=head1 NAME
-EVP_DigestInit, EVP_DigestUpdate, EVP_DigestFinal - EVP digest routines
+EVP_MD_CTX_init, EVP_MD_CTX_create, EVP_DigestInit_ex, EVP_DigestUpdate,
+EVP_DigestFinal_ex, EVP_MD_CTX_cleanup, EVP_MD_CTX_destroy, EVP_MAX_MD_SIZE,
+EVP_MD_CTX_copy_ex, 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_sha, EVP_sha1,
+EVP_sha224, EVP_sha256, EVP_sha384, EVP_sha512, EVP_dss, EVP_dss1, EVP_mdc2,
+EVP_ripemd160, EVP_get_digestbyname, EVP_get_digestbynid, EVP_get_digestbyobj -
+EVP digest routines
=head1 SYNOPSIS
#include <openssl/evp.h>
- void EVP_DigestInit(EVP_MD_CTX *ctx, const EVP_MD *type);
- void EVP_DigestUpdate(EVP_MD_CTX *ctx, const void *d, unsigned int cnt);
- void EVP_DigestFinal(EVP_MD_CTX *ctx, unsigned char *md,
+ void EVP_MD_CTX_init(EVP_MD_CTX *ctx);
+ EVP_MD_CTX *EVP_MD_CTX_create(void);
+
+ 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);
- #define EVP_MAX_MD_SIZE (16+20) /* The SSLv3 md5+sha1 type */
+ int EVP_MD_CTX_cleanup(EVP_MD_CTX *ctx);
+ void EVP_MD_CTX_destroy(EVP_MD_CTX *ctx);
+
+ 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_MD_type(e) ((e)->type)
- #define EVP_MD_pkey_type(e) ((e)->pkey_type)
- #define EVP_MD_size(e) ((e)->md_size)
- #define EVP_MD_block_size(e) ((e)->block_size)
+ #define EVP_MAX_MD_SIZE 64 /* SHA512 */
- #define EVP_MD_CTX_md(e) (e)->digest)
- #define EVP_MD_CTX_size(e) EVP_MD_size((e)->digest)
+ 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);
+ #define EVP_MD_CTX_size(e) EVP_MD_size(EVP_MD_CTX_md(e))
#define EVP_MD_CTX_block_size(e) EVP_MD_block_size((e)->digest)
#define EVP_MD_CTX_type(e) EVP_MD_type((e)->digest)
- EVP_MD *EVP_md_null(void);
- EVP_MD *EVP_md2(void);
- EVP_MD *EVP_md5(void);
- EVP_MD *EVP_sha(void);
- EVP_MD *EVP_sha1(void);
- EVP_MD *EVP_dss(void);
- EVP_MD *EVP_dss1(void);
- EVP_MD *EVP_mdc2(void);
- EVP_MD *EVP_ripemd160(void);
+ const EVP_MD *EVP_md_null(void);
+ const EVP_MD *EVP_md2(void);
+ const EVP_MD *EVP_md5(void);
+ const EVP_MD *EVP_sha(void);
+ const EVP_MD *EVP_sha1(void);
+ const EVP_MD *EVP_dss(void);
+ const EVP_MD *EVP_dss1(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);
#define EVP_get_digestbynid(a) EVP_get_digestbyname(OBJ_nid2sn(a))
The EVP digest routines are a high level interface to message digests.
-EVP_DigestInit() initialises a digest context B<ctx> to use a digest
-B<type>: this will typically be supplied by a function such as
-EVP_sha1().
+EVP_MD_CTX_init() initializes digest context B<ctx>.
+
+EVP_MD_CTX_create() allocates, initializes and returns a digest context.
+
+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 functionsuch 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 funtion can be called several times on the
+digest context B<ctx>. This function can be called several times on the
same B<ctx> to hash additional data.
-EVP_DigestFinal() retrieves the digest value from B<ctx> and places
+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() no additional calls to EVP_DigestUpdate()
-can be made, but EVP_DigestInit() can be called to initialiase a new
+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() can be used to copy the message digest state from
+EVP_MD_CTX_cleanup() cleans up digest context B<ctx>, it should be called
+after a digest context is no longer needed.
+
+EVP_MD_CTX_destroy() cleans up digest context B<ctx> and frees up the
+space allocated to it, it should be called only on a context created
+using EVP_MD_CTX_create().
+
+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.
+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
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>. This "link" between digests and signature
-algorithms may not be retained in future versions of OpenSSL.
+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_sha(), EVP_sha1(), EVP_mdc2() and EVP_ripemd160()
-return B<EVP_MD> structures for the MD2, MD5, SHA, SHA1, MDC2 and RIPEMD160 digest
-algorithms respectively. The associated signature algorithm is RSA in each case.
+EVP_md2(), EVP_md5(), EVP_sha(), EVP_sha1(), EVP_sha224(), EVP_sha256(),
+EVP_sha384(), EVP_sha512(), EVP_mdc2() and EVP_ripemd160() return B<EVP_MD>
+structures for the MD2, MD5, SHA, SHA1, SHA224, SHA256, SHA384, SHA512, MDC2
+and RIPEMD160 digest algorithms respectively.
EVP_dss() and EVP_dss1() return B<EVP_MD> structures for SHA and SHA1 digest
-algorithms but using DSS (DSA) for the signature algorithm.
+algorithms but using DSS (DSA) for the signature algorithm. Note: there is
+no need to use these pseudo-digests in OpenSSL 1.0.0 and later, they are
+however retained for compatibility.
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 initialised
+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(), EVP_DigestUpdate() and EVP_DigestFinal() do not return values.
+EVP_DigestInit_ex(), EVP_DigestUpdate() and EVP_DigestFinal_ex() return 1 for
+success and 0 for failure.
-EVP_MD_CTX_copy() returns 1 if successful or 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.
preference to the low level interfaces. This is because the code then becomes
transparent to the digest used and much more flexible.
-SHA1 is the digest of choice for new applications. The other digest algorithms
-are still in common use.
+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.
+
+In OpenSSL 0.9.7 and later if digest contexts are not cleaned up after use
+memory leaks will occur.
+
+Stack allocation of EVP_MD_CTX structures is common, for example:
+
+ EVP_MD_CTX mctx;
+ EVP_MD_CTX_init(&mctx);
+
+This will cause binary compatibility issues if the size of EVP_MD_CTX
+structure changes (this will only happen with a major release of OpenSSL).
+Applications wishing to avoid this should use EVP_MD_CTX_create() instead:
+
+ EVP_MD_CTX *mctx;
+ mctx = EVP_MD_CTX_create();
+
=head1 EXAMPLE
main(int argc, char *argv[])
{
- EVP_MD_CTX mdctx;
+ EVP_MD_CTX *mdctx;
const EVP_MD *md;
char mess1[] = "Test Message\n";
char mess2[] = "Hello World\n";
exit(1);
}
- EVP_DigestInit(&mdctx, md);
- EVP_DigestUpdate(&mdctx, mess1, strlen(mess1));
- EVP_DigestUpdate(&mdctx, mess2, strlen(mess2));
- EVP_DigestFinal(&mdctx, md_value, &md_len);
+ mdctx = EVP_MD_CTX_create();
+ 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_destroy(mdctx);
printf("Digest is: ");
for(i = 0; i < md_len; i++) printf("%02x", md_value[i]);
printf("\n");
}
-=head1 BUGS
-
-Several of the functions do not return values: maybe they should. Although the
-internal digest operations will never fail some future hardware based operations
-might.
-
-The link between digests and signing algorithms results in a situation where
-EVP_sha1() must be used with RSA and EVP_dss1() must be used with DSS
-even though they are identical digests.
-
-The size of an B<EVP_MD_CTX> structure is determined at compile time: this results
-in code that must be recompiled if the size of B<EVP_MD_CTX> increases.
-
=head1 SEE ALSO
L<evp(3)|evp(3)>, L<hmac(3)|hmac(3)>, L<md2(3)|md2(3)>,
L<md5(3)|md5(3)>, L<mdc2(3)|mdc2(3)>, L<ripemd(3)|ripemd(3)>,
-L<sha(3)|sha(3)>, L<digest(1)|digest(1)>
+L<sha(3)|sha(3)>, L<dgst(1)|dgst(1)>
=head1 HISTORY
EVP_DigestInit(), EVP_DigestUpdate() and EVP_DigestFinal() are
available in all versions of SSLeay and OpenSSL.
+EVP_MD_CTX_init(), EVP_MD_CTX_create(), EVP_MD_CTX_copy_ex(),
+EVP_MD_CTX_cleanup(), EVP_MD_CTX_destroy(), EVP_DigestInit_ex()
+and EVP_DigestFinal_ex() were added in OpenSSL 0.9.7.
+
+EVP_md_null(), EVP_md2(), EVP_md5(), EVP_sha(), EVP_sha1(),
+EVP_dss(), EVP_dss1(), EVP_mdc2() and EVP_ripemd160() were
+changed to return truely const EVP_MD * in OpenSSL 0.9.7.
+
+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, there is no need to
+use EVP_dss1() any more.
+
+OpenSSL 1.0 and later does not include the MD2 digest algorithm in the
+default configuration due to its security weaknesses.
+
=cut
projects / openssl.git / blobdiff