Added --simulate-json option to write the simulated change set as JSON

cf-agent/cf-agent.c

@@ -112,6 +112,7 @@ static bool ALLCLASSESREPORT = false; /* GLOBAL_P */
 static bool ALWAYS_VALIDATE = false; /* GLOBAL_P */
 static bool CFPARANOID = false; /* GLOBAL_P */
 static bool PERFORM_DB_CHECK = false;
+static char *SIMULATE_JSON_FILE = NULL;
 
 static const Rlist *ACCESSLIST = NULL; /* GLOBAL_P */
 
@@ -221,6 +222,7 @@ static const struct option OPTIONS[] =
     {"skip-bootstrap-service-start", no_argument, 0, 0 },
     {"skip-db-check", optional_argument, 0, 0 },
     {"simulate", required_argument, 0, 0},
+    {"simulate-json", required_argument, 0, 0},
     {NULL, 0, 0, '\0'}
 };
 
@@ -257,6 +259,7 @@ static const char *const HINTS[] =
     "Do not start CFEngine services as part of the bootstrap process",
     "Do not run database integrity checks and repairs at startup",
     "Run in simulate mode, either 'manifest', 'manifest-full' or 'diff'",
+    "Write the change set of a --simulate run to the given file as JSON",
     NULL
 };
 
@@ -385,6 +388,26 @@ int main(int argc, char *argv[])
 
     Nova_NoteAgentExecutionPerformance(config->input_file, start);
 
+    /* The simulated change set includes digests of file contents, so it has
+     * to be written before GenericAgentFinalize() deinitializes the crypto
+     * (OpenSSL) library. */
+    if (SIMULATE_JSON_FILE != NULL)
+    {
+        if (!WriteChangesJson(SIMULATE_JSON_FILE))
+        {
+            Log(LOG_LEVEL_ERR,
+                "Failed to write the simulated change set to '%s'",
+                SIMULATE_JSON_FILE);
+
+            /* A consumer of the change set must not see a successful run
+             * without the document it asked for. */
+            if (ret == 0)
+            {
+                ret = EXIT_FAILURE;
+            }
+        }
+    }
+
     GenericAgentFinalize(ctx, config);
 
     StringSetDestroy(SINGLE_COPY_CACHE);
@@ -795,6 +818,26 @@ static GenericAgentConfig *CheckOpts(int argc, char **argv)
                     DoCleanupAndExit(EXIT_FAILURE);
                 }
             }
+            else if (StringEqual(option_name, "simulate-json"))
+            {
+                if (optarg == NULL)
+                {
+                    Log(LOG_LEVEL_ERR,
+                        "Missing argument for --simulate-json, a file path required");
+                    DoCleanupAndExit(EXIT_FAILURE);
+                }
+                else if (!IsAbsPath(optarg))
+                {
+                    Log(LOG_LEVEL_ERR,
+                        "Invalid argument for --simulate-json, an absolute path required, not '%s'",
+                        optarg);
+                    DoCleanupAndExit(EXIT_FAILURE);
+                }
+                else
+                {
+                    SIMULATE_JSON_FILE = xstrdup(optarg);
+                }
+            }
             break;
         }
         default:
@@ -822,6 +865,13 @@ static GenericAgentConfig *CheckOpts(int argc, char **argv)
         DoCleanupAndExit(EXIT_FAILURE);
     }
 
+    if ((SIMULATE_JSON_FILE != NULL) && !ChrootChanges())
+    {
+        Log(LOG_LEVEL_ERR,
+            "Option --simulate-json can only be used together with --simulate");
+        DoCleanupAndExit(EXIT_FAILURE);
+    }
+
     FreeFixedStringArray(argc_new, argv_new);
 
     return config;