bionic (3) EVP_DigestVerifyUpdate.3ssl.gz

NAME

       EVP_DigestVerifyInit, EVP_DigestVerifyUpdate, EVP_DigestVerifyFinal, EVP_DigestVerify - EVP signature
       verification functions

SYNOPSIS

        #include <openssl/evp.h>

        int EVP_DigestVerifyInit(EVP_MD_CTX *ctx, EVP_PKEY_CTX **pctx,
                                 const EVP_MD *type, ENGINE *e, EVP_PKEY *pkey);
        int EVP_DigestVerifyUpdate(EVP_MD_CTX *ctx, const void *d, size_t cnt);
        int EVP_DigestVerifyFinal(EVP_MD_CTX *ctx, const unsigned char *sig,
                                  size_t siglen);
        int EVP_DigestVerify(EVP_MD_CTX *ctx, const unsigned char *sigret,
                             size_t siglen, const unsigned char *tbs, size_t tbslen);

DESCRIPTION

       The EVP signature routines are a high level interface to digital signatures.

       EVP_DigestVerifyInit() sets up verification context ctx to use digest type from ENGINE e and public key
       pkey. ctx must be created with EVP_MD_CTX_new() before calling this function. If pctx is not NULL, the
       EVP_PKEY_CTX of the verification operation will be written to *pctx: this can be used to set alternative
       verification options. Note that any existing value in *pctx is overwritten. The EVP_PKEY_CTX value
       returned must not be freed directly by the application if ctx is not assigned an EVP_PKEY_CTX value
       before being passed to EVP_DigestSignInit() (which means the EVP_PKEY_CTX is created inside
       EVP_DigestSignInit() and it will be freed automatically when the EVP_MD_CTX is freed).

       No EVP_PKEY_CTX will be created by EVP_DigsetSignInit() if the passed ctx has already been assigned one
       via EVP_MD_CTX_set_ctx(3). See also SM2(7).

       EVP_DigestVerifyUpdate() hashes cnt bytes of data at d into the verification context ctx. This function
       can be called several times on the same ctx to include additional data. This function is currently
       implemented using a macro.

       EVP_DigestVerifyFinal() verifies the data in ctx against the signature in sig of length siglen.

       EVP_DigestVerify() verifies tbslen bytes at tbs against the signature in sig of length siglen.

RETURN VALUES

       EVP_DigestVerifyInit() and EVP_DigestVerifyUpdate() return 1 for success and 0 for failure.

       EVP_DigestVerifyFinal() and EVP_DigestVerify() return 1 for success; any other value indicates failure.
       A return value of zero indicates that the signature did not verify successfully (that is, tbs did not
       match the original data or the signature had an invalid form), while other values indicate a more serious
       error (and sometimes also indicate an invalid signature form).

       The error codes can be obtained from ERR_get_error(3).

NOTES

       The EVP interface to digital signatures should almost always be used in preference to the low level
       interfaces. This is because the code then becomes transparent to the algorithm used and much more
       flexible.

       EVP_DigestVerify() is a one shot operation which verifies a single block of data in one function. For
       algorithms that support streaming it is equivalent to calling EVP_DigestVerifyUpdate() and
       EVP_DigestVerifyFinal(). For algorithms which do not support streaming (e.g. PureEdDSA) it is the only
       way to verify data.

       In previous versions of OpenSSL there was a link between message digest types and public key algorithms.
       This meant that "clone" digests such as EVP_dss1() needed to be used to sign using SHA1 and DSA. This is
       no longer necessary and the use of clone digest is now discouraged.

       For some key types and parameters the random number generator must be seeded or the operation will fail.

       The call to EVP_DigestVerifyFinal() internally finalizes a copy of the digest context. This means that
       EVP_VerifyUpdate() and EVP_VerifyFinal() can be called later to digest and verify additional data.

       Since only a copy of the digest context is ever finalized, the context must be cleaned up after use by
       calling EVP_MD_CTX_free() or a memory leak will occur.

SEE ALSO

       EVP_DigestSignInit(3), EVP_DigestInit(3), evp(7), HMAC(3), MD2(3), MD5(3), MDC2(3), RIPEMD160(3),
       SHA1(3), dgst(1)

HISTORY

       EVP_DigestVerifyInit(), EVP_DigestVerifyUpdate() and EVP_DigestVerifyFinal() were first added to OpenSSL
       1.0.0.

COPYRIGHT

       Copyright 2006-2018 The OpenSSL Project Authors. All Rights Reserved.

       Licensed under the OpenSSL license (the "License").  You may not use this file except in compliance with
       the License.  You can obtain a copy in the file LICENSE in the source distribution or at
       <https://www.openssl.org/source/license.html>.