Skip to content

fix(scan): truncate shodan banners on rune boundaries #326

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
vmfunc merged 1 commit into from
Jul 22, 2026
Merged

fix(scan): truncate shodan banners on rune boundaries #326

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
4 changes: 2 additions & 2 deletions internal/scan/shodan.go
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -260,8 +260,8 @@ func truncateBanner(banner string, maxLen int) string {
banner = strings.ReplaceAll(banner, "\r\n", " ")
banner = strings.ReplaceAll(banner, "\n", " ")

if len(banner) > maxLen {
return banner[:maxLen] + "..."
if runes := []rune(banner); len(runes) > maxLen {
return string(runes[:maxLen]) + "..."
}
return banner
}
Expand Down
7 changes: 7 additions & 0 deletions internal/scan/shodan_test.go
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -18,6 +18,7 @@ import (
"net/http/httptest"
"testing"
"time"
"unicode/utf8"
)

func TestResolveHostname_IP(t *testing.T) {
Expand Down Expand Up @@ -50,13 +51,19 @@ func TestTruncateBanner(t *testing.T) {
{"this is a long banner", 10, "this is a ..."},
{"with\nnewlines\r\n", 50, "with newlines"},
{" trimmed ", 50, "trimmed"},
// truncation must land on a rune boundary, not split a multibyte rune
{"aaaé", 4, "aaaé"},
{"日本語テスト", 3, "日本語..."},
}

for _, tt := range tests {
result := truncateBanner(tt.input, tt.maxLen)
if result != tt.expected {
t.Errorf("truncateBanner(%q, %d) = %q, want %q", tt.input, tt.maxLen, result, tt.expected)
}
if !utf8.ValidString(result) {
t.Errorf("truncateBanner(%q, %d) produced invalid UTF-8: %q", tt.input, tt.maxLen, result)
}
}
}

Expand Down
Loading