Add support for modified UTF-8 in JKS
When parsing JKS entries, BC C# previously failed to parse entries with
UTF-8 entries. This is because Java encodes them using a modified UTF-8
wherein NULL bytes and 4-byte extended values do not appear.
Add support for both reading and writing this modified method of UTF-8
within the JKS parsing code.
Signed-off-by: Alexander Scheel <alexander.scheel@keyfactor.com>
3 files changed, 141 insertions, 19 deletions
diff --git a/crypto/src/security/JksStore.cs b/crypto/src/security/JksStore.cs
index 4df0b39db..a7d3f6ca3 100644
--- a/crypto/src/security/JksStore.cs
+++ b/crypto/src/security/JksStore.cs
@@ -726,20 +726,81 @@ namespace Org.BouncyCastle.Security
private static string ReadUtf(BinaryReader br)
{
- byte[] utfBytes = ReadBufferWithInt16Length(br);
+ byte[] mUtfBytes = ReadBufferWithInt16Length(br);
+
+ int i = 0;
+ MemoryStream utfBytes = new MemoryStream(mUtfBytes.Length);
+
+ while (i < mUtfBytes.Length)
+ {
+ // Modified UTF-8 differs from regular UTF-8 in the following
+ // ways:
+ //
+ // 1. NULL bytes never occur in the stream and are always
+ // two-byte encoded.
+ // 2. There are no four-byte values and are instead always
+ // encoded using surrogate pairs.
+ //
+ // See also: https://docs.oracle.com/en/java/javase/16/docs/api/java.base/java/io/DataInput.html#modified-utf-8
+ byte mUtfByte = mUtfBytes[i];
+ if (mUtfByte == 0)
+ throw new NotSupportedException("Unexpected NULL byte in modified UTF-8 encoding in JKS");
+
+ if ((mUtfByte & 0x80) == 0)
+ {
+ // No transformation is applied to non-NULL ASCII bytes.
+ utfBytes.WriteByte(mUtfByte);
+ i += 1;
+ }
+ else if ((mUtfByte & 0xE0) == 0xC0)
+ {
+ // Validate we have another byte.
+ if ((i + 1) >= mUtfBytes.Length)
+ throw new NotSupportedException("Two-byte sentinel found at end of input stream");
- /*
- * FIXME JKS actually uses a "modified UTF-8" format. For the moment we will just support single-byte
- * encodings that aren't null bytes.
- */
- for (int i = 0; i < utfBytes.Length; ++i)
- {
- byte utfByte = utfBytes[i];
- if (utfByte == 0 || (utfByte & 0x80) != 0)
- throw new NotSupportedException("Currently missing support for modified UTF-8 encoding in JKS");
+ byte mUtfByteSecond = mUtfBytes[i+1];
+ if ((mUtfByteSecond & 0xC0) != 0x80)
+ throw new NotSupportedException("Second byte in two-byte modified UTF-8 encoding malformed");
+
+ // We might have encoded the NULL byte as two bytes.
+ if (mUtfByte == 0xC0 && mUtfByteSecond == 0x80)
+ {
+ utfBytes.WriteByte(0x00);
+ } else {
+ utfBytes.WriteByte(mUtfByte);
+ utfBytes.WriteByte(mUtfByteSecond);
+ }
+
+ i += 2;
+ }
+ else if ((mUtfByte & 0xF0) == 0xE0)
+ {
+ // Validate we have enough bytes.
+ if ((i + 2) >= mUtfBytes.Length)
+ throw new NotSupportedException("Three-byte sentinel found at end of input stream");
+
+ byte mUtfByteSecond = mUtfBytes[i+1];
+ if ((mUtfByteSecond & 0xC0) != 0x80)
+ throw new NotSupportedException("Second byte in two-byte modified UTF-8 encoding malformed");
+
+ byte mUtfByteThird = mUtfBytes[i+2];
+ if ((mUtfByteThird & 0xC0) != 0x80)
+ throw new NotSupportedException("Third byte in two-byte modified UTF-8 encoding malformed");
+
+ utfBytes.WriteByte(mUtfByte);
+ utfBytes.WriteByte(mUtfByteSecond);
+ utfBytes.WriteByte(mUtfByteThird);
+
+ i += 3;
+ }
+ else
+ {
+ // Reachable when we have a non-standard four-byte sentinel mask.
+ throw new NotSupportedException("Malformed modified UTF-8 encoding at index " + i);
+ }
}
- return Encoding.UTF8.GetString(utfBytes);
+ return Encoding.UTF8.GetString(utfBytes.ToArray());
}
private static void WriteBufferWithInt16Length(BinaryWriter bw, byte[] buffer)
@@ -770,18 +831,63 @@ namespace Org.BouncyCastle.Security
{
byte[] utfBytes = Encoding.UTF8.GetBytes(s);
- /*
- * FIXME JKS actually uses a "modified UTF-8" format. For the moment we will just support single-byte
- * encodings that aren't null bytes.
- */
- for (int i = 0; i < utfBytes.Length; ++i)
+ int i = 0;
+ MemoryStream mUtfBytes = new MemoryStream();
+ while (i < utfBytes.Length)
{
byte utfByte = utfBytes[i];
- if (utfByte == 0 || (utfByte & 0x80) != 0)
- throw new NotSupportedException("Currently missing support for modified UTF-8 encoding in JKS");
+ if (utfByte == 0)
+ {
+ // The NULL byte is encoded in two byte format.
+ mUtfBytes.WriteByte(0xC0);
+ mUtfBytes.WriteByte(0x80);
+ i += 1;
+ }
+ else if ((utfByte & 0x80) == 0)
+ {
+ // One byte UTF-8 bytes are written directly.
+ mUtfBytes.WriteByte(utfByte);
+ i += 1;
+ }
+ else if ((utfByte & 0xE0) == 0xC0)
+ {
+ // Two byte UTF-8 values are preserved as-is.
+ if ((i + 1) >= utfBytes.Length)
+ throw new NotSupportedException("Malformed UTF-8: trailing two-byte character at end of string");
+
+ if ((utfBytes[i+1] & 0xC0) != 0x80)
+ throw new NotSupportedException("Malformed UTF-8: second byte has invalid prefix");
+
+ mUtfBytes.WriteByte(utfByte);
+ mUtfBytes.WriteByte(utfBytes[i+1]);
+ i += 2;
+ }
+ else if ((utfByte & 0xF0) == 0xE0)
+ {
+ // Three byte UTF-8 values are preserved as-is.
+ if ((i + 2) >= utfBytes.Length)
+ throw new NotSupportedException("Malformed UTF-8: trailing three-byte character at end of string");
+
+ if ((utfBytes[i+1] & 0xC0) != 0x80)
+ throw new NotSupportedException("Malformed UTF-8: second byte has invalid prefix");
+
+ if ((utfBytes[i+2] & 0xC0) != 0x80)
+ throw new NotSupportedException("Malformed UTF-8: third byte has invalid prefix");
+
+ mUtfBytes.WriteByte(utfByte);
+ mUtfBytes.WriteByte(utfBytes[i+1]);
+ mUtfBytes.WriteByte(utfBytes[i+2]);
+ i += 3;
+
+ }
+ else
+ {
+ // Reachable when we have a non-standard four-byte sentinel mask.
+ throw new NotSupportedException("Malformed modified UTF-8 encoding at index " + i);
+ }
}
- WriteBufferWithInt16Length(bw, utfBytes);
+ WriteBufferWithInt16Length(bw, mUtfBytes.ToArray());
}
/**
diff --git a/crypto/test/data/jks/cacerts.jks b/crypto/test/data/jks/cacerts.jks
new file mode 100644
index 000000000..ca0cbd33e
--- /dev/null
+++ b/crypto/test/data/jks/cacerts.jks
Binary files differdiff --git a/crypto/test/src/security/test/JksStoreTest.cs b/crypto/test/src/security/test/JksStoreTest.cs
index 335786f5e..8794d48a6 100644
--- a/crypto/test/src/security/test/JksStoreTest.cs
+++ b/crypto/test/src/security/test/JksStoreTest.cs
@@ -9,6 +9,8 @@ using Org.BouncyCastle.Crypto.Parameters;
using Org.BouncyCastle.Math;
using Org.BouncyCastle.Utilities.Encoders;
+using Org.BouncyCastle.Utilities.Test;
+
namespace Org.BouncyCastle.Security.Tests
{
[TestFixture]
@@ -177,5 +179,19 @@ namespace Org.BouncyCastle.Security.Tests
// Expected
}
}
+
+ [Test]
+ public void TestJksModifiedUtf8Roundtrip()
+ {
+ JksStore ks = new JksStore();
+ Stream fIn = SimpleTest.GetTestDataAsStream("jks.cacerts.jks");
+
+ ks.Load(fIn, "changeit".ToCharArray());
+
+ MemoryStream bOut = new MemoryStream();
+ ks.Save(bOut, "changedit".ToCharArray());
+
+ ks.Load(new MemoryStream(bOut.ToArray()), "changedit".ToCharArray());
+ }
}
}
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