openssl-4.0.0

[Bruce Dubbs]

New major version.

[Bruce Dubbs]

# Major changes between OpenSSL 3.6 and OpenSSL 4.0.0 [14 Apr 2026]

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 via atexit().

• BIO_snprintf() now uses snprintf() 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 include const qualifiers for argument and return types, where suitable.

• Deprecated X509_cmp_time(), X509_cmp_current_time(), and X509_cmp_timeframe() in favor of X509_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 the OPENSSL_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 the enable-ec_explicit_curves configuration option.

• Removed c_rehash script tool. Use openssl rehash instead.

• Removed the deprecated msie-hack option from the openssl 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, and EVP_PKEY_ASN1 methods.

• Removed deprecated fixed SSL/TLS version method functions.

• Removed deprecated functions ERR_get_state(), ERR_remove_state() and ERR_remove_thread_state(). The ERR_STATE object is now always opaque.

• Dropped darwin-i386{,-cc} and darwin-ppc{,64}{,-cc} targets from Configurations.

This release adds the following new features:

• Support for Encrypted Client Hello (ECH, [RFC 9849]). See doc/designs/ech-api.md for details.

• Support for [RFC 8998], signature algorithm sm2sig_sm3, key exchange group curveSM2, 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 the openssl 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].

[Bruce Dubbs]

Did a test build in chroot. Looked pretty clean but I did not log it.

All tests successful.

Files=361, Tests=4374, 37 wallclock secs ( 5.31 usr 0.42 sys + 339.35 cusr 43.32 csys = 388.40 CPU)

I don't understand cusr or csys. User and system I guess.

[Bruce Dubbs]

Again in chroot, openssh built without issue.

[pierre]

I think the problem might rather lie in dependent packages, since there are changes to the API.

[pierre]

Replying to Bruce Dubbs:

Did a test build in chroot. Looked pretty clean but I did not log it.

All tests successful.

Files=361, Tests=4374, 37 wallclock secs ( 5.31 usr 0.42 sys + 339.35 cusr 43.32 csys = 388.40 CPU)

I don't understand cusr or csys. User and system I guess.

I think cusr is total computing time for user, that is sum of user times for each core. And similarly for csys.

[Xi Ruoyao]

An incomplete (found on my system) list of things requiring a rebuild for openssl:

• openssh
• git
• sudo
• wpa_supplicant
• coreutils
• kmod
• systemd
• rustc
• cargo-c
• lynx
• libarchive
• openldap
• ruby
• cryptsetup
• neon
• krb5
• python
• libnvme
• pipewire
• pulseaudio
• Net::SSLeay
• libssh2
• libevent
• cups
• gst-plugins-bad
• curl

[Xi Ruoyao]

It looks like "make test" now automatically uses all cores so we no longer need to set HARNESS_JOBS.

[Xi Ruoyao]

The Python 3 _ssl module fails to build. ​https://github.com/python/cpython/pull/146217 allows it to build but there's still an unresolved yet runtime issue: ​https://github.com/python/cpython/issues/148292

[Xi Ruoyao]

krb5 needs ​https://github.com/krb5/krb5/pull/1489 and ​https://github.com/krb5/krb5/pull/1490. Apply 1490 first, then 1489, to avoid conflict.

[Xi Ruoyao]

sudo needs ​https://github.com/sudo-project/sudo/pull/483 (manual operation needed).

[Bruce Dubbs]

Replying to Xi Ruoyao:

It looks like "make test" now automatically uses all cores so we no longer need to set HARNESS_JOBS.

We probably still need it for timing purposes, but other than mentioning it in the timing, we can probably remove it for the test instruction in the book.

[Xi Ruoyao]

wpa_supplicant needs ​https://git.w1.fi/cgit/hostap/commit/?id=141abf49a432c9a0f4f38c47a477ab258ec9e239.

[Xi Ruoyao]

If libssh2 is enabled, several curl tests fail with Failure establishing ssh session: -43, Failed getting banner. I don't know which package to blame. More strangely, if running one of those tests directly with ./runtests.pl in tests/ it passes.

[Xi Ruoyao]

systemd needs ​https://github.com/systemd/systemd/pull/41639.

[Xi Ruoyao]

openldap needs at least (I only tried a lib-only build) sed -e 's/cn->length/ASN1_STRING_length(cn)/g' -e 's/cn->data/ASN1_STRING_get0_data(cn)/g' -i libraries/libldap/tls_o.c (not submitted upstream yet).

[Xi Ruoyao]

gst-plugins-bad rebuilds fine but there are one new test failure in elements_dtls.

[Xi Ruoyao]

ruby needs ​https://github.com/ruby/openssl/pull/1019.

[Xi Ruoyao]

rustc is a little complicated, we need to update (or patch but I don't think patching is easier than updating) the shipped openssl and openssl-sys crates (used by cargo) to support openssl-4.0.0.

curl https://github.com/lfs-book/rust-openssl/archive/v0.10.77+openssl4/rust-openssl-0.10.77+openssl4.tar.gz -LO

cd rustc-1.94.1-src
tar xf ../rust-openssl-0.10.77+openssl4.tar.gz
mv rust-openssl-0.10.77+openssl4 rust-openssl

cat >> Cargo.toml << EOF   
[patch.crates-io]                                      
openssl = { path = "../../../rust-openssl/openssl" }                  
openssl-sys = { path = "../../../rust-openssl/openssl-sys" }
EOF

sed -ri src/tools/cargo/Cargo.lock.orig \
    -e '/name = "openssl-sys"/,/^$/{/source|checksum/d;s/0.9.111/0.9.113/}' \
    -e '/name = "openssl"/,/^$/{/source|checksum/d;s/0.10.75/0.10.77/}'     \
    -e '/name = "openssl-macros"/,/^$/{/source|checksum/d}'

I guess cargo-c needs something similar as it ships some code from cargo.

[Xi Ruoyao]

Net::SSLeay ​https://github.com/radiator-software/p5-net-ssleay/pull/553. Not merged yet but the test suite passes on 1.96 (the book has 1.94 now).

[Xi Ruoyao]

Git needs ​https://git.kernel.org/pub/scm/git/git.git/commit/?id=74137b733e59faaf3f3c6428af34c3798ce92757.