diff options
Diffstat (limited to 'openssl-1.1.0h/doc/crypto/EVP_DigestInit.pod')
-rw-r--r-- | openssl-1.1.0h/doc/crypto/EVP_DigestInit.pod | 259 |
1 files changed, 259 insertions, 0 deletions
diff --git a/openssl-1.1.0h/doc/crypto/EVP_DigestInit.pod b/openssl-1.1.0h/doc/crypto/EVP_DigestInit.pod new file mode 100644 index 0000000..bb7ef7a --- /dev/null +++ b/openssl-1.1.0h/doc/crypto/EVP_DigestInit.pod @@ -0,0 +1,259 @@ +=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_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_blake2b512, EVP_blake2s256, 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); + + 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_size(const EVP_MD *ctx); + int EVP_MD_CTX_block_size(const EVP_MD *ctx); + int EVP_MD_CTX_type(const EVP_MD *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_blake2b512(void); + const EVP_MD *EVP_blake2s256(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(), EVP_ripemd160(), EVP_blake2b512(), and +EVP_blake2s256() return B<EVP_MD> structures for the MD2, MD5, SHA1, SHA224, +SHA256, SHA384, SHA512, MDC2, RIPEMD160, BLAKE2b-512, and BLAKE2s-256 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. + +=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(), EVP_ripemd160(), EVP_blake2b512(), and EVP_blake2s256() 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; + + 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"); + + exit(0); + } + +=head1 SEE ALSO + +L<dgst(1)>, +L<evp(7)> + +=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 + +=head1 COPYRIGHT + +Copyright 2000-2016 The OpenSSL Project Authors. All Rights Reserved. + +Licensed under the OpenSSL license (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 +L<https://www.openssl.org/source/license.html>. + +=cut |