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Remove RFC 2047 encoding from Content-Disposition filename #36328

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Remove RFC 2047 encoding from Content-Disposition filename #36328

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57 changes: 3 additions & 54 deletions spring-web/src/main/java/org/springframework/http/ContentDisposition.java
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Original file line number Diff line number Diff line change
Expand Up @@ -21,7 +21,6 @@
import java.nio.charset.StandardCharsets;
import java.util.ArrayList;
import java.util.Base64;
import java.util.BitSet;
import java.util.HexFormat;
import java.util.List;
import java.util.Locale;
Expand Down Expand Up @@ -59,23 +58,9 @@ public final class ContentDisposition {
private static final String INVALID_HEADER_FIELD_PARAMETER_FORMAT =
"Invalid header field parameter format (as defined in RFC 5987)";

private static final BitSet PRINTABLE = new BitSet(256);

private static final HexFormat HEX_FORMAT = HexFormat.of().withUpperCase();


static {
// RFC 2045, Section 6.7, and RFC 2047, Section 4.2
for (int i=33; i<= 126; i++) {
PRINTABLE.set(i);
}
PRINTABLE.set(34, false); // "
PRINTABLE.set(61, false); // =
PRINTABLE.set(63, false); // ?
PRINTABLE.set(95, false); // _
}


private final @Nullable String type;

private final @Nullable String name;
Expand Down Expand Up @@ -195,7 +180,7 @@ public String toString() {
}
else {
sb.append("; filename=\"");
sb.append(encodeQuotedPrintableFilename(this.filename, this.charset)).append('\"');
sb.append(toIso88591(encodeQuotedPairs(this.filename))).append('\"');
sb.append("; filename*=");
sb.append(encodeRfc5987Filename(this.filename, this.charset));
}
Expand Down Expand Up @@ -446,44 +431,8 @@ else if (b == '=' && index < value.length - 2) {
return StreamUtils.copyToString(baos, charset);
}

/**
* Encode the given header field param as described in RFC 2047.
* @param filename the filename
* @param charset the charset for the filename
* @return the encoded header field param
* @see <a href="https://tools.ietf.org/html/rfc2047">RFC 2047</a>
*/
private static String encodeQuotedPrintableFilename(String filename, Charset charset) {
Assert.notNull(filename, "'filename' must not be null");
Assert.notNull(charset, "'charset' must not be null");

byte[] source = filename.getBytes(charset);
StringBuilder sb = new StringBuilder(source.length << 1);
sb.append("=?");
sb.append(charset.name());
sb.append("?Q?");
for (byte b : source) {
if (b == 32) { // RFC 2047, section 4.2, rule (2)
sb.append('_');
}
else if (isPrintable(b)) {
sb.append((char) b);
}
else {
sb.append('=');
HEX_FORMAT.toHexDigits(sb, b);
}
}
sb.append("?=");
return sb.toString();
}

private static boolean isPrintable(byte c) {
int b = c;
if (b < 0) {
b = 256 + b;
}
return PRINTABLE.get(b);
private static String toIso88591(String input) {
return new String(input.getBytes(StandardCharsets.ISO_8859_1));
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@shardt68 shardt68 Mar 11, 2026 •
edited
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this would lead to Questionmarks "?" in the propose filename, which is not allowed in most filesystems,
I would rather propose an underline in place of non ascii characters
Suggetion:
// NFD decomposition splits characters like ä into base character 'a' + combining diacritic.
// Removing the combining diacritics (Unicode category Mn) gives a readable ASCII approximation
// (e.g. "Schöne Äpfel" → "Schone Apfel") without resorting to '?' which is a forbidden
// filename character on Windows.
String decomposed = java.text.Normalizer.normalize(input, java.text.Normalizer.Form.NFD);
return decomposed
.replaceAll("\p{InCombiningDiacriticalMarks}", "")
.replaceAll("[^\\x20-\\x7E]", "_");

}

private static String encodeQuotedPairs(String filename) {
Expand Down
8 changes: 4 additions & 4 deletions spring-web/src/test/java/org/springframework/http/ContentDispositionTests.java
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Original file line number Diff line number Diff line change
Expand Up @@ -221,7 +221,7 @@ void formatWithEncodedFilename() {
.filename("中文.txt", StandardCharsets.UTF_8)
.build().toString())
.isEqualTo("form-data; name=\"name\"; " +
"filename=\"=?UTF-8?Q?=E4=B8=AD=E6=96=87.txt?=\"; " +
"filename=\"??.txt\"; " +
"filename*=UTF-8''%E4%B8%AD%E6%96%87.txt");
}

Expand Down Expand Up @@ -272,7 +272,7 @@ void formatWithFilenameWithQuotes() {
void formatWithUtf8FilenameWithQuotes() {
String filename = "\"中文.txt";
assertThat(ContentDisposition.formData().filename(filename, StandardCharsets.UTF_8).build().toString())
.isEqualTo("form-data; filename=\"=?UTF-8?Q?=22=E4=B8=AD=E6=96=87.txt?=\"; filename*=UTF-8''%22%E4%B8%AD%E6%96%87.txt");
.isEqualTo("form-data; filename=\"\\\"??.txt\"; filename*=UTF-8''%22%E4%B8%AD%E6%96%87.txt");
}

@Test
Expand Down Expand Up @@ -303,14 +303,14 @@ void parseFormattedWithQuestionMark() {
.build();
String result = cd.toString();
assertThat(result).isEqualTo("attachment; " +
"filename=\"=?UTF-8?Q?filename_with_=3F=E9=97=AE=E5=8F=B7.txt?=\"; " +
"filename=\"filename with ???.txt\"; " +
"filename*=UTF-8''filename%20with%20%3F%E9%97%AE%E5%8F%B7.txt");

String[] parts = result.split("; ");

String quotedPrintableFilename = parts[0] + "; " + parts[1];
assertThat(ContentDisposition.parse(quotedPrintableFilename).getFilename())
.isEqualTo(filename);
.isEqualTo("filename with ???.txt");

String rfc5987Filename = parts[0] + "; " + parts[2];
assertThat(ContentDisposition.parse(rfc5987Filename).getFilename())
Expand Down