fix github skill URL host validation

pkg/skills/installer.go

@@ -168,6 +168,36 @@ func parseGitHubRefPathParts(repoURL *url.URL, githubBaseURL string) []string {
 	return parts[len(baseParts):]
 }
 
+func isSupportedGitHubURL(repoURL *url.URL, githubBaseURL string) bool {
+	if repoURL == nil {
+		return false
+	}
+	if matchesGitHubWebBase(repoURL, "https://github.com") {
+		return true
+	}
+	trimmedBaseURL := strings.TrimSpace(githubBaseURL)
+	if trimmedBaseURL == "" {
+		return false
+	}
+	return matchesGitHubWebBase(repoURL, trimmedBaseURL)
+}
+
+func matchesGitHubWebBase(repoURL *url.URL, webBaseURL string) bool {
+	baseURL, err := url.Parse(strings.TrimSpace(webBaseURL))
+	if err != nil {
+		return false
+	}
+	if !strings.EqualFold(repoURL.Host, baseURL.Host) {
+		return false
+	}
+	basePath := strings.Trim(baseURL.Path, "/")
+	if basePath == "" {
+		return true
+	}
+	repoPath := strings.Trim(repoURL.Path, "/")
+	return repoPath == basePath || strings.HasPrefix(repoPath, basePath+"/")
+}
+
 func splitGitHubTreeOrBlobRefPath(parts []string, defaultRef string) (string, string) {
 	if len(parts) == 0 {
 		return defaultRef, ""
@@ -216,6 +246,9 @@ func parseGitHubRefWithBaseURL(repo, githubBaseURL, defaultRef string) (GitHubRe
 		if err != nil {
 			return GitHubRef{}, fmt.Errorf("invalid URL: %w", err)
 		}
+		if !isSupportedGitHubURL(u, githubBaseURL) {
+			return GitHubRef{}, fmt.Errorf("invalid GitHub URL host %q", u.Host)
+		}
 		parts := parseGitHubRefPathParts(u, githubBaseURL)
 		if len(parts) < 2 {
 			return GitHubRef{}, fmt.Errorf("invalid GitHub URL")

pkg/skills/installer_test.go

@@ -89,6 +89,12 @@ func TestParseGitHubRef(t *testing.T) {
 			wantRef:      "main",
 			wantSubPath:  "",
 		},
+		{
+			name:           "invalid non github host",
+			repo:           "https://gitlab.com/sipeed/picoclaw/-/tree/main/skills/test",
+			wantErr:        true,
+			wantErrContain: `invalid GitHub URL host "gitlab.com"`,
+		},
 	}
 
 	for _, tt := range tests {
@@ -182,6 +188,18 @@ func TestParseGitHubRefWithBaseURL(t *testing.T) {
 	if ref.SubPath != ".agents/skills/pr-review" {
 		t.Fatalf("subPath = %q, want .agents/skills/pr-review", ref.SubPath)
 	}
+
+	_, err = parseGitHubRefWithBaseURL(
+		"https://gitlab.example.com/org/repo/-/tree/dev/skills/test",
+		"https://ghe.example.com/git",
+		"main",
+	)
+	if err == nil {
+		t.Fatal("parseGitHubRefWithBaseURL() error = nil, want invalid host error")
+	}
+	if !strings.Contains(err.Error(), `invalid GitHub URL host "gitlab.example.com"`) {
+		t.Fatalf("unexpected error = %v", err)
+	}
 }
 
 func TestSkillInstallerResolveGitHubRefUsesDefaultBranch(t *testing.T) {