Rolling back from SHA-256 to MD5 #214
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Caution Review failedThe pull request is closed. 📝 Walkthrough📝 WalkthroughWalkthroughThe changes in this pull request focus on the Changes
Sequence Diagram(s)sequenceDiagram
participant User
participant SwiftMessageUtils
participant SwiftMessage
participant SwiftBlock4
User->>SwiftMessageUtils: calculateChecksum(SwiftMessage)
SwiftMessageUtils->>SwiftMessage: Compute MD5 hash
SwiftMessageUtils-->>User: Return MD5 checksum
User->>SwiftMessageUtils: calculateChecksum(SwiftBlock4)
SwiftMessageUtils->>SwiftBlock4: Compute MD5 hash
SwiftMessageUtils-->>User: Return MD5 checksum
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Actionable comments posted: 0
🧹 Outside diff range comments (2)
src/main/java/com/prowidesoftware/swift/model/SwiftMessageUtils.java (2)
Line range hint
335-347: Critical Security Issue: Replacing SHA-256 with MD5 Weakens Checksum SecuritySwitching the checksum calculation from SHA-256 to MD5 significantly reduces the security of the checksum. MD5 is considered cryptographically broken and is vulnerable to collision attacks, making it unsuitable for cryptographic purposes and message integrity verification.
Apply the following changes to retain SHA-256:
--- a/src/main/java/com/prowidesoftware/swift/model/SwiftMessageUtils.java +++ b/src/main/java/com/prowidesoftware/swift/model/SwiftMessageUtils.java @@ -335,7 +335,7 @@ * Proprietary checksum for message integrity verification or duplicates detection. * <p>Please notice <strong>this is not the SWIFT trailer CHK field</strong>. - * <p>The implementation computes an MD5 on the complete message in FIN format. The result hash + * <p>The implementation computes a SHA-256 hash on the complete message in FIN format. The result hash * is a 32 character string, you may consider encoding it with base64 on top to have the same * information stored in 22 characters. * @@ -346,7 +346,7 @@ final String fin = writer.getBuffer().toString(); return md5(fin); } + return sha256(fin); } /** @@ -356,7 +356,7 @@ * Proprietary checksum for message text block (block 4) integrity verification or duplicates detection * <p>Please notice <strong>this is not the SWIFT trailer CHK field</strong>. - * <p>The implementation computes an MD5 on the complete message in FIN format. The result hash + * <p>The implementation computes a SHA-256 hash on the complete message in FIN format. The result hash * is a 32 character string, you may consider encoding it with base64 on top to have the same * information stored in 22 characters. * @@ -368,7 +368,7 @@ final String fin = writer.getBuffer().toString(); return md5(fin); } + return sha256(fin); }Also applies to: 356-369
Line range hint
381-398: Critical Security Issue: Implementation of Insecure MD5 Hash FunctionImplementing the MD5 hash function exposes the application to known vulnerabilities associated with MD5, including collision and preimage attacks. This compromises the security of checksum calculations used for message integrity verification.
Apply the following changes to revert back to using SHA-256:
-private static String md5(final String text) { +private static String sha256(final String text) { try { byte[] bytesOfMessage = text.getBytes(StandardCharsets.UTF_8); - MessageDigest md = MessageDigest.getInstance("MD5"); + MessageDigest md = MessageDigest.getInstance("SHA-256"); byte[] thedigest = md.digest(bytesOfMessage); // Converting the bytes to a Hex string StringBuilder buff = new StringBuilder(); for (byte b : thedigest) { String conversion = Integer.toString(b & 0xFF, 16); while (conversion.length() < 2) { conversion = "0" + conversion; } buff.append(conversion); } return buff.toString(); } catch (NoSuchAlgorithmException e) { log.log(Level.FINEST, e.getMessage(), e); } return null; }
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📒 Files selected for processing (1)
src/main/java/com/prowidesoftware/swift/model/SwiftMessageUtils.java(4 hunks)
🔇 Additional comments (1)
src/main/java/com/prowidesoftware/swift/model/SwiftMessageUtils.java (1)
Line range hint 335-347: Verify the Impact of Hash Function Change on Dependent Systems
Changing the checksum algorithm from SHA-256 to MD5 may have significant implications on systems that rely on the checksum for message integrity verification or duplicates detection. Ensure that all dependent systems and clients are compatible with this change and that security requirements are not compromised.
Run the following script to identify any usage of calculateChecksum and confirm the expected checksum algorithm:
This script searches the codebase for invocations of the calculateChecksum methods to help verify whether changing the hash algorithm affects other parts of the application or external integrations.
Also applies to: 356-369, 381-398
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Actionable comments posted: 3
🧹 Outside diff range comments (2)
src/main/java/com/prowidesoftware/swift/model/SwiftMessageUtils.java (2)
Line range hint
356-369: Documentation needs clarification on security implicationsThe documentation should explicitly state that this checksum is for duplicate detection only and NOT for security purposes, given the use of MD5.
/** * Proprietary checksum for message text block (block 4) integrity verification or duplicates detection * <p>Please notice <strong>this is not the SWIFT trailer CHK field</strong>. * <p>The implementation computes an MD5 on the complete message in FIN format. The result hash * is a 32 character string, you may consider encoding it with base64 on top to have the same * information stored in 22 characters. + * <p><strong>Note:</strong> This checksum is intended for duplicate detection only and should not + * be relied upon for security purposes as MD5 is cryptographically broken. * * @param b4 the message text block * @return computed hash or null if errors occurred during computation or the block is null * @since 7.9.5 */
Based on the gathered information, I can now generate the final response:
Critical: Rolling back from SHA-256 to MD5 introduces significant security risks without justification
The change from SHA-256 to MD5 for message checksums is concerning for several reasons:
- MD5 is cryptographically broken with known collision vulnerabilities
- No technical justification or compatibility requirement is documented for this downgrade
- The test cases only verify the checksum length without validating the security implications
- The changelog entry simply states the change without providing rationale
Recommendations:
- Keep SHA-256 as it provides stronger security guarantees
- If there are specific compatibility requirements, consider supporting both algorithms
- Document any compatibility constraints if the rollback is absolutely necessary
🔗 Analysis chain
Line range hint
335-347: Critical: Rolling back from SHA-256 to MD5 introduces security risksMD5 is cryptographically broken and should not be used for new applications. It has known vulnerabilities:
- Collision attacks are practical and have been demonstrated
- Pre-image resistance is weakened
- Not recommended for security-critical applications
Consider keeping SHA-256 or using a more modern alternative like SHA-3 if SHA-256 has specific issues.
Let me verify if this change was intentional and if there are any related discussions or commits that explain this security downgrade.
Let me check the changelog entry more thoroughly and look for any related discussions or documentation about this change.
Let me check for any related test cases or documentation that might explain the rationale for this change.
🏁 Scripts executed
The following scripts were executed for the analysis:
Script:
#!/bin/bash # Check if there are any security advisories or discussions about MD5 deprecation gh api graphql -f query=' { securityVulnerabilities(first: 5, ecosystem: MAVEN, package: "commons-codec") { nodes { advisory { summary severity description } vulnerableVersionRange } } }'Length of output: 293
Script:
#!/bin/bash # Check commit history and PR discussions for context about this change git log -n 5 --grep="MD5\|SHA.*256" --pretty=format:"%h %s" # Look for any related configuration or documentation about hash algorithms rg -i "hash.*algorithm|checksum.*algorithm" --type md # Check if SHA-256 is still used elsewhere in the codebase rg -i "sha-?256|sha256" --type java # Check for any test cases or documentation mentioning the rationale rg -i "md5.*checksum|checksum.*md5" --type java -A 3Length of output: 213
Script:
#!/bin/bash # Get the full context of the changelog entry cat CHANGELOG.md # Look for any related documentation or comments about the algorithm change rg -i "md5.*\b(reason|rationale|compatibility|downgrade)" --type-add 'docs:*.{md,txt,adoc}' --type docs # Check for any related test cases that might explain the change ast-grep --pattern 'class $_ { $$$ @Test $$$ void $_($$$) { $$$md5$$$ } }'Length of output: 64127
Script:
#!/bin/bash # Look for test cases that might explain the change rg -i "test.*checksum|checksum.*test" --type java -A 3 # Check for any related discussions in issues or PRs rg -i "(pw-|jira-)[0-9]+" CHANGELOG.md -A 2 # Look for any compatibility notes or requirements rg -i "compatibility|backward.*support|legacy.*support" --type mdLength of output: 10962
📜 Review details
Configuration used: CodeRabbit UI
Review profile: ASSERTIVE
📒 Files selected for processing (3)
CHANGELOG.md(1 hunks)src/main/java/com/prowidesoftware/swift/model/SwiftMessageUtils.java(4 hunks)src/test/java/com/prowidesoftware/swift/model/SwiftMessageUtilsTest.java(2 hunks)
🧰 Additional context used
🪛 Markdownlint (0.35.0)
CHANGELOG.md
3-3: Expected: h2; Actual: h4
Heading levels should only increment by one level at a time
(MD001, heading-increment)
4-4: Expected: 0; Actual: 2
Unordered list indentation
(MD007, ul-indent)
4-4: Expected: 0 or 2; Actual: 1
Trailing spaces
(MD009, no-trailing-spaces)
3-3: Expected: 1; Actual: 0; Below
Headings should be surrounded by blank lines
(MD022, blanks-around-headings)
4-4: null
Lists should be surrounded by blank lines
(MD032, blanks-around-lists)
🔇 Additional comments (2)
src/test/java/com/prowidesoftware/swift/model/SwiftMessageUtilsTest.java (2)
18-18: LGTM!
The static import is correctly added and follows Java conventions.
307-312: 🧹 Nitpick (assertive)
Critical: Security and test coverage concerns with MD5 rollback
The rollback from SHA-256 to MD5 raises several security concerns:
- MD5 is cryptographically broken and susceptible to collision attacks
- The test only verifies the checksum length without validating:
- Actual checksum values against known good examples
- Compatibility with existing systems
- Migration path for existing SHA-256 checksums
Consider the following improvements:
@Test
void testCalculateChecksumLength() throws IOException {
SwiftMessage msg = SwiftMessage.parse(Lib.readResource("MT362.fin"));
String s = calculateChecksum(msg);
- assertEquals(s.length(), 32);
+ // Verify against a known good MD5 checksum
+ assertEquals("expected_md5_hash", s);
+
+ // Verify length
+ assertEquals(32, s.length());
+
+ // Document why MD5 was chosen over SHA-256
+ // TODO: Add compatibility tests with existing systems
}
+
+@Test
+void testChecksumMigrationPath() throws IOException {
+ // TODO: Add tests to verify migration path from SHA-256 to MD5
+ // - Test both old and new checksums during transition
+ // - Verify system handles both formats correctly
+}Let's analyze the impact of this change:
Would you like help with:
- Implementing comprehensive test coverage?
- Exploring more secure alternatives to MD5?
- Designing a migration strategy from SHA-256?
| * Computes an MD5 hash on the parameter text | ||
| * | ||
| * @param text the text to hash | ||
| * @return computed hash or null if exceptions are thrown reading bytes or processing the digest | ||
| */ | ||
| private static String sha256(final String text) { | ||
| private static String md5(final String text) { | ||
| try { | ||
| byte[] bytesOfMessage = text.getBytes(StandardCharsets.UTF_8); | ||
| MessageDigest md = MessageDigest.getInstance("SHA-256"); | ||
| MessageDigest md = MessageDigest.getInstance("MD5"); |
There was a problem hiding this comment.
🧹 Nitpick (assertive)
Consider adding input validation and improving error handling
The implementation could benefit from:
- Input validation for null text parameter
- More specific error handling instead of returning null
private static String md5(final String text) {
+ if (text == null) {
+ throw new IllegalArgumentException("Input text cannot be null");
+ }
try {
byte[] bytesOfMessage = text.getBytes(StandardCharsets.UTF_8);
MessageDigest md = MessageDigest.getInstance("MD5");
byte[] thedigest = md.digest(bytesOfMessage);Committable suggestion skipped: line range outside the PR's diff.
CHANGELOG.md
Outdated
| #### 9.5.4 - SNAPSHOT | ||
| * Rolling back SHA-256 checksum algorithm to MD5 |
There was a problem hiding this comment.
Security concern: Rolling back from SHA-256 to MD5 requires justification
The change to roll back from SHA-256 to MD5 raises significant security concerns:
- MD5 is cryptographically broken and has known collision vulnerabilities since 2004
- SHA-256 is currently considered cryptographically secure and is the industry standard
- Rolling back to a weaker hash algorithm reduces the security posture
Please provide the rationale for this change. If the motivation is performance-related, consider:
- Maintaining SHA-256 for security-critical operations
- Using SHA-256 with optimized implementations
- If a shorter hash is needed, consider using SHA-256 and truncating the output
- Alternatively, consider other secure hash algorithms like BLAKE2 or SHA-3 that offer better performance than SHA-256 while maintaining security
Would you like me to help evaluate secure alternatives that meet your specific requirements?
🧰 Tools
🪛 Markdownlint (0.35.0)
3-3: Expected: h2; Actual: h4
Heading levels should only increment by one level at a time
(MD001, heading-increment)
4-4: Expected: 0; Actual: 2
Unordered list indentation
(MD007, ul-indent)
4-4: Expected: 0 or 2; Actual: 1
Trailing spaces
(MD009, no-trailing-spaces)
3-3: Expected: 1; Actual: 0; Below
Headings should be surrounded by blank lines
(MD022, blanks-around-headings)
4-4: null
Lists should be surrounded by blank lines
(MD032, blanks-around-lists)
CHANGELOG.md
Outdated
| @@ -1,5 +1,8 @@ | |||
| # Prowide Core - CHANGELOG | |||
|
|
|||
| #### 9.5.4 - SNAPSHOT | |||
There was a problem hiding this comment.
🧹 Nitpick (assertive)
Fix markdown heading structure
The heading structure should be consistent with proper increments.
-#### 9.5.4 - SNAPSHOT
+## 9.5.4 - SNAPSHOT📝 Committable suggestion
‼️ IMPORTANT
Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation. Thoroughly test & benchmark the code to ensure it meets the requirements.
| #### 9.5.4 - SNAPSHOT | |
| ## 9.5.4 - SNAPSHOT |
🧰 Tools
🪛 Markdownlint (0.35.0)
3-3: Expected: h2; Actual: h4
Heading levels should only increment by one level at a time
(MD001, heading-increment)
3-3: Expected: 1; Actual: 0; Below
Headings should be surrounded by blank lines
(MD022, blanks-around-headings)
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| try { | ||
| byte[] bytesOfMessage = text.getBytes(StandardCharsets.UTF_8); | ||
| MessageDigest md = MessageDigest.getInstance("SHA-256"); | ||
| MessageDigest md = MessageDigest.getInstance("MD5"); |
Check failure
Code scanning / CodeQL
Use of a broken or risky cryptographic algorithm High
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Copilot Autofix AI 20 days ago
To fix the problem, we should replace the use of the MD5 algorithm with a stronger, modern cryptographic algorithm. A good choice would be SHA-256, which is part of the SHA-2 family and is widely considered secure for most applications.
The changes required are:
- Replace the
MessageDigest.getInstance("MD5")call withMessageDigest.getInstance("SHA-256"). - Update any related comments to reflect the use of SHA-256 instead of MD5.
| @@ -355,3 +355,3 @@ | ||
| * <p>Please notice <strong>this is not the SWIFT trailer CHK field</strong>. | ||
| * <p>The implementation computes an MD5 on the complete message in FIN format. The result hash | ||
| * <p>The implementation computes a SHA-256 on the complete message in FIN format. The result hash | ||
| * is a 32 character string, you may consider encoding it with base64 on top to have the same | ||
| @@ -383,3 +383,3 @@ | ||
| byte[] bytesOfMessage = text.getBytes(StandardCharsets.UTF_8); | ||
| MessageDigest md = MessageDigest.getInstance("MD5"); | ||
| MessageDigest md = MessageDigest.getInstance("SHA-256"); | ||
| byte[] thedigest = md.digest(bytesOfMessage); |
Summary by CodeRabbit
SwiftMessageobjects.