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fix: Improved Portainer authentication jwt expiry handling #113

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fix: Improved Portainer authentication jwt expiry handling #113

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36 changes: 36 additions & 0 deletions PatchPanda.Web/Helpers/JwtHelper.cs
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Original file line number Diff line number Diff line change
@@ -0,0 +1,36 @@
using System.Text.Json;

namespace PatchPanda.Web.Helpers;

public class JwtHelper
{
public static DateTime? GetJwtExpiry(string jwt)
{
try
{
var parts = jwt.Split('.');
if (parts.Length < 2) return null;
Comment on lines +7 to +12
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@coderabbitai coderabbitai bot Jan 21, 2026

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⚠️ Potential issue | 🟡 Minor

Guard against null/whitespace and malformed JWTs to avoid invalid caching.

jwt can still be null/empty at runtime, and accepting 2-part tokens can treat malformed JWTs as valid. Add an early guard and require exactly 3 parts.

🛠️ Proposed fix 
public static DateTime? GetJwtExpiry(string jwt)
{
+    if (string.IsNullOrWhiteSpace(jwt)) return null;
     try
     {
         var parts = jwt.Split('.');
-        if (parts.Length < 2) return null;
+        if (parts.Length != 3) return null;
📝 Committable suggestion

‼️ IMPORTANT
Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation. Thoroughly test & benchmark the code to ensure it meets the requirements.

Suggested change
public static DateTime? GetJwtExpiry(string jwt)
{
try
{
var parts = jwt.Split('.');
if (parts.Length < 2) return null;
public static DateTime? GetJwtExpiry(string jwt)
{
if (string.IsNullOrWhiteSpace(jwt)) return null;
try
{
var parts = jwt.Split('.');
if (parts.Length != 3) return null;
🤖 Prompt for AI Agents 
In `@PatchPanda.Web/Helpers/JwtHelper.cs` around lines 7 - 12, GetJwtExpiry
currently accepts null/empty and 2-part strings which can treat malformed tokens
as valid; add an early guard in GetJwtExpiry to return null if the jwt parameter
is null, empty, or whitespace, then require that jwt.Split('.') yields exactly 3
parts (not >=2) before proceeding; if the parts count is not 3, return null to
avoid parsing invalid tokens and invalid caching.


var payload = parts[1];
var base64 = payload.Replace('-', '+').Replace('_', '/');
switch (base64.Length % 4)
{
case 2: base64 += "=="; break;
case 3: base64 += "="; break;
}

var bytes = Convert.FromBase64String(base64);
using var doc = JsonDocument.Parse(bytes);
if (doc.RootElement.TryGetProperty("exp", out var expElement) && expElement.TryGetInt64(out var exp))
{
return DateTimeOffset.FromUnixTimeSeconds(exp).UtcDateTime;
}
}
catch
{
return null;
}

return null;
}
}
7 changes: 5 additions & 2 deletions PatchPanda.Web/Services/PortainerService.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -67,6 +67,8 @@ private async Task EnsureAuthenticatedAsync()
return;
}

_logger.LogInformation("Using username and password to authenticate with Portainer...");

var payload = JsonSerializer.Serialize(new { username = _username, password = _password });
var resp = await _httpClient.PostAsync(
"/api/auth",
Expand Down Expand Up @@ -94,10 +96,11 @@ private async Task EnsureAuthenticatedAsync()
"Bearer",
_jwt
);
_jwtExpiry = DateTime.UtcNow.AddHours(8);
_jwtExpiry = JwtHelper.GetJwtExpiry(_jwt) ?? DateTime.UtcNow.AddHours(8);
_logger.LogInformation("Portainer authentication successful.");
Comment on lines +99 to +100
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@coderabbitai coderabbitai bot Jan 21, 2026

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🧹 Nitpick | 🔵 Trivial

Consider a small clock-skew buffer when storing JWT expiry.

Using the exact exp can cause near-expiry requests to fail if clocks drift or the request is in-flight.

🧩 Suggested tweak 
-            _jwtExpiry = JwtHelper.GetJwtExpiry(_jwt) ?? DateTime.UtcNow.AddHours(8);
+            var exp = JwtHelper.GetJwtExpiry(_jwt);
+            _jwtExpiry = exp?.AddSeconds(-60) ?? DateTime.UtcNow.AddHours(8);
📝 Committable suggestion

‼️ IMPORTANT
Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation. Thoroughly test & benchmark the code to ensure it meets the requirements.

Suggested change
_jwtExpiry = JwtHelper.GetJwtExpiry(_jwt) ?? DateTime.UtcNow.AddHours(8);
_logger.LogInformation("Portainer authentication successful.");
var exp = JwtHelper.GetJwtExpiry(_jwt);
_jwtExpiry = exp?.AddSeconds(-60) ?? DateTime.UtcNow.AddHours(8);
_logger.LogInformation("Portainer authentication successful.");
🤖 Prompt for AI Agents 
In `@PatchPanda.Web/Services/PortainerService.cs` around lines 99 - 100, Adjust
how the JWT expiry is stored to include a small clock-skew buffer: when setting
_jwtExpiry from JwtHelper.GetJwtExpiry(_jwt) (or the fallback
DateTime.UtcNow.AddHours(8)), subtract a short buffer (e.g., 1–2 minutes) so you
consider tokens expired slightly before the exact exp claim to avoid
near-expiry/in-flight failures; update the assignment to compute the expiry
value, apply TimeSpan.FromMinutes(1) (or chosen buffer) subtraction, and store
that in _jwtExpiry.

}
else
_logger.LogWarning("Failed parsing Portainer auth response");
_logger.LogWarning("Failed parsing Portainer auth response.");
}

private async Task<PortainerStackDto?> GetStack(string stackName)
Expand Down
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