doc/crypto/EVP_DigestInit.pod - third_party/openssl - Git at Google

 =pod

 =head1 NAME

 EVP_MD_CTX_new, EVP_MD_CTX_reset, EVP_MD_CTX_free, EVP_MD_CTX_copy_ex,
 EVP_DigestInit_ex, EVP_DigestUpdate, EVP_DigestFinal_ex, EVP_MAX_MD_SIZE,
 EVP_DigestInit, EVP_DigestFinal, EVP_MD_CTX_copy, EVP_MD_type,
 EVP_MD_pkey_type, EVP_MD_size, EVP_MD_block_size, EVP_MD_CTX_md, EVP_MD_CTX_size,
 EVP_MD_CTX_block_size, EVP_MD_CTX_type, EVP_md_null, EVP_md2, EVP_md5, EVP_sha1,
 EVP_sha224, EVP_sha256, EVP_sha384, EVP_sha512, EVP_mdc2,
 EVP_ripemd160, EVP_get_digestbyname, EVP_get_digestbynid, EVP_get_digestbyobj -
 EVP digest routines

 =head1 SYNOPSIS

  #include <openssl/evp.h>

  EVP_MD_CTX *EVP_MD_CTX_new(void);
  int EVP_MD_CTX_reset(EVP_MD_CTX *ctx);
  void EVP_MD_CTX_free(EVP_MD_CTX *ctx);

  int EVP_DigestInit_ex(EVP_MD_CTX *ctx, const EVP_MD *type, ENGINE *impl);
  int EVP_DigestUpdate(EVP_MD_CTX *ctx, const void *d, size_t cnt);
  int EVP_DigestFinal_ex(EVP_MD_CTX *ctx, unsigned char *md,
         unsigned int *s);

  int EVP_MD_CTX_copy_ex(EVP_MD_CTX *out,const EVP_MD_CTX *in);

  int EVP_DigestInit(EVP_MD_CTX *ctx, const EVP_MD *type);
  int EVP_DigestFinal(EVP_MD_CTX *ctx, unsigned char *md,
         unsigned int *s);

  int EVP_MD_CTX_copy(EVP_MD_CTX *out,EVP_MD_CTX *in);

  #define EVP_MAX_MD_SIZE 64	/* SHA512 */

  int EVP_MD_type(const EVP_MD *md);
  int EVP_MD_pkey_type(const EVP_MD *md);
  int EVP_MD_size(const EVP_MD *md);
  int EVP_MD_block_size(const EVP_MD *md);

  const EVP_MD *EVP_MD_CTX_md(const EVP_MD_CTX *ctx);
  int (*EVP_MD_CTX_update_fn(EVP_MD_CTX *ctx))(EVP_MD_CTX *ctx,
                                               const void *data, size_t count);
  void EVP_MD_CTX_set_update_fn(EVP_MD_CTX *ctx,
                                int (*update) (EVP_MD_CTX *ctx,
                                               const void *data, size_t count));
  int EVP_MD_CTX_size(const EVP_MD *ctx);
  int EVP_MD_CTX_block_size(const EVP_MD *ctx);
  int EVP_MD_CTX_type(const EVP_MD *ctx);
  EVP_PKEY_CTX *EVP_MD_CTX_pkey_ctx(const EVP_MD_CTX *ctx);
  void *EVP_MD_CTX_md_data(const EVP_MD_CTX *ctx);

  const EVP_MD *EVP_md_null(void);
  const EVP_MD *EVP_md2(void);
  const EVP_MD *EVP_md5(void);
  const EVP_MD *EVP_sha1(void);
  const EVP_MD *EVP_mdc2(void);
  const EVP_MD *EVP_ripemd160(void);

  const EVP_MD *EVP_sha224(void);
  const EVP_MD *EVP_sha256(void);
  const EVP_MD *EVP_sha384(void);
  const EVP_MD *EVP_sha512(void);

  const EVP_MD *EVP_get_digestbyname(const char *name);
  const EVP_MD *EVP_get_digestbynid(int type);
  const EVP_MD *EVP_get_digestbyobj(const ASN1_OBJECT *o);

 =head1 DESCRIPTION

 The EVP digest routines are a high level interface to message digests,
 and should be used instead of the cipher-specific functions.

 EVP_MD_CTX_new() allocates, initializes and returns a digest context.

 EVP_MD_CTX_reset() resets the digest context B<ctx>.  This can be used
 to reuse an already existing context.

 EVP_MD_CTX_free() cleans up digest context B<ctx> and frees up the
 space allocated to it.

 EVP_DigestInit_ex() sets up digest context B<ctx> to use a digest
 B<type> from ENGINE B<impl>. B<ctx> must be initialized before calling this
 function. B<type> will typically be supplied by a function such as EVP_sha1().
 If B<impl> is NULL then the default implementation of digest B<type> is used.

 EVP_DigestUpdate() hashes B<cnt> bytes of data at B<d> into the
 digest context B<ctx>. This function can be called several times on the
 same B<ctx> to hash additional data.

 EVP_DigestFinal_ex() retrieves the digest value from B<ctx> and places
 it in B<md>. If the B<s> parameter is not NULL then the number of
 bytes of data written (i.e. the length of the digest) will be written
 to the integer at B<s>, at most B<EVP_MAX_MD_SIZE> bytes will be written.
 After calling EVP_DigestFinal_ex() no additional calls to EVP_DigestUpdate()
 can be made, but EVP_DigestInit_ex() can be called to initialize a new
 digest operation.

 EVP_MD_CTX_copy_ex() can be used to copy the message digest state from
 B<in> to B<out>. This is useful if large amounts of data are to be
 hashed which only differ in the last few bytes. B<out> must be initialized
 before calling this function.

 EVP_DigestInit() behaves in the same way as EVP_DigestInit_ex() except
 the passed context B<ctx> does not have to be initialized, and it always
 uses the default digest implementation.

 EVP_DigestFinal() is similar to EVP_DigestFinal_ex() except the digest
 context B<ctx> is automatically cleaned up.

 EVP_MD_CTX_copy() is similar to EVP_MD_CTX_copy_ex() except the destination
 B<out> does not have to be initialized.

 EVP_MD_size() and EVP_MD_CTX_size() return the size of the message digest
 when passed an B<EVP_MD> or an B<EVP_MD_CTX> structure, i.e. the size of the
 hash.

 EVP_MD_block_size() and EVP_MD_CTX_block_size() return the block size of the
 message digest when passed an B<EVP_MD> or an B<EVP_MD_CTX> structure.

 EVP_MD_type() and EVP_MD_CTX_type() return the NID of the OBJECT IDENTIFIER
 representing the given message digest when passed an B<EVP_MD> structure.
 For example EVP_MD_type(EVP_sha1()) returns B<NID_sha1>. This function is
 normally used when setting ASN1 OIDs.

 EVP_MD_CTX_md() returns the B<EVP_MD> structure corresponding to the passed
 B<EVP_MD_CTX>.

 EVP_MD_pkey_type() returns the NID of the public key signing algorithm associated
 with this digest. For example EVP_sha1() is associated with RSA so this will
 return B<NID_sha1WithRSAEncryption>. Since digests and signature algorithms
 are no longer linked this function is only retained for compatibility
 reasons.

 EVP_md2(), EVP_md5(), EVP_sha1(), EVP_sha224(), EVP_sha256(),
 EVP_sha384(), EVP_sha512(), EVP_mdc2() and EVP_ripemd160() return B<EVP_MD>
 structures for the MD2, MD5, SHA1, SHA224, SHA256, SHA384, SHA512, MDC2
 and RIPEMD160 digest algorithms respectively.

 EVP_md_null() is a "null" message digest that does nothing: i.e. the hash it
 returns is of zero length.

 EVP_get_digestbyname(), EVP_get_digestbynid() and EVP_get_digestbyobj()
 return an B<EVP_MD> structure when passed a digest name, a digest NID or
 an ASN1_OBJECT structure respectively. The digest table must be initialized
 using, for example, OpenSSL_add_all_digests() for these functions to work.

 =head1 RETURN VALUES

 EVP_DigestInit_ex(), EVP_DigestUpdate() and EVP_DigestFinal_ex() return 1 for
 success and 0 for failure.

 EVP_MD_CTX_copy_ex() returns 1 if successful or 0 for failure.

 EVP_MD_type(), EVP_MD_pkey_type() and EVP_MD_type() return the NID of the
 corresponding OBJECT IDENTIFIER or NID_undef if none exists.

 EVP_MD_size(), EVP_MD_block_size(), EVP_MD_CTX_size() and
 EVP_MD_CTX_block_size() return the digest or block size in bytes.

 EVP_md_null(), EVP_md2(), EVP_md5(), EVP_sha1(),
 EVP_mdc2() and EVP_ripemd160() return pointers to the
 corresponding EVP_MD structures.

 EVP_get_digestbyname(), EVP_get_digestbynid() and EVP_get_digestbyobj()
 return either an B<EVP_MD> structure or NULL if an error occurs.

 =head1 NOTES

 The B<EVP> interface to message digests should almost always be used in
 preference to the low level interfaces. This is because the code then becomes
 transparent to the digest used and much more flexible.

 New applications should use the SHA2 digest algorithms such as SHA256.
 The other digest algorithms are still in common use.

 For most applications the B<impl> parameter to EVP_DigestInit_ex() will be
 set to NULL to use the default digest implementation.

 The functions EVP_DigestInit(), EVP_DigestFinal() and EVP_MD_CTX_copy() are
 obsolete but are retained to maintain compatibility with existing code. New
 applications should use EVP_DigestInit_ex(), EVP_DigestFinal_ex() and
 EVP_MD_CTX_copy_ex() because they can efficiently reuse a digest context
 instead of initializing and cleaning it up on each call and allow non default
 implementations of digests to be specified.

 If digest contexts are not cleaned up after use
 memory leaks will occur.

 EVP_MD_CTX_size(), EVP_MD_CTX_block_size(), EVP_MD_CTX_type(),
 EVP_get_digestbynid() and EVP_get_digestbyobj() are defined as
 macros.


 =head1 EXAMPLE

 This example digests the data "Test Message\n" and "Hello World\n", using the
 digest name passed on the command line.

  #include <stdio.h>
  #include <openssl/evp.h>

  main(int argc, char *argv[])
  {
  EVP_MD_CTX *mdctx;
  const EVP_MD *md;
  char mess1[] = "Test Message\n";
  char mess2[] = "Hello World\n";
  unsigned char md_value[EVP_MAX_MD_SIZE];
  int md_len, i;

  OpenSSL_add_all_digests();

  if(!argv[1]) {
  	printf("Usage: mdtest digestname\n");
 	exit(1);
  }

  md = EVP_get_digestbyname(argv[1]);

  if(!md) {
  	printf("Unknown message digest %s\n", argv[1]);
 	exit(1);
  }

  mdctx = EVP_MD_CTX_new();
  EVP_DigestInit_ex(mdctx, md, NULL);
  EVP_DigestUpdate(mdctx, mess1, strlen(mess1));
  EVP_DigestUpdate(mdctx, mess2, strlen(mess2));
  EVP_DigestFinal_ex(mdctx, md_value, &md_len);
  EVP_MD_CTX_free(mdctx);

  printf("Digest is: ");
  for(i = 0; i < md_len; i++)
  	printf("%02x", md_value[i]);
  printf("\n");

  /* Call this once before exit. */
  EVP_cleanup();
  exit(0);
  }

 =head1 SEE ALSO

 L<dgst(1)>,
 L<evp(3)>

 =head1 HISTORY

 B<EVP_MD_CTX> became opaque in OpenSSL 1.1.  Consequently, stack
 allocated B<EVP_MD_CTX>s are no longer supported.

 EVP_MD_CTX_create() and EVP_MD_CTX_destroy() were renamed to
 EVP_MD_CTX_new() and EVP_MD_CTX_free() in OpenSSL 1.1.

 The link between digests and signing algorithms was fixed in OpenSSL 1.0 and
 later, so now EVP_sha1() can be used with RSA and DSA. The legacy EVP_dss1()
 was removed in OpenSSL 1.1.0

 =cut
	=pod

	=head1 NAME

	EVP_MD_CTX_new, EVP_MD_CTX_reset, EVP_MD_CTX_free, EVP_MD_CTX_copy_ex,
	EVP_DigestInit_ex, EVP_DigestUpdate, EVP_DigestFinal_ex, EVP_MAX_MD_SIZE,
	EVP_DigestInit, EVP_DigestFinal, EVP_MD_CTX_copy, EVP_MD_type,
	EVP_MD_pkey_type, EVP_MD_size, EVP_MD_block_size, EVP_MD_CTX_md, EVP_MD_CTX_size,
	EVP_MD_CTX_block_size, EVP_MD_CTX_type, EVP_md_null, EVP_md2, EVP_md5, EVP_sha1,
	EVP_sha224, EVP_sha256, EVP_sha384, EVP_sha512, EVP_mdc2,
	EVP_ripemd160, EVP_get_digestbyname, EVP_get_digestbynid, EVP_get_digestbyobj -
	EVP digest routines

	=head1 SYNOPSIS

	#include <openssl/evp.h>

	EVP_MD_CTX *EVP_MD_CTX_new(void);
	int EVP_MD_CTX_reset(EVP_MD_CTX *ctx);
	void EVP_MD_CTX_free(EVP_MD_CTX *ctx);

	int EVP_DigestInit_ex(EVP_MD_CTX ctx, const EVP_MD type, ENGINE *impl);
	int EVP_DigestUpdate(EVP_MD_CTX ctx, const void d, size_t cnt);
	int EVP_DigestFinal_ex(EVP_MD_CTX ctx, unsigned char md,
	unsigned int *s);

	int EVP_MD_CTX_copy_ex(EVP_MD_CTX out,const EVP_MD_CTX in);

	int EVP_DigestInit(EVP_MD_CTX ctx, const EVP_MD type);
	int EVP_DigestFinal(EVP_MD_CTX ctx, unsigned char md,
	unsigned int *s);

	int EVP_MD_CTX_copy(EVP_MD_CTX out,EVP_MD_CTX in);

	#define EVP_MAX_MD_SIZE 64 /* SHA512 */

	int EVP_MD_type(const EVP_MD *md);
	int EVP_MD_pkey_type(const EVP_MD *md);
	int EVP_MD_size(const EVP_MD *md);
	int EVP_MD_block_size(const EVP_MD *md);

	const EVP_MD EVP_MD_CTX_md(const EVP_MD_CTX ctx);
	int (EVP_MD_CTX_update_fn(EVP_MD_CTX ctx))(EVP_MD_CTX *ctx,
	const void *data, size_t count);
	void EVP_MD_CTX_set_update_fn(EVP_MD_CTX *ctx,
	int (update) (EVP_MD_CTX ctx,
	const void *data, size_t count));
	int EVP_MD_CTX_size(const EVP_MD *ctx);
	int EVP_MD_CTX_block_size(const EVP_MD *ctx);
	int EVP_MD_CTX_type(const EVP_MD *ctx);
	EVP_PKEY_CTX EVP_MD_CTX_pkey_ctx(const EVP_MD_CTX ctx);
	void EVP_MD_CTX_md_data(const EVP_MD_CTX ctx);

	const EVP_MD *EVP_md_null(void);
	const EVP_MD *EVP_md2(void);
	const EVP_MD *EVP_md5(void);
	const EVP_MD *EVP_sha1(void);
	const EVP_MD *EVP_mdc2(void);
	const EVP_MD *EVP_ripemd160(void);

	const EVP_MD *EVP_sha224(void);
	const EVP_MD *EVP_sha256(void);
	const EVP_MD *EVP_sha384(void);
	const EVP_MD *EVP_sha512(void);

	const EVP_MD EVP_get_digestbyname(const char name);
	const EVP_MD *EVP_get_digestbynid(int type);
	const EVP_MD EVP_get_digestbyobj(const ASN1_OBJECT o);

	=head1 DESCRIPTION

	The EVP digest routines are a high level interface to message digests,
	and should be used instead of the cipher-specific functions.

	EVP_MD_CTX_new() allocates, initializes and returns a digest context.

	EVP_MD_CTX_reset() resets the digest context B<ctx>. This can be used
	to reuse an already existing context.

	EVP_MD_CTX_free() cleans up digest context B<ctx> and frees up the
	space allocated to it.

	EVP_DigestInit_ex() sets up digest context B<ctx> to use a digest
	B<type> from ENGINE B<impl>. B<ctx> must be initialized before calling this
	function. B<type> will typically be supplied by a function such as EVP_sha1().
	If B<impl> is NULL then the default implementation of digest B<type> is used.

	EVP_DigestUpdate() hashes B<cnt> bytes of data at B<d> into the
	digest context B<ctx>. This function can be called several times on the
	same B<ctx> to hash additional data.

	EVP_DigestFinal_ex() retrieves the digest value from B<ctx> and places
	it in B<md>. If the B<s> parameter is not NULL then the number of
	bytes of data written (i.e. the length of the digest) will be written
	to the integer at B<s>, at most B<EVP_MAX_MD_SIZE> bytes will be written.
	After calling EVP_DigestFinal_ex() no additional calls to EVP_DigestUpdate()
	can be made, but EVP_DigestInit_ex() can be called to initialize a new
	digest operation.

	EVP_MD_CTX_copy_ex() can be used to copy the message digest state from
	B<in> to B<out>. This is useful if large amounts of data are to be
	hashed which only differ in the last few bytes. B<out> must be initialized
	before calling this function.

	EVP_DigestInit() behaves in the same way as EVP_DigestInit_ex() except
	the passed context B<ctx> does not have to be initialized, and it always
	uses the default digest implementation.

	EVP_DigestFinal() is similar to EVP_DigestFinal_ex() except the digest
	context B<ctx> is automatically cleaned up.

	EVP_MD_CTX_copy() is similar to EVP_MD_CTX_copy_ex() except the destination
	B<out> does not have to be initialized.

	EVP_MD_size() and EVP_MD_CTX_size() return the size of the message digest
	when passed an B<EVP_MD> or an B<EVP_MD_CTX> structure, i.e. the size of the
	hash.

	EVP_MD_block_size() and EVP_MD_CTX_block_size() return the block size of the
	message digest when passed an B<EVP_MD> or an B<EVP_MD_CTX> structure.

	EVP_MD_type() and EVP_MD_CTX_type() return the NID of the OBJECT IDENTIFIER
	representing the given message digest when passed an B<EVP_MD> structure.
	For example EVP_MD_type(EVP_sha1()) returns B<NID_sha1>. This function is
	normally used when setting ASN1 OIDs.

	EVP_MD_CTX_md() returns the B<EVP_MD> structure corresponding to the passed
	B<EVP_MD_CTX>.

	EVP_MD_pkey_type() returns the NID of the public key signing algorithm associated
	with this digest. For example EVP_sha1() is associated with RSA so this will
	return B<NID_sha1WithRSAEncryption>. Since digests and signature algorithms
	are no longer linked this function is only retained for compatibility
	reasons.

	EVP_md2(), EVP_md5(), EVP_sha1(), EVP_sha224(), EVP_sha256(),
	EVP_sha384(), EVP_sha512(), EVP_mdc2() and EVP_ripemd160() return B<EVP_MD>
	structures for the MD2, MD5, SHA1, SHA224, SHA256, SHA384, SHA512, MDC2
	and RIPEMD160 digest algorithms respectively.

	EVP_md_null() is a "null" message digest that does nothing: i.e. the hash it
	returns is of zero length.

	EVP_get_digestbyname(), EVP_get_digestbynid() and EVP_get_digestbyobj()
	return an B<EVP_MD> structure when passed a digest name, a digest NID or
	an ASN1_OBJECT structure respectively. The digest table must be initialized
	using, for example, OpenSSL_add_all_digests() for these functions to work.

	=head1 RETURN VALUES

	EVP_DigestInit_ex(), EVP_DigestUpdate() and EVP_DigestFinal_ex() return 1 for
	success and 0 for failure.

	EVP_MD_CTX_copy_ex() returns 1 if successful or 0 for failure.

	EVP_MD_type(), EVP_MD_pkey_type() and EVP_MD_type() return the NID of the
	corresponding OBJECT IDENTIFIER or NID_undef if none exists.

	EVP_MD_size(), EVP_MD_block_size(), EVP_MD_CTX_size() and
	EVP_MD_CTX_block_size() return the digest or block size in bytes.

	EVP_md_null(), EVP_md2(), EVP_md5(), EVP_sha1(),
	EVP_mdc2() and EVP_ripemd160() return pointers to the
	corresponding EVP_MD structures.

	EVP_get_digestbyname(), EVP_get_digestbynid() and EVP_get_digestbyobj()
	return either an B<EVP_MD> structure or NULL if an error occurs.

	=head1 NOTES

	The B<EVP> interface to message digests should almost always be used in
	preference to the low level interfaces. This is because the code then becomes
	transparent to the digest used and much more flexible.

	New applications should use the SHA2 digest algorithms such as SHA256.
	The other digest algorithms are still in common use.

	For most applications the B<impl> parameter to EVP_DigestInit_ex() will be
	set to NULL to use the default digest implementation.

	The functions EVP_DigestInit(), EVP_DigestFinal() and EVP_MD_CTX_copy() are
	obsolete but are retained to maintain compatibility with existing code. New
	applications should use EVP_DigestInit_ex(), EVP_DigestFinal_ex() and
	EVP_MD_CTX_copy_ex() because they can efficiently reuse a digest context
	instead of initializing and cleaning it up on each call and allow non default
	implementations of digests to be specified.

	If digest contexts are not cleaned up after use
	memory leaks will occur.

	EVP_MD_CTX_size(), EVP_MD_CTX_block_size(), EVP_MD_CTX_type(),
	EVP_get_digestbynid() and EVP_get_digestbyobj() are defined as
	macros.


	=head1 EXAMPLE

	This example digests the data "Test Message\n" and "Hello World\n", using the
	digest name passed on the command line.

	#include <stdio.h>
	#include <openssl/evp.h>

	main(int argc, char *argv[])
	{
	EVP_MD_CTX *mdctx;
	const EVP_MD *md;
	char mess1[] = "Test Message\n";
	char mess2[] = "Hello World\n";
	unsigned char md_value[EVP_MAX_MD_SIZE];
	int md_len, i;

	OpenSSL_add_all_digests();

	if(!argv[1]) {
	printf("Usage: mdtest digestname\n");
	exit(1);
	}

	md = EVP_get_digestbyname(argv[1]);

	if(!md) {
	printf("Unknown message digest %s\n", argv[1]);
	exit(1);
	}

	mdctx = EVP_MD_CTX_new();
	EVP_DigestInit_ex(mdctx, md, NULL);
	EVP_DigestUpdate(mdctx, mess1, strlen(mess1));
	EVP_DigestUpdate(mdctx, mess2, strlen(mess2));
	EVP_DigestFinal_ex(mdctx, md_value, &md_len);
	EVP_MD_CTX_free(mdctx);

	printf("Digest is: ");
	for(i = 0; i < md_len; i++)
	printf("%02x", md_value[i]);
	printf("\n");

	/* Call this once before exit. */
	EVP_cleanup();
	exit(0);
	}

	=head1 SEE ALSO

	L<dgst(1)>,
	L<evp(3)>

	=head1 HISTORY

	B<EVP_MD_CTX> became opaque in OpenSSL 1.1. Consequently, stack
	allocated B<EVP_MD_CTX>s are no longer supported.

	EVP_MD_CTX_create() and EVP_MD_CTX_destroy() were renamed to
	EVP_MD_CTX_new() and EVP_MD_CTX_free() in OpenSSL 1.1.

	The link between digests and signing algorithms was fixed in OpenSSL 1.0 and
	later, so now EVP_sha1() can be used with RSA and DSA. The legacy EVP_dss1()
	was removed in OpenSSL 1.1.0

	=cut