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Prevent quadratic DoS in chart number-format bracket parsing #1923

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Merged
PrzemyslawKlys merged 1 commit into from
Jun 16, 2026
Merged

Prevent quadratic DoS in chart number-format bracket parsing #1923

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11 changes: 8 additions & 3 deletions OfficeIMO.Drawing/OfficeChartDrawingRenderer.Text.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -596,6 +596,7 @@ private static string NormalizeDataLabelFormatLiteral(string value) {
var builder = new System.Text.StringBuilder(value.Length);
bool inQuotedLiteral = false;
bool escaped = false;
int nextClosingBracket = value.IndexOf(']');
for (int i = 0; i < value.Length; i++) {
char c = value[i];
if (escaped) {
Expand All @@ -615,9 +616,13 @@ private static string NormalizeDataLabelFormatLiteral(string value) {
}

if (!inQuotedLiteral && c == '[') {
int close = value.IndexOf(']', i + 1);
if (close > i) {
i = close;
while (nextClosingBracket >= 0 && nextClosingBracket < i) {
nextClosingBracket = value.IndexOf(']', nextClosingBracket + 1);
}

if (nextClosingBracket > i) {
i = nextClosingBracket;
nextClosingBracket = value.IndexOf(']', nextClosingBracket + 1);
continue;
}
}
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11 changes: 11 additions & 0 deletions OfficeIMO.Tests/Pdf/PdfDocumentChartDrawingTests.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -408,6 +408,17 @@ public void FlowDrawing_AppliesScalingCommasInDataLabelNumberFormats() {
Assert.Equal("1,235 K", literalSuffix);
}

[Fact]
public void FlowDrawing_IgnoresBracketDirectivesInDataLabelNumberFormatsLinearly() {
MethodInfo method = typeof(OfficeChartDrawingRenderer).GetMethod("FormatDataLabelValue", BindingFlags.NonPublic | BindingFlags.Static)!;
string unmatchedPrefixFormat = new string('[', 4096) + "0";
string directivePrefix = (string)method.Invoke(null, new object?[] { 123D, "[Red]$0" })!;
string unmatchedPrefix = (string)method.Invoke(null, new object?[] { 123D, unmatchedPrefixFormat })!;

Assert.Equal("$123", directivePrefix);
Assert.Equal(new string('[', 4096) + "123", unmatchedPrefix);
}

[Fact]
public void FlowDrawing_AppliesNumberFormatsToPercentDataLabels() {
OfficeDrawing drawing = OfficeChartDrawingRenderer.Render(new OfficeChartSnapshot(
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