diff --git a/otafault/config.cpp b/otafault/config.cpp
index c87f9a6..b456739 100644
--- a/otafault/config.cpp
+++ b/otafault/config.cpp
@@ -20,6 +20,8 @@
 #include <stdio.h>
 #include <unistd.h>
 
+#include <android-base/stringprintf.h>
+
 #include "minzip/Zip.h"
 #include "config.h"
 #include "ota_io.h"
@@ -27,12 +29,10 @@
 #define OTAIO_MAX_FNAME_SIZE 128
 
 static ZipArchive* archive;
-static std::map<const char*, bool> should_inject_cache;
+static std::map<std::string, bool> should_inject_cache;
 
-static const char* get_type_path(const char* io_type) {
-    char* path = (char*)calloc(strlen(io_type) + strlen(OTAIO_BASE_DIR) + 2, sizeof(char));
-    sprintf(path, "%s/%s", OTAIO_BASE_DIR, io_type);
-    return path;
+static std::string get_type_path(const char* io_type) {
+    return android::base::StringPrintf("%s/%s", OTAIO_BASE_DIR, io_type);
 }
 
 void ota_io_init(ZipArchive* za) {
@@ -41,13 +41,17 @@
 }
 
 bool should_fault_inject(const char* io_type) {
-    if (should_inject_cache.find(io_type) != should_inject_cache.end()) {
-        return should_inject_cache[io_type];
+    // archive will be NULL if we used an entry point other
+    // than updater/updater.cpp:main
+    if (archive == NULL) {
+        return false;
     }
-    const char* type_path = get_type_path(io_type);
-    const ZipEntry* entry = mzFindZipEntry(archive, type_path);
+    const std::string type_path = get_type_path(io_type);
+    if (should_inject_cache.find(type_path) != should_inject_cache.end()) {
+        return should_inject_cache[type_path];
+    }
+    const ZipEntry* entry = mzFindZipEntry(archive, type_path.c_str());
     should_inject_cache[type_path] = entry != nullptr;
-    free((void*)type_path);
     return entry != NULL;
 }
 
@@ -56,10 +60,10 @@
 }
 
 std::string fault_fname(const char* io_type) {
-    const char* type_path = get_type_path(io_type);
-    char* fname = (char*) calloc(OTAIO_MAX_FNAME_SIZE, sizeof(char));
-    const ZipEntry* entry = mzFindZipEntry(archive, type_path);
-    mzReadZipEntry(archive, entry, fname, OTAIO_MAX_FNAME_SIZE);
-    free((void*)type_path);
-    return std::string(fname);
+    std::string type_path = get_type_path(io_type);
+    std::string fname;
+    fname.resize(OTAIO_MAX_FNAME_SIZE);
+    const ZipEntry* entry = mzFindZipEntry(archive, type_path.c_str());
+    mzReadZipEntry(archive, entry, &fname[0], OTAIO_MAX_FNAME_SIZE);
+    return fname;
 }