Make env/arg sanity check failure messages more useful

This change doesn't alter any checks, but it gives more specific
errors when a sanity check of env vars or argv does not pass, which
can point to limits to raise or at least give us better detailed bug
reports.

Signed-off-by: Hank Leininger <[email protected]>
Bug: #3678
Bug: #3851
Bug: #4633

Author: hlein

src/firejail/main.c

@@ -935,6 +935,10 @@ static void run_builder(int argc, char **argv) {
 	if (setresuid(-1, getuid(), getuid()) != 0)
 		errExit("setresuid");
 
+	if (env_get("LD_PRELOAD") != NULL)
+	{
+		fprintf(stderr, "run_builder: LD_PRELOAD is: '%s'\n", env_get("LD_PRELOAD"));
+	}
 	assert(env_get("LD_PRELOAD") == NULL);
 	assert(getenv("LD_PRELOAD") == NULL);
 	umask(orig_umask);
@@ -1003,18 +1007,18 @@ int main(int argc, char **argv, char **envp) {
 		fprintf(stderr, "Error: argv is invalid\n");
 		exit(1);
 	} else if (argc >= MAX_ARGS) {
-		fprintf(stderr, "Error: too many arguments\n");
+		fprintf(stderr, "Error: too many arguments: argc (%d) >= MAX_ARGS (%d)\n", argc, MAX_ARGS);
 		exit(1);
 	}
 
 	// sanity check for arguments
 	for (i = 0; i < argc; i++) {
 		if (*argv[i] == 0) {
-			fprintf(stderr, "Error: too short arguments\n");
+			fprintf(stderr, "Error: too short arguments: argv[%d] is empty\n", i);
 			exit(1);
 		}
 		if (strlen(argv[i]) >= MAX_ARG_LEN) {
-			fprintf(stderr, "Error: too long arguments\n");
+			fprintf(stderr, "Error: too long arguments: argv[%d] len (%d) >= MAX_ARG_LEN (%d)\n", i, strlen(argv[i]), MAX_ARG_LEN);
 			exit(1);
 		}
 	}
@@ -1025,7 +1029,7 @@ int main(int argc, char **argv, char **envp) {
 
 	// sanity check for environment variables
 	if (i >= MAX_ENVS) {
-		fprintf(stderr, "Error: too many environment variables\n");
+		fprintf(stderr, "Error: too many environment variables: >= MAX_ENVS (%d)\n", MAX_ENVS);
 		exit(1);
 	}
 

src/firejail/run_symlink.c

@@ -76,6 +76,10 @@ void run_symlink(int argc, char **argv, int run_as_is) {
 		a[i + 2] = argv[i + 1];
 	}
 	a[i + 2] = NULL;
+	if (env_get("LD_PRELOAD") != NULL)
+	{
+		fprintf(stderr, "run_symlink: LD_PRELOAD is: '%s'\n", env_get("LD_PRELOAD"));
+	}
 	assert(env_get("LD_PRELOAD") == NULL);
 	assert(getenv("LD_PRELOAD") == NULL);
 	execvp(a[0], a);