:-'Generic Commit'

dropshell-tool/openssl-1.1.1w/crypto/dh/dh_gen.c

@@ -0,0 +1,128 @@
+/*
+ * Copyright 1995-2020 The OpenSSL Project Authors. All Rights Reserved.
+ *
+ * Licensed under the OpenSSL license (the "License").  You may not use
+ * this file except in compliance with the License.  You can obtain a copy
+ * in the file LICENSE in the source distribution or at
+ * https://www.openssl.org/source/license.html
+ */
+
+/*
+ * NB: These functions have been upgraded - the previous prototypes are in
+ * dh_depr.c as wrappers to these ones.  - Geoff
+ */
+
+#include <stdio.h>
+#include "internal/cryptlib.h"
+#include <openssl/bn.h>
+#include "dh_local.h"
+
+static int dh_builtin_genparams(DH *ret, int prime_len, int generator,
+                                BN_GENCB *cb);
+
+int DH_generate_parameters_ex(DH *ret, int prime_len, int generator,
+                              BN_GENCB *cb)
+{
+    if (ret->meth->generate_params)
+        return ret->meth->generate_params(ret, prime_len, generator, cb);
+    return dh_builtin_genparams(ret, prime_len, generator, cb);
+}
+
+/*-
+ * We generate DH parameters as follows
+ * find a prime p which is prime_len bits long,
+ * where q=(p-1)/2 is also prime.
+ * In the following we assume that g is not 0, 1 or p-1, since it
+ * would generate only trivial subgroups.
+ * For this case, g is a generator of the order-q subgroup if
+ * g^q mod p == 1.
+ * Or in terms of the Legendre symbol: (g/p) == 1.
+ *
+ * Having said all that,
+ * there is another special case method for the generators 2, 3 and 5.
+ * Using the quadratic reciprocity law it is possible to solve
+ * (g/p) == 1 for the special values 2, 3, 5:
+ * (2/p) == 1 if p mod 8 == 1 or 7.
+ * (3/p) == 1 if p mod 12 == 1 or 11.
+ * (5/p) == 1 if p mod 5 == 1 or 4.
+ * See for instance: https://en.wikipedia.org/wiki/Legendre_symbol
+ *
+ * Since all safe primes > 7 must satisfy p mod 12 == 11
+ * and all safe primes > 11 must satisfy p mod 5 != 1
+ * we can further improve the condition for g = 2, 3 and 5:
+ * for 2, p mod 24 == 23
+ * for 3, p mod 12 == 11
+ * for 5, p mod 60 == 59
+ *
+ * However for compatibility with previous versions we use:
+ * for 2, p mod 24 == 11
+ * for 5, p mod 60 == 23
+ */
+static int dh_builtin_genparams(DH *ret, int prime_len, int generator,
+                                BN_GENCB *cb)
+{
+    BIGNUM *t1, *t2;
+    int g, ok = -1;
+    BN_CTX *ctx = NULL;
+
+    ctx = BN_CTX_new();
+    if (ctx == NULL)
+        goto err;
+    BN_CTX_start(ctx);
+    t1 = BN_CTX_get(ctx);
+    t2 = BN_CTX_get(ctx);
+    if (t2 == NULL)
+        goto err;
+
+    /* Make sure 'ret' has the necessary elements */
+    if (!ret->p && ((ret->p = BN_new()) == NULL))
+        goto err;
+    if (!ret->g && ((ret->g = BN_new()) == NULL))
+        goto err;
+
+    if (generator <= 1) {
+        DHerr(DH_F_DH_BUILTIN_GENPARAMS, DH_R_BAD_GENERATOR);
+        goto err;
+    }
+    if (generator == DH_GENERATOR_2) {
+        if (!BN_set_word(t1, 24))
+            goto err;
+        if (!BN_set_word(t2, 11))
+            goto err;
+        g = 2;
+    } else if (generator == DH_GENERATOR_5) {
+        if (!BN_set_word(t1, 60))
+            goto err;
+        if (!BN_set_word(t2, 23))
+            goto err;
+        g = 5;
+    } else {
+        /*
+         * in the general case, don't worry if 'generator' is a generator or
+         * not: since we are using safe primes, it will generate either an
+         * order-q or an order-2q group, which both is OK
+         */
+        if (!BN_set_word(t1, 12))
+            goto err;
+        if (!BN_set_word(t2, 11))
+            goto err;
+        g = generator;
+    }
+
+    if (!BN_generate_prime_ex(ret->p, prime_len, 1, t1, t2, cb))
+        goto err;
+    if (!BN_GENCB_call(cb, 3, 0))
+        goto err;
+    if (!BN_set_word(ret->g, g))
+        goto err;
+    ok = 1;
+ err:
+    if (ok == -1) {
+        DHerr(DH_F_DH_BUILTIN_GENPARAMS, ERR_R_BN_LIB);
+        ok = 0;
+    }
+
+    BN_CTX_end(ctx);
+    BN_CTX_free(ctx);
+    return ok;
+}