Add CRYPTO_alloc_ex_data()

This allows allocation of items at indexes that were created after the
CRYPTO_EX_DATA variable was initialized, using the exact same method
that was used then.

Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/8225)

1 files changed, 30 insertions, 0 deletions

diff --git a/crypto/ex_data.c b/crypto/ex_data.c
index 33f43bf2e7..a728bfbbd3 100644
--- a/crypto/ex_data.c
+++ b/crypto/ex_data.c
@@ -363,6 +363,36 @@ void CRYPTO_free_ex_data(int class_index, void *obj, CRYPTO_EX_DATA *ad)
 }
 
 /*
+ * Allocate a given CRYPTO_EX_DATA item using the class specific allocation
+ * function
+ */
+int CRYPTO_alloc_ex_data(int class_index, void *obj, CRYPTO_EX_DATA *ad,
+                         int idx)
+{
+    EX_CALLBACK *f;
+    EX_CALLBACKS *ip;
+    void *curval;
+
+    curval = CRYPTO_get_ex_data(ad, idx);
+
+    /* Already there, no need to allocate */
+    if (curval != NULL)
+        return 1;
+
+    ip = get_and_lock(class_index);
+    f = sk_EX_CALLBACK_value(ip->meth, idx);
+    CRYPTO_THREAD_unlock(ex_data_lock);
+
+    /*
+     * This should end up calling CRYPTO_set_ex_data(), which allocates
+     * everything necessary to support placing the new data in the right spot.
+     */
+    f->new_func(obj, curval, ad, idx, f->argl, f->argp);
+
+    return 1;
+}
+
+/*
  * For a given CRYPTO_EX_DATA variable, set the value corresponding to a
  * particular index in the class used by this variable
  */