Add build-time OpenSSL version checks

attestation-ca/Cargo.toml

@@ -11,3 +11,6 @@ serde.workspace = true
 tracing.workspace = true
 openssl.workspace = true
 uuid = { workspace = true, features = ["serde"] }
+
+[build-dependencies]
+openssl.workspace = true

attestation-ca/build.rs

@@ -0,0 +1,21 @@
+use openssl::version::{number, version};
+
+const OPENSSL_DOC: &str = "https://github.com/kanidm/webauthn-rs/blob/master/OpenSSL.md";
+
+fn main() {
+    // LibreSSL reports as OpenSSL v2 (which was skipped).
+    if number() < 0x2_00_00_00_0 {
+        println!(
+            r#"
+Your version of OpenSSL is out of date, and not supported by this library.
+
+Please upgrade to OpenSSL v3.0.0 or later.
+
+More info: {OPENSSL_DOC}
+OpenSSL version string: {}
+"#,
+            version(),
+        );
+        panic!("The installed version of OpenSSL is unusable.");
+    }
+}

webauthn-rs-core/Cargo.toml

@@ -42,3 +42,6 @@ uuid = { workspace = true, features = ["serde"] }
 hex-literal = "0.3"
 tracing-subscriber.workspace = true
 webauthn-rs-device-catalog.workspace = true
+
+[build-dependencies]
+openssl.workspace = true

webauthn-rs-core/build.rs

@@ -0,0 +1,21 @@
+use openssl::version::{number, version};
+
+const OPENSSL_DOC: &str = "https://github.com/kanidm/webauthn-rs/blob/master/OpenSSL.md";
+
+fn main() {
+    // LibreSSL reports as OpenSSL v2.
+    if number() < 0x2_00_00_00_0 {
+        println!(
+            r#"
+Your version of OpenSSL is out of date, and not supported by this library.
+
+Please upgrade to OpenSSL v3.0.0 or later.
+
+More info: {OPENSSL_DOC}
+OpenSSL version string: {}
+"#,
+            version(),
+        );
+        panic!("The installed version of OpenSSL is unusable.");
+    }
+}