bpo-38134: Remove PKBDF2_HMAC_fast from _hashopenssl (GH-16028)

Signed-off-by: Christian Heimes <christian@python.org>
(cherry picked from commit 64117e0)

Co-authored-by: Christian Heimes <christian@python.org>

Author: miss-islington

Misc/NEWS.d/next/Library/2019-09-12-13-18-55.bpo-38134.gXJTbP.rst

@@ -0,0 +1,2 @@
+Remove obsolete copy of PBKDF2_HMAC_fast. All supported OpenSSL versions
+contain a fast implementation.

Modules/_hashopenssl.c

@@ -28,18 +28,6 @@
 
 #define MUNCH_SIZE INT_MAX
 
-#if (OPENSSL_VERSION_NUMBER < 0x10100000L) || defined(LIBRESSL_VERSION_NUMBER)
-/* OpenSSL < 1.1.0 */
-#define EVP_MD_CTX_new EVP_MD_CTX_create
-#define EVP_MD_CTX_free EVP_MD_CTX_destroy
-#define HAS_FAST_PKCS5_PBKDF2_HMAC 0
-#include <openssl/hmac.h>
-#else
-/* OpenSSL >= 1.1.0 */
-#define HAS_FAST_PKCS5_PBKDF2_HMAC 1
-#endif
-
-
 typedef struct {
     PyObject_HEAD
     PyObject            *name;  /* name of this hash algorithm */
@@ -481,97 +469,6 @@ EVP_new_impl(PyObject *module, PyObject *name_obj, PyObject *data_obj)
     return ret_obj;
 }
 
-#if (OPENSSL_VERSION_NUMBER >= 0x10000000 && !defined(OPENSSL_NO_HMAC) \
-     && !defined(OPENSSL_NO_SHA))
-
-#define PY_PBKDF2_HMAC 1
-
-#if !HAS_FAST_PKCS5_PBKDF2_HMAC
-/* Improved implementation of PKCS5_PBKDF2_HMAC()
- *
- * PKCS5_PBKDF2_HMAC_fast() hashes the password exactly one time instead of
- * `iter` times. Today (2013) the iteration count is typically 100,000 or
- * more. The improved algorithm is not subject to a Denial-of-Service
- * vulnerability with overly large passwords.
- *
- * Also OpenSSL < 1.0 don't provide PKCS5_PBKDF2_HMAC(), only
- * PKCS5_PBKDF2_SHA1.
- */
-static int
-PKCS5_PBKDF2_HMAC_fast(const char *pass, int passlen,
-                       const unsigned char *salt, int saltlen,
-                       int iter, const EVP_MD *digest,
-                       int keylen, unsigned char *out)
-{
-    unsigned char digtmp[EVP_MAX_MD_SIZE], *p, itmp[4];
-    int cplen, j, k, tkeylen, mdlen;
-    unsigned long i = 1;
-    HMAC_CTX hctx_tpl, hctx;
-
-    mdlen = EVP_MD_size(digest);
-    if (mdlen < 0)
-        return 0;
-
-    HMAC_CTX_init(&hctx_tpl);
-    HMAC_CTX_init(&hctx);
-    p = out;
-    tkeylen = keylen;
-    if (!HMAC_Init_ex(&hctx_tpl, pass, passlen, digest, NULL)) {
-        HMAC_CTX_cleanup(&hctx_tpl);
-        return 0;
-    }
-    while (tkeylen) {
-        if (tkeylen > mdlen)
-            cplen = mdlen;
-        else
-            cplen = tkeylen;
-        /* We are unlikely to ever use more than 256 blocks (5120 bits!)
-         * but just in case...
-         */
-        itmp[0] = (unsigned char)((i >> 24) & 0xff);
-        itmp[1] = (unsigned char)((i >> 16) & 0xff);
-        itmp[2] = (unsigned char)((i >> 8) & 0xff);
-        itmp[3] = (unsigned char)(i & 0xff);
-        if (!HMAC_CTX_copy(&hctx, &hctx_tpl)) {
-            HMAC_CTX_cleanup(&hctx_tpl);
-            return 0;
-        }
-        if (!HMAC_Update(&hctx, salt, saltlen)
-                || !HMAC_Update(&hctx, itmp, 4)
-                || !HMAC_Final(&hctx, digtmp, NULL)) {
-            HMAC_CTX_cleanup(&hctx_tpl);
-            HMAC_CTX_cleanup(&hctx);
-            return 0;
-        }
-        HMAC_CTX_cleanup(&hctx);
-        memcpy(p, digtmp, cplen);
-        for (j = 1; j < iter; j++) {
-            if (!HMAC_CTX_copy(&hctx, &hctx_tpl)) {
-                HMAC_CTX_cleanup(&hctx_tpl);
-                return 0;
-            }
-            if (!HMAC_Update(&hctx, digtmp, mdlen)
-                    || !HMAC_Final(&hctx, digtmp, NULL)) {
-                HMAC_CTX_cleanup(&hctx_tpl);
-                HMAC_CTX_cleanup(&hctx);
-                return 0;
-            }
-            HMAC_CTX_cleanup(&hctx);
-            for (k = 0; k < cplen; k++) {
-                p[k] ^= digtmp[k];
-            }
-        }
-        tkeylen-= cplen;
-        i++;
-        p+= cplen;
-    }
-    HMAC_CTX_cleanup(&hctx_tpl);
-    return 1;
-}
-#endif
-
-
-
 /*[clinic input]
 _hashlib.pbkdf2_hmac as pbkdf2_hmac
 
@@ -652,17 +549,10 @@ pbkdf2_hmac_impl(PyObject *module, const char *hash_name,
     key = PyBytes_AS_STRING(key_obj);
 
     Py_BEGIN_ALLOW_THREADS
-#if HAS_FAST_PKCS5_PBKDF2_HMAC
     retval = PKCS5_PBKDF2_HMAC((char*)password->buf, (int)password->len,
                                (unsigned char *)salt->buf, (int)salt->len,
                                iterations, digest, dklen,
                                (unsigned char *)key);
-#else
-    retval = PKCS5_PBKDF2_HMAC_fast((char*)password->buf, (int)password->len,
-                                    (unsigned char *)salt->buf, (int)salt->len,
-                                    iterations, digest, dklen,
-                                    (unsigned char *)key);
-#endif
     Py_END_ALLOW_THREADS
 
     if (!retval) {
@@ -675,8 +565,6 @@ pbkdf2_hmac_impl(PyObject *module, const char *hash_name,
     return key_obj;
 }
 
-#endif
-
 #if OPENSSL_VERSION_NUMBER > 0x10100000L && !defined(OPENSSL_NO_SCRYPT) && !defined(LIBRESSL_VERSION_NUMBER)
 #define PY_SCRYPT 1
 
@@ -986,9 +874,7 @@ GEN_CONSTRUCTOR(sha512)
 
 static struct PyMethodDef EVP_functions[] = {
     EVP_NEW_METHODDEF
-#ifdef PY_PBKDF2_HMAC
     PBKDF2_HMAC_METHODDEF
-#endif
     _HASHLIB_SCRYPT_METHODDEF
     _HASHLIB_HMAC_DIGEST_METHODDEF
     CONSTRUCTOR_METH_DEF(md5),