Don't keep the store open in by_store_ctrl_ex

Previously #27529 made a change to `by_store_ctrl_ex` in order to open
the OSSL_STORE early. The reason given in that PR is:

"This way, we can call OSSL_STORE_open_ex() in by_store_ctrl_ex(), and
get to see possible errors when the URI is loaded"

That PR then kept the store open until cache_objects is called and then
reused it. Unfortunately by the time cache_objects() is called we could be
in a multi-threaded scenario where the X509_STORE is being shared by
multiple threads. We then get a race condition where multiple threads are
all using (and ultimately closing) the same `OSSL_STORE_CTX`.

The purpose of keeping the `OSSL_STORE` object between by_store_ctrl_ex()
and `cache_objects` is presumably an optimisation to avoid having to open
the store twice. But this does not work because of the above issue.

We just take the hit and open it again.

Fixes #28171

Reviewed-by: Tomas Mraz <tomas@openssl.org>
Reviewed-by: Saša Nedvědický <sashan@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/28385)

diff --git a/crypto/x509/by_store.c b/crypto/x509/by_store.c
index e486fb0a9d9429cfbca15b08c26a5d840d29bae0..c9ef0b6a4e4aa782bad1c97bd13b3174d6749763 100644 (file)
--- a/crypto/x509/by_store.c
+++ b/crypto/x509/by_store.c
@@ -17,7 +17,6 @@ typedef struct cached_store_st {
     char *uri;
     OSSL_LIB_CTX *libctx;
     char *propq;
-    OSSL_STORE_CTX *ctx;
 } CACHED_STORE;
 
 DEFINE_STACK_OF(CACHED_STORE)
@@ -27,14 +26,12 @@ static int cache_objects(X509_LOOKUP *lctx, CACHED_STORE *store,
                          const OSSL_STORE_SEARCH *criterion, int depth)
 {
     int ok = 0;
-    OSSL_STORE_CTX *ctx = store->ctx;
+    OSSL_STORE_CTX *ctx;
     X509_STORE *xstore = X509_LOOKUP_get_store(lctx);
 
-    if (ctx == NULL
-        && (ctx = OSSL_STORE_open_ex(store->uri, store->libctx, store->propq,
-                                     NULL, NULL, NULL, NULL, NULL)) == NULL)
+    if ((ctx = OSSL_STORE_open_ex(store->uri, store->libctx, store->propq,
+                                  NULL, NULL, NULL, NULL, NULL)) == NULL)
         return 0;
-    store->ctx = ctx;
 
     /*
      * We try to set the criterion, but don't care if it was valid or not.
@@ -79,7 +76,6 @@ static int cache_objects(X509_LOOKUP *lctx, CACHED_STORE *store,
                 substore.uri = (char *)OSSL_STORE_INFO_get0_NAME(info);
                 substore.libctx = store->libctx;
                 substore.propq = store->propq;
-                substore.ctx = NULL;
                 ok = cache_objects(lctx, &substore, criterion, depth - 1);
             }
         } else {
@@ -105,7 +101,6 @@ static int cache_objects(X509_LOOKUP *lctx, CACHED_STORE *store,
             break;
     }
     OSSL_STORE_close(ctx);
-    store->ctx = NULL;
 
     return ok;
 }
@@ -114,7 +109,6 @@ static int cache_objects(X509_LOOKUP *lctx, CACHED_STORE *store,
 static void free_store(CACHED_STORE *store)
 {
     if (store != NULL) {
-        OSSL_STORE_close(store->ctx);
         OPENSSL_free(store->uri);
         OPENSSL_free(store->propq);
         OPENSSL_free(store);
@@ -148,6 +142,7 @@ static int by_store_ctrl_ex(X509_LOOKUP *ctx, int cmd, const char *argp,
         {
             STACK_OF(CACHED_STORE) *stores = X509_LOOKUP_get_method_data(ctx);
             CACHED_STORE *store = OPENSSL_zalloc(sizeof(*store));
+            OSSL_STORE_CTX *sctx;
 
             if (store == NULL) {
                 return 0;
@@ -157,14 +152,20 @@ static int by_store_ctrl_ex(X509_LOOKUP *ctx, int cmd, const char *argp,
             store->libctx = libctx;
             if (propq != NULL)
                 store->propq = OPENSSL_strdup(propq);
-            store->ctx = OSSL_STORE_open_ex(argp, libctx, propq, NULL, NULL,
-                                           NULL, NULL, NULL);
-            if (store->ctx == NULL
+            /*
+             * We open this to check for errors now - so we can report those
+             * errors early.
+             */
+            sctx = OSSL_STORE_open_ex(argp, libctx, propq, NULL, NULL,
+                                      NULL, NULL, NULL);
+            if (sctx == NULL
                 || (propq != NULL && store->propq == NULL)
                 || store->uri == NULL) {
+                OSSL_STORE_close(sctx);
                 free_store(store);
                 return use_default;
             }
+            OSSL_STORE_close(sctx);
 
             if (stores == NULL) {
                 stores = sk_CACHED_STORE_new_null();
@@ -184,7 +185,6 @@ static int by_store_ctrl_ex(X509_LOOKUP *ctx, int cmd, const char *argp,
         store.uri = (char *)argp;
         store.libctx = libctx;
         store.propq = (char *)propq;
-        store.ctx = NULL;
         return cache_objects(ctx, &store, NULL, 0);
     }
     default: