feat: implement permission filtering system (fixes #177)

docs/permission-system.md

@@ -0,0 +1,297 @@
+# Permission Filtering System
+
+The SonarQube MCP server includes a comprehensive permission filtering system that ensures users only see data they're authorized to access based on their groups and roles from the OAuth token.
+
+## Overview
+
+The permission system provides:
+
+- **Group-based access control**: Map OAuth token groups/roles to permissions
+- **Project filtering**: Control access to projects using regex patterns
+- **Tool authorization**: Allow/deny access to specific MCP tools
+- **Issue filtering**: Filter issues by severity and status
+- **Sensitive data redaction**: Hide author/assignee information when needed
+- **Write operation control**: Separate read and write permissions
+- **Performance optimization**: Built-in caching for permission checks
+
+## Configuration
+
+### Environment Variable
+
+Set the path to your permission configuration file:
+
+```bash
+export MCP_PERMISSION_CONFIG_PATH=/path/to/permissions.json
+```
+
+### Configuration File Format
+
+The permission configuration is a JSON file with the following structure:
+
+```json
+{
+  "rules": [
+    {
+      "groups": ["admin", "sonarqube-admin"],
+      "allowedProjects": [".*"],
+      "allowedTools": [
+        "projects", "metrics", "issues", "markIssueFalsePositive",
+        "markIssueWontFix", "markIssuesFalsePositive", "markIssuesWontFix",
+        "addCommentToIssue", "assignIssue", "confirmIssue", "unconfirmIssue",
+        "resolveIssue", "reopenIssue", "system_health", "system_status",
+        "system_ping", "measures_component", "measures_components",
+        "measures_history", "quality_gates", "quality_gate",
+        "quality_gate_status", "source_code", "scm_blame",
+        "hotspots", "hotspot", "update_hotspot_status", "components"
+      ],
+      "readonly": false,
+      "priority": 100
+    },
+    {
+      "groups": ["developer", "dev"],
+      "allowedProjects": ["^(dev-|feature-|test-).*"],
+      "allowedTools": [
+        "projects", "metrics", "issues", "markIssueFalsePositive",
+        "markIssueWontFix", "addCommentToIssue", "assignIssue",
+        "confirmIssue", "unconfirmIssue", "measures_component",
+        "measures_components", "measures_history", "quality_gate_status",
+        "source_code", "scm_blame", "components"
+      ],
+      "deniedTools": ["system_health", "system_status"],
+      "readonly": false,
+      "maxSeverity": "CRITICAL",
+      "priority": 50
+    },
+    {
+      "groups": ["qa", "quality-assurance"],
+      "allowedProjects": [".*"],
+      "allowedTools": [
+        "projects", "metrics", "issues", "measures_component",
+        "measures_components", "measures_history", "quality_gates",
+        "quality_gate", "quality_gate_status", "source_code",
+        "hotspots", "hotspot", "components"
+      ],
+      "readonly": true,
+      "priority": 40
+    },
+    {
+      "groups": ["guest", "viewer"],
+      "allowedProjects": ["^public-.*"],
+      "allowedTools": [
+        "projects", "metrics", "issues", "quality_gate_status"
+      ],
+      "readonly": true,
+      "maxSeverity": "MAJOR",
+      "hideSensitiveData": true,
+      "priority": 10
+    }
+  ],
+  "defaultRule": {
+    "allowedProjects": [],
+    "allowedTools": [],
+    "readonly": true
+  },
+  "enableCaching": true,
+  "cacheTtl": 300,
+  "enableAudit": false
+}
+```
+
+## Permission Rule Properties
+
+### Required Properties
+
+- **`allowedProjects`** (string[]): Array of regex patterns for allowed projects
+  - Use `[".*"]` to allow all projects
+  - Use `["^prefix-.*"]` to allow projects starting with "prefix-"
+  - Empty array `[]` means no projects allowed
+
+- **`allowedTools`** (string[]): Array of allowed MCP tool names
+  - See "Available Tools" section for complete list
+  - Empty array means no tools allowed
+
+- **`readonly`** (boolean): Whether the user has read-only access
+  - `true`: Can only use read tools
+  - `false`: Can use both read and write tools
+
+### Optional Properties
+
+- **`groups`** (string[]): Groups this rule applies to
+  - If omitted, rule applies to all groups
+  - Matches against groups/roles from OAuth token
+
+- **`deniedTools`** (string[]): Tools explicitly denied
+  - Takes precedence over `allowedTools`
+  - Useful for exceptions
+
+- **`maxSeverity`** (string): Maximum issue severity visible
+  - Options: `INFO`, `MINOR`, `MAJOR`, `CRITICAL`, `BLOCKER`
+  - Users won't see issues above this severity
+
+- **`allowedStatuses`** (string[]): Allowed issue statuses
+  - Options: `OPEN`, `CONFIRMED`, `REOPENED`, `RESOLVED`, `CLOSED`
+  - If specified, only these statuses are visible
+
+- **`hideSensitiveData`** (boolean): Redact sensitive information
+  - Hides author, assignee, comments, and changelog
+
+- **`priority`** (number): Rule priority (higher = higher priority)
+  - Default: 0
+  - When user has multiple groups, highest priority rule applies
+
+## Available Tools
+
+### Read Operations
+- `projects` - List all projects
+- `metrics` - Get available metrics
+- `issues` - Search and filter issues
+- `system_health` - Get system health status
+- `system_status` - Get system status
+- `system_ping` - Ping the system
+- `measures_component` - Get measures for a component
+- `measures_components` - Get measures for multiple components
+- `measures_history` - Get measures history
+- `quality_gates` - List quality gates
+- `quality_gate` - Get quality gate details
+- `quality_gate_status` - Get quality gate status
+- `source_code` - View source code
+- `scm_blame` - Get SCM blame information
+- `hotspots` - Search security hotspots
+- `hotspot` - Get hotspot details
+- `components` - Search and navigate components
+
+### Write Operations
+- `markIssueFalsePositive` - Mark issue as false positive
+- `markIssueWontFix` - Mark issue as won't fix
+- `markIssuesFalsePositive` - Bulk mark issues as false positive
+- `markIssuesWontFix` - Bulk mark issues as won't fix
+- `addCommentToIssue` - Add comment to issue
+- `assignIssue` - Assign/unassign issue
+- `confirmIssue` - Confirm issue
+- `unconfirmIssue` - Unconfirm issue
+- `resolveIssue` - Resolve issue
+- `reopenIssue` - Reopen issue
+- `update_hotspot_status` - Update security hotspot status
+
+## Group Extraction
+
+The system extracts groups from OAuth tokens using these claim names:
+- `groups` (preferred)
+- `group`
+- `roles`
+- `role`
+- `authorities`
+
+Groups can be:
+- Array: `["admin", "developer"]`
+- Comma-separated string: `"admin,developer"`
+- Space-separated string: `"admin developer"`
+
+## Security Considerations
+
+### Fail-Closed Design
+- If no rules match, access is denied by default
+- Explicit `defaultRule` required to change this behavior
+- No information leakage in error messages
+
+### Rule Evaluation
+1. Rules are sorted by priority (descending)
+2. First matching rule is applied
+3. `deniedTools` takes precedence over `allowedTools`
+4. Write operations require `readonly: false`
+
+### Performance
+- Permission checks are cached (configurable TTL)
+- Regex patterns are compiled once and reused
+- Audit logging available for debugging
+
+## Examples
+
+### Development Team Configuration
+
+```json
+{
+  "rules": [
+    {
+      "groups": ["frontend-team"],
+      "allowedProjects": ["^frontend-.*", "^ui-.*"],
+      "allowedTools": ["issues", "measures_component", "source_code"],
+      "readonly": false,
+      "maxSeverity": "CRITICAL"
+    },
+    {
+      "groups": ["backend-team"],
+      "allowedProjects": ["^api-.*", "^service-.*"],
+      "allowedTools": ["issues", "measures_component", "source_code", "hotspots"],
+      "readonly": false
+    }
+  ],
+  "defaultRule": {
+    "allowedProjects": [],
+    "allowedTools": [],
+    "readonly": true
+  }
+}
+```
+
+### Multi-Environment Configuration
+
+```json
+{
+  "rules": [
+    {
+      "groups": ["prod-access"],
+      "allowedProjects": ["^prod-.*"],
+      "allowedTools": ["issues", "quality_gate_status", "measures_component"],
+      "readonly": true,
+      "hideSensitiveData": true
+    },
+    {
+      "groups": ["staging-access"],
+      "allowedProjects": ["^staging-.*"],
+      "allowedTools": ["issues", "quality_gate_status", "measures_component", "source_code"],
+      "readonly": false,
+      "maxSeverity": "CRITICAL"
+    }
+  ]
+}
+```
+
+## Testing Your Configuration
+
+1. Create a test configuration file
+2. Set the environment variable
+3. Start the server with HTTP transport
+4. Make authenticated requests with different group claims
+5. Verify filtering behavior
+
+## Troubleshooting
+
+### Enable Audit Logging
+
+Set `"enableAudit": true` in your configuration to log all permission checks:
+
+```json
+{
+  "enableAudit": true,
+  "rules": [...]
+}
+```
+
+### Common Issues
+
+1. **No projects visible**: Check `allowedProjects` regex patterns
+2. **Tools access denied**: Verify tool names in `allowedTools`
+3. **Write operations failing**: Ensure `readonly: false`
+4. **Wrong rule applied**: Check rule priorities and group matching
+
+## Integration with OAuth Providers
+
+The permission system integrates with any OAuth 2.0 provider that includes group/role information in tokens:
+
+- **Keycloak**: Configure client mappers to include groups
+- **Auth0**: Add groups to custom claims
+- **Okta**: Include groups in token claims
+- **Azure AD**: Map AD groups to token claims
+
+Ensure your OAuth provider is configured to include group information in the access token or ID token used for authentication.