Custom OpenSSL Build

The Eviden KMS dynamic package links against OpenSSL at runtime. You can redirect the service to a custom OpenSSL build — for example, a vendor-supplied or hardware-accelerated variant — without touching any Cosmian-owned files, by overriding the systemd service environment.

Applies to dynamic builds only

Static builds embed OpenSSL at compile time and cannot be redirected at runtime.

How it works

The KMS systemd unit (/lib/systemd/system/cosmian_kms.service) sets three environment variables that together control which OpenSSL is loaded:

Variable	Default value (package install)	Purpose
`LD_LIBRARY_PATH`	`/usr/local/cosmian/lib`	Directory searched first for `libssl.so.3` / `libcrypto.so.3`
`OPENSSL_CONF`	`/usr/local/cosmian/lib/ssl/openssl.cnf`	OpenSSL configuration file
`OPENSSL_MODULES`	`/usr/local/cosmian/lib/ossl-modules`	Directory containing provider modules (e.g. `fips.so, legacy.so`)

Pointing all three at your custom OpenSSL installation is sufficient to make the service use it exclusively.

On startup the server logs the active OpenSSL version:

INFO cosmian_kms: [run] OpenSSL version: OpenSSL 3.X.Y DD Mon YYYY,
     in OPENSSLDIR: "/usr/local/ssl", number: 30X000Y0

Overriding via systemd drop-in

1. Install your custom OpenSSL build

Place the libraries anywhere that is accessible to the cosmian_kms service (i.e. not under /home/ — the systemd unit sets ProtectHome=yes). Recommended locations: /opt/ or /usr/local/lib/.

Vendor CC/FIPS packages commonly ship with a nested usr/local/ tree inside the archive. Copy the whole folder as-is:

sudo cp -r /path/to/openssl-<version>-linux-x86_64 /usr/local/lib/

Resulting layout:

/usr/local/lib/openssl-<version>-linux-x86_64/
  usr/
    local/
      lib64/
        libssl.so.3
        libcrypto.so.3
        ossl-modules/
          fips.so
          legacy.so
      ssl/
        openssl.cnf
        fipsmodule.cnf

In the override.conf you then reference the nested usr/local/lib64/ path:

LD_LIBRARY_PATH=/usr/local/lib/openssl-<version>-linux-x86_64/usr/local/lib64
OPENSSL_MODULES=/usr/local/lib/openssl-<version>-linux-x86_64/usr/local/lib64/ossl-modules

If the archive extracts directly to lib64/ at the top level (no usr/local/ subdirectory), use a simpler install path such as /opt/openssl-custom/ and reference lib64/ directly.

2. Create the systemd drop-in override

sudo systemctl edit cosmian_kms

This opens $EDITOR with a drop-in template saved at /etc/systemd/system/cosmian_kms.service.d/override.conf. Add the three environment variables, replacing the paths with those of your installation:

[Service]
Environment="LD_LIBRARY_PATH=/opt/openssl-custom/lib"
Environment="OPENSSL_CONF=/opt/openssl-custom/ssl/openssl.cnf"
Environment="OPENSSL_MODULES=/opt/openssl-custom/lib/ossl-modules"
# Required when OIDC/JWKS auth is enabled: the default unit blocks outbound
# traffic to public IPs.  See "Network firewall" below.
IPAddressAllow=any

3. Reload and restart

sudo systemctl daemon-reload
sudo systemctl restart cosmian_kms

4. Verify

sudo journalctl -u cosmian_kms --no-pager | grep "OpenSSL version"

The log line should reflect your custom build string.

Network firewall

Affects OIDC / JWKS authentication

The default systemd unit ships with IPAddressDeny=any and only allows traffic to localhost and RFC-1918 private ranges:

IPAddressDeny=any
IPAddressAllow=localhost
IPAddressAllow=10.0.0.0/8
IPAddressAllow=172.16.0.0/12
IPAddressAllow=192.168.0.0/16

When jwt_auth_provider is configured, the KMS fetches JWKS keys from a public OIDC endpoint (e.g. login.microsoftonline.com) at startup. Because the endpoint's IP is not in the allowed list, the BPF firewall silently drops the outbound SYN packets — the service hangs indefinitely at the Refreshing JWKS log line and never starts listening.

Fix: allow outbound HTTPS in the drop-in

Add IPAddressAllow=any to the override.conf drop-in (taking precedence over the IPAddressDeny=any in the unit):

[Service]
# … OpenSSL entries …
IPAddressAllow=any

If a stricter policy is preferred, add only the OIDC provider's IP ranges instead of any. For Microsoft Entra ID / Azure AD (as of 2026), the range is documented in the Microsoft 365 IP address list.

FIPS provider setup for custom builds

If the custom OpenSSL was compiled with OPENSSLDIR=/usr/local/ssl (check via openssl version -a), the FIPS provider looks for its configuration at that path regardless of OPENSSL_CONF. Create the path and run fipsinstall before starting the service:

sudo mkdir -p /usr/local/ssl
sudo env LD_LIBRARY_PATH=/opt/openssl-custom/lib64 \
  /opt/openssl-custom/bin/openssl fipsinstall \
  -module /opt/openssl-custom/lib64/ossl-modules/fips.so \
  -out /usr/local/ssl/fipsmodule.cnf

# Create a minimal openssl.cnf at the compiled-in OPENSSLDIR
sudo tee /usr/local/ssl/openssl.cnf > /dev/null <<'EOF'
openssl_conf = openssl_init
config_diagnostics = 1
.include /usr/local/ssl/fipsmodule.cnf

[openssl_init]
providers = provider_sect

[provider_sect]
fips = fips_sect
default = default_sect

[default_sect]
activate = 1
EOF

Verify FIPS loads before restarting the service:

sudo env LD_LIBRARY_PATH=/opt/openssl-custom/lib64 \
  OPENSSL_MODULES=/opt/openssl-custom/lib64/ossl-modules \
  /opt/openssl-custom/bin/openssl list -providers
# Expected: both "default" and "fips" providers show status: active

Then reload and restart:

sudo systemctl daemon-reload
sudo systemctl restart cosmian_kms

ProtectHome restriction

The systemd unit sets ProtectHome=yes. Custom OpenSSL builds placed under /home/… are inaccessible to the service. Install custom builds under /opt/ or /usr/local/ so the service can load them.

Rollback

Remove the drop-in override file and restart the service to revert to the Cosmian-bundled OpenSSL:

sudo rm -f /etc/systemd/system/cosmian_kms.service.d/override.conf
sudo systemctl daemon-reload
sudo systemctl restart cosmian_kms

Notes

ABI compatibility: libssl.so.3 / libcrypto.so.3 must be ABI-compatible with OpenSSL 3.x (major version 3).
Provider modules: legacy.so (or any other provider) must be compiled against the same OpenSSL version as the libraries you are installing.
Package upgrades: a deb/rpm upgrade does not touch the drop-in override file, so the custom OpenSSL remains active after an upgrade.

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