OpenSSL 4.0.0

OpenSSL 4.0.0 is a feature release adding significant new functionality

to OpenSSL.

This release incorporates the following potentially significant or incompatible

changes:

Removed extra leading '00:' when printing key data such as an RSA modulus

in hexadecimal format where the first (most significant) byte is >= 0x80. - Standardized the width of hexadecimal dumps to 24 bytes for signatures

(to stay within the 80 characters limit) and 16 bytes for everything else. - Lower bounds checks are now enforced when using

PKCS5_PBKDF2_HMAC

API

with FIPS provider. - Added AKID verification checks when

X509_V_FLAG_X509_STRICT

is set. - Augmented CRL verification process with several additional checks.

libcrypto

no longer cleans up globally allocated data viaatexit()

. - BIO_snprintf()

now usessnprintf()

provided by libc instead of internal

implementation. - OPENSSL_cleanup()

now runs in a global destructor, or not at all

by default. - ASN1_STRING

has been made opaque. - Signatures of numerous API functions, including those that are related

to X509 processing, are changed to includeconst

qualifiers for argument

and return types, where suitable. - Deprecated

X509_cmp_time()

,X509_cmp_current_time()

,

andX509_cmp_timeframe()

in favor ofX509_check_certificate_times()

. - Removed support for the SSLv2 Client Hello.

Removed support for SSLv3. SSLv3 has been deprecated since 2015,

and OpenSSL had it disabled by default since version 1.1.0 (2016). - Removed support for engines. The

no-engine

build option

and theOPENSSL_NO_ENGINE

macro are always present. - Support of deprecated elliptic curves in TLS according to RFC 8422 was

disabled at compile-time by default. To enable it, use the

enable-tls-deprecated-ec

configuration option. - Support of explicit EC curves was disabled at compile-time by default.

To enable it, use theenable-ec_explicit_curves

configuration option. - Removed

c_rehash

script tool. Useopenssl rehash

instead. - Removed the deprecated

msie-hack

option from theopenssl ca

command. - Removed

BIO_f_reliable()

implementation without replacement.

It was broken since 3.0 release without any complaints. - Removed deprecated support for custom

EVP_CIPHER

,EVP_MD

,EVP_PKEY

,

andEVP_PKEY_ASN1

methods. - Removed deprecated fixed SSL/TLS version method functions.

Removed deprecated functions

ERR_get_state()

,ERR_remove_state()

andERR_remove_thread_state()

. TheERR_STATE

object is now always

opaque. - Dropped

darwin-i386{,-cc}

anddarwin-ppc{,64}{,-cc}

targets

from Configurations.

This release adds the following new features:

Support for Encrypted Client Hello (ECH, RFC 9849).

Seedoc/designs/ech-api.md

for details. - Support for RFC 8998, signature algorithm

sm2sig_sm3

, key exchange

groupcurveSM2

, and [tls-hybrid-sm2-mlkem] post-quantum group

curveSM2MLKEM768

. - cSHAKE function support as per SP 800-185.

"ML-DSA-MU" digest algorithm support.

Support for SNMP KDF and SRTP KDF.

FIPS self tests can now be deferred and run as needed when installing

the FIPS module with the-defer_tests

option of theopenssl fipsinstall

command. - Support for using either static or dynamic VC runtime linkage

on Windows. - Support for negotiated FFDHE key exchange in TLS 1.2 in accordance

with RFC 7919.