[openssl/openssl] 2fb934: Implement dupctx for chacha20 cipher

[Neil Horman]

  Branch: refs/heads/openssl-3.0
  Home:   https://github.com/openssl/openssl
  Commit: 2fb934d9cfec4914a1549bc2b1c4e5658236ab29
      https://github.com/openssl/openssl/commit/2fb934d9cfec4914a1549bc2b1c4e5658236ab29
  Author: Neil Horman <nhorman at openssl.org>
  Date:   2023-09-04 (Mon, 04 Sep 2023)

  Changed paths:
    M providers/implementations/ciphers/cipher_chacha20.c

  Log Message:
  -----------
  Implement dupctx for chacha20 cipher

Implement the dupctx method for the chacha20 cipher, so that
EVP_PKEY_CTX_copy works

Its pretty straightforward, its basically just a memdup.  Checking the
pointers that might need fixing up:

in PROV_CHACHA20_CTX all members are statically declared, so memduping
should be fine

in PROV_CHACHA20_CTX->base (PROV_CIPHER_CTX):
        Non statically declared members:
                *tlsmac needs to get memduped to avoid double free
                 conditions, but only if base.alloced is set
                *hw pointer is always assigned to the chacha20_hw global
                 variable, so can be left alone
                *libctx can be left alone as provctx is always NULL in
                 chacha20_newctx
                *ks appears unused by chacha20, so can be ignored
Fixes #20978

Reviewed-by: Richard Levitte <levitte at openssl.org>
Reviewed-by: Tomas Mraz <tomas at openssl.org>
Reviewed-by: Shane Lontis <shane.lontis at oracle.com>
Reviewed-by: Paul Dale <pauli at openssl.org>
(Merged from https://github.com/openssl/openssl/pull/21878)

(cherry picked from commit 61cfc22b60e33bc77b1e1944759af48c8e58f0d2)