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Update docs.

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Dr. Stephen Henson 2001-10-16 02:22:59 +00:00
parent 20d2186c87
commit e72d734d5f
1 changed files with 71 additions and 23 deletions
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94
doc/crypto/EVP_DigestInit.pod
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@ -2,9 +2,10 @@
=head1 NAME
EVP_DigestInit, EVP_DigestUpdate, EVP_DigestFinal, EVP_MAX_MD_SIZE,
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_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_ripemd160, EVP_get_digestbyname, EVP_get_digestbynid, EVP_get_digestbyobj -
EVP digest routines
@ -13,14 +14,27 @@ EVP digest routines
#include <openssl/evp.h>
int EVP_DigestInit(EVP_MD_CTX *ctx, const EVP_MD *type);
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, unsigned int cnt);
int EVP_DigestFinal_ex(EVP_MD_CTX *ctx, unsigned char *md,
unsigned int *s);
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_MAX_MD_SIZE (16+20) /* The SSLv3 md5+sha1 type */
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)
@ -50,25 +64,48 @@ EVP digest routines
The EVP digest routines are a high level interface to message digests.
EVP_DigestInit() initializes 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 contet B<ctx>.
EVP_MD_CTX_create() allocates, initializes and returns a digest contet.
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 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 initialize 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
contet 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
@ -107,10 +144,10 @@ using, for example, OpenSSL_add_all_digests() for these functions to work.
=head1 RETURN VALUES
EVP_DigestInit(), EVP_DigestUpdate() and EVP_DigestFinal() return 1 for
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.
@ -135,9 +172,18 @@ 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.
The functions EVP_DigestInit(), EVP_DigestUpdate() and EVP_DigestFinal(),
did not return errors in OpenSSL versions before 0.9.7 or earlier. Software only
versions of digest algorithms will never return error codes for these functions.
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.
=head1 EXAMPLE
@ -170,10 +216,12 @@ digest name passed on the command line.
exit(1);
}
EVP_DigestInit(&mdctx, md);
EVP_MD_CTX_init(&mdctx);
EVP_DigestInit_ex(&mdctx, md, NULL);
EVP_DigestUpdate(&mdctx, mess1, strlen(mess1));
EVP_DigestUpdate(&mdctx, mess2, strlen(mess2));
EVP_DigestFinal(&mdctx, md_value, &md_len);
EVP_DigestFinal_ex(&mdctx, md_value, &md_len);
EVP_MD_CTX_cleanup(&mdctx);
printf("Digest is: ");
for(i = 0; i < md_len; i++) printf("%02x", md_value[i]);
@ -186,9 +234,6 @@ 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)>,
@ -200,4 +245,7 @@ L<sha(3)|sha(3)>, L<digest(1)|digest(1)>
EVP_DigestInit(), EVP_DigestUpdate() and EVP_DigestFinal() are
available in all versions of SSLeay and OpenSSL.
EVP_DigestInit_ex(), EVP_DigestFinal_ex() and EVP_MD_CTX_copy_ex()
were added in OpenSSL 0.9.7.
=cut