update rather ancient EVP digest documentation

doc/crypto/EVP_DigestInit.pod

@@ -6,7 +6,8 @@ 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_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_dss, EVP_dss1, EVP_mdc2,
+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
 
@@ -33,16 +34,15 @@ EVP digest routines
 
  int EVP_MD_CTX_copy(EVP_MD_CTX *out,EVP_MD_CTX *in);  
 
- #define EVP_MAX_MD_SIZE (16+20) /* The SSLv3 md5+sha1 type */
+ #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);
 
- #define EVP_MD_type(e)			((e)->type)
+ const EVP_MD *EVP_MD_CTX_md(const EVP_MD_CTX *ctx);
- #define EVP_MD_pkey_type(e)		((e)->pkey_type)
+ #define EVP_MD_CTX_size(e)		EVP_MD_size(EVP_MD_CTX_md(e))
- #define EVP_MD_size(e)			((e)->md_size)
- #define EVP_MD_block_size(e)		((e)->block_size)
-
- #define EVP_MD_CTX_md(e)		(e)->digest)
- #define EVP_MD_CTX_size(e)		EVP_MD_size((e)->digest)
  #define EVP_MD_CTX_block_size(e)	EVP_MD_block_size((e)->digest)
  #define EVP_MD_CTX_type(e)		EVP_MD_type((e)->digest)
 
@@ -56,6 +56,11 @@ EVP digest routines
  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))
  #define EVP_get_digestbyobj(a) EVP_get_digestbynid(OBJ_obj2nid(a))
@@ -124,12 +129,14 @@ 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>. This "link" between digests and signature
+return B<NID_sha1WithRSAEncryption>. Since digests and signature algorithms
-algorithms may not be retained in future versions of OpenSSL.
+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()
+EVP_md2(), EVP_md5(), EVP_sha(), EVP_sha1(), EVP_sha224(), EVP_sha256(),
-return B<EVP_MD> structures for the MD2, MD5, SHA, SHA1, MDC2 and RIPEMD160 digest
+EVP_sha384(), EVP_sha512(), EVP_mdc2() and EVP_ripemd160() return B<EVP_MD>
-algorithms respectively. The associated signature algorithm is RSA in each case.
+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. Note: there is 
@@ -171,8 +178,8 @@ 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.
 
-SHA1 is the digest of choice for new applications. The other digest algorithms
+New applications should use the SHA2 digest algorithms such as SHA256. 
-are still in common use.
+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.
@@ -187,6 +194,19 @@ 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
 
 This example digests the data "Test Message\n" and "Hello World\n", using the
@@ -197,7 +217,7 @@ digest name passed on the command line.
 
  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";
@@ -218,12 +238,12 @@ digest name passed on the command line.
 	exit(1);
  }
 
- EVP_MD_CTX_init(&mdctx);
+ mdctx = EVP_MD_CTX_create();
- EVP_DigestInit_ex(&mdctx, md, NULL);
+ EVP_DigestInit_ex(mdctx, md, NULL);
- EVP_DigestUpdate(&mdctx, mess1, strlen(mess1));
+ EVP_DigestUpdate(mdctx, mess1, strlen(mess1));
- EVP_DigestUpdate(&mdctx, mess2, strlen(mess2));
+ EVP_DigestUpdate(mdctx, mess2, strlen(mess2));
- EVP_DigestFinal_ex(&mdctx, md_value, &md_len);
+ EVP_DigestFinal_ex(mdctx, md_value, &md_len);
- EVP_MD_CTX_cleanup(&mdctx);
+ EVP_MD_CTX_destroy(mdctx);
 
  printf("Digest is: ");
  for(i = 0; i < md_len; i++) printf("%02x", md_value[i]);