EVP_VerifyInit3ssl

Usage

 #include <openssl/evp.h>
 int EVP_VerifyInit_ex(EVP_MD_CTX *ctx, const EVP_MD *type, ENGINE *impl);
 int EVP_VerifyUpdate(EVP_MD_CTX *ctx, const void *d, unsigned int cnt);
 int EVP_VerifyFinal_ex(EVP_MD_CTX *ctx, const unsigned char *sigbuf,
                        unsigned int siglen, EVP_PKEY *pkey,
                        OSSL_LIB_CTX *libctx, const char *propq);
 int EVP_VerifyFinal(EVP_MD_CTX *ctx, unsigned char *sigbuf, unsigned int siglen,
                     EVP_PKEY *pkey);
 int EVP_VerifyInit(EVP_MD_CTX *ctx, const EVP_MD *type);

Overview

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

EVP_VerifyInit_ex() sets up verification context ctx to use digest type from ENGINE impl. ctx must be created by calling EVP_MD_CTX_new() before calling this function.

EVP_VerifyUpdate() 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.

EVP_VerifyFinal_ex() verifies the data in ctx using the public key pkey and siglen bytes in sigbuf. The library context libctx and property query propq are used when creating a context to use with the key pkey.

EVP_VerifyFinal() is similar to EVP_VerifyFinal_ex() but uses default values of NULL for the library context libctx and the property query propq.

EVP_VerifyInit() initializes verification context ctx to use the default implementation of digest type.

Return values

EVP_VerifyInit_ex() and EVP_VerifyUpdate() return 1 for success and 0 for failure.

EVP_VerifyFinal_ex() and EVP_VerifyFinal() return 1 for a correct signature, 0 for failure and a negative value if some other error occurred.

The error codes can be obtained by 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.

The call to EVP_VerifyFinal() internally finalizes a copy of the digest context. This means that calls to EVP_VerifyUpdate() and EVP_VerifyFinal() can be called later to digest and verify additional data. Applications may disable this behavior by setting the EVP_MD_CTX_FLAG_FINALISE context flag via EVP_MD_CTX_set_flags(3).

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.

Note that not all providers support continuation, in case the selected provider does not allow to duplicate contexts EVP_VerifyFinal() will finalize the digest context and attempting to process additional data via EVP_VerifyUpdate() will result in an error.