Fully unexport X509_VAL.

After https://boringssl-review.googlesource.com/c/boringssl/+/45965,
X509_VAL became largely unusable. While it did still exist as an
ASN1_ITEM and we emitted d2i/i2d/new/free functions, there is no way to
access its contents. Thus, hide it entirely.

Interestingly, although we got that to stick a while ago, I missed that
OpenSSL actually keeps X509_VAL exported, so it's possible we'll find 3p
code that uses this later. Since a standalone X509_VAL isn't especially
useful to construct or encode, this is most likely to come up in code
defining new types with <openssl/asn1t.h>.

Still, if we need to rexport this later (revert this *and* bring back
the struct), it won't be a big deal. Nothing in the public API even
constrains X509 to use X509_VAL.

Update-Note: The last remnants of the now (barely usable) X509_VAL are
no longer exported. It is unlikely anyone was relying on this.

Bug: 425
Change-Id: I90975f2f7ec27753675d2b5fa18b5cc4716319f4
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/50085
Reviewed-by: Adam Langley <[email protected]>

crypto/x509/internal.h

@@ -70,10 +70,12 @@ extern "C" {
 
 /* Internal structures. */
 
-struct X509_val_st {
+typedef struct X509_val_st {
   ASN1_TIME *notBefore;
   ASN1_TIME *notAfter;
-} /* X509_VAL */;
+} X509_VAL;
+
+DECLARE_ASN1_FUNCTIONS(X509_VAL)
 
 struct X509_pubkey_st {
   X509_ALGOR *algor;

include/openssl/base.h

@@ -376,7 +376,6 @@ typedef struct X509_name_st X509_NAME;
 typedef struct X509_pubkey_st X509_PUBKEY;
 typedef struct X509_req_st X509_REQ;
 typedef struct X509_sig_st X509_SIG;
-typedef struct X509_val_st X509_VAL;
 typedef struct bignum_ctx BN_CTX;
 typedef struct bignum_st BIGNUM;
 typedef struct bio_method_st BIO_METHOD;

include/openssl/x509.h

@@ -831,7 +831,6 @@ OPENSSL_EXPORT X509_REQ *X509_to_X509_REQ(X509 *x, EVP_PKEY *pkey,
                                           const EVP_MD *md);
 
 DECLARE_ASN1_ENCODE_FUNCTIONS(X509_ALGORS, X509_ALGORS, X509_ALGORS)
-DECLARE_ASN1_FUNCTIONS(X509_VAL)
 
 DECLARE_ASN1_FUNCTIONS(X509_PUBKEY)