Make EVP_CIPHER opaque.

If we're to have any hope of fixing EVP_CIPHER_CTX's calling convention, we
need to be able to change the shape of its method table.

Looking back, it looks like we exported this in
https://boringssl-review.googlesource.com/4330, for OpenSSH. I don't
remember exactly what OpenSSH was doing, but I see in this commit, they
removed a bunch of custom EVP_CIPHERs which would definitely have
required an exported EVP_CIPHER struct:
https://github.com/openssh/openssh-portable/commit/cdccebdf85204bf7542b7fcc1aa2ea3f36661833

That's been gone for a while now, so hopefully we can hide it again. (If
a project needs a cipher not implemented by OpenSSL, it's not strictly
necessarily to make a custom EVP_CIPHER. It might be convenient to reuse
the abstraction, but you can always just call your own APIs directly.)

Update-Note: EVP_CIPHER is now opaque. Use accessors instead.
Bug: 494
Change-Id: I9344690c3cfe7d19d6ca12fb66484ced57dbe869
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/52725
Reviewed-by: Bob Beck <bbe@google.com>
Commit-Queue: Bob Beck <bbe@google.com>

crypto/cipher_extra/derive_key.c

@@ -69,12 +69,12 @@ int EVP_BytesToKey(const EVP_CIPHER *type, const EVP_MD *md,
                    unsigned count, uint8_t *key, uint8_t *iv) {
   EVP_MD_CTX c;
   uint8_t md_buf[EVP_MAX_MD_SIZE];
-  unsigned niv, nkey, addmd = 0;
+  unsigned addmd = 0;
   unsigned mds = 0, i;
   int rv = 0;
 
-  nkey = type->key_len;
-  niv = type->iv_len;
+  unsigned nkey = EVP_CIPHER_key_length(type);
+  unsigned niv = EVP_CIPHER_iv_length(type);
 
   assert(nkey <= EVP_MAX_KEY_LENGTH);
   assert(niv <= EVP_MAX_IV_LENGTH);
@@ -143,7 +143,7 @@ int EVP_BytesToKey(const EVP_CIPHER *type, const EVP_MD *md,
       break;
     }
   }
-  rv = type->key_len;
+  rv = EVP_CIPHER_key_length(type);
 
 err:
   EVP_MD_CTX_cleanup(&c);

crypto/cipher_extra/e_des.c

@@ -58,6 +58,7 @@
 #include <openssl/des.h>
 #include <openssl/nid.h>
 
+#include "../fipsmodule/cipher/internal.h"
 #include "internal.h"
 
 

crypto/cipher_extra/e_null.c

@@ -60,6 +60,7 @@
 
 #include <openssl/nid.h>
 
+#include "../fipsmodule/cipher/internal.h"
 #include "../internal.h"
 
 

crypto/cipher_extra/e_rc2.c

@@ -57,6 +57,7 @@
 #include <openssl/cipher.h>
 #include <openssl/nid.h>
 
+#include "../fipsmodule/cipher/internal.h"
 #include "../internal.h"
 
 

crypto/cipher_extra/e_rc4.c

@@ -61,6 +61,8 @@
 #include <openssl/nid.h>
 #include <openssl/rc4.h>
 
+#include "../fipsmodule/cipher/internal.h"
+
 
 static int rc4_init_key(EVP_CIPHER_CTX *ctx, const uint8_t *key,
                         const uint8_t *iv, int enc) {

crypto/fipsmodule/cipher/internal.h

@@ -112,6 +112,45 @@ struct evp_aead_st {
                     size_t extra_in_len);
 };
 
+struct evp_cipher_st {
+  // type contains a NID identifying the cipher. (e.g. NID_aes_128_gcm.)
+  int nid;
+
+  // block_size contains the block size, in bytes, of the cipher, or 1 for a
+  // stream cipher.
+  unsigned block_size;
+
+  // key_len contains the key size, in bytes, for the cipher. If the cipher
+  // takes a variable key size then this contains the default size.
+  unsigned key_len;
+
+  // iv_len contains the IV size, in bytes, or zero if inapplicable.
+  unsigned iv_len;
+
+  // ctx_size contains the size, in bytes, of the per-key context for this
+  // cipher.
+  unsigned ctx_size;
+
+  // flags contains the OR of a number of flags. See |EVP_CIPH_*|.
+  uint32_t flags;
+
+  // app_data is a pointer to opaque, user data.
+  void *app_data;
+
+  int (*init)(EVP_CIPHER_CTX *ctx, const uint8_t *key, const uint8_t *iv,
+              int enc);
+
+  int (*cipher)(EVP_CIPHER_CTX *ctx, uint8_t *out, const uint8_t *in,
+                size_t inl);
+
+  // cleanup, if non-NULL, releases memory associated with the context. It is
+  // called if |EVP_CTRL_INIT| succeeds. Note that |init| may not have been
+  // called at this point.
+  void (*cleanup)(EVP_CIPHER_CTX *);
+
+  int (*ctrl)(EVP_CIPHER_CTX *, int type, int arg, void *ptr);
+};
+
 // aes_ctr_set_key initialises |*aes_key| using |key_bytes| bytes from |key|,
 // where |key_bytes| must either be 16, 24 or 32. If not NULL, |*out_block| is
 // set to a function that encrypts single blocks. If not NULL, |*gcm_key| is

decrepit/blowfish/blowfish.c

@@ -61,6 +61,7 @@
 #include <assert.h>
 #include <string.h>
 
+#include "../../crypto/fipsmodule/cipher/internal.h"
 #include "../../crypto/internal.h"
 #include "../macros.h"
 

decrepit/cast/cast.c

@@ -64,6 +64,7 @@ OPENSSL_MSVC_PRAGMA(warning(push, 3))
 OPENSSL_MSVC_PRAGMA(warning(pop))
 #endif
 
+#include "../../crypto/fipsmodule/cipher/internal.h"
 #include "../../crypto/internal.h"
 #include "internal.h"
 #include "../macros.h"

decrepit/cfb/cfb.c

@@ -19,6 +19,7 @@
 #include <openssl/aes.h>
 #include <openssl/obj.h>
 
+#include "../../crypto/fipsmodule/cipher/internal.h"
 #include "../../crypto/internal.h"
 
 typedef struct {

decrepit/xts/xts.c

@@ -53,7 +53,8 @@
 #include <openssl/aes.h>
 #include <openssl/cipher.h>
 
-#include "../crypto/fipsmodule/modes/internal.h"
+#include "../../crypto/fipsmodule/cipher/internal.h"
+#include "../../crypto/fipsmodule/modes/internal.h"
 
 
 typedef struct xts128_context {

include/openssl/cipher.h

@@ -582,45 +582,6 @@ typedef struct evp_cipher_info_st {
   unsigned char iv[EVP_MAX_IV_LENGTH];
 } EVP_CIPHER_INFO;
 
-struct evp_cipher_st {
-  // type contains a NID identifing the cipher. (e.g. NID_aes_128_gcm.)
-  int nid;
-
-  // block_size contains the block size, in bytes, of the cipher, or 1 for a
-  // stream cipher.
-  unsigned block_size;
-
-  // key_len contains the key size, in bytes, for the cipher. If the cipher
-  // takes a variable key size then this contains the default size.
-  unsigned key_len;
-
-  // iv_len contains the IV size, in bytes, or zero if inapplicable.
-  unsigned iv_len;
-
-  // ctx_size contains the size, in bytes, of the per-key context for this
-  // cipher.
-  unsigned ctx_size;
-
-  // flags contains the OR of a number of flags. See |EVP_CIPH_*|.
-  uint32_t flags;
-
-  // app_data is a pointer to opaque, user data.
-  void *app_data;
-
-  int (*init)(EVP_CIPHER_CTX *ctx, const uint8_t *key, const uint8_t *iv,
-              int enc);
-
-  int (*cipher)(EVP_CIPHER_CTX *ctx, uint8_t *out, const uint8_t *in,
-                size_t inl);
-
-  // cleanup, if non-NULL, releases memory associated with the context. It is
-  // called if |EVP_CTRL_INIT| succeeds. Note that |init| may not have been
-  // called at this point.
-  void (*cleanup)(EVP_CIPHER_CTX *);
-
-  int (*ctrl)(EVP_CIPHER_CTX *, int type, int arg, void *ptr);
-};
-
 
 #if defined(__cplusplus)
 }  // extern C