[PATCH] wintrust: Add parameter check in WTHelperGetProvCertFromChain

[Alistair Leslie-Hughes]

Signed-off-by: Alistair Leslie-Hughes 
---
 dlls/wintrust/tests/softpub.c | 9 +++++++++
 dlls/wintrust/wintrust_main.c | 2 +-
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/dlls/wintrust/tests/softpub.c b/dlls/wintrust/tests/softpub.c
index 6e7913f710..eb72512ddc 100644
--- a/dlls/wintrust/tests/softpub.c
+++ b/dlls/wintrust/tests/softpub.c
@@ -929,6 +929,14 @@ static void test_get_known_usages(void)
      "expected ERROR_INVALID_PARAMETER, got %d\n", GetLastError());
 }

+static void test_WTHelperGetProvCertFromChain(void)
+{
+    CRYPT_PROVIDER_CERT *cert;
+
+    cert = WTHelperGetProvCertFromChain(NULL, 0);
+    ok(!cert, "got certificate\n");
+}
+
 START_TEST(softpub)
 {
     InitFunctionPtrs();
@@ -936,4 +944,5 @@ START_TEST(softpub)
     test_sip_create_indirect_data();
     test_wintrust();
     test_get_known_usages();
+    test_WTHelperGetProvCertFromChain();
 }
diff --git a/dlls/wintrust/wintrust_main.c b/dlls/wintrust/wintrust_main.c
index 58e3ac39c0..bb5228286f 100644
--- a/dlls/wintrust/wintrust_main.c
+++ b/dlls/wintrust/wintrust_main.c
@@ -787,7 +787,7 @@ CRYPT_PROVIDER_CERT * WINAPI WTHelperGetProvCertFromChain(

TRACE("(%p %d)\n", pSgnr, idxCert);

-    if (idxCert >= pSgnr->csCertChain || !pSgnr->pasCertChain)
+    if (!pSgnr || idxCert >= pSgnr->csCertChain || !pSgnr->pasCertChain)
         return NULL;
     cert = &pSgnr->pasCertChain[idxCert];
     TRACE("returning %p\n", cert);