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Merge pull request #13812 from obsidiansystems/url-parse-leniency

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Limit to lenient parsing of non-standard URLs only where needed
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John Ericson 2025-08-23 10:53:59 -04:00 • committed by GitHub
commit 2fa2c0b09f
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8 changed files with 76 additions and 51 deletions
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12
src/libutil/include/nix/util/url.hh
View file

@ -96,14 +96,18 @@ MakeError(BadURL, Error);
std::string percentDecode(std::string_view in);
std::string percentEncode(std::string_view s, std::string_view keep = "");
StringMap decodeQuery(const std::string & query);
/**
* @param lenient @see parseURL
*/
StringMap decodeQuery(std::string_view query, bool lenient = false);
std::string encodeQuery(const StringMap & query);
/**
* Parse a Nix URL into a ParsedURL.
* Parse a URL into a ParsedURL.
*
* Nix URI is mostly compliant with RFC3986, but with some deviations:
* @parm lenient Also allow some long-supported Nix URIs that are not quite compliant with RFC3986.
* Here are the deviations:
* - Fragments can contain unescaped (not URL encoded) '^', '"' or space literals.
* - Queries may contain unescaped '"' or spaces.
*
@ -111,7 +115,7 @@ std::string encodeQuery(const StringMap & query);
*
* @throws BadURL
*/
ParsedURL parseURL(std::string_view url);
ParsedURL parseURL(std::string_view url, bool lenient = false);
/**
* Although that’s not really standardized anywhere, an number of tools

68
src/libutil/url.cc
View file

@ -108,41 +108,48 @@ static std::string percentEncodeCharSet(std::string_view s, auto charSet)
return res;
}
ParsedURL parseURL(std::string_view url)
ParsedURL parseURL(std::string_view url, bool lenient)
try {
/* Account for several non-standard properties of nix urls (for back-compat):
* - Allow unescaped spaces ' ' and '"' characters in queries.
* - Allow '"', ' ' and '^' characters in the fragment component.
* We could write our own grammar for this, but fixing it up here seems
* more concise, since the deviation is rather minor.
*
* If `!lenient` don't bother initializing, because we can just
* parse `url` directly`.
*/
std::string fixedEncodedUrl = [&]() {
std::string fixed;
std::string_view view = url;
std::string fixedEncodedUrl;
if (auto beforeQuery = splitPrefixTo(view, '?')) {
fixed += *beforeQuery;
fixed += '?';
auto fragmentStart = view.find('#');
auto queryView = view.substr(0, fragmentStart);
auto fixedQuery = percentEncodeCharSet(queryView, extraAllowedCharsInQuery);
fixed += fixedQuery;
view.remove_prefix(std::min(fragmentStart, view.size()));
}
if (lenient) {
fixedEncodedUrl = [&] {
std::string fixed;
std::string_view view = url;
if (auto beforeFragment = splitPrefixTo(view, '#')) {
fixed += *beforeFragment;
fixed += '#';
auto fixedFragment = percentEncodeCharSet(view, extraAllowedCharsInFragment);
fixed += fixedFragment;
if (auto beforeQuery = splitPrefixTo(view, '?')) {
fixed += *beforeQuery;
fixed += '?';
auto fragmentStart = view.find('#');
auto queryView = view.substr(0, fragmentStart);
auto fixedQuery = percentEncodeCharSet(queryView, extraAllowedCharsInQuery);
fixed += fixedQuery;
view.remove_prefix(std::min(fragmentStart, view.size()));
}
if (auto beforeFragment = splitPrefixTo(view, '#')) {
fixed += *beforeFragment;
fixed += '#';
auto fixedFragment = percentEncodeCharSet(view, extraAllowedCharsInFragment);
fixed += fixedFragment;
return fixed;
}
fixed += view;
return fixed;
}
}();
}
fixed += view;
return fixed;
}();
auto urlView = boost::urls::url_view(fixedEncodedUrl);
auto urlView = boost::urls::url_view(lenient ? fixedEncodedUrl : url);
if (!urlView.has_scheme())
throw BadURL("'%s' doesn't have a scheme", url);
@ -179,7 +186,7 @@ try {
.scheme = scheme,
.authority = authority,
.path = path,
.query = decodeQuery(std::string(query)),
.query = decodeQuery(query, lenient),
.fragment = fragment,
};
} catch (boost::system::system_error & e) {
@ -201,14 +208,17 @@ std::string percentEncode(std::string_view s, std::string_view keep)
s, [keep](char c) { return boost::urls::unreserved_chars(c) || keep.find(c) != keep.npos; });
}
StringMap decodeQuery(const std::string & query)
StringMap decodeQuery(std::string_view query, bool lenient)
try {
/* For back-compat unescaped characters are allowed. */
auto fixedEncodedQuery = percentEncodeCharSet(query, extraAllowedCharsInQuery);
/* When `lenient = true`, for back-compat unescaped characters are allowed. */
std::string fixedEncodedQuery;
if (lenient) {
fixedEncodedQuery = percentEncodeCharSet(query, extraAllowedCharsInQuery);
}
StringMap result;
auto encodedQuery = boost::urls::params_encoded_view(fixedEncodedQuery);
auto encodedQuery = boost::urls::params_encoded_view(lenient ? fixedEncodedQuery : query);
for (auto && [key, value, value_specified] : encodedQuery) {
if (!value_specified) {
warn("dubious URI query '%s' is missing equal sign '%s', ignoring", std::string_view(key), "=");