gh-141801: Use accessors for ASN1_STRING fields in libssl (GH-141802)

* gh-141801: Use accessors for ASN1_STRING fields

While ASN1_STRING is currently exposed, it is better to use the
accessors. See openssl/openssl#29117 where, if
the type were opaque, OpenSSL's X509 objects could be much more
memory-efficient.

* Update Modules/_ssl.c

Co-authored-by: Bénédikt Tran <10796600+picnixz@users.noreply.github.com>

* Update Modules/_ssl.c

Co-authored-by: Bénédikt Tran <10796600+picnixz@users.noreply.github.com>

---------

Co-authored-by: Bénédikt Tran <10796600+picnixz@users.noreply.github.com>

Author: davidben

Modules/_ssl.c

@@ -1437,14 +1437,14 @@ _get_peer_alt_names (_sslmodulestate *state, X509 *certificate) {
                 }
                 PyTuple_SET_ITEM(t, 0, v);
 
-                if (name->d.ip->length == 4) {
-                    unsigned char *p = name->d.ip->data;
+                if (ASN1_STRING_length(name->d.ip) == 4) {
+                    const unsigned char *p = ASN1_STRING_get0_data(name->d.ip);
                     v = PyUnicode_FromFormat(
                         "%d.%d.%d.%d",
                         p[0], p[1], p[2], p[3]
                     );
-                } else if (name->d.ip->length == 16) {
-                    unsigned char *p = name->d.ip->data;
+                } else if (ASN1_STRING_length(name->d.ip) == 16) {
+                    const unsigned char *p = ASN1_STRING_get0_data(name->d.ip);
                     v = PyUnicode_FromFormat(
                         "%X:%X:%X:%X:%X:%X:%X:%X",
                         p[0] << 8 | p[1],
@@ -1575,8 +1575,9 @@ _get_aia_uri(X509 *certificate, int nid) {
             continue;
         }
         uri = ad->location->d.uniformResourceIdentifier;
-        ostr = PyUnicode_FromStringAndSize((char *)uri->data,
-                                           uri->length);
+        ostr = PyUnicode_FromStringAndSize(
+                   (const char *)ASN1_STRING_get0_data(uri),
+                   ASN1_STRING_length(uri));
         if (ostr == NULL) {
             goto fail;
         }
@@ -1642,8 +1643,9 @@ _get_crl_dp(X509 *certificate) {
                 continue;
             }
             uri = gn->d.uniformResourceIdentifier;
-            ouri = PyUnicode_FromStringAndSize((char *)uri->data,
-                                               uri->length);
+            ouri = PyUnicode_FromStringAndSize(
+                       (const char *)ASN1_STRING_get0_data(uri),
+                       ASN1_STRING_length(uri));
             if (ouri == NULL)
                 goto done;