EVP_VERIFYINIT(3ossl)

📦
version 15.1 · 2 versions
, in freebsd 15.1

💖 EVP_VERIFYINIT(3ossl) 💖

okay so bestie, this is the OpenSSL manpage for EVP_VERIFYINIT(3ossl) — yes the whole squad of EVP signature verification functions, and honestly? it's giving "crypto but make it comprehensible." come sit with me 🫶

✨ NAME ✨

EVP_VerifyInit_ex, EVP_VerifyInit, EVP_VerifyUpdate, EVP_VerifyFinal_ex, EVP_VerifyFinal — the EVP signature verification functions. that's the whole lineup, no gatekeeping 💅

🌸 SYNOPSIS 🌸

#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);

like, copy-paste these exactly bestie, they're load-bearing 😭

🦋 DESCRIPTION 🦋

the EVP signature verification routines are a high-level interface to digital signatures. high-level = we're not down in the weeds, we're living that main character energy ✨

  • EVP_VerifyInit_ex() — sets up the verification context ctx to use digest type from ENGINE impl. lowkey important: ctx must be created by calling EVP_MD_CTX_new() before you call this function. no shortcuts 🔥
  • EVP_VerifyUpdate() — hashes cnt bytes of data at d into the verification context ctx. and the slay part? you can call this function several times on the same ctx to include additional data. incremental hashing, we love to see it 💜
  • 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. fancy, contextual, we're obsessed 🎀
  • EVP_VerifyFinal() — similar to EVP_VerifyFinal_ex() but uses default values of NULL for the library context libctx and the property query propq. the chill, no-frills twin fr fr 🌈
  • EVP_VerifyInit() — initializes verification context ctx to use the default implementation of digest type. yes bestie, just the default. no ENGINE drama 💅

⭐ RETURN VALUES ⭐

okay listen up, the numbers actually matter here:

  • 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. yep, three outcomes, not me having to remember that 😭

the error codes can be obtained by ERR_get_error(3). go get 'em.

🧚 NOTES 🧚

okay this part is important, bestie, no cap:

the EVP interface to digital signatures should almost always be used in preference to the low-level interfaces. why? because the code then becomes transparent to the algorithm used and much more flexible. icon behavior, honestly 👑

the call to EVP_VerifyFinal() internally finalizes a copy of the digest context. meaning what? meaning 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). iykyk 🦋

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. literally do not forget this, bestie 💀

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. so like... vibe check your provider first 🙈

💀 BUGS 💀

yes we're airing out the lore:

  • older versions of this documentation wrongly stated that calls to EVP_VerifyUpdate() could not be made after calling EVP_VerifyFinal(). not true, past docs were lying to us 😭
  • since the public key is passed in the call to EVP_SignFinal() any error relating to the private key (for example an unsuitable key and digest combination) will not be indicated until after potentially large amounts of data have been passed through EVP_SignUpdate(). so you find out late. tragic.
  • it is not possible to change the signing parameters using these function. nope. can't. sorry bestie.
  • the previous two bugs are fixed in the newer EVP_DigestVerify*() function. so like, there's a glow-up available if you want it ✨

🍓 SEE ALSO 🍓

evp(7), EVP_SignInit(3), EVP_DigestInit(3), evp(7), HMAC(3), MD2(3), MD5(3), MDC2(3), RIPEMD160(3), SHA1(3), openssl-dgst(1)

(yes evp(7) is in there twice. no i'm not fixing it. that's just how the page is, periodt 💅)

🌈 HISTORY 🌈

the function EVP_VerifyFinal_ex() was added in OpenSSL 3.0. new-ish, still iconic 🎀

Copyright 2000-2023 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the Apache License 2.0 (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>.

and that's the whole page, bestie 🫶 this was OpenSSL 3.5.6, dated 2026-04-07, published under EVP_VERIFYINIT(3ossl) — go verify something iconic today 💖🧚‍♀️

📦 where this page comes from