Add X509_STORE_CTX_get0_chain.

In OpenSSL 1.1.x, the preferred spelling of X509_STORE_CTX_get_chain is
X509_STORE_CTX_get0_chain.

Change-Id: I20281c7ae86371a72ac70fb9a8719f4810e0747c
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/40366
Commit-Queue: David Benjamin <davidben@google.com>
Commit-Queue: Adam Langley <agl@google.com>
Reviewed-by: Adam Langley <agl@google.com>
diff --git a/crypto/x509/x509_vfy.c b/crypto/x509/x509_vfy.c
index 23bbeb5..87dcb47 100644
--- a/crypto/x509/x509_vfy.c
+++ b/crypto/x509/x509_vfy.c
@@ -2148,6 +2148,11 @@
     return ctx->chain;
 }
 
+STACK_OF(X509) *X509_STORE_CTX_get0_chain(X509_STORE_CTX *ctx)
+{
+    return ctx->chain;
+}
+
 STACK_OF(X509) *X509_STORE_CTX_get1_chain(X509_STORE_CTX *ctx)
 {
     if (!ctx->chain)
diff --git a/include/openssl/x509_vfy.h b/include/openssl/x509_vfy.h
index f262334..73dd470 100644
--- a/include/openssl/x509_vfy.h
+++ b/include/openssl/x509_vfy.h
@@ -578,6 +578,7 @@
 OPENSSL_EXPORT X509_CRL *X509_STORE_CTX_get0_current_crl(X509_STORE_CTX *ctx);
 OPENSSL_EXPORT X509_STORE_CTX *X509_STORE_CTX_get0_parent_ctx(X509_STORE_CTX *ctx);
 OPENSSL_EXPORT STACK_OF(X509) *X509_STORE_CTX_get_chain(X509_STORE_CTX *ctx);
+OPENSSL_EXPORT STACK_OF(X509) *X509_STORE_CTX_get0_chain(X509_STORE_CTX *ctx);
 OPENSSL_EXPORT STACK_OF(X509) *X509_STORE_CTX_get1_chain(X509_STORE_CTX *ctx);
 OPENSSL_EXPORT void	X509_STORE_CTX_set_cert(X509_STORE_CTX *c,X509 *x);
 OPENSSL_EXPORT void	X509_STORE_CTX_set_chain(X509_STORE_CTX *c,STACK_OF(X509) *sk);