kali834x commented on code in PR #780:
URL: https://github.com/apache/commons-compress/pull/780#discussion_r3534037907
##########
src/test/java/org/apache/commons/compress/archivers/tar/SparseFilesTest.java:
##########
@@ -532,4 +536,89 @@ void testTarFilePaxGNU() throws IOException {
assertPaxGNUEntry(entries.get(2), "1.0");
}
}
+
+ private static void appendPadded(final ByteArrayOutputStream out, final
byte[] data) {
+ out.write(data, 0, data.length);
+ final int rem = data.length % 512;
+ if (rem != 0) {
+ out.write(new byte[512 - rem], 0, 512 - rem);
+ }
+ }
+
+ private static String paxRecord(final String key, final String value) {
+ final int size = key.length() + value.length() + 3; // ' ', '=', '\n'
+ int len = size + Integer.toString(size).length();
+ while (len != size + Integer.toString(len).length()) {
+ len = size + Integer.toString(len).length();
+ }
+ return len + " " + key + "=" + value + "\n";
+ }
+
+ private static void putField(final byte[] header, final int offset, final
int length, final String value) {
+ final byte[] bytes =
value.getBytes(java.nio.charset.StandardCharsets.US_ASCII);
+ System.arraycopy(bytes, 0, header, offset, Math.min(length,
bytes.length));
+ }
+
+ private static void putOctal(final byte[] header, final int offset, final
int length, final long value) {
+ putField(header, offset, length, String.format("%0" + (length - 1) +
"o", value));
+ }
+
+ private static byte[] ustarHeader(final String name, final long size,
final char typeFlag) {
+ final byte[] header = new byte[512];
+ putField(header, 0, 100, name);
+ putOctal(header, 100, 8, 0644);
+ putOctal(header, 108, 8, 0);
+ putOctal(header, 116, 8, 0);
+ putOctal(header, 124, 12, size);
+ putOctal(header, 136, 12, 0);
+ java.util.Arrays.fill(header, 148, 156, (byte) ' '); // checksum
placeholder
+ header[156] = (byte) typeFlag;
+ putField(header, 257, 6, "ustar");
+ header[263] = '0';
+ header[264] = '0';
+ long checksum = 0;
+ for (final byte b : header) {
+ checksum += b & 0xff;
+ }
+ putField(header, 148, 6, String.format("%06o", checksum));
+ header[154] = 0;
+ header[155] = ' ';
+ return header;
+ }
+
+ // Builds a PAX GNU 0.1 sparse entry whose stored size is 4 bytes but
whose sparse map claims a
+ // single 1 MiB data block. realsize equals the block size, so the
existing realSize check passes.
+ // A second entry follows, whose bytes must not be reachable through the
sparse entry.
+ private byte[] sparseArchiveWithNumbytesLargerThanSize() {
+ final ByteArrayOutputStream bos = new ByteArrayOutputStream();
+ final String pax = paxRecord("GNU.sparse.size", "1048576") +
paxRecord("GNU.sparse.map", "0,1048576");
+ final byte[] paxData =
pax.getBytes(java.nio.charset.StandardCharsets.US_ASCII);
+ appendPadded(bos, ustarHeader("PaxHeaders/sparse.bin", paxData.length,
'x'));
+ appendPadded(bos, paxData);
+ appendPadded(bos, ustarHeader("sparse.bin", 4, '0'));
+ appendPadded(bos, new byte[] { 1, 2, 3, 4 });
+ final byte[] payload = "the following
entry".getBytes(java.nio.charset.StandardCharsets.US_ASCII);
+ appendPadded(bos, ustarHeader("next.bin", payload.length, '0'));
+ appendPadded(bos, payload);
+ bos.write(new byte[1024], 0, 1024); // two zero EOF records
Review Comment:
Not a coincidence, it's exactly two 512-byte end-of-archive records. Now
written as 2 * TarConstants.DEFAULT_RCDSIZE so the relationship is explicit.
##########
src/test/java/org/apache/commons/compress/archivers/tar/SparseFilesTest.java:
##########
@@ -532,4 +536,89 @@ void testTarFilePaxGNU() throws IOException {
assertPaxGNUEntry(entries.get(2), "1.0");
}
}
+
+ private static void appendPadded(final ByteArrayOutputStream out, final
byte[] data) {
+ out.write(data, 0, data.length);
+ final int rem = data.length % 512;
+ if (rem != 0) {
+ out.write(new byte[512 - rem], 0, 512 - rem);
+ }
+ }
+
+ private static String paxRecord(final String key, final String value) {
+ final int size = key.length() + value.length() + 3; // ' ', '=', '\n'
+ int len = size + Integer.toString(size).length();
+ while (len != size + Integer.toString(len).length()) {
+ len = size + Integer.toString(len).length();
+ }
+ return len + " " + key + "=" + value + "\n";
+ }
+
+ private static void putField(final byte[] header, final int offset, final
int length, final String value) {
+ final byte[] bytes =
value.getBytes(java.nio.charset.StandardCharsets.US_ASCII);
+ System.arraycopy(bytes, 0, header, offset, Math.min(length,
bytes.length));
+ }
+
+ private static void putOctal(final byte[] header, final int offset, final
int length, final long value) {
+ putField(header, offset, length, String.format("%0" + (length - 1) +
"o", value));
+ }
+
+ private static byte[] ustarHeader(final String name, final long size,
final char typeFlag) {
+ final byte[] header = new byte[512];
+ putField(header, 0, 100, name);
+ putOctal(header, 100, 8, 0644);
+ putOctal(header, 108, 8, 0);
+ putOctal(header, 116, 8, 0);
+ putOctal(header, 124, 12, size);
+ putOctal(header, 136, 12, 0);
+ java.util.Arrays.fill(header, 148, 156, (byte) ' '); // checksum
placeholder
+ header[156] = (byte) typeFlag;
+ putField(header, 257, 6, "ustar");
+ header[263] = '0';
+ header[264] = '0';
+ long checksum = 0;
+ for (final byte b : header) {
+ checksum += b & 0xff;
+ }
+ putField(header, 148, 6, String.format("%06o", checksum));
+ header[154] = 0;
+ header[155] = ' ';
+ return header;
+ }
+
+ // Builds a PAX GNU 0.1 sparse entry whose stored size is 4 bytes but
whose sparse map claims a
+ // single 1 MiB data block. realsize equals the block size, so the
existing realSize check passes.
+ // A second entry follows, whose bytes must not be reachable through the
sparse entry.
+ private byte[] sparseArchiveWithNumbytesLargerThanSize() {
+ final ByteArrayOutputStream bos = new ByteArrayOutputStream();
+ final String pax = paxRecord("GNU.sparse.size", "1048576") +
paxRecord("GNU.sparse.map", "0,1048576");
Review Comment:
Yes, intentionally the same value: realsize has to equal the map's numbytes
sum so the archive passes the existing realSize check and only the new bound
rejects it. Pulled it into a SPARSE_MAP_NUMBYTES constant used by both records.
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