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| EVP_DIGESTINIT(3) | Library Functions Manual | EVP_DIGESTINIT(3) |
NAME
EVP_MD_CTX_new, EVP_MD_CTX_reset, EVP_MD_CTX_free, EVP_MD_CTX_init, EVP_MD_CTX_create, EVP_MD_CTX_cleanup, EVP_MD_CTX_destroy, EVP_MD_CTX_ctrl, EVP_DigestInit_ex, EVP_DigestUpdate, EVP_DigestFinal_ex, EVP_Digest, EVP_MD_CTX_copy_ex, EVP_DigestInit, EVP_DigestFinal, EVP_MD_CTX_copy, EVP_MAX_MD_SIZE, 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_md5, EVP_md5_sha1, EVP_sha1, EVP_sha224, EVP_sha256, EVP_sha384, EVP_sha512, EVP_dss, EVP_dss1, EVP_ripemd160, EVP_get_digestbyname, EVP_get_digestbynid, EVP_get_digestbyobj — EVP digest routinesSYNOPSIS
#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); void
EVP_MD_CTX_init(EVP_MD_CTX *ctx); EVP_MD_CTX *
EVP_MD_CTX_create(void); int
EVP_MD_CTX_cleanup(EVP_MD_CTX *ctx); void
EVP_MD_CTX_destroy(EVP_MD_CTX *ctx); int
EVP_MD_CTX_ctrl(EVP_MD_CTX *ctx, int cmd, int p1, void* p2); 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_Digest(const void *d, size_t cnt, unsigned char *md, unsigned int *s, const EVP_MD *type, ENGINE *impl); 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 64 /* SHA512 */ 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_md5(void); const EVP_MD *
EVP_md5_sha1(void); const EVP_MD *
EVP_sha1(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_dss(void); const EVP_MD *
EVP_dss1(void); const EVP_MD *
EVP_ripemd160(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);
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 a new, empty digest context. EVP_MD_CTX_reset() cleans up ctx and resets it to the state it had after EVP_MD_CTX_new(), such that it can be reused. It is also suitable for digest contexts on the stack that were used and are no longer needed. EVP_MD_CTX_free() cleans up ctx and frees the space allocated to it. EVP_MD_CTX_init() is a deprecated function to clear a digest context on the stack before use. Do not use it on a digest context returned from EVP_MD_CTX_new() or one that was already used. EVP_MD_CTX_create(), EVP_MD_CTX_cleanup(), and EVP_MD_CTX_destroy() are deprecated aliases for EVP_MD_CTX_new(), EVP_MD_CTX_reset(), and EVP_MD_CTX_free(), respectively. EVP_MD_CTX_ctrl() performs digest-specific control actions on the context ctx. EVP_DigestInit_ex() sets up the digest context ctx to use a digest type from ENGINE impl. The type will typically be supplied by a function such as EVP_sha1(). If impl isNULL, then the default implementation of
digest type is used. If
ctx points to an unused object on the stack,
it must be initialized with EVP_MD_CTX_init()
before calling this function.
EVP_DigestUpdate() hashes
cnt bytes of data at
d into the digest context
ctx. This function can be called several
times on the same ctx to hash additional
data.
EVP_DigestFinal_ex() retrieves the digest value
from ctx and places it in
md. If the 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 s; at most
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_Digest() is a simple wrapper function to hash
cnt bytes of data at
d using the digest
type from
ENGINE impl
in a one-shot operation and place the digest value into
md, and, unless
s is NULL,
the length of the digest in bytes into *s.
This wrapper uses a temporary digest context and passes its arguments to
EVP_DigestInit_ex(),
EVP_DigestUpdate(), and
EVP_DigestFinal_ex() internally.
EVP_MD_CTX_copy_ex() can be used to copy the
message digest state from in to
out. This is useful if large amounts of data
are to be hashed which only differ in the last few bytes. If
out points to an unused object on the stack,
it must be initialized with EVP_MD_CTX_init()
before calling this function.
EVP_DigestInit() is a deprecated function behaving
like EVP_DigestInit_ex() except that it always
uses the default digest implementation and that it requires
EVP_MD_CTX_reset() before it can be used on a
context that was already used.
EVP_DigestFinal() is a deprecated function behaving
like EVP_DigestFinal_ex() except that the digest
context ctx is automatically cleaned up after
use by calling EVP_MD_CTX_reset() internally.
EVP_MD_CTX_copy() is a deprecated function behaving
like EVP_MD_CTX_copy_ex() except that it requires
EVP_MD_CTX_reset() before a context that was
already used can be passed as out.
EVP_MD_size() and
EVP_MD_CTX_size() return the size of the message
digest when passed an EVP_MD or an
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 EVP_MD or
an 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
EVP_MD structure. For example
EVP_MD_type(EVP_sha1())
returns NID_sha1. This function is normally
used when setting ASN.1 OIDs.
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 NID_sha1WithRSAEncryption. Since
digests and signature algorithms are no longer linked this function is only
retained for compatibility reasons.
EVP_md5(), EVP_sha1(),
EVP_sha224(),
EVP_sha256(),
EVP_sha384(),
EVP_sha512(), and
EVP_ripemd160() return
EVP_MD structures for the MD5, SHA1, SHA224,
SHA256, SHA384, SHA512 and RIPEMD160 digest algorithms respectively.
EVP_md5_sha1() returns an
EVP_MD structure that provides concatenated
MD5 and SHA1 message digests.
EVP_dss() and
EVP_dss1() return
EVP_MD structures for SHA1 digest algorithms
but using DSS (DSA) for the signature algorithm. Note: there is no need to use
these pseudo-digests in OpenSSL 1.0.0 and later; they are however retained for
compatibility.
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
EVP_MD structure when passed a digest name, a
digest NID, or an ASN1_OBJECT structure respectively.
EVP_MD_CTX_size(),
EVP_MD_CTX_block_size(),
EVP_MD_CTX_type(),
EVP_get_digestbynid(), and
EVP_get_digestbyobj() are implemented as macros.
The 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 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.
RETURN VALUES
EVP_MD_CTX_new() and EVP_MD_CTX_create() return the new EVP_MD_CTX object orNULL for failure.
EVP_MD_CTX_reset() and
EVP_MD_CTX_cleanup() always return 1.
EVP_MD_CTX_ctrl(),
EVP_DigestInit_ex(),
EVP_DigestUpdate(),
EVP_DigestFinal_ex(),
EVP_Digest(),
EVP_MD_CTX_copy_ex(),
EVP_DigestInit(),
EVP_DigestFinal(), and
EVP_MD_CTX_copy() return 1 for success or 0 for
failure.
EVP_MD_type(),
EVP_MD_pkey_type(), and
EVP_MD_CTX_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_CTX_md() returns the
EVP_MD object used by
ctx, or
NULL if
ctx is
NULL.
EVP_md_null(),
EVP_md5(),
EVP_md5_sha1(),
EVP_sha1(),
EVP_dss(),
EVP_dss1(), and
EVP_ripemd160() return pointers to the
corresponding EVP_MD structures.
EVP_get_digestbyname(),
EVP_get_digestbynid(), and
EVP_get_digestbyobj() return either an
EVP_MD structure or
NULL if an error occurs.
EXAMPLES
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>
int
main(int argc, char *argv[])
{
EVP_MD_CTX *mdctx;
const EVP_MD *md;
const char mess1[] = "Test Message\n";
const char mess2[] = "Hello World\n";
unsigned char md_value[EVP_MAX_MD_SIZE];
int md_len, i;
if (argc <= 1) {
printf("Usage: mdtest digestname\n");
exit(1);
}
md = EVP_get_digestbyname(argv[1]);
if (md == NULL) {
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");
return 0;
}
SEE ALSO
BIO_f_md(3), CMAC_Init(3), evp(3), EVP_BytesToKey(3), EVP_DigestSignInit(3), EVP_DigestVerifyInit(3), EVP_PKEY_CTX_set_signature_md(3), EVP_PKEY_meth_set_signctx(3), EVP_SignInit(3), EVP_sm3(3), EVP_VerifyInit(3), EVP_whirlpool(3), HMAC(3), OCSP_basic_sign(3), OCSP_request_sign(3), PKCS5_PBKDF2_HMAC(3), PKCS7_sign_add_signer(3), X509_ALGOR_set_md(3), X509_digest(3), X509_sign(3)HISTORY
EVP_DigestInit(), EVP_DigestUpdate(), EVP_DigestFinal(),EVP_MAX_MD_SIZE,
EVP_md5(), and
EVP_sha1() first appeared in SSLeay 0.5.1.
EVP_dss() and
EVP_dss1() first appeared in SSLeay 0.6.0.
EVP_MD_size() first appeared in SSLeay 0.6.6.
EVP_MD_CTX_size(),
EVP_MD_CTX_type(),
EVP_md_null(), and
EVP_get_digestbyname() first appeared in SSLeay
0.8.0. EVP_MD_type(),
EVP_MD_pkey_type(),
EVP_get_digestbynid(), and
EVP_get_digestbyobj() first appeared in SSLeay
0.8.1. EVP_MD_block_size(),
EVP_MD_CTX_size(),
EVP_MD_CTX_block_size(),
EVP_rc4_40(),
EVP_rc2_40_cbc(), and
EVP_ripemd160() first appeared in SSLeay 0.9.0.
All these functions have been available since OpenBSD
2.4.
EVP_MD_CTX_copy() first appeared in OpenSSL 0.9.2b
and has been available since OpenBSD 2.6.
EVP_MD_CTX_md() first appeared in OpenSSL 0.9.5 and
has been available since OpenBSD 2.7.
EVP_MD_CTX_init(),
EVP_MD_CTX_create(),
EVP_MD_CTX_cleanup(),
EVP_MD_CTX_destroy(),
EVP_DigestInit_ex(),
EVP_DigestFinal_ex(),
EVP_Digest(), and
EVP_MD_CTX_copy_ex() first appeared in OpenSSL
0.9.7 and have been available since OpenBSD 3.2.
EVP_sha224(),
EVP_sha256(),
EVP_sha384(), and
EVP_sha512() first appeared in OpenSSL 0.9.7h and
0.9.8a and have been available since OpenBSD 4.0.
EVP_MD_CTX_ctrl() first appeared in OpenSSL 1.1.0
and has been available since OpenBSD 5.7.
EVP_MD_CTX_new(),
EVP_MD_CTX_reset(),
EVP_MD_CTX_free(), and
EVP_md5_sha1() first appeared in OpenSSL 1.1.0
and have been available since OpenBSD 6.3.
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; there is no need to use EVP_dss1() any
more.| September 10, 2021 | Debian |