fix(fmt): stop share-URI query values from being decoded twice or dropped (#10027)

`Utils.ParseQueryString` already unescapes every value, and
`BaseFmt.GetQueryDecoded` unescaped it again. A value that still held a
valid percent sequence after the first pass decayed on the second: an
obfuscation password of `ob%41fs` is exported as `ob%2541fs` and imported
back as `obAfs`. Only well-formed sequences are affected, which is why the
damage is silent - `100%` and `66%ff` survive untouched.

The same function also split each pair on every `=`, and skipped the pair
unless exactly two halves came out. RFC 3986 lists `=` among the
sub-delimiters a query value may carry, so only the first one separates the
key from the value, and `HttpUtility.ParseQueryString` reads a query string
the same way. Splitting on all of them discarded a syntactically valid
pair: `?ech=AAj+DQAEAAAAAA==` was lost entirely, and so was a `plugin`
value in the non-canonical SIP002 spelling, since those are `;` separated
`key=value` lists.

v2rayN percent-encodes both on export, so its own links were never
affected; what changes is that the parser now follows the grammar instead
of discarding a pair it cannot split in two.

Splitting on the first `=` only, and reading the value the parser already
decoded, fixes both. `ParseQueryString` keeps decoding because
`ConfigHandler` reads its result directly.

`GetQueryDecoded` and `GetQueryValue` are now equivalent; they are left
separate to keep this change small, and can be collapsed if you prefer.

v2rayN/ServiceLib.Tests/Fmt/ShareUriQueryTests.cs

@@ -0,0 +1,73 @@
+namespace ServiceLib.Tests.Fmt;
+
+public class ShareUriQueryTests
+{
+    [Test]
+    [Arguments("ob%41fs")]
+    [Arguments("66%ff")]
+    [Arguments("100%")]
+    public async Task GetShareUriAndResolveConfig_QueryValueWithPercent_ShouldSurviveTheRoundTrip(string obfsPassword)
+    {
+        var source = new ProfileItem
+        {
+            ConfigType = EConfigType.Hysteria2,
+            Remarks = "percent demo",
+            Address = "hy2.example",
+            Port = 8443,
+            Password = "pw",
+        };
+        source.SetProtocolExtra(new ProtocolExtraItem { SalamanderPass = obfsPassword, });
+
+        var uri = FmtHandler.GetShareUri(source);
+
+        await uri.Should().NotBeNull();
+
+        var resolved = FmtHandler.ResolveConfig(uri!, out var msg);
+
+        await resolved.Should().NotBeNull().Because($"uri: {uri}, msg: {msg}");
+        await resolved!.GetProtocolExtra().SalamanderPass.Should().BeEqualTo(obfsPassword);
+    }
+
+    // RFC 3986 lists '=' among the sub-delimiters a query value may carry, so only the first one
+    // separates the key from the value. Splitting on every '=' discarded the pair outright.
+    [Test]
+    public async Task ResolveConfig_QueryValueWithUnescapedEquals_ShouldNotBeDropped()
+    {
+        const string shareUri = "hysteria2://pw@hy2.example:8443/?ech=AAj+DQAEAAAAAA==&sni=real.example";
+
+        var resolved = FmtHandler.ResolveConfig(shareUri, out var msg);
+
+        await resolved.Should().NotBeNull().Because($"uri: {shareUri}, msg: {msg}");
+        await resolved!.EchConfigList.Should().BeEqualTo("AAj+DQAEAAAAAA==");
+        await resolved.Sni.Should().BeEqualTo("real.example");
+    }
+
+    // Canonical SIP002 percent-encodes the plugin argument, and that is what this client's own
+    // exporter emits. This covers the non-canonical spelling instead: the options are a ';'
+    // separated list of 'key=value' pairs, so left unescaped the value always carries '='.
+    [Test]
+    public async Task ResolveConfig_NonCanonicalSip002PluginWithLiteralEquals_ShouldConfigureObfs()
+    {
+        const string shareUri =
+            "ss://YWVzLTEyOC1nY206cGFzczEyMw==@1.2.3.4:8388/?plugin=obfs-local;obfs=http;obfs-host=example.com#ss";
+
+        var resolved = FmtHandler.ResolveConfig(shareUri, out var msg);
+
+        await resolved.Should().NotBeNull().Because($"uri: {shareUri}, msg: {msg}");
+        await resolved!.ConfigType.Should().BeEqualTo(EConfigType.Shadowsocks);
+        await resolved.GetTransportExtra().Host.Should().BeEqualTo("example.com");
+        await resolved.GetTransportExtra().RawHeaderType.Should().BeEqualTo(Global.RawHeaderHttp);
+    }
+
+    [Test]
+    public async Task ResolveConfig_EscapedQueryValue_ShouldStillDecodeExactlyOnce()
+    {
+        const string shareUri = "hysteria2://pw@hy2.example:8443/?ech=AAj%2BDQAEAAAAAA%3D%3D&obfs=salamander&obfs-password=a%20b";
+
+        var resolved = FmtHandler.ResolveConfig(shareUri, out var msg);
+
+        await resolved.Should().NotBeNull().Because($"uri: {shareUri}, msg: {msg}");
+        await resolved!.EchConfigList.Should().BeEqualTo("AAj+DQAEAAAAAA==");
+        await resolved.GetProtocolExtra().SalamanderPass.Should().BeEqualTo("a b");
+    }
+}

v2rayN/ServiceLib/Common/Utils.cs

@@ -200,7 +200,9 @@ public class Utils
         var parts = query[1..].Split('&', StringSplitOptions.RemoveEmptyEntries);
         foreach (var part in parts)
         {
-            var keyValue = part.Split('=');
+            // Split on the FIRST '=' only: RFC 3986 lists '=' among the sub-delimiters a query
+            // value may carry, so everything after the first one belongs to the value.
+            var keyValue = part.Split('=', 2);
             if (keyValue.Length != 2)
             {
                 continue;

v2rayN/ServiceLib/Handler/Fmt/BaseFmt.cs

@@ -342,8 +342,13 @@ public class BaseFmt
         return query[key] ?? defaultValue;
     }
 
+    /// <summary>
+    /// Values are already unescaped by <see cref="Utils.ParseQueryString" />, so this must not
+    /// unescape them a second time: a value that still holds a valid percent sequence after the
+    /// first pass - an obfuscation password of "ob%41fs", say - would decay into "obAfs".
+    /// </summary>
     protected static string GetQueryDecoded(NameValueCollection query, string key, string defaultValue = "")
     {
-        return Utils.UrlDecode(GetQueryValue(query, key, defaultValue));
+        return GetQueryValue(query, key, defaultValue);
     }
 }