1. package com.fosspowered.peist.service;
2.  
3. import com.fosspowered.peist.model.dao.Paste;
4. import com.fosspowered.peist.model.exceptions.PeistAccessDeniedException;
5. import com.fosspowered.peist.model.exceptions.PeistInternalException;
6. import com.fosspowered.peist.model.exceptions.PeistInvalidRequestException;
7. import com.fosspowered.peist.model.exceptions.PeistNotFoundException;
8. import com.fosspowered.peist.model.json.PasteRequest;
9. import com.fosspowered.peist.model.json.PasteResponse;
10. import com.fosspowered.peist.repository.PasteRepository;
11. import java.nio.charset.StandardCharsets;
12. import java.security.InvalidKeyException;
13. import java.security.MessageDigest;
14. import java.security.NoSuchAlgorithmException;
15. import java.sql.Date;
16. import java.util.ArrayList;
17. import java.util.Base64;
18. import java.util.Calendar;
19. import java.util.List;
20. import java.util.Optional;
21. import java.util.UUID;
22. import java.util.stream.Collectors;
23. import javax.crypto.BadPaddingException;
24. import javax.crypto.Cipher;
25. import javax.crypto.IllegalBlockSizeException;
26. import javax.crypto.NoSuchPaddingException;
27. import javax.crypto.spec.SecretKeySpec;
28. import lombok.extern.log4j.Log4j2;
29. import org.apache.commons.lang3.StringUtils;
30. import org.springframework.beans.factory.annotation.Value;
31. import org.springframework.stereotype.Service;
32.  
33. @Service
34. @Log4j2
35. public class PasteService {
36.   private final PasteRepository pasteRepository;
37.  
38.   private final String systemKey;
39.  
40.   PasteService(PasteRepository pasteRepository, @Value("${system-key}") String systemKey) {
41.     this.pasteRepository = pasteRepository;
42.     this.systemKey = systemKey;
43.   }
44.  
45.   public PasteResponse addPaste(PasteRequest request) {
46.     Paste paste = buildPasteData(request);
47.     this.pasteRepository.save(paste);
48.     return buildPasteResponse(paste);
49.   }
50.  
51.   private String convertToCipher(Date creationDate, String key, String text) {
52.     SecretKeySpec keySpec = buildSpec(creationDate, key);
53.     try {
54.       Cipher cipher = Cipher.getInstance("AES");
55.       cipher.init(Cipher.ENCRYPT_MODE, keySpec);
56.       byte[] cipherBytes = cipher.doFinal(text.getBytes(StandardCharsets.UTF_8));
57.       return Base64.getEncoder().encodeToString(cipherBytes);
58.     } catch (InvalidKeyException
59.         | IllegalBlockSizeException
60.         | BadPaddingException
61.         | NoSuchAlgorithmException
62.         | NoSuchPaddingException e) {
63.       throw new RuntimeException(e);
64.     }
65.   }
66.  
67.   private String convertFromCipher(Date creationDate, String key, String cipherText) {
68.     SecretKeySpec keySpec = buildSpec(creationDate, key);
69.  
70.     try {
71.       Cipher cipher = Cipher.getInstance("AES");
72.       cipher.init(Cipher.DECRYPT_MODE, keySpec);
73.       return new String(cipher.doFinal(Base64.getDecoder().decode(cipherText)));
74.     } catch (BadPaddingException e) {
75.       throw new PeistAccessDeniedException("Access denied for paste.");
76.     } catch (NoSuchAlgorithmException
77.         | InvalidKeyException
78.         | NoSuchPaddingException
79.         | IllegalBlockSizeException e) {
80.       log.error("Error while processing", e);
81.       throw new PeistInternalException("Error while processing");
82.     }
83.   }
84.  
85.   private SecretKeySpec buildSpec(Date creationDate, String key) {
86.     String keyStr =
87.         String.format(
88.             "%s%s%s", systemKey, StringUtils.isNotBlank(key) ? key : "", creationDate.getTime());
89.     try {
90.       MessageDigest sha = MessageDigest.getInstance("SHA-256");
91.       return new SecretKeySpec(sha.digest(keyStr.getBytes(StandardCharsets.UTF_8)), "AES");
92.     } catch (NoSuchAlgorithmException e) {
93.       throw new RuntimeException(e);
94.     }
95.   }
96.  
97.   public PasteResponse fetchPaste(String urlId) {
98.     return fetchPaste(urlId, null);
99.   }
100.  
101.   public PasteResponse fetchPaste(String urlId, String key) {
102.     Paste paste = fetchPasteFromDB(urlId);
103.     String text = convertFromCipher(paste.getCreationDate(), key, paste.getPasteData());
104.     paste.setPasteData(text);
105.     return buildPasteResponse(paste);
106.   }
107.  
108.   private Paste fetchPasteFromDB(String urlId) {
109.     if (StringUtils.isBlank(urlId)) {
110.       throw new PeistInvalidRequestException("Invalid request as urlId is invalid: " + urlId);
111.     }
112.     Optional<Paste> paste = this.pasteRepository.findByUrlId(urlId);
113.     if (paste.isPresent()) {
114.       return paste.get();
115.     } else {
116.       throw new PeistNotFoundException("Paste not found for urlId: " + urlId);
117.     }
118.   }
119.  
120.   public List<PasteResponse> fetchRecentPastes() {
121.     List<Paste> pasteList = new ArrayList<>(this.pasteRepository.findAll());
122.     return pasteList.stream().map(this::buildPasteResponse).collect(Collectors.toList());
123.   }
124.  
125.   private PasteResponse buildPasteResponse(Paste paste) {
126.  
127.     return PasteResponse.builder()
128.         .urlId(paste.getUrlId())
129.         .creationDate(paste.getCreationDate())
130.         .author(paste.getAuthor())
131.         .language(paste.getLanguage())
132.         .title(paste.getTitle())
133.         .expiryDate(paste.getExpiryDate())
134.         .isVisible(paste.getIsVisible())
135.         .pasteData(paste.getPasteData())
136.         .build();
137.   }
138.  
139.   private Paste buildPasteData(PasteRequest pasteRequest) {
140.     Calendar now = Calendar.getInstance();
141.     Date creationDate = new Date(now.getTime().getTime());
142.     now.add(Calendar.SECOND, pasteRequest.getTtl());
143.     Date expiryDate = new Date(now.getTime().getTime());
144.  
145.     String secretKey = pasteRequest.getSecretKey();
146.     boolean isVisible = StringUtils.isNotBlank(pasteRequest.getSecretKey());
147.     String text = convertToCipher(creationDate, secretKey, pasteRequest.getPasteData());
148.  
149.     Paste paste = new Paste();
150.     paste.setUrlId(UUID.randomUUID().toString());
151.     paste.setCreationDate(creationDate);
152.     paste.setTitle(pasteRequest.getTitle());
153.     paste.setAuthor(pasteRequest.getAuthor());
154.     paste.setLanguage(pasteRequest.getLanguage());
155.     paste.setExpiryDate(expiryDate);
156.     paste.setIsVisible(isVisible);
157.     paste.setPasteData(text);
158.     return paste;
159.   }
160. }
161.