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Diffstat (limited to 'src/lib/libcrypto/doc/EVP_DigestInit.pod')
| -rw-r--r-- | src/lib/libcrypto/doc/EVP_DigestInit.pod | 197 |
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diff --git a/src/lib/libcrypto/doc/EVP_DigestInit.pod b/src/lib/libcrypto/doc/EVP_DigestInit.pod new file mode 100644 index 0000000000..345b1ddfa7 --- /dev/null +++ b/src/lib/libcrypto/doc/EVP_DigestInit.pod | |||
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| 1 | =pod | ||
| 2 | |||
| 3 | =head1 NAME | ||
| 4 | |||
| 5 | EVP_DigestInit, EVP_DigestUpdate, EVP_DigestFinal - EVP digest routines | ||
| 6 | |||
| 7 | =head1 SYNOPSIS | ||
| 8 | |||
| 9 | #include <openssl/evp.h> | ||
| 10 | |||
| 11 | void EVP_DigestInit(EVP_MD_CTX *ctx, const EVP_MD *type); | ||
| 12 | void EVP_DigestUpdate(EVP_MD_CTX *ctx, const void *d, unsigned int cnt); | ||
| 13 | void EVP_DigestFinal(EVP_MD_CTX *ctx, unsigned char *md, | ||
| 14 | unsigned int *s); | ||
| 15 | |||
| 16 | #define EVP_MAX_MD_SIZE (16+20) /* The SSLv3 md5+sha1 type */ | ||
| 17 | |||
| 18 | int EVP_MD_CTX_copy(EVP_MD_CTX *out,EVP_MD_CTX *in); | ||
| 19 | |||
| 20 | #define EVP_MD_type(e) ((e)->type) | ||
| 21 | #define EVP_MD_pkey_type(e) ((e)->pkey_type) | ||
| 22 | #define EVP_MD_size(e) ((e)->md_size) | ||
| 23 | #define EVP_MD_block_size(e) ((e)->block_size) | ||
| 24 | |||
| 25 | #define EVP_MD_CTX_md(e) (e)->digest) | ||
| 26 | #define EVP_MD_CTX_size(e) EVP_MD_size((e)->digest) | ||
| 27 | #define EVP_MD_CTX_block_size(e) EVP_MD_block_size((e)->digest) | ||
| 28 | #define EVP_MD_CTX_type(e) EVP_MD_type((e)->digest) | ||
| 29 | |||
| 30 | EVP_MD *EVP_md_null(void); | ||
| 31 | EVP_MD *EVP_md2(void); | ||
| 32 | EVP_MD *EVP_md5(void); | ||
| 33 | EVP_MD *EVP_sha(void); | ||
| 34 | EVP_MD *EVP_sha1(void); | ||
| 35 | EVP_MD *EVP_dss(void); | ||
| 36 | EVP_MD *EVP_dss1(void); | ||
| 37 | EVP_MD *EVP_mdc2(void); | ||
| 38 | EVP_MD *EVP_ripemd160(void); | ||
| 39 | |||
| 40 | const EVP_MD *EVP_get_digestbyname(const char *name); | ||
| 41 | #define EVP_get_digestbynid(a) EVP_get_digestbyname(OBJ_nid2sn(a)) | ||
| 42 | #define EVP_get_digestbyobj(a) EVP_get_digestbynid(OBJ_obj2nid(a)) | ||
| 43 | |||
| 44 | =head1 DESCRIPTION | ||
| 45 | |||
| 46 | The EVP digest routines are a high level interface to message digests. | ||
| 47 | |||
| 48 | EVP_DigestInit() initialises a digest context B<ctx> to use a digest | ||
| 49 | B<type>: this will typically be supplied by a function such as | ||
| 50 | EVP_sha1(). | ||
| 51 | |||
| 52 | EVP_DigestUpdate() hashes B<cnt> bytes of data at B<d> into the | ||
| 53 | digest context B<ctx>. This funtion can be called several times on the | ||
| 54 | same B<ctx> to hash additional data. | ||
| 55 | |||
| 56 | EVP_DigestFinal() retrieves the digest value from B<ctx> and places | ||
| 57 | it in B<md>. If the B<s> parameter is not NULL then the number of | ||
| 58 | bytes of data written (i.e. the length of the digest) will be written | ||
| 59 | to the integer at B<s>, at most B<EVP_MAX_MD_SIZE> bytes will be written. | ||
| 60 | After calling EVP_DigestFinal() no additional calls to EVP_DigestUpdate() | ||
| 61 | can be made, but EVP_DigestInit() can be called to initialiase a new | ||
| 62 | digest operation. | ||
| 63 | |||
| 64 | EVP_MD_CTX_copy() can be used to copy the message digest state from | ||
| 65 | B<in> to B<out>. This is useful if large amounts of data are to be | ||
| 66 | hashed which only differ in the last few bytes. | ||
| 67 | |||
| 68 | EVP_MD_size() and EVP_MD_CTX_size() return the size of the message digest | ||
| 69 | when passed an B<EVP_MD> or an B<EVP_MD_CTX> structure, i.e. the size of the | ||
| 70 | hash. | ||
| 71 | |||
| 72 | EVP_MD_block_size() and EVP_MD_CTX_block_size() return the block size of the | ||
| 73 | message digest when passed an B<EVP_MD> or an B<EVP_MD_CTX> structure. | ||
| 74 | |||
| 75 | EVP_MD_type() and EVP_MD_CTX_type() return the NID of the OBJECT IDENTIFIER | ||
| 76 | representing the given message digest when passed an B<EVP_MD> structure. | ||
| 77 | For example EVP_MD_type(EVP_sha1()) returns B<NID_sha1>. This function is | ||
| 78 | normally used when setting ASN1 OIDs. | ||
| 79 | |||
| 80 | EVP_MD_CTX_md() returns the B<EVP_MD> structure corresponding to the passed | ||
| 81 | B<EVP_MD_CTX>. | ||
| 82 | |||
| 83 | EVP_MD_pkey_type() returns the NID of the public key signing algorithm associated | ||
| 84 | with this digest. For example EVP_sha1() is associated with RSA so this will | ||
| 85 | return B<NID_sha1WithRSAEncryption>. This "link" between digests and signature | ||
| 86 | algorithms may not be retained in future versions of OpenSSL. | ||
| 87 | |||
| 88 | EVP_md2(), EVP_md5(), EVP_sha(), EVP_sha1(), EVP_mdc2() and EVP_ripemd160() | ||
| 89 | return B<EVP_MD> structures for the MD2, MD5, SHA, SHA1, MDC2 and RIPEMD160 digest | ||
| 90 | algorithms respectively. The associated signature algorithm is RSA in each case. | ||
| 91 | |||
| 92 | EVP_dss() and EVP_dss1() return B<EVP_MD> structures for SHA and SHA1 digest | ||
| 93 | algorithms but using DSS (DSA) for the signature algorithm. | ||
| 94 | |||
| 95 | EVP_md_null() is a "null" message digest that does nothing: i.e. the hash it | ||
| 96 | returns is of zero length. | ||
| 97 | |||
| 98 | EVP_get_digestbyname(), EVP_get_digestbynid() and EVP_get_digestbyobj() | ||
| 99 | return an B<EVP_MD> structure when passed a digest name, a digest NID or | ||
| 100 | an ASN1_OBJECT structure respectively. The digest table must be initialised | ||
| 101 | using, for example, OpenSSL_add_all_digests() for these functions to work. | ||
| 102 | |||
| 103 | =head1 RETURN VALUES | ||
| 104 | |||
| 105 | EVP_DigestInit(), EVP_DigestUpdate() and EVP_DigestFinal() do not return values. | ||
| 106 | |||
| 107 | EVP_MD_CTX_copy() returns 1 if successful or 0 for failure. | ||
| 108 | |||
| 109 | EVP_MD_type(), EVP_MD_pkey_type() and EVP_MD_type() return the NID of the | ||
| 110 | corresponding OBJECT IDENTIFIER or NID_undef if none exists. | ||
| 111 | |||
| 112 | EVP_MD_size(), EVP_MD_block_size(), EVP_MD_CTX_size(e), EVP_MD_size(), | ||
| 113 | EVP_MD_CTX_block_size() and EVP_MD_block_size() return the digest or block | ||
| 114 | size in bytes. | ||
| 115 | |||
| 116 | EVP_md_null(), EVP_md2(), EVP_md5(), EVP_sha(), EVP_sha1(), EVP_dss(), | ||
| 117 | EVP_dss1(), EVP_mdc2() and EVP_ripemd160() return pointers to the | ||
| 118 | corresponding EVP_MD structures. | ||
| 119 | |||
| 120 | EVP_get_digestbyname(), EVP_get_digestbynid() and EVP_get_digestbyobj() | ||
| 121 | return either an B<EVP_MD> structure or NULL if an error occurs. | ||
| 122 | |||
| 123 | =head1 NOTES | ||
| 124 | |||
| 125 | The B<EVP> interface to message digests should almost always be used in | ||
| 126 | preference to the low level interfaces. This is because the code then becomes | ||
| 127 | transparent to the digest used and much more flexible. | ||
| 128 | |||
| 129 | SHA1 is the digest of choice for new applications. The other digest algorithms | ||
| 130 | are still in common use. | ||
| 131 | |||
| 132 | =head1 EXAMPLE | ||
| 133 | |||
| 134 | This example digests the data "Test Message\n" and "Hello World\n", using the | ||
| 135 | digest name passed on the command line. | ||
| 136 | |||
| 137 | #include <stdio.h> | ||
| 138 | #include <openssl/evp.h> | ||
| 139 | |||
| 140 | main(int argc, char *argv[]) | ||
| 141 | { | ||
| 142 | EVP_MD_CTX mdctx; | ||
| 143 | const EVP_MD *md; | ||
| 144 | char mess1[] = "Test Message\n"; | ||
| 145 | char mess2[] = "Hello World\n"; | ||
| 146 | unsigned char md_value[EVP_MAX_MD_SIZE]; | ||
| 147 | int md_len, i; | ||
| 148 | |||
| 149 | OpenSSL_add_all_digests(); | ||
| 150 | |||
| 151 | if(!argv[1]) { | ||
| 152 | printf("Usage: mdtest digestname\n"); | ||
| 153 | exit(1); | ||
| 154 | } | ||
| 155 | |||
| 156 | md = EVP_get_digestbyname(argv[1]); | ||
| 157 | |||
| 158 | if(!md) { | ||
| 159 | printf("Unknown message digest %s\n", argv[1]); | ||
| 160 | exit(1); | ||
| 161 | } | ||
| 162 | |||
| 163 | EVP_DigestInit(&mdctx, md); | ||
| 164 | EVP_DigestUpdate(&mdctx, mess1, strlen(mess1)); | ||
| 165 | EVP_DigestUpdate(&mdctx, mess2, strlen(mess2)); | ||
| 166 | EVP_DigestFinal(&mdctx, md_value, &md_len); | ||
| 167 | |||
| 168 | printf("Digest is: "); | ||
| 169 | for(i = 0; i < md_len; i++) printf("%02x", md_value[i]); | ||
| 170 | printf("\n"); | ||
| 171 | } | ||
| 172 | |||
| 173 | =head1 BUGS | ||
| 174 | |||
| 175 | Several of the functions do not return values: maybe they should. Although the | ||
| 176 | internal digest operations will never fail some future hardware based operations | ||
| 177 | might. | ||
| 178 | |||
| 179 | The link between digests and signing algorithms results in a situation where | ||
| 180 | EVP_sha1() must be used with RSA and EVP_dss1() must be used with DSS | ||
| 181 | even though they are identical digests. | ||
| 182 | |||
| 183 | The size of an B<EVP_MD_CTX> structure is determined at compile time: this results | ||
| 184 | in code that must be recompiled if the size of B<EVP_MD_CTX> increases. | ||
| 185 | |||
| 186 | =head1 SEE ALSO | ||
| 187 | |||
| 188 | L<evp(3)|evp(3)>, L<hmac(3)|hmac(3)>, L<md2(3)|md2(3)>, | ||
| 189 | L<md5(3)|md5(3)>, L<mdc2(3)|mdc2(3)>, L<ripemd(3)|ripemd(3)>, | ||
| 190 | L<sha(3)|sha(3)>, L<digest(1)|digest(1)> | ||
| 191 | |||
| 192 | =head1 HISTORY | ||
| 193 | |||
| 194 | EVP_DigestInit(), EVP_DigestUpdate() and EVP_DigestFinal() are | ||
| 195 | available in all versions of SSLeay and OpenSSL. | ||
| 196 | |||
| 197 | =cut | ||
