[release-branch.go1.17] path/filepath: do not remove prefix "." when following path contains ":".

For #52476
Fixes #52478
Fixes CVE-2022-29804

Change-Id: I9eb72ac7dbccd6322d060291f31831dc389eb9bb
Reviewed-on: https://go-review.googlesource.com/c/go/+/401595
Auto-Submit: Ian Lance Taylor <iant@google.com>
Reviewed-by: Alex Brainman <alex.brainman@gmail.com>
Run-TryBot: Ian Lance Taylor <iant@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Reviewed-by: Damien Neil <dneil@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-on: https://go-review.googlesource.com/c/go/+/405235
Reviewed-by: Yasuhiro Matsumoto <mattn.jp@gmail.com>

1 files changed, 26 insertions, 0 deletions

diff --git a/src/path/filepath/path_windows_test.go b/src/path/filepath/path_windows_test.go
index 76a459ac96..3edafb5a85 100644
--- a/src/path/filepath/path_windows_test.go
+++ b/src/path/filepath/path_windows_test.go
@@ -530,3 +530,29 @@ func TestNTNamespaceSymlink(t *testing.T) {
 		t.Errorf(`EvalSymlinks(%q): got %q, want %q`, filelink, got, want)
 	}
 }
+
+func TestIssue52476(t *testing.T) {
+	tests := []struct {
+		lhs, rhs string
+		want     string
+	}{
+		{`..\.`, `C:`, `..\C:`},
+		{`..`, `C:`, `..\C:`},
+		{`.`, `:`, `:`},
+		{`.`, `C:`, `.\C:`},
+		{`.`, `C:/a/b/../c`, `.\C:\a\c`},
+		{`.`, `\C:`, `.\C:`},
+		{`C:\`, `.`, `C:\`},
+		{`C:\`, `C:\`, `C:\C:`},
+		{`C`, `:`, `C\:`},
+		{`\.`, `C:`, `\C:`},
+		{`\`, `C:`, `\C:`},
+	}
+
+	for _, test := range tests {
+		got := filepath.Join(test.lhs, test.rhs)
+		if got != test.want {
+			t.Errorf(`Join(%q, %q): got %q, want %q`, test.lhs, test.rhs, got, test.want)
+		}
+	}
+}