On 11/11/2022 00:49, James Muir wrote:
On 2022-11-10 18:35, f...@plutonium24.de wrote:
I have been using EVP_PKEY_get_raw_public_key with OpenSSL 1.1.1
without any problems to extract a raw public key (secp521r1, NIST
curve P-521). With OpenSSL 3.0 this fails. I'm using this call to get
the raw public key and to compare it with a reference value I have and
I also check that the group name is "secp521r1".
That doesn't work in 3.0.
Quoting from
https://www.openssl.org/docs/manmaster/man3/EVP_PKEY_new.html :
<quote>
EVP_PKEY_get_raw_public_key() fills the buffer provided by pub with raw
public key data. The size of the pub buffer should be in *len on entry
to the function, and on exit *len is updated with the number of bytes
actually written. If the buffer pub is NULL then *len is populated with
the number of bytes required to hold the key. The calling application is
responsible for ensuring that the buffer is large enough to receive the
public key data. This function only works for algorithms that support
raw public keys. Currently this is: EVP_PKEY_X25519, EVP_PKEY_ED25519,
EVP_PKEY_X448 or EVP_PKEY_ED448.
</quote>
That text exists even in the 1.1.1 version of the man page:
https://www.openssl.org/docs/man1.1.1/man3/EVP_PKEY_get_raw_public_key.html
I am surprised that this was working in 1.1.1....from code inspection I
can't see how it would since EC keys seem to lack the necessary support.
I threw together some test code to check this using 1.1.1:
#include <openssl/ec.h>
#include <openssl/evp.h>
#include <openssl/bio.h>
#include <openssl/err.h>
#include <stdio.h>
#include <stdlib.h>
int main(void)
{
EC_KEY *key = EC_KEY_new_by_curve_name(NID_secp521r1);
EVP_PKEY *pkey = EVP_PKEY_new();
unsigned char rawkey[1024];
size_t keylen = sizeof(rawkey);
if (key == NULL || pkey == NULL) {
printf("Failed to allocate keys\n");
goto err;
}
if (!EC_KEY_generate_key(key)) {
printf("Failed to generate key\n");
goto err;
}
if (!EVP_PKEY_assign_EC_KEY(pkey, key)) {
printf("Failed to assign EC_KEY\n");
goto err;
}
if (!EVP_PKEY_get_raw_public_key(pkey, rawkey, &keylen)) {
printf("Failed to get raw public key\n");
goto err;
}
printf("Raw key is:\n");
BIO_dump_fp(stdout, rawkey, keylen);
printf("\n");
return EXIT_SUCCESS;
err:
ERR_print_errors_fp(stdout);
return EXIT_FAILURE;
}
Running this I get:
$ openssl version
OpenSSL 1.1.1t-dev xx XXX xxxx
$ ./eckeygen
Failed to get raw public key
140164760770368:error:060CB096:digital envelope
routines:EVP_PKEY_get_raw_public_key:operation not supported for this
keytype:crypto/evp/p_lib.c:309:
So, I don't understand how this ever worked for you. There must be
something slightly strange about your key/setup??
Matt
You were reading the P521 public-key previously (with 1.1.1), but in
what format was it sent you? Do you want just the bytes of the public
EC point?
-James M
