoObject, MySignInfoObject)

	/* new,	free, d2i & i2d	functions for MySignInfoObject */
	IMPLEMENT_ASN1_FUNCTIONS(MySignInfoObject)

	/* The ASN1 definition of MyObject */
	ASN1_SEQUENCE_cb(MyObject, NULL) = {
	    ASN1_EMBED(MyObject, info, MySignInfoObject),
	    ASN1_EMBED(MyObject, sig_alg, X509_ALGOR),
	    ASN1_SIMPLE(MyObject, signature, ASN1_BIT_STRING)
	} ASN1_SEQUENCE_END_cb(MyObject, MyObject)

	/* new,	free, d2i & i2d	functions for MyObject */
	IMPLEMENT_ASN1_FUNCTIONS(MyObject)

	int test_asn1_item_sign_verify(const char *mdname, EVP_PKEY *pkey, long	version)
	{
	   int ret = 0;
	   unsigned char *obj_der = NULL;
	   const unsigned char *p = NULL;
	   MyObject *obj = NULL, *loaded_obj = NULL;
	   const ASN1_ITEM *it = ASN1_ITEM_rptr(MySignInfoObject);
	   EVP_MD_CTX *sctx = NULL, *vctx = NULL;
	   int len;

	   /* Create MyObject and set its version */
	   obj = MyObject_new();
	   if (obj == NULL)
	       goto err;
	   if (!ASN1_INTEGER_set(obj->info.version, version))
	       goto err;

	   /* Set the key and digest used for signing */
	   sctx	= EVP_MD_CTX_new();
	   if (sctx == NULL
	       || !EVP_DigestSignInit_ex(sctx, NULL, mdname, NULL, NULL, pkey))
	       goto err;

	   /*
	    * it contains the mapping between ASN.1 data and an	object MySignInfoObject
	    * obj->info	is the 'MySignInfoObject' object that will be
	    *	converted into DER data	and then signed.
	    * obj->signature will contain the output signature.
	    * obj->sig_alg is filled with the private key's signing algorithm id.
	    * obj->info.sig_alg	is another copy	of the signing algorithm id that sits
	    * within MyObject.
	    */
	   len = ASN1_item_sign_ctx(it,	&obj->sig_alg, &obj->info.sig_alg,
				    obj->signature, &obj->info,	sctx);
	   if (len <= 0
	       || X509_ALGOR_cmp(&obj->sig_alg,	&obj->info.sig_alg) != 0)
	       goto err;

	   /* Output MyObject in der form */
	   len = i2d_MyObject(obj, &obj_der);
	   if (len <= 0)
	       goto err;

	   /* Set the key and digest used for verifying	*/
	   vctx	= EVP_MD_CTX_new();
	   if (vctx == NULL
	       || !EVP_DigestVerifyInit_ex(vctx, NULL, mdname, NULL, NULL, pkey))
	       goto err;

	   /* Load the der data	back into an object */
	   p = obj_der;
	   loaded_obj =	d2i_MyObject(NULL, &p, len);
	   if (loaded_obj == NULL)
	       goto err;
	   /* Verify the loaded	object */
	   ret = ASN1_item_verify_ctx(it, &loaded_obj->sig_alg,	loaded_obj->signature,
				      &loaded_obj->info, vctx);
       err:
	   OPENSSL_free(obj_der);
	   MyObject_free(loaded_obj);
	   MyObject_free(obj);
	   EVP_MD_CTX_free(sctx);
	   EVP_MD_CTX_free(vctx);
	   return ret;
	}

SEE ALSO
       X509_sign(3), X509_verify(3)

HISTORY
       ASN1_item_sign_ex() and ASN1_item_verify_ex() were added	in OpenSSL
       3.0.

COPYRIGHT
       Copyright 2020-2021 The OpenSSL Project Authors.	All Rights Reserved.

       Licensed	under the Apache License 2.0 (the "License").  You may not use
       this file except	in compliance with the License.	 You can obtain	a copy
       in the file LICENSE in the source distribution or at
       <https://www.openssl.org/source/license.html>.

3.0.0-alpha12			  2021-02-18		     ASN1_ITEM_SIGN(3)

NAME | SYNOPSIS | DESCRIPTION | RETURN VALUES | EXAMPLES | SEE ALSO | HISTORY | COPYRIGHT

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