Add test for OEMCrypto_ERROR_TOO_MANY_SESSIONS

Also restore the requirement that OEMCrypto shall support at least
8 sessions.

Bug: 19641109

Merged from Widevine CDM repo:
https://widevine-internal-review.googlesource.com/#/c/13570/

Change-Id: I0aca81b9fe1f4f6505ddf91bcf399ac910b654aa

libwvdrmengine/oemcrypto/mock/src/oemcrypto_engine_mock.h

@@ -239,6 +239,12 @@ class CryptoEngine {
 
   size_t GetNumberOfOpenSessions() { return sessions_.size(); }
 
+  size_t GetMaxNumberOfSessions() {
+    // An arbitrary limit for mock implementation.
+    static const size_t kMaxSupportedOEMCryptoSessions = 64;
+    return kMaxSupportedOEMCryptoSessions;
+  }
+
   void set_current_session_(SessionContext* current) {
     current_session_ = current;
   }

libwvdrmengine/oemcrypto/mock/src/oemcrypto_mock.cpp

@@ -80,6 +80,11 @@ OEMCryptoResult OEMCrypto_OpenSession(OEMCrypto_SESSION* session) {
     LOGI("-- OEMCryptoResult OEMCrypto_OpenSession"
          "(OEMCrypto_SESSION *session)\n");
   }
+  if (crypto_engine->GetNumberOfOpenSessions() >=
+      crypto_engine->GetMaxNumberOfSessions()) {
+    LOGE("[OEMCrypto_OpenSession(): failed due to too many sessions]");
+    return OEMCrypto_ERROR_TOO_MANY_SESSIONS;
+  }
   SessionId sid = crypto_engine->CreateSession();
   *session = (OEMCrypto_SESSION)sid;
   if (LogCategoryEnabled(kLoggingTraceOEMCryptoCalls)) {
@@ -1040,8 +1045,7 @@ OEMCryptoResult OEMCrypto_GetMaxNumberOfSessions(size_t* maximum) {
     LOGI("-- OEMCryptoResult OEMCrypto_GetMaxNumberOfSessions(%p)\n", maximum);
   }
   if (maximum == NULL) return OEMCrypto_ERROR_UNKNOWN_FAILURE;
-  const size_t kMaxSupportedOEMCryptoSessions = 64;
+  *maximum = crypto_engine->GetMaxNumberOfSessions();
-  *maximum = kMaxSupportedOEMCryptoSessions;
   return OEMCrypto_SUCCESS;
 }
 

libwvdrmengine/oemcrypto/test/oemcrypto_test.cpp

@@ -1746,12 +1746,26 @@ TEST_F(OEMCryptoClientTest, MaxSessionsOpenClose) {
   ASSERT_EQ(0, sessions_count);
   size_t max_sessions;
   ASSERT_EQ(OEMCrypto_SUCCESS, OEMCrypto_GetMaxNumberOfSessions(&max_sessions));
-  ASSERT_GT(max_sessions, 0);
+  // We expect OEMCrypto implementations support at least 8 sessions.
+  const size_t kMinimumSupportedMaxNumberOfSessions = 8u;
+  ASSERT_GE(max_sessions, kMinimumSupportedMaxNumberOfSessions);
 
   vector<OEMCrypto_SESSION> sessions;
-  for (int i = 0; i < max_sessions; i++) {
+  // Limit the number of sessions for testing.
+  const size_t kMaxNumberOfSessionsForTesting = 0x100u;
+  for (int i = 0; i < kMaxNumberOfSessionsForTesting; i++) {
     OEMCrypto_SESSION session_id;
-    ASSERT_EQ(OEMCrypto_SUCCESS, OEMCrypto_OpenSession(&session_id));
+    OEMCryptoResult sts = OEMCrypto_OpenSession(&session_id);
+    // GetMaxNumberOfSessions might be an estimate. We allow OEMCrypto to report
+    // a max that is less than what is actually supported. Assume the number
+    // returned is |max|. OpenSessions shall not fail if number of active
+    // sessions is less than |max|; OpenSessions should fail with
+    // OEMCrypto_ERROR_TOO_MANY_SESSIONS if too many sessions are open.
+    if (sts != OEMCrypto_SUCCESS) {
+      ASSERT_EQ(OEMCrypto_ERROR_TOO_MANY_SESSIONS, sts);
+      ASSERT_GE(i, max_sessions);
+      break;
+    }
     ASSERT_EQ(OEMCrypto_SUCCESS,
               OEMCrypto_GetNumberOfOpenSessions(&sessions_count));
     ASSERT_EQ(i + 1, sessions_count);
@@ -1763,6 +1777,13 @@ TEST_F(OEMCryptoClientTest, MaxSessionsOpenClose) {
               OEMCrypto_GetNumberOfOpenSessions(&sessions_count));
     ASSERT_EQ(sessions.size() - i - 1, sessions_count);
   }
+  if (sessions.size() == kMaxNumberOfSessionsForTesting) {
+    printf(
+        "             MaxSessionsOpenClose: reaches "
+        "kMaxNumberOfSessionsForTesting(%zu). GetMaxNumberOfSessions = %zu. "
+        "ERROR_TOO_MANY_SESSIONS not tested.",
+        kMaxNumberOfSessionsForTesting, max_sessions);
+  }
 }
 
 TEST_F(OEMCryptoClientTest, GenerateNonce) {