expose new FIPS related APIs

* Ability to instantiate the FIPS default `crypto_provider` using a new
  function `rustls_default_fips_provider()`, available only when the
  fips feature is activated.

* Ability to determine if a given `crypto_provider` is in FIPS mode
  using a new function `rustls_crypto_provider_fips()`.

* Ability to determine if a given `rustls_client_config` would create
  connections that are FIPS compatible with a new function
  `rustls_client_config_fips()`.

* Ability to determine if a given `rustls_server_config` would create
  connections that are FIPS compatible with a new function
  `rustls_server_config_fips()`.

* Ability to determine if a given `rustls_connection` was created from
  a `rustls_client_config` or `rustls_server_config` that was FIPS
  enabled with a new function `rustls_connection_fips()`.

cbindgen.toml

@@ -14,7 +14,8 @@ include = ["rustls_tls_version"]
 "feature = read_buf" = "DEFINE_READ_BUF"
 "feature = aws-lc-rs" = "DEFINE_AWS_LC_RS"
 "feature = ring" = "DEFINE_RING"
+"feature = fips" = "DEFINE_FIPS"
 
 [parse.expand]
 crates = ["rustls-ffi"]
-features = ["read_buf", "aws-lc-rs", "ring"]
+features = ["read_buf", "aws-lc-rs", "ring", "fips"]

src/client.rs

@@ -582,6 +582,19 @@ impl rustls_client_config_builder {
 }
 
 impl rustls_client_config {
+    /// Returns true if a `rustls_connection` created from the `rustls_client_config` will
+    /// operate in FIPS mode.
+    ///
+    /// This is different from `rustls_crypto_provider_fips` which is concerned
+    /// only with cryptography, whereas this also covers TLS-level configuration that NIST
+    /// recommends, as well as ECH HPKE suites if applicable.
+    #[no_mangle]
+    pub extern "C" fn rustls_client_config_fips(config: *const rustls_client_config) -> bool {
+        ffi_panic_boundary! {
+            try_ref_from_ptr!(config).fips()
+        }
+    }
+
     /// "Free" a `rustls_client_config` previously returned from
     /// `rustls_client_config_builder_build`.
     ///

src/connection.rs

@@ -613,6 +613,23 @@ impl rustls_connection {
         }
     }
 
+    /// Returns true if the `rustls_connection` was made with a `rustls_client_config`
+    /// or `rustls_server_config` that is FIPS compatible.
+    ///
+    /// This is different from `rustls_crypto_provider_fips` which is concerned
+    /// only with cryptography, whereas this also covers TLS-level configuration that NIST
+    /// recommends, as well as ECH HPKE suites if applicable.
+    #[no_mangle]
+    pub extern "C" fn rustls_connection_fips(conn: *const rustls_connection) -> bool {
+        ffi_panic_boundary! {
+            let conn = try_ref_from_ptr!(conn);
+            match &conn.conn {
+                rustls::Connection::Client(c) => c.fips(),
+                rustls::Connection::Server(c) => c.fips(),
+            }
+        }
+    }
+
     /// Free a rustls_connection. Calling with NULL is fine.
     /// Must not be called twice with the same value.
     #[no_mangle]

src/crypto_provider.rs

@@ -248,6 +248,26 @@ pub extern "C" fn rustls_aws_lc_rs_crypto_provider() -> *const rustls_crypto_pro
     }
 }
 
+/// Return a `rustls_crypto_provider` that uses FIPS140-3 approved cryptography.
+///
+/// Using this function expresses in your code that you require FIPS-approved cryptography,
+/// and will not compile if you make a mistake with cargo features.
+///
+/// See the upstream [rustls FIPS documentation][FIPS] for more information.
+///
+/// The caller owns the returned `rustls_crypto_provider` and must free it using
+/// `rustls_crypto_provider_free`.
+///
+/// [FIPS]: https://docs.rs/rustls/latest/rustls/manual/_06_fips/index.html
+#[no_mangle]
+#[cfg(feature = "fips")]
+pub extern "C" fn rustls_default_fips_provider() -> *const rustls_crypto_provider {
+    ffi_panic_boundary! {
+        Arc::into_raw(Arc::new(rustls::crypto::default_fips_provider()))
+            as *const rustls_crypto_provider
+    }
+}
+
 /// Retrieve a pointer to the process default `rustls_crypto_provider`.
 ///
 /// This may return `NULL` if no process default provider has been set using
@@ -364,6 +384,19 @@ pub extern "C" fn rustls_crypto_provider_random(
     }
 }
 
+/// Returns true if the `rustls_crypto_provider` is operating in FIPS mode.
+///
+/// This covers only the cryptographic parts of FIPS approval. There are also
+/// TLS protocol-level recommendations made by NIST. You should prefer to call
+/// `rustls_client_config_fips` or `rustls_server_config_fips` which take these
+/// into account.
+#[no_mangle]
+pub extern "C" fn rustls_crypto_provider_fips(provider: *const rustls_crypto_provider) -> bool {
+    ffi_panic_boundary! {
+        try_ref_from_ptr!(provider).fips()
+    }
+}
+
 /// Frees the `rustls_crypto_provider`.
 ///
 /// Calling with `NULL` is fine.

src/rustls.h

@@ -1758,6 +1758,16 @@ rustls_result rustls_client_config_builder_build(struct rustls_client_config_bui
  */
 void rustls_client_config_builder_free(struct rustls_client_config_builder *config);
 
+/**
+ * Returns true if a `rustls_connection` created from the `rustls_client_config` will
+ * operate in FIPS mode.
+ *
+ * This is different from `rustls_crypto_provider_fips` which is concerned
+ * only with cryptography, whereas this also covers TLS-level configuration that NIST
+ * recommends, as well as ECH HPKE suites if applicable.
+ */
+bool rustls_client_config_fips(const struct rustls_client_config *config);
+
 /**
  * "Free" a `rustls_client_config` previously returned from
  * `rustls_client_config_builder_build`.
@@ -2047,6 +2057,16 @@ rustls_result rustls_connection_read_2(struct rustls_connection *conn,
                                        size_t *out_n);
 #endif
 
+/**
+ * Returns true if the `rustls_connection` was made with a `rustls_client_config`
+ * or `rustls_server_config` that is FIPS compatible.
+ *
+ * This is different from `rustls_crypto_provider_fips` which is concerned
+ * only with cryptography, whereas this also covers TLS-level configuration that NIST
+ * recommends, as well as ECH HPKE suites if applicable.
+ */
+bool rustls_connection_fips(const struct rustls_connection *conn);
+
 /**
  * Free a rustls_connection. Calling with NULL is fine.
  * Must not be called twice with the same value.
@@ -2172,6 +2192,23 @@ const struct rustls_crypto_provider *rustls_ring_crypto_provider(void);
 const struct rustls_crypto_provider *rustls_aws_lc_rs_crypto_provider(void);
 #endif
 
+#if defined(DEFINE_FIPS)
+/**
+ * Return a `rustls_crypto_provider` that uses FIPS140-3 approved cryptography.
+ *
+ * Using this function expresses in your code that you require FIPS-approved cryptography,
+ * and will not compile if you make a mistake with cargo features.
+ *
+ * See the upstream [rustls FIPS documentation][FIPS] for more information.
+ *
+ * The caller owns the returned `rustls_crypto_provider` and must free it using
+ * `rustls_crypto_provider_free`.
+ *
+ * [FIPS]: https://docs.rs/rustls/latest/rustls/manual/_06_fips/index.html
+ */
+const struct rustls_crypto_provider *rustls_default_fips_provider(void);
+#endif
+
 /**
  * Retrieve a pointer to the process default `rustls_crypto_provider`.
  *
@@ -2233,6 +2270,16 @@ rustls_result rustls_crypto_provider_random(const struct rustls_crypto_provider
                                             uint8_t *buff,
                                             size_t len);
 
+/**
+ * Returns true if the `rustls_crypto_provider` is operating in FIPS mode.
+ *
+ * This covers only the cryptographic parts of FIPS approval. There are also
+ * TLS protocol-level recommendations made by NIST. You should prefer to call
+ * `rustls_client_config_fips` or `rustls_server_config_fips` which take these
+ * into account.
+ */
+bool rustls_crypto_provider_fips(const struct rustls_crypto_provider *provider);
+
 /**
  * Frees the `rustls_crypto_provider`.
  *
@@ -2497,6 +2544,16 @@ rustls_result rustls_server_config_builder_set_certified_keys(struct rustls_serv
 rustls_result rustls_server_config_builder_build(struct rustls_server_config_builder *builder,
                                                  const struct rustls_server_config **config_out);
 
+/**
+ * Returns true if a `rustls_connection` created from the `rustls_server_config` will
+ * operate in FIPS mode.
+ *
+ * This is different from `rustls_crypto_provider_fips` which is concerned
+ * only with cryptography, whereas this also covers TLS-level configuration that NIST
+ * recommends, as well as ECH HPKE suites if applicable.
+ */
+bool rustls_server_config_fips(const struct rustls_server_config *config);
+
 /**
  * "Free" a rustls_server_config previously returned from
  * rustls_server_config_builder_build.

src/server.rs

@@ -377,6 +377,19 @@ impl rustls_server_config_builder {
 }
 
 impl rustls_server_config {
+    /// Returns true if a `rustls_connection` created from the `rustls_server_config` will
+    /// operate in FIPS mode.
+    ///
+    /// This is different from `rustls_crypto_provider_fips` which is concerned
+    /// only with cryptography, whereas this also covers TLS-level configuration that NIST
+    /// recommends, as well as ECH HPKE suites if applicable.
+    #[no_mangle]
+    pub extern "C" fn rustls_server_config_fips(config: *const rustls_server_config) -> bool {
+        ffi_panic_boundary! {
+            try_ref_from_ptr!(config).fips()
+        }
+    }
+
     /// "Free" a rustls_server_config previously returned from
     /// rustls_server_config_builder_build.
     ///