cipher: don't set dummy encryption key in Cipher#initialize
Remove the encryption key initialization from Cipher#initialize. This
is effectively a revert of r32723 ("Avoid possible SEGV from AES
encryption/decryption", 2011-07-28).

r32723, which added the key initialization, was a workaround for
Ruby Bug #2768. For some certain ciphers, calling EVP_CipherUpdate()
before setting an encryption key caused segfault. It was not a problem
until OpenSSL implemented GCM mode - the encryption key could be
overridden by repeated calls of EVP_CipherInit_ex(). But, it is not the
case for AES-GCM ciphers. Setting a key, an IV, a key, in this order
causes the IV to be reset to an all-zero IV.

The problem of Bug #2768 persists on the current versions of OpenSSL.
So, make Cipher#update raise an exception if a key is not yet set by the
user. Since encrypting or decrypting without key does not make any
sense, this should not break existing applications.

Users can still call Cipher#key= and Cipher#iv= multiple times with
their own responsibility.

Reference: https://bugs.ruby-lang.org/issues/2768
Reference: https://bugs.ruby-lang.org/issues/8221

Upstream-Status: Backport
CVE: CVE-2016-7798

Signed-off-by: Thiruvadi Rajaraman <trajaraman@mvista.com>

Index: ruby-2.2.2/ext/openssl/ossl_cipher.c
===================================================================
--- ruby-2.2.2.orig/ext/openssl/ossl_cipher.c
+++ ruby-2.2.2/ext/openssl/ossl_cipher.c
@@ -35,6 +35,7 @@
  */
 VALUE cCipher;
 VALUE eCipherError;
+static ID id_key_set;
 
 static VALUE ossl_cipher_alloc(VALUE klass);
 static void ossl_cipher_free(void *ptr);
@@ -119,7 +120,6 @@ ossl_cipher_initialize(VALUE self, VALUE
     EVP_CIPHER_CTX *ctx;
     const EVP_CIPHER *cipher;
     char *name;
-    unsigned char key[EVP_MAX_KEY_LENGTH];
 
     name = StringValuePtr(str);
     GetCipherInit(self, ctx);
@@ -131,14 +131,7 @@ ossl_cipher_initialize(VALUE self, VALUE
     if (!(cipher = EVP_get_cipherbyname(name))) {
 	ossl_raise(rb_eRuntimeError, "unsupported cipher algorithm (%s)", name);
     }
-    /*
-     * The EVP which has EVP_CIPH_RAND_KEY flag (such as DES3) allows
-     * uninitialized key, but other EVPs (such as AES) does not allow it.
-     * Calling EVP_CipherUpdate() without initializing key causes SEGV so we
-     * set the data filled with "\0" as the key by default.
-     */
-    memset(key, 0, EVP_MAX_KEY_LENGTH);
-    if (EVP_CipherInit_ex(ctx, cipher, NULL, key, NULL, -1) != 1)
+    if (EVP_CipherInit_ex(ctx, cipher, NULL, NULL, NULL, -1) != 1)
 	ossl_raise(eCipherError, NULL);
 
     return self;
@@ -256,6 +249,8 @@ ossl_cipher_init(int argc, VALUE *argv,
     if (EVP_CipherInit_ex(ctx, NULL, NULL, p_key, p_iv, mode) != 1) {
 	ossl_raise(eCipherError, NULL);
     }
+    if (p_key)
+	rb_ivar_set(self, id_key_set, Qtrue);
 
     return self;
 }
@@ -343,6 +338,8 @@ ossl_cipher_pkcs5_keyivgen(int argc, VAL
     OPENSSL_cleanse(key, sizeof key);
     OPENSSL_cleanse(iv, sizeof iv);
 
+    rb_ivar_set(self, id_key_set, Qtrue);
+
     return Qnil;
 }
 
@@ -396,6 +393,9 @@ ossl_cipher_update(int argc, VALUE *argv
 
     rb_scan_args(argc, argv, "11", &data, &str);
 
+    if (!RTEST(rb_attr_get(self, id_key_set)))
+	ossl_raise(eCipherError, "key not set");
+
     StringValue(data);
     in = (unsigned char *)RSTRING_PTR(data);
     if ((in_len = RSTRING_LEN(data)) == 0)
@@ -495,6 +495,8 @@ ossl_cipher_set_key(VALUE self, VALUE ke
     if (EVP_CipherInit_ex(ctx, NULL, NULL, (unsigned char *)RSTRING_PTR(key), NULL, -1) != 1)
         ossl_raise(eCipherError, NULL);
 
+    rb_ivar_set(self, id_key_set, Qtrue);
+
     return key;
 }
 
@@ -1013,5 +1015,7 @@ Init_ossl_cipher(void)
     rb_define_method(cCipher, "iv_len", ossl_cipher_iv_length, 0);
     rb_define_method(cCipher, "block_size", ossl_cipher_block_size, 0);
     rb_define_method(cCipher, "padding=", ossl_cipher_set_padding, 1);
+    
+    id_key_set = rb_intern_const("key_set");
 }
 
Index: ruby-2.2.2/test/openssl/test_cipher.rb
===================================================================
--- ruby-2.2.2.orig/test/openssl/test_cipher.rb
+++ ruby-2.2.2/test/openssl/test_cipher.rb
@@ -80,6 +80,7 @@ class OpenSSL::TestCipher < Test::Unit::
 
   def test_empty_data
     @c1.encrypt
+    @c1.random_key
     assert_raise(ArgumentError){ @c1.update("") }
   end
 
@@ -127,13 +128,10 @@ class OpenSSL::TestCipher < Test::Unit::
         assert_equal(pt, c2.update(ct) + c2.final)
       }
     end
-
-    def test_AES_crush
-      500.times do
-        assert_nothing_raised("[Bug #2768]") do
-          # it caused OpenSSL SEGV by uninitialized key
-          OpenSSL::Cipher::AES128.new("ECB").update "." * 17
-        end
+    def test_update_raise_if_key_not_set
+    assert_raise(OpenSSL::Cipher::CipherError) do
+      # it caused OpenSSL SEGV by uninitialized key [Bug #2768]
+      OpenSSL::Cipher::AES128.new("ECB").update "." * 17
       end
     end
   end
@@ -236,6 +234,23 @@ class OpenSSL::TestCipher < Test::Unit::
     end
 
   end
+  def test_aes_gcm_key_iv_order_issue
+    pt = "[ruby/openssl#49]"
+    cipher = OpenSSL::Cipher.new("aes-128-gcm").encrypt
+    cipher.key = "x" * 16
+    cipher.iv = "a" * 12
+    ct1 = cipher.update(pt) << cipher.final
+    tag1 = cipher.auth_tag
+
+    cipher = OpenSSL::Cipher.new("aes-128-gcm").encrypt
+    cipher.iv = "a" * 12
+    cipher.key = "x" * 16
+    ct2 = cipher.update(pt) << cipher.final
+    tag2 = cipher.auth_tag
+
+    assert_equal ct1, ct2
+    assert_equal tag1, tag2
+  end if has_cipher?("aes-128-gcm")
 
   private