Skip to content

IO-475: Fix UNC path prefix validation in FilenameUtils #825

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
MiriamCohenDev wants to merge 5 commits into
base: master
Choose a base branch
from
Open

IO-475: Fix UNC path prefix validation in FilenameUtils #825

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
5 commits
Select commit Hold shift + click to select a range
ba525f1
[IO-745] Fix FilenameUtils#getPrefixLength for UNC paths without trai…
MiriamCohenDev Jan 21, 2026
318c919
[IO-745] Fix FilenameUtilsTest Adding and modifying tests to match th…
MiriamCohenDev Jan 21, 2026
64038e1
IO-475: Address all review comments from Grigory
MiriamCohenDev Jan 26, 2026
cc47983
Merge remote-tracking branch 'upstream/master' into IO-475-fix-unc-pr…
MiriamCohenDev Feb 2, 2026
860bc20
Fix Checkstyle violations and address review comments
MiriamCohenDev Feb 2, 2026
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
21 changes: 16 additions & 5 deletions src/main/java/org/apache/commons/io/FilenameUtils.java
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -930,15 +930,25 @@ public static int getPrefixLength(final String fileName) {
if (!isSeparator(ch0) || !isSeparator(ch1)) {
return isSeparator(ch0) ? 1 : 0;
}
// UNC path: //hostname or //hostname/...
int posUnix = fileName.indexOf(UNIX_NAME_SEPARATOR, 2);
int posWin = fileName.indexOf(WINDOWS_NAME_SEPARATOR, 2);
if (posUnix == NOT_FOUND && posWin == NOT_FOUND || posUnix == 2 || posWin == 2) {

if (posUnix == 2 || posWin == 2) {
return NOT_FOUND;
}
posUnix = posUnix == NOT_FOUND ? posWin : posUnix;
posWin = posWin == NOT_FOUND ? posUnix : posWin;
final int pos = Math.min(posUnix, posWin) + 1;
final String hostnamePart = fileName.substring(2, pos - 1);
final int pos;
final String hostnamePart;
if (posUnix == NOT_FOUND && posWin == NOT_FOUND) {
pos = fileName.length();
hostnamePart = fileName.substring(2);
} else {
posUnix = posUnix == NOT_FOUND ? posWin : posUnix;
posWin = posWin == NOT_FOUND ? posUnix : posWin;
pos = Math.min(posUnix, posWin) + 1;
hostnamePart = fileName.substring(2, pos - 1);
}

return isValidHostName(hostnamePart) ? pos : NOT_FOUND;
}

Expand Down Expand Up @@ -1683,3 +1693,4 @@ public FilenameUtils() {
// empty
}
}

25 changes: 16 additions & 9 deletions src/test/java/org/apache/commons/io/FilenameUtilsTest.java
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -192,7 +192,7 @@ void testEqualsNormalized() {
void testEqualsNormalizedError_IO_128() {
assertFalse(FilenameUtils.equalsNormalizedOnSystem("//file.txt", "file.txt"));
assertFalse(FilenameUtils.equalsNormalizedOnSystem("file.txt", "//file.txt"));
assertFalse(FilenameUtils.equalsNormalizedOnSystem("//file.txt", "//file.txt"));
Comment thread
MiriamCohenDev marked this conversation as resolved.
assertTrue(FilenameUtils.equalsNormalizedOnSystem("//file.txt", "//file.txt"));
}

@Test
Expand Down Expand Up @@ -275,7 +275,7 @@ void testGetFullPath() {
assertNull(FilenameUtils.getFullPath("1:"));
assertNull(FilenameUtils.getFullPath("1:a"));
assertNull(FilenameUtils.getFullPath("///a/b/c.txt"));
assertNull(FilenameUtils.getFullPath("//a"));
Comment thread
MiriamCohenDev marked this conversation as resolved.
assertEquals("//a", FilenameUtils.getFullPath("//a"));

assertEquals("", FilenameUtils.getFullPath(""));

Expand Down Expand Up @@ -317,7 +317,7 @@ void testGetFullPathNoEndSeparator() {
assertNull(FilenameUtils.getFullPathNoEndSeparator("1:"));
assertNull(FilenameUtils.getFullPathNoEndSeparator("1:a"));
assertNull(FilenameUtils.getFullPathNoEndSeparator("///a/b/c.txt"));
assertNull(FilenameUtils.getFullPathNoEndSeparator("//a"));
Comment thread
MiriamCohenDev marked this conversation as resolved.
assertEquals("//a", FilenameUtils.getFullPathNoEndSeparator("//a"));

assertEquals("", FilenameUtils.getFullPathNoEndSeparator(""));

Expand All @@ -330,6 +330,7 @@ void testGetFullPathNoEndSeparator() {

assertEquals("C:/", FilenameUtils.getFullPathNoEndSeparator("C:/"));
assertEquals("//server/", FilenameUtils.getFullPathNoEndSeparator("//server/"));
assertEquals("//server", FilenameUtils.getFullPathNoEndSeparator("//server"));
assertEquals("~", FilenameUtils.getFullPathNoEndSeparator("~"));
assertEquals("~/", FilenameUtils.getFullPathNoEndSeparator("~/"));
assertEquals("~user", FilenameUtils.getFullPathNoEndSeparator("~user"));
Expand Down Expand Up @@ -408,7 +409,7 @@ void testGetPath() {
assertNull(FilenameUtils.getPath("1:"));
assertNull(FilenameUtils.getPath("1:a"));
assertNull(FilenameUtils.getPath("///a/b/c.txt"));
assertNull(FilenameUtils.getPath("//a"));
Comment thread
MiriamCohenDev marked this conversation as resolved.
assertEquals("", FilenameUtils.getPath("//a"));

assertEquals("", FilenameUtils.getPath(""));
assertEquals("", FilenameUtils.getPath(DRIVE_C));
Expand Down Expand Up @@ -450,12 +451,13 @@ void testGetPathNoEndSeparator() {
assertNull(FilenameUtils.getPathNoEndSeparator("1:"));
assertNull(FilenameUtils.getPathNoEndSeparator("1:a"));
assertNull(FilenameUtils.getPathNoEndSeparator("///a/b/c.txt"));
assertNull(FilenameUtils.getPathNoEndSeparator("//a"));
Comment thread
MiriamCohenDev marked this conversation as resolved.
assertEquals("", FilenameUtils.getPathNoEndSeparator("//a"));

assertEquals("", FilenameUtils.getPathNoEndSeparator(""));
assertEquals("", FilenameUtils.getPathNoEndSeparator(DRIVE_C));
assertEquals("", FilenameUtils.getPathNoEndSeparator("C:/"));
assertEquals("", FilenameUtils.getPathNoEndSeparator("//server/"));
assertEquals("", FilenameUtils.getPathNoEndSeparator("//server"));
assertEquals("", FilenameUtils.getPathNoEndSeparator("~"));
assertEquals("", FilenameUtils.getPathNoEndSeparator("~/"));
assertEquals("", FilenameUtils.getPathNoEndSeparator("~user"));
Expand Down Expand Up @@ -484,7 +486,7 @@ void testGetPrefix() {
assertNull(FilenameUtils.getPrefix("1:"));
assertNull(FilenameUtils.getPrefix("1:a"));
assertNull(FilenameUtils.getPrefix("\\\\\\a\\b\\c.txt"));
assertNull(FilenameUtils.getPrefix("\\\\a"));
Comment thread
MiriamCohenDev marked this conversation as resolved.
assertEquals("\\\\a", FilenameUtils.getPrefix("\\\\a"));

assertEquals("", FilenameUtils.getPrefix(""));
assertEquals("\\", FilenameUtils.getPrefix("\\"));
Expand All @@ -498,6 +500,7 @@ void testGetPrefix() {

assertEquals("C:\\", FilenameUtils.getPrefix("C:\\"));
assertEquals("//server/", FilenameUtils.getPrefix("//server/"));
assertEquals("//server", FilenameUtils.getPrefix("//server"));
assertEquals("~/", FilenameUtils.getPrefix("~"));
assertEquals("~/", FilenameUtils.getPrefix("~/"));
assertEquals("~user/", FilenameUtils.getPrefix("~user"));
Expand Down Expand Up @@ -534,7 +537,7 @@ void testGetPrefixLength() {
assertEquals(-1, FilenameUtils.getPrefixLength("1:"));
assertEquals(-1, FilenameUtils.getPrefixLength("1:a"));
assertEquals(-1, FilenameUtils.getPrefixLength("\\\\\\a\\b\\c.txt"));
assertEquals(-1, FilenameUtils.getPrefixLength("\\\\a"));
Comment thread
MiriamCohenDev marked this conversation as resolved.
assertEquals(3, FilenameUtils.getPrefixLength("\\\\a"));

assertEquals(0, FilenameUtils.getPrefixLength(""));
assertEquals(1, FilenameUtils.getPrefixLength("\\"));
Expand All @@ -548,6 +551,7 @@ void testGetPrefixLength() {

assertEquals(3, FilenameUtils.getPrefixLength("C:\\"));
assertEquals(9, FilenameUtils.getPrefixLength("//server/"));
assertEquals(8, FilenameUtils.getPrefixLength("//server"));
assertEquals(2, FilenameUtils.getPrefixLength("~"));
assertEquals(2, FilenameUtils.getPrefixLength("~/"));
assertEquals(6, FilenameUtils.getPrefixLength("~user"));
Expand Down Expand Up @@ -775,7 +779,7 @@ void testNormalize() {
assertNull(FilenameUtils.normalize("1:"));
assertNull(FilenameUtils.normalize("1:a"));
assertNull(FilenameUtils.normalize("\\\\\\a\\b\\c.txt"));
assertNull(FilenameUtils.normalize("\\\\a"));
Comment thread
MiriamCohenDev marked this conversation as resolved.
assertEquals(SEP + SEP + "a", FilenameUtils.normalize("\\\\a"));

assertEquals("a" + SEP + "b" + SEP + "c.txt", FilenameUtils.normalize("a\\b/c.txt"));
assertEquals("" + SEP + "a" + SEP + "b" + SEP + "c.txt", FilenameUtils.normalize("\\a\\b/c.txt"));
Expand Down Expand Up @@ -915,6 +919,7 @@ void testNormalize() {
assertNull(FilenameUtils.normalize("//server/../a"));
assertNull(FilenameUtils.normalize("//server/.."));
assertEquals(SEP + SEP + "server" + SEP + "", FilenameUtils.normalize("//server/"));
assertEquals(SEP + SEP + "server", FilenameUtils.normalize("//server"));

assertEquals(SEP + SEP + "127.0.0.1" + SEP + "a" + SEP + "b" + SEP + "c.txt", FilenameUtils.normalize("\\\\127.0.0.1\\a\\b\\c.txt"));
assertEquals(SEP + SEP + "::1" + SEP + "a" + SEP + "b" + SEP + "c.txt", FilenameUtils.normalize("\\\\::1\\a\\b\\c.txt"));
Expand Down Expand Up @@ -986,7 +991,7 @@ void testNormalizeNoEndSeparator() {
assertNull(FilenameUtils.normalizeNoEndSeparator("1:"));
assertNull(FilenameUtils.normalizeNoEndSeparator("1:a"));
assertNull(FilenameUtils.normalizeNoEndSeparator("\\\\\\a\\b\\c.txt"));
assertNull(FilenameUtils.normalizeNoEndSeparator("\\\\a"));
Comment thread
MiriamCohenDev marked this conversation as resolved.
assertEquals(SEP + SEP + "a", FilenameUtils.normalizeNoEndSeparator("\\\\a"));

assertEquals("a" + SEP + "b" + SEP + "c.txt", FilenameUtils.normalizeNoEndSeparator("a\\b/c.txt"));
assertEquals("" + SEP + "a" + SEP + "b" + SEP + "c.txt", FilenameUtils.normalizeNoEndSeparator("\\a\\b/c.txt"));
Expand Down Expand Up @@ -1127,6 +1132,7 @@ void testNormalizeNoEndSeparator() {
assertNull(FilenameUtils.normalizeNoEndSeparator("//server/../a"));
assertNull(FilenameUtils.normalizeNoEndSeparator("//server/.."));
assertEquals(SEP + SEP + "server" + SEP + "", FilenameUtils.normalizeNoEndSeparator("//server/"));
assertEquals(SEP + SEP + "server", FilenameUtils.normalizeNoEndSeparator("//server"));
}

@Test
Expand Down Expand Up @@ -1208,4 +1214,5 @@ void testSeparatorsToWindows() {
assertEquals("\\a\\b\\c", FilenameUtils.separatorsToWindows("/a/b/c"));
assertEquals("D:\\a\\b\\c", FilenameUtils.separatorsToWindows("D:/a/b/c"));
}

}
Loading