From e72d734d5fef981371db695125cc1c3d236a8768 Mon Sep 17 00:00:00 2001 From: "Dr. Stephen Henson" Date: Tue, 16 Oct 2001 02:22:59 +0000 Subject: [PATCH] Update docs. --- doc/crypto/EVP_DigestInit.pod | 94 ++++++++++++++++++++++++++--------- 1 file changed, 71 insertions(+), 23 deletions(-) diff --git a/doc/crypto/EVP_DigestInit.pod b/doc/crypto/EVP_DigestInit.pod index df17928b5d..b3a61f1c5d 100644 --- a/doc/crypto/EVP_DigestInit.pod +++ b/doc/crypto/EVP_DigestInit.pod @@ -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 - 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 to use a digest -B: this will typically be supplied by a function such as -EVP_sha1(). +EVP_MD_CTX_init() initializes digest contet B. + +EVP_MD_CTX_create() allocates, initializes and returns a digest contet. + +EVP_DigestInit_ex() sets up digest context B to use a digest +B from ENGINE B. B must be initialized before calling this +function. B will typically be supplied by a functionsuch as EVP_sha1(). +If B is NULL then the default implementation of digest B is used. EVP_DigestUpdate() hashes B bytes of data at B into the digest context B. This function can be called several times on the same B to hash additional data. -EVP_DigestFinal() retrieves the digest value from B and places +EVP_DigestFinal_ex() retrieves the digest value from B and places it in B. If the B 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, at most B 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, it should be called +after a digest context is no longer needed. + +EVP_MD_CTX_destroy() cleans up digest context B 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 to B. 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 must be initialized +before calling this function. + +EVP_DigestInit() behaves in the same way as EVP_DigestInit_ex() except +the passed context B 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 is automatically cleaned up. + +EVP_MD_CTX_copy() is similar to EVP_MD_CTX_copy_ex() except the destination +B 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 or an B 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 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 structure is determined at compile time: this results -in code that must be recompiled if the size of B increases. - =head1 SEE ALSO L, L, L, @@ -200,4 +245,7 @@ L, L 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 -- 2.25.1