bpo-9216: Expose OpenSSL FIPS_mode() as _hashlib.get_fips_mode() (GH-19703)

test.pythoninfo logs OpenSSL FIPS_mode() and Linux
/proc/sys/crypto/fips_enabled in a new "fips" section.

Co-Authored-By: Petr Viktorin <encukou@gmail.com>

1 files changed, 43 insertions, 0 deletions

diff --git a/Modules/_hashopenssl.c b/Modules/_hashopenssl.c
index 0919cd3..91834e5 100644
--- a/Modules/_hashopenssl.c
+++ b/Modules/_hashopenssl.c
@@ -25,6 +25,8 @@
 #include <openssl/objects.h>
 #include "openssl/err.h"
 
+#include <openssl/crypto.h>       // FIPS_mode()
+
 #if (OPENSSL_VERSION_NUMBER < 0x10100000L) || defined(LIBRESSL_VERSION_NUMBER)
 /* OpenSSL < 1.1.0 */
 #define EVP_MD_CTX_new EVP_MD_CTX_create
@@ -1096,12 +1098,53 @@ generate_hash_name_list(void)
     return state.set;
 }
 
+/* LibreSSL doesn't support FIPS:
+   https://marc.info/?l=openbsd-misc&m=139819485423701&w=2
+
+   Ted Unangst wrote: "I figured I should mention our current libressl policy
+   wrt FIPS mode.  It's gone and it's not coming back." */
+#ifndef LIBRESSL_VERSION_NUMBER
+/*[clinic input]
+_hashlib.get_fips_mode -> int
+
+Determine the OpenSSL FIPS mode of operation.
+
+Effectively any non-zero return value indicates FIPS mode;
+values other than 1 may have additional significance.
+
+See OpenSSL documentation for the FIPS_mode() function for details.
+[clinic start generated code]*/
+
+static int
+_hashlib_get_fips_mode_impl(PyObject *module)
+/*[clinic end generated code: output=87eece1bab4d3fa9 input=c2799c3132a36d6c]*/
+
+{
+    ERR_clear_error();
+    int result = FIPS_mode();
+    if (result == 0) {
+        // "If the library was built without support of the FIPS Object Module,
+        // then the function will return 0 with an error code of
+        // CRYPTO_R_FIPS_MODE_NOT_SUPPORTED (0x0f06d065)."
+        // But 0 is also a valid result value.
+        unsigned long errcode = ERR_peek_last_error();
+        if (errcode) {
+            _setException(PyExc_ValueError);
+            return -1;
+        }
+    }
+    return result;
+}
+#endif  // !LIBRESSL_VERSION_NUMBER
+
+
 /* List of functions exported by this module */
 
 static struct PyMethodDef EVP_functions[] = {
     EVP_NEW_METHODDEF
     PBKDF2_HMAC_METHODDEF
     _HASHLIB_SCRYPT_METHODDEF
+    _HASHLIB_GET_FIPS_MODE_METHODDEF
     _HASHLIB_HMAC_DIGEST_METHODDEF
     _HASHLIB_OPENSSL_MD5_METHODDEF
     _HASHLIB_OPENSSL_SHA1_METHODDEF