EVP_DigestInit.pod revision 238405
1=pod 2 3=head1 NAME 4 5EVP_MD_CTX_init, EVP_MD_CTX_create, EVP_DigestInit_ex, EVP_DigestUpdate, 6EVP_DigestFinal_ex, EVP_MD_CTX_cleanup, EVP_MD_CTX_destroy, EVP_MAX_MD_SIZE, 7EVP_MD_CTX_copy_ex, EVP_MD_CTX_copy, EVP_MD_type, EVP_MD_pkey_type, EVP_MD_size, 8EVP_MD_block_size, EVP_MD_CTX_md, EVP_MD_CTX_size, EVP_MD_CTX_block_size, EVP_MD_CTX_type, 9EVP_md_null, EVP_md2, EVP_md5, EVP_sha, EVP_sha1, EVP_sha224, EVP_sha256, 10EVP_sha384, EVP_sha512, EVP_dss, EVP_dss1, EVP_mdc2, 11EVP_ripemd160, EVP_get_digestbyname, EVP_get_digestbynid, EVP_get_digestbyobj - 12EVP digest routines 13 14=head1 SYNOPSIS 15 16 #include <openssl/evp.h> 17 18 void EVP_MD_CTX_init(EVP_MD_CTX *ctx); 19 EVP_MD_CTX *EVP_MD_CTX_create(void); 20 21 int EVP_DigestInit_ex(EVP_MD_CTX *ctx, const EVP_MD *type, ENGINE *impl); 22 int EVP_DigestUpdate(EVP_MD_CTX *ctx, const void *d, size_t cnt); 23 int EVP_DigestFinal_ex(EVP_MD_CTX *ctx, unsigned char *md, 24 unsigned int *s); 25 26 int EVP_MD_CTX_cleanup(EVP_MD_CTX *ctx); 27 void EVP_MD_CTX_destroy(EVP_MD_CTX *ctx); 28 29 int EVP_MD_CTX_copy_ex(EVP_MD_CTX *out,const EVP_MD_CTX *in); 30 31 int EVP_DigestInit(EVP_MD_CTX *ctx, const EVP_MD *type); 32 int EVP_DigestFinal(EVP_MD_CTX *ctx, unsigned char *md, 33 unsigned int *s); 34 35 int EVP_MD_CTX_copy(EVP_MD_CTX *out,EVP_MD_CTX *in); 36 37 #define EVP_MAX_MD_SIZE 64 /* SHA512 */ 38 39 int EVP_MD_type(const EVP_MD *md); 40 int EVP_MD_pkey_type(const EVP_MD *md); 41 int EVP_MD_size(const EVP_MD *md); 42 int EVP_MD_block_size(const EVP_MD *md); 43 44 const EVP_MD *EVP_MD_CTX_md(const EVP_MD_CTX *ctx); 45 #define EVP_MD_CTX_size(e) EVP_MD_size(EVP_MD_CTX_md(e)) 46 #define EVP_MD_CTX_block_size(e) EVP_MD_block_size((e)->digest) 47 #define EVP_MD_CTX_type(e) EVP_MD_type((e)->digest) 48 49 const EVP_MD *EVP_md_null(void); 50 const EVP_MD *EVP_md2(void); 51 const EVP_MD *EVP_md5(void); 52 const EVP_MD *EVP_sha(void); 53 const EVP_MD *EVP_sha1(void); 54 const EVP_MD *EVP_dss(void); 55 const EVP_MD *EVP_dss1(void); 56 const EVP_MD *EVP_mdc2(void); 57 const EVP_MD *EVP_ripemd160(void); 58 59 const EVP_MD *EVP_sha224(void); 60 const EVP_MD *EVP_sha256(void); 61 const EVP_MD *EVP_sha384(void); 62 const EVP_MD *EVP_sha512(void); 63 64 const EVP_MD *EVP_get_digestbyname(const char *name); 65 #define EVP_get_digestbynid(a) EVP_get_digestbyname(OBJ_nid2sn(a)) 66 #define EVP_get_digestbyobj(a) EVP_get_digestbynid(OBJ_obj2nid(a)) 67 68=head1 DESCRIPTION 69 70The EVP digest routines are a high level interface to message digests. 71 72EVP_MD_CTX_init() initializes digest context B<ctx>. 73 74EVP_MD_CTX_create() allocates, initializes and returns a digest context. 75 76EVP_DigestInit_ex() sets up digest context B<ctx> to use a digest 77B<type> from ENGINE B<impl>. B<ctx> must be initialized before calling this 78function. B<type> will typically be supplied by a functionsuch as EVP_sha1(). 79If B<impl> is NULL then the default implementation of digest B<type> is used. 80 81EVP_DigestUpdate() hashes B<cnt> bytes of data at B<d> into the 82digest context B<ctx>. This function can be called several times on the 83same B<ctx> to hash additional data. 84 85EVP_DigestFinal_ex() retrieves the digest value from B<ctx> and places 86it in B<md>. If the B<s> parameter is not NULL then the number of 87bytes of data written (i.e. the length of the digest) will be written 88to the integer at B<s>, at most B<EVP_MAX_MD_SIZE> bytes will be written. 89After calling EVP_DigestFinal_ex() no additional calls to EVP_DigestUpdate() 90can be made, but EVP_DigestInit_ex() can be called to initialize a new 91digest operation. 92 93EVP_MD_CTX_cleanup() cleans up digest context B<ctx>, it should be called 94after a digest context is no longer needed. 95 96EVP_MD_CTX_destroy() cleans up digest context B<ctx> and frees up the 97space allocated to it, it should be called only on a context created 98using EVP_MD_CTX_create(). 99 100EVP_MD_CTX_copy_ex() can be used to copy the message digest state from 101B<in> to B<out>. This is useful if large amounts of data are to be 102hashed which only differ in the last few bytes. B<out> must be initialized 103before calling this function. 104 105EVP_DigestInit() behaves in the same way as EVP_DigestInit_ex() except 106the passed context B<ctx> does not have to be initialized, and it always 107uses the default digest implementation. 108 109EVP_DigestFinal() is similar to EVP_DigestFinal_ex() except the digest 110context B<ctx> is automatically cleaned up. 111 112EVP_MD_CTX_copy() is similar to EVP_MD_CTX_copy_ex() except the destination 113B<out> does not have to be initialized. 114 115EVP_MD_size() and EVP_MD_CTX_size() return the size of the message digest 116when passed an B<EVP_MD> or an B<EVP_MD_CTX> structure, i.e. the size of the 117hash. 118 119EVP_MD_block_size() and EVP_MD_CTX_block_size() return the block size of the 120message digest when passed an B<EVP_MD> or an B<EVP_MD_CTX> structure. 121 122EVP_MD_type() and EVP_MD_CTX_type() return the NID of the OBJECT IDENTIFIER 123representing the given message digest when passed an B<EVP_MD> structure. 124For example EVP_MD_type(EVP_sha1()) returns B<NID_sha1>. This function is 125normally used when setting ASN1 OIDs. 126 127EVP_MD_CTX_md() returns the B<EVP_MD> structure corresponding to the passed 128B<EVP_MD_CTX>. 129 130EVP_MD_pkey_type() returns the NID of the public key signing algorithm associated 131with this digest. For example EVP_sha1() is associated with RSA so this will 132return B<NID_sha1WithRSAEncryption>. Since digests and signature algorithms 133are no longer linked this function is only retained for compatibility 134reasons. 135 136EVP_md2(), EVP_md5(), EVP_sha(), EVP_sha1(), EVP_sha224(), EVP_sha256(), 137EVP_sha384(), EVP_sha512(), EVP_mdc2() and EVP_ripemd160() return B<EVP_MD> 138structures for the MD2, MD5, SHA, SHA1, SHA224, SHA256, SHA384, SHA512, MDC2 139and RIPEMD160 digest algorithms respectively. 140 141EVP_dss() and EVP_dss1() return B<EVP_MD> structures for SHA and SHA1 digest 142algorithms but using DSS (DSA) for the signature algorithm. Note: there is 143no need to use these pseudo-digests in OpenSSL 1.0.0 and later, they are 144however retained for compatibility. 145 146EVP_md_null() is a "null" message digest that does nothing: i.e. the hash it 147returns is of zero length. 148 149EVP_get_digestbyname(), EVP_get_digestbynid() and EVP_get_digestbyobj() 150return an B<EVP_MD> structure when passed a digest name, a digest NID or 151an ASN1_OBJECT structure respectively. The digest table must be initialized 152using, for example, OpenSSL_add_all_digests() for these functions to work. 153 154=head1 RETURN VALUES 155 156EVP_DigestInit_ex(), EVP_DigestUpdate() and EVP_DigestFinal_ex() return 1 for 157success and 0 for failure. 158 159EVP_MD_CTX_copy_ex() returns 1 if successful or 0 for failure. 160 161EVP_MD_type(), EVP_MD_pkey_type() and EVP_MD_type() return the NID of the 162corresponding OBJECT IDENTIFIER or NID_undef if none exists. 163 164EVP_MD_size(), EVP_MD_block_size(), EVP_MD_CTX_size(e), EVP_MD_size(), 165EVP_MD_CTX_block_size() and EVP_MD_block_size() return the digest or block 166size in bytes. 167 168EVP_md_null(), EVP_md2(), EVP_md5(), EVP_sha(), EVP_sha1(), EVP_dss(), 169EVP_dss1(), EVP_mdc2() and EVP_ripemd160() return pointers to the 170corresponding EVP_MD structures. 171 172EVP_get_digestbyname(), EVP_get_digestbynid() and EVP_get_digestbyobj() 173return either an B<EVP_MD> structure or NULL if an error occurs. 174 175=head1 NOTES 176 177The B<EVP> interface to message digests should almost always be used in 178preference to the low level interfaces. This is because the code then becomes 179transparent to the digest used and much more flexible. 180 181New applications should use the SHA2 digest algorithms such as SHA256. 182The other digest algorithms are still in common use. 183 184For most applications the B<impl> parameter to EVP_DigestInit_ex() will be 185set to NULL to use the default digest implementation. 186 187The functions EVP_DigestInit(), EVP_DigestFinal() and EVP_MD_CTX_copy() are 188obsolete but are retained to maintain compatibility with existing code. New 189applications should use EVP_DigestInit_ex(), EVP_DigestFinal_ex() and 190EVP_MD_CTX_copy_ex() because they can efficiently reuse a digest context 191instead of initializing and cleaning it up on each call and allow non default 192implementations of digests to be specified. 193 194In OpenSSL 0.9.7 and later if digest contexts are not cleaned up after use 195memory leaks will occur. 196 197Stack allocation of EVP_MD_CTX structures is common, for example: 198 199 EVP_MD_CTX mctx; 200 EVP_MD_CTX_init(&mctx); 201 202This will cause binary compatibility issues if the size of EVP_MD_CTX 203structure changes (this will only happen with a major release of OpenSSL). 204Applications wishing to avoid this should use EVP_MD_CTX_create() instead: 205 206 EVP_MD_CTX *mctx; 207 mctx = EVP_MD_CTX_create(); 208 209 210=head1 EXAMPLE 211 212This example digests the data "Test Message\n" and "Hello World\n", using the 213digest name passed on the command line. 214 215 #include <stdio.h> 216 #include <openssl/evp.h> 217 218 main(int argc, char *argv[]) 219 { 220 EVP_MD_CTX *mdctx; 221 const EVP_MD *md; 222 char mess1[] = "Test Message\n"; 223 char mess2[] = "Hello World\n"; 224 unsigned char md_value[EVP_MAX_MD_SIZE]; 225 int md_len, i; 226 227 OpenSSL_add_all_digests(); 228 229 if(!argv[1]) { 230 printf("Usage: mdtest digestname\n"); 231 exit(1); 232 } 233 234 md = EVP_get_digestbyname(argv[1]); 235 236 if(!md) { 237 printf("Unknown message digest %s\n", argv[1]); 238 exit(1); 239 } 240 241 mdctx = EVP_MD_CTX_create(); 242 EVP_DigestInit_ex(mdctx, md, NULL); 243 EVP_DigestUpdate(mdctx, mess1, strlen(mess1)); 244 EVP_DigestUpdate(mdctx, mess2, strlen(mess2)); 245 EVP_DigestFinal_ex(mdctx, md_value, &md_len); 246 EVP_MD_CTX_destroy(mdctx); 247 248 printf("Digest is: "); 249 for(i = 0; i < md_len; i++) printf("%02x", md_value[i]); 250 printf("\n"); 251 } 252 253=head1 SEE ALSO 254 255L<evp(3)|evp(3)>, L<hmac(3)|hmac(3)>, L<md2(3)|md2(3)>, 256L<md5(3)|md5(3)>, L<mdc2(3)|mdc2(3)>, L<ripemd(3)|ripemd(3)>, 257L<sha(3)|sha(3)>, L<dgst(1)|dgst(1)> 258 259=head1 HISTORY 260 261EVP_DigestInit(), EVP_DigestUpdate() and EVP_DigestFinal() are 262available in all versions of SSLeay and OpenSSL. 263 264EVP_MD_CTX_init(), EVP_MD_CTX_create(), EVP_MD_CTX_copy_ex(), 265EVP_MD_CTX_cleanup(), EVP_MD_CTX_destroy(), EVP_DigestInit_ex() 266and EVP_DigestFinal_ex() were added in OpenSSL 0.9.7. 267 268EVP_md_null(), EVP_md2(), EVP_md5(), EVP_sha(), EVP_sha1(), 269EVP_dss(), EVP_dss1(), EVP_mdc2() and EVP_ripemd160() were 270changed to return truely const EVP_MD * in OpenSSL 0.9.7. 271 272The link between digests and signing algorithms was fixed in OpenSSL 1.0 and 273later, so now EVP_sha1() can be used with RSA and DSA, there is no need to 274use EVP_dss1() any more. 275 276OpenSSL 1.0 and later does not include the MD2 digest algorithm in the 277default configuration due to its security weaknesses. 278 279=cut 280