.\" $OpenBSD: EVP_DigestInit.3,v 1.31 2023/09/07 19:59:58 schwarze Exp $ .\" full merge up to: OpenSSL 7f572e95 Dec 2 13:57:04 2015 +0000 .\" selective merge up to: OpenSSL 24a535ea Sep 22 13:14:20 2020 +0100 .\" .\" This file is a derived work. .\" The changes are covered by the following Copyright and license: .\" .\" Copyright (c) 2019, 2023 Ingo Schwarze .\" .\" Permission to use, copy, modify, and distribute this software for any .\" purpose with or without fee is hereby granted, provided that the above .\" copyright notice and this permission notice appear in all copies. .\" .\" THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES .\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF .\" MERCHANTABILITY AND FITNESS. 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IN NO EVENT SHALL THE OpenSSL PROJECT OR .\" ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, .\" SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT .\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; .\" LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, .\" STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) .\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED .\" OF THE POSSIBILITY OF SUCH DAMAGE. .\" .Dd $Mdocdate: September 7 2023 $ .Dt EVP_DIGESTINIT 3 .Os .Sh NAME .Nm EVP_MD_CTX_new , .Nm EVP_MD_CTX_reset , .Nm EVP_MD_CTX_free , .Nm EVP_MD_CTX_init , .Nm EVP_MD_CTX_create , .Nm EVP_MD_CTX_cleanup , .Nm EVP_MD_CTX_destroy , .Nm EVP_DigestInit_ex , .Nm EVP_DigestUpdate , .Nm EVP_DigestFinal_ex , .Nm EVP_Digest , .Nm EVP_MD_CTX_copy_ex , .Nm EVP_DigestInit , .Nm EVP_DigestFinal , .Nm EVP_MD_CTX_copy , .Nm EVP_MD_CTX_md , .Nm EVP_md_null , .Nm EVP_sha224 , .Nm EVP_sha256 , .Nm EVP_sha384 , .Nm EVP_sha512 , .Nm EVP_sha512_224 , .Nm EVP_sha512_256 , .Nm EVP_ripemd160 , .Nm EVP_get_digestbyname , .Nm EVP_get_digestbynid , .Nm EVP_get_digestbyobj .Nd EVP digest routines .Sh SYNOPSIS .In openssl/evp.h .Ft EVP_MD_CTX * .Fn EVP_MD_CTX_new void .Ft int .Fo EVP_MD_CTX_reset .Fa "EVP_MD_CTX *ctx" .Fc .Ft void .Fo EVP_MD_CTX_free .Fa "EVP_MD_CTX *ctx" .Fc .Ft void .Fo EVP_MD_CTX_init .Fa "EVP_MD_CTX *ctx" .Fc .Ft EVP_MD_CTX * .Fn EVP_MD_CTX_create void .Ft int .Fo EVP_MD_CTX_cleanup .Fa "EVP_MD_CTX *ctx" .Fc .Ft void .Fo EVP_MD_CTX_destroy .Fa "EVP_MD_CTX *ctx" .Fc .Ft int .Fo EVP_DigestInit_ex .Fa "EVP_MD_CTX *ctx" .Fa "const EVP_MD *type" .Fa "ENGINE *impl" .Fc .Ft int .Fo EVP_DigestUpdate .Fa "EVP_MD_CTX *ctx" .Fa "const void *d" .Fa "size_t cnt" .Fc .Ft int .Fo EVP_DigestFinal_ex .Fa "EVP_MD_CTX *ctx" .Fa "unsigned char *md" .Fa "unsigned int *s" .Fc .Ft int .Fo EVP_Digest .Fa "const void *d" .Fa "size_t cnt" .Fa "unsigned char *md" .Fa "unsigned int *s" .Fa "const EVP_MD *type" .Fa "ENGINE *impl" .Fc .Ft int .Fo EVP_MD_CTX_copy_ex .Fa "EVP_MD_CTX *out" .Fa "const EVP_MD_CTX *in" .Fc .Ft int .Fo EVP_DigestInit .Fa "EVP_MD_CTX *ctx" .Fa "const EVP_MD *type" .Fc .Ft int .Fo EVP_DigestFinal .Fa "EVP_MD_CTX *ctx" .Fa "unsigned char *md" .Fa "unsigned int *s" .Fc .Ft int .Fo EVP_MD_CTX_copy .Fa "EVP_MD_CTX *out" .Fa "EVP_MD_CTX *in" .Fc .Ft const EVP_MD * .Fo EVP_MD_CTX_md .Fa "const EVP_MD_CTX *ctx" .Fc .Ft const EVP_MD * .Fn EVP_md_null void .Ft const EVP_MD * .Fn EVP_sha224 void .Ft const EVP_MD * .Fn EVP_sha256 void .Ft const EVP_MD * .Fn EVP_sha384 void .Ft const EVP_MD * .Fn EVP_sha512 void .Ft const EVP_MD * .Fn EVP_sha512_224 void .Ft const EVP_MD * .Fn EVP_sha512_256 void .Ft const EVP_MD * .Fn EVP_ripemd160 void .Ft const EVP_MD * .Fo EVP_get_digestbyname .Fa "const char *name" .Fc .Ft const EVP_MD * .Fo EVP_get_digestbynid .Fa "int type" .Fc .Ft const EVP_MD * .Fo EVP_get_digestbyobj .Fa "const ASN1_OBJECT *o" .Fc .Sh DESCRIPTION The EVP digest routines are a high-level interface to message digests and should be used instead of the cipher-specific functions. .Pp .Fn EVP_MD_CTX_new allocates a new, empty digest context. .Pp .Fn EVP_MD_CTX_reset cleans up .Fa ctx and resets it to the state it had after .Fn EVP_MD_CTX_new , such that it can be reused. .Pp .Fn EVP_MD_CTX_free cleans up .Fa ctx and frees the space allocated to it. .Pp .Fn 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 .Fn EVP_MD_CTX_new or one that was already used. .Pp .Fn EVP_MD_CTX_create , .Fn EVP_MD_CTX_cleanup , and .Fn EVP_MD_CTX_destroy are deprecated aliases for .Fn EVP_MD_CTX_new , .Fn EVP_MD_CTX_reset , and .Fn EVP_MD_CTX_free , respectively. .Pp .Fn EVP_DigestInit_ex sets up the digest context .Fa ctx to use a digest .Fa type from .Vt ENGINE .Fa impl . The .Fa type will typically be supplied by a function such as .Fn EVP_sha512 . If .Fa impl is .Dv NULL , then the default implementation of digest .Fa type is used. .Pp .Fn EVP_DigestUpdate hashes .Fa cnt bytes of data at .Fa d into the digest context .Fa ctx . This function can be called several times on the same .Fa ctx to hash additional data. .Pp .Fn EVP_DigestFinal_ex retrieves the digest value from .Fa ctx and places it in .Fa md . If the .Fa s parameter is not .Dv NULL , then the number of bytes of data written (i.e. the length of the digest) will be written to the integer at .Fa s ; at most .Dv EVP_MAX_MD_SIZE bytes will be written. After calling .Fn EVP_DigestFinal_ex , no additional calls to .Fn EVP_DigestUpdate can be made, but .Fn EVP_DigestInit_ex can be called to initialize a new digest operation. .Pp .Fn EVP_Digest is a simple wrapper function to hash .Fa cnt bytes of data at .Fa d using the digest .Fa type from .Vt ENGINE .Fa impl in a one-shot operation and place the digest value into .Fa md , and, unless .Fa s is .Dv NULL , the length of the digest in bytes into .Pf * Fa s . This wrapper uses a temporary digest context and passes its arguments to .Fn EVP_DigestInit_ex , .Fn EVP_DigestUpdate , and .Fn EVP_DigestFinal_ex internally. .Pp .Fn EVP_MD_CTX_copy_ex can be used to copy the message digest state from .Fa in to .Fa out . This is useful if large amounts of data are to be hashed which only differ in the last few bytes. .Pp .Fn EVP_DigestInit is a deprecated function behaving like .Fn EVP_DigestInit_ex except that it always uses the default digest implementation and that it requires .Fn EVP_MD_CTX_reset before it can be used on a context that was already used. .Pp .Fn EVP_DigestFinal is a deprecated function behaving like .Fn EVP_DigestFinal_ex except that the digest context .Fa ctx is automatically cleaned up after use by calling .Fn EVP_MD_CTX_reset internally. .Pp .Fn EVP_MD_CTX_copy is a deprecated function behaving like .Fn EVP_MD_CTX_copy_ex except that it requires .Fn EVP_MD_CTX_reset before a context that was already used can be passed as .Fa out . .Pp .Fn EVP_sha224 , .Fn EVP_sha256 , .Fn EVP_sha384 , .Fn EVP_sha512 , and .Fn EVP_ripemd160 return .Vt EVP_MD structures for the SHA224, SHA256, SHA384, SHA512 and RIPEMD160 digest algorithms respectively. .Pp .Fn EVP_sha512_224 and .Fn EVP_sha512_256 return an .Vt EVP_MD structure that provides the truncated SHA512 variants SHA512/224 and SHA512/256, respectively. .Pp .Fn EVP_md_null is a "null" message digest that does nothing: i.e. the hash it returns is of zero length. .Pp .Fn EVP_get_digestbyname , .Fn EVP_get_digestbynid , and .Fn EVP_get_digestbyobj return an .Vt EVP_MD structure when passed a digest name, a digest NID, or an ASN1_OBJECT structure respectively. .Pp .Fn EVP_get_digestbynid and .Fn EVP_get_digestbyobj are implemented as macros. .Pp 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. .Pp For most applications the .Fa impl parameter to .Fn EVP_DigestInit_ex will be set to NULL to use the default digest implementation. .Pp The functions .Fn EVP_DigestInit , .Fn EVP_DigestFinal , and .Fn EVP_MD_CTX_copy are obsolete but are retained to maintain compatibility with existing code. New applications should use .Fn EVP_DigestInit_ex , .Fn EVP_DigestFinal_ex , and .Fn 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. .Pp If digest contexts are not cleaned up after use, memory leaks will occur. .Sh RETURN VALUES .Fn EVP_MD_CTX_new and .Fn EVP_MD_CTX_create return the new .Vt EVP_MD_CTX object or .Dv NULL for failure. .Pp .Fn EVP_MD_CTX_reset and .Fn EVP_MD_CTX_cleanup always return 1. .Pp .Fn EVP_DigestInit_ex , .Fn EVP_DigestUpdate , .Fn EVP_DigestFinal_ex , .Fn EVP_Digest , .Fn EVP_MD_CTX_copy_ex , .Fn EVP_DigestInit , .Fn EVP_DigestFinal , and .Fn EVP_MD_CTX_copy return 1 for success or 0 for failure. .Pp .Fn EVP_MD_CTX_md returns the .Vt EVP_MD object used by .Fa ctx , or .Dv NULL if .Fa ctx is .Dv NULL or does not have any message digest algorithm assigned yet. .Pp .Fn EVP_md_null , .Fn EVP_sha224 , .Fn EVP_sha256 , .Fn EVP_sha384 , .Fn EVP_sha512 , .Fn EVP_sha512_224 , .Fn EVP_sha512_256 , and .Fn EVP_ripemd160 return pointers to constant static objects owned by the library. .Pp .Fn EVP_get_digestbyname , .Fn EVP_get_digestbynid , and .Fn EVP_get_digestbyobj return either an .Vt EVP_MD structure or .Dv NULL if an error occurs. .Sh EXAMPLES This example digests the data "Test Message\en" and "Hello World\en", using the digest name passed on the command line. .Bd -literal -offset indent #include #include #include int main(int argc, char *argv[]) { EVP_MD_CTX *mdctx; const EVP_MD *md; const char mess1[] = "Test Message\en"; const char mess2[] = "Hello World\en"; unsigned char md_value[EVP_MAX_MD_SIZE]; unsigned int md_len, i; if (argc <= 1) { printf("Usage: mdtest digestname\en"); exit(1); } md = EVP_get_digestbyname(argv[1]); if (md == NULL) { printf("Unknown message digest %s\en", 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("\en"); return 0; } .Ed .Sh SEE ALSO .Xr BIO_f_md 3 , .Xr CMAC_Init 3 , .Xr evp 3 , .Xr EVP_BytesToKey 3 , .Xr EVP_DigestSignInit 3 , .Xr EVP_DigestVerifyInit 3 , .Xr EVP_MD_CTX_ctrl 3 , .Xr EVP_MD_meth_new 3 , .Xr EVP_MD_nid 3 , .Xr EVP_PKEY_CTX_set_signature_md 3 , .Xr EVP_PKEY_meth_set_signctx 3 , .Xr EVP_sha1 3 , .Xr EVP_sha3_224 3 , .Xr EVP_SignInit 3 , .Xr EVP_sm3 3 , .Xr EVP_VerifyInit 3 , .Xr EVP_whirlpool 3 , .Xr HMAC 3 , .Xr OCSP_basic_sign 3 , .Xr OCSP_request_sign 3 , .Xr PKCS5_PBKDF2_HMAC 3 , .Xr PKCS7_sign_add_signer 3 , .Xr X509_ALGOR_set_md 3 , .Xr X509_digest 3 , .Xr X509_sign 3 .Sh HISTORY .Fn EVP_DigestInit , .Fn EVP_DigestUpdate , and .Fn EVP_DigestFinal first appeared in SSLeay 0.5.1. .Fn EVP_md_null and .Fn EVP_get_digestbyname first appeared in SSLeay 0.8.0. .Fn EVP_get_digestbynid and .Fn EVP_get_digestbyobj first appeared in SSLeay 0.8.1. .Fn EVP_ripemd160 first appeared in SSLeay 0.9.0. All these functions have been available since .Ox 2.4 . .Pp .Fn EVP_MD_CTX_copy first appeared in OpenSSL 0.9.2b and has been available since .Ox 2.6 . .Pp .Fn EVP_MD_CTX_md first appeared in OpenSSL 0.9.5 and has been available since .Ox 2.7 . .Pp .Fn EVP_MD_CTX_init , .Fn EVP_MD_CTX_create , .Fn EVP_MD_CTX_cleanup , .Fn EVP_MD_CTX_destroy , .Fn EVP_DigestInit_ex , .Fn EVP_DigestFinal_ex , .Fn EVP_Digest , and .Fn EVP_MD_CTX_copy_ex first appeared in OpenSSL 0.9.7 and have been available since .Ox 3.2 . .Pp .Fn EVP_sha224 , .Fn EVP_sha256 , .Fn EVP_sha384 , and .Fn EVP_sha512 first appeared in OpenSSL 0.9.7h and 0.9.8a and have been available since .Ox 4.0 . .Pp .Fn EVP_MD_CTX_new , .Fn EVP_MD_CTX_reset , and .Fn EVP_MD_CTX_free first appeared in OpenSSL 1.1.0 and have been available since .Ox 6.3 . .Pp .Fn EVP_sha512_224 and .Fn EVP_sha512_256 first appeared in OpenSSL 1.1.1 and have been available since .Ox 7.4 .