imap-send: use the OpenSSL API to access the subject alternative names

The OpenSSL 4.0 master branch has made the ASN1_STRING structure opaque,
forbidding access to its internal fields. Use the official accessor
functions instead. They have existed since OpenSSL v1.1.0.

Signed-off-by: Beat Bolli <dev+git@drbeat.li>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: bbolli

imap-send.c

@@ -244,10 +244,14 @@ static int verify_hostname(X509 *cert, const char *hostname)
 	if ((subj_alt_names = X509_get_ext_d2i(cert, NID_subject_alt_name, NULL, NULL))) {
 		int num_subj_alt_names = sk_GENERAL_NAME_num(subj_alt_names);
 		for (i = 0; !found && i < num_subj_alt_names; i++) {
+			int ntype;
 			GENERAL_NAME *subj_alt_name = sk_GENERAL_NAME_value(subj_alt_names, i);
-			if (subj_alt_name->type == GEN_DNS &&
-			    strlen((const char *)subj_alt_name->d.ia5->data) == (size_t)subj_alt_name->d.ia5->length &&
-			    host_matches(hostname, (const char *)(subj_alt_name->d.ia5->data)))
+			ASN1_STRING *subj_alt_str = GENERAL_NAME_get0_value(subj_alt_name, &ntype);
+
+			if (ntype == GEN_DNS &&
+			    strlen((const char *)ASN1_STRING_get0_data(subj_alt_str)) ==
+				    ASN1_STRING_length(subj_alt_str) &&
+			    host_matches(hostname, (const char *)ASN1_STRING_get0_data(subj_alt_str)))
 				found = 1;
 		}
 		sk_GENERAL_NAME_pop_free(subj_alt_names, GENERAL_NAME_free);