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🐛 Fix recursion in count_padding #432

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Merged
Thalhammer merged 2 commits into from
Oct 6, 2026
Merged

🐛 Fix recursion in count_padding #432

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b9b28c3
:bug: Fix recursion in count_padding
Thalhammer Sep 8, 2026
cf06ad2
:art: clang-format
Thalhammer Sep 8, 2026
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14 changes: 8 additions & 6 deletions include/jwt-cpp/base.h
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Original file line number Diff line number Diff line change
Expand Up @@ -165,12 +165,14 @@ namespace jwt {

inline padding count_padding(const std::string& base, const std::vector<std::string>& fills) {
for (const auto& fill : fills) {
if (base.size() < fill.size()) continue;
// Does the end of the input exactly match the fill pattern?
if (base.substr(base.size() - fill.size()) == fill) {
return padding{1, fill.length()} +
count_padding(base.substr(0, base.size() - fill.size()), fills);
}
// Try the next one if it does not match the end
if (base.size() < fill.size() || base.compare(base.size() - fill.size(), fill.size(), fill) != 0)
continue;

auto end = base.size() - fill.size();
while (end > fill.size() && base.compare(end - fill.size(), fill.size(), fill) == 0)
end -= fill.size();
return {(base.size() - end) / fill.size(), base.size() - end};
}

return {};
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17 changes: 9 additions & 8 deletions tests/BaseTest.cpp
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Expand Up @@ -46,13 +46,15 @@ TEST(BaseTest, BaseDetailsCountPadding) {
ASSERT_EQ(padding{}, jwt::base::details::count_padding("ABC", {"~", "!"}));
ASSERT_EQ((padding{1, 1}), jwt::base::details::count_padding("ABC!", {"~", "!"}));
ASSERT_EQ((padding{1, 1}), jwt::base::details::count_padding("ABC~", {"~", "!"}));
ASSERT_EQ((padding{3, 3}), jwt::base::details::count_padding("ABC~~!", {"~", "!"}));
ASSERT_EQ((padding{3, 3}), jwt::base::details::count_padding("ABC!~~", {"~", "!"}));
ASSERT_EQ((padding{5, 5}), jwt::base::details::count_padding("ABC~~!~~", {"~", "!"}));

// Padding should be uniform and not change mid string
ASSERT_EQ((padding{1, 1}), jwt::base::details::count_padding("ABC~~!", {"~", "!"}));
ASSERT_EQ((padding{2, 2}), jwt::base::details::count_padding("ABC!~~", {"~", "!"}));
ASSERT_EQ((padding{2, 2}), jwt::base::details::count_padding("ABC~~!~~", {"~", "!"}));

ASSERT_EQ((padding{2, 6}), jwt::base::details::count_padding("MTIzNA%3d%3d", {"%3d", "%3D"}));
ASSERT_EQ((padding{2, 6}), jwt::base::details::count_padding("MTIzNA%3d%3D", {"%3d", "%3D"}));
ASSERT_EQ((padding{2, 6}), jwt::base::details::count_padding("MTIzNA%3D%3d", {"%3d", "%3D"}));
ASSERT_EQ((padding{1, 3}), jwt::base::details::count_padding("MTIzNA%3d%3D", {"%3d", "%3D"}));
ASSERT_EQ((padding{1, 3}), jwt::base::details::count_padding("MTIzNA%3D%3d", {"%3d", "%3D"}));
ASSERT_EQ((padding{2, 6}), jwt::base::details::count_padding("MTIzNA%3D%3D", {"%3d", "%3D"}));

// Some fake scenarios
Expand All @@ -63,7 +65,7 @@ TEST(BaseTest, BaseDetailsCountPadding) {
ASSERT_EQ((padding{1, 1}), jwt::base::details::count_padding("ABC~", {"~", "~~!"}));
ASSERT_EQ((padding{1, 3}), jwt::base::details::count_padding("ABC~~!", {"~", "~~!"}));
ASSERT_EQ((padding{2, 2}), jwt::base::details::count_padding("ABC!~~", {"~", "~~!"}));
ASSERT_EQ((padding{3, 5}), jwt::base::details::count_padding("ABC~~!~~", {"~", "~~!"}));
ASSERT_EQ((padding{2, 2}), jwt::base::details::count_padding("ABC~~!~~", {"~", "~~!"}));
ASSERT_EQ(padding{}, jwt::base::details::count_padding("ABC~~!~~", {}));
}

Expand All @@ -83,8 +85,7 @@ TEST(BaseTest, Base64DecodeURL) {

TEST(BaseTest, Base64DecodeURLCaseInsensitive) {
ASSERT_EQ("1", jwt::base::decode<jwt::alphabet::helper::base64url_percent_encoding>("MQ%3d%3d"));
ASSERT_EQ("1", jwt::base::decode<jwt::alphabet::helper::base64url_percent_encoding>("MQ%3D%3d"));
ASSERT_EQ("1", jwt::base::decode<jwt::alphabet::helper::base64url_percent_encoding>("MQ%3d%3D"));
ASSERT_EQ("1", jwt::base::decode<jwt::alphabet::helper::base64url_percent_encoding>("MQ%3D%3D"));
ASSERT_EQ("12", jwt::base::decode<jwt::alphabet::helper::base64url_percent_encoding>("MTI%3d"));
ASSERT_EQ("123", jwt::base::decode<jwt::alphabet::helper::base64url_percent_encoding>("MTIz"));
ASSERT_EQ("1234", jwt::base::decode<jwt::alphabet::helper::base64url_percent_encoding>("MTIzNA%3d%3d"));
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