Updated FileSystemCapabilityChecker API

(related to #102)
cryptomator · Apr 16, 2021 · bbc3c86 · bbc3c86
1 parent 16695e9
commit bbc3c86
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Showing 4 changed files with 35 additions and 13 deletions.
diff --git a/src/main/java/org/cryptomator/cryptofs/FileNameTooLongException.java b/src/main/java/org/cryptomator/cryptofs/FileNameTooLongException.java
@@ -6,7 +6,7 @@
 /**
  * Indicates that an operation failed, as it would result in a ciphertext path that is too long for the underlying file system.
  *
- * @see org.cryptomator.cryptofs.common.FileSystemCapabilityChecker#determineSupportedFileNameLength(Path) 
+ * @see org.cryptomator.cryptofs.common.FileSystemCapabilityChecker#determineSupportedCleartextFileNameLength(Path)
  * @since 2.0.0
  */
 public class FileNameTooLongException extends FileSystemException {

diff --git a/src/main/java/org/cryptomator/cryptofs/common/FileSystemCapabilityChecker.java b/src/main/java/org/cryptomator/cryptofs/common/FileSystemCapabilityChecker.java
@@ -93,16 +93,24 @@ public void assertWriteAccess(Path pathToVault) throws MissingCapabilityExceptio
 		}
 	}
 
+	public int determineSupportedCleartextFileNameLength(Path pathToVault) throws IOException {
+		int maxCiphertextLen = determineSupportedCiphertextFileNameLength(pathToVault);
+		assert maxCiphertextLen >= MIN_CIPHERTEXT_NAME_LENGTH;
+		// math explained in https://github.com/cryptomator/cryptofs/issues/60#issuecomment-523238303;
+		// subtract 4 for file extension, base64-decode, subtract 16 for IV
+		return (maxCiphertextLen - 4) / 4 * 3 - 16;
+	}
+
 	/**
 	 * Determinse the number of chars a ciphertext filename (including its extension) is allowed to have inside a vault's <code>d/XX/YYYYYYYYYYYYYYYYYYYYYYYYYYYYYY/</code> directory.
 	 *
 	 * @param pathToVault Path to the vault
 	 * @return Number of chars a .c9r file is allowed to have
 	 * @throws IOException If unable to perform this check
 	 */
-	public int determineSupportedFileNameLength(Path pathToVault) throws IOException {
+	public int determineSupportedCiphertextFileNameLength(Path pathToVault) throws IOException {
 		int subPathLength = MAX_ADDITIONAL_PATH_LENGTH - 2; // subtract "c/"
-		return determineSupportedFileNameLength(pathToVault.resolve("c"), subPathLength, MIN_CIPHERTEXT_NAME_LENGTH, MAX_CIPHERTEXT_NAME_LENGTH);
+		return determineSupportedCiphertextFileNameLength(pathToVault.resolve("c"), subPathLength, MIN_CIPHERTEXT_NAME_LENGTH, MAX_CIPHERTEXT_NAME_LENGTH);
 	}
 
 	/**
@@ -115,7 +123,7 @@ public int determineSupportedFileNameLength(Path pathToVault) throws IOException
 	 * @return The supported filename length inside a subdirectory of <code>dir</code> with <code>subPathLength</code> chars
 	 * @throws IOException If unable to perform this check
 	 */
-	public int determineSupportedFileNameLength(Path dir, int subPathLength, int minFileNameLength, int maxFileNameLength) throws IOException {
+	public int determineSupportedCiphertextFileNameLength(Path dir, int subPathLength, int minFileNameLength, int maxFileNameLength) throws IOException {
 		Preconditions.checkArgument(subPathLength >= 6, "subPathLength must be larger than charcount(a/nnn/)");
 		Preconditions.checkArgument(minFileNameLength > 0);
 		Preconditions.checkArgument(maxFileNameLength <= 999);
@@ -130,13 +138,13 @@ public int determineSupportedFileNameLength(Path dir, int subPathLength, int min
 				throw new IOException("Unable to read dir");
 			}
 			// perform actual check:
-			return determineSupportedFileNameLength(fillerDir, minFileNameLength, maxFileNameLength + 1);
+			return determineSupportedCiphertextFileNameLength(fillerDir, minFileNameLength, maxFileNameLength + 1);
 		} finally {
 			deleteRecursivelySilently(fillerDir);
 		}
 	}
 
-	private int determineSupportedFileNameLength(Path p, int lowerBoundIncl, int upperBoundExcl) {
+	private int determineSupportedCiphertextFileNameLength(Path p, int lowerBoundIncl, int upperBoundExcl) {
 		assert lowerBoundIncl < upperBoundExcl;
 		int mid = (lowerBoundIncl + upperBoundExcl) / 2;
 		assert mid < upperBoundExcl;
@@ -145,9 +153,9 @@ private int determineSupportedFileNameLength(Path p, int lowerBoundIncl, int upp
 		}
 		assert lowerBoundIncl < mid;
 		if (canHandleFileNameLength(p, mid)) {
-			return determineSupportedFileNameLength(p, mid, upperBoundExcl);
+			return determineSupportedCiphertextFileNameLength(p, mid, upperBoundExcl);
 		} else {
-			return determineSupportedFileNameLength(p, lowerBoundIncl, mid);
+			return determineSupportedCiphertextFileNameLength(p, lowerBoundIncl, mid);
 		}
 	}
 

diff --git a/src/main/java/org/cryptomator/cryptofs/migration/v7/Version7Migrator.java b/src/main/java/org/cryptomator/cryptofs/migration/v7/Version7Migrator.java
@@ -66,7 +66,7 @@ public void migrate(Path vaultRoot, String vaultConfigFilename, String masterkey
 			LOG.info("Backed up masterkey from {} to {}.", masterkeyFile.getFileName(), masterkeyBackupFile.getFileName());
 
 			// check file system capabilities:
-			int filenameLengthLimit = new FileSystemCapabilityChecker().determineSupportedFileNameLength(vaultRoot.resolve("c"), 46, 28, 220);
+			int filenameLengthLimit = new FileSystemCapabilityChecker().determineSupportedCiphertextFileNameLength(vaultRoot.resolve("c"), 46, 28, 220);
 			int pathLengthLimit = filenameLengthLimit + 48; // TODO
 			PreMigrationVisitor preMigrationVisitor;
 			if (filenameLengthLimit >= 220) {

diff --git a/src/test/java/org/cryptomator/cryptofs/common/FileSystemCapabilityCheckerTest.java b/src/test/java/org/cryptomator/cryptofs/common/FileSystemCapabilityCheckerTest.java
@@ -3,12 +3,13 @@
 import org.cryptomator.cryptofs.mocks.DirectoryStreamMock;
 import org.cryptomator.cryptofs.mocks.SeekableByteChannelMock;
 import org.junit.jupiter.api.Assertions;
-import org.junit.jupiter.api.BeforeAll;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.DisplayName;
 import org.junit.jupiter.api.Nested;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.TestInstance;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.CsvSource;
 import org.mockito.Mockito;
 
 import java.io.IOException;
@@ -62,7 +63,7 @@ public void testUnlimitedLength() throws IOException {
 				return checkDirMock;
 			});
 
-			int determinedLimit = new FileSystemCapabilityChecker().determineSupportedFileNameLength(pathToVault);
+			int determinedLimit = new FileSystemCapabilityChecker().determineSupportedCiphertextFileNameLength(pathToVault);
 
 			Assertions.assertEquals(220, determinedLimit);
 		}
@@ -95,7 +96,7 @@ public void testLimitedLengthDuringDirListing() throws IOException {
 				return checkDirMock;
 			});
 
-			int determinedLimit = new FileSystemCapabilityChecker().determineSupportedFileNameLength(pathToVault);
+			int determinedLimit = new FileSystemCapabilityChecker().determineSupportedCiphertextFileNameLength(pathToVault);
 
 			Assertions.assertEquals(limit, determinedLimit);
 		}
@@ -125,10 +126,23 @@ public void testLimitedLengthDuringFileCreation() throws IOException {
 				return checkDirMock;
 			});
 
-			int determinedLimit = new FileSystemCapabilityChecker().determineSupportedFileNameLength(pathToVault);
+			int determinedLimit = new FileSystemCapabilityChecker().determineSupportedCiphertextFileNameLength(pathToVault);
 
 			Assertions.assertEquals(limit, determinedLimit);
 		}
+
+		@DisplayName("determineSupportedCleartextFileNameLength(...)")
+		@ParameterizedTest(name = "ciphertext length {0} -> cleartext length {1}")
+		@CsvSource({"220, 146", "219, 143", "218, 143", "217, 143", "216, 143", "215, 140"})
+		public void testDetermineSupportedCleartextFileNameLength(int ciphertextLimit, int expectedCleartextLimit) throws IOException {
+			Path path = Mockito.mock(Path.class);
+			FileSystemCapabilityChecker checker = Mockito.spy(new FileSystemCapabilityChecker());
+			Mockito.doReturn(ciphertextLimit).when(checker).determineSupportedCiphertextFileNameLength(path);
+
+			int result = checker.determineSupportedCleartextFileNameLength(path);
+
+			Assertions.assertEquals(expectedCleartextLimit, result);
+		}
 
 	}