Restore |RSA_generate_key()| from OpenSSL at b4f0d1a.

The callback arguments are required to be NULL.

Change-Id: I266ec46efdaca411a7f0c2b645883b2c5bec1c96
Reviewed-on: https://boringssl-review.googlesource.com/5160
Reviewed-by: Adam Langley <agl@google.com>
diff --git a/decrepit/CMakeLists.txt b/decrepit/CMakeLists.txt
index a486c1b..4365d41 100644
--- a/decrepit/CMakeLists.txt
+++ b/decrepit/CMakeLists.txt
@@ -1,6 +1,7 @@
-add_subdirectory(cast)
-add_subdirectory(blowfish)
 add_subdirectory(bio)
+add_subdirectory(blowfish)
+add_subdirectory(cast)
+add_subdirectory(rsa)
 
 add_library(
   decrepit
@@ -8,4 +9,5 @@
   $<TARGET_OBJECTS:bio_decrepit>
   $<TARGET_OBJECTS:blowfish>
   $<TARGET_OBJECTS:cast>
+  $<TARGET_OBJECTS:rsa_decrepit>
 )
diff --git a/decrepit/rsa/CMakeLists.txt b/decrepit/rsa/CMakeLists.txt
new file mode 100644
index 0000000..d499acd
--- /dev/null
+++ b/decrepit/rsa/CMakeLists.txt
@@ -0,0 +1,9 @@
+include_directories(. ../../include)
+
+add_library(
+  rsa_decrepit
+
+  OBJECT
+
+  rsa_decrepit.c
+)
diff --git a/decrepit/rsa/rsa_decrepit.c b/decrepit/rsa/rsa_decrepit.c
new file mode 100644
index 0000000..c238f46
--- /dev/null
+++ b/decrepit/rsa/rsa_decrepit.c
@@ -0,0 +1,86 @@
+/* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
+ * All rights reserved.
+ *
+ * This package is an SSL implementation written
+ * by Eric Young (eay@cryptsoft.com).
+ * The implementation was written so as to conform with Netscapes SSL.
+ *
+ * This library is free for commercial and non-commercial use as long as
+ * the following conditions are aheared to.  The following conditions
+ * apply to all code found in this distribution, be it the RC4, RSA,
+ * lhash, DES, etc., code; not just the SSL code.  The SSL documentation
+ * included with this distribution is covered by the same copyright terms
+ * except that the holder is Tim Hudson (tjh@cryptsoft.com).
+ *
+ * Copyright remains Eric Young's, and as such any Copyright notices in
+ * the code are not to be removed.
+ * If this package is used in a product, Eric Young should be given attribution
+ * as the author of the parts of the library used.
+ * This can be in the form of a textual message at program startup or
+ * in documentation (online or textual) provided with the package.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. All advertising materials mentioning features or use of this software
+ *    must display the following acknowledgement:
+ *    "This product includes cryptographic software written by
+ *     Eric Young (eay@cryptsoft.com)"
+ *    The word 'cryptographic' can be left out if the rouines from the library
+ *    being used are not cryptographic related :-).
+ * 4. If you include any Windows specific code (or a derivative thereof) from
+ *    the apps directory (application code) you must include an acknowledgement:
+ *    "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
+ *
+ * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ *
+ * The licence and distribution terms for any publically available version or
+ * derivative of this code cannot be changed.  i.e. this code cannot simply be
+ * copied and put under another distribution licence
+ * [including the GNU Public Licence.] */
+
+#include <openssl/rsa.h>
+
+#include <assert.h>
+
+#include <openssl/bn.h>
+
+
+RSA *RSA_generate_key(int bits, unsigned long e_value, void *callback,
+                      void *cb_arg) {
+  assert(callback == NULL);
+  assert(cb_arg == NULL);
+
+  RSA *rsa = RSA_new();
+  BIGNUM *e = BN_new();
+
+  if (rsa == NULL ||
+      e == NULL ||
+      !BN_set_word(e, e_value) ||
+      !RSA_generate_key_ex(rsa, bits, e, NULL)) {
+    goto err;
+  }
+
+  BN_free(e);
+  return rsa;
+
+err:
+  BN_free(e);
+  RSA_free(rsa);
+  return NULL;
+}
diff --git a/include/openssl/rsa.h b/include/openssl/rsa.h
index 61e1069..4a9d36d 100644
--- a/include/openssl/rsa.h
+++ b/include/openssl/rsa.h
@@ -409,6 +409,13 @@
 /* RSA_blinding_on returns one. */
 OPENSSL_EXPORT int RSA_blinding_on(RSA *rsa, BN_CTX *ctx);
 
+/* RSA_generate_key behaves like |RSA_generate_key_ex|, which is what you
+ * should use instead. It returns NULL on error, or a newly-allocated |RSA| on
+ * success. This function is provided for compatibility only. The |callback|
+ * and |cb_arg| parameters must be NULL. */
+OPENSSL_EXPORT RSA *RSA_generate_key(int bits, unsigned long e, void *callback,
+                                     void *cb_arg);
+
 
 struct rsa_meth_st {
   struct openssl_method_common_st common;