mirror of https://github.com/ospab/ostp.git
74 lines
2.3 KiB
Rust
74 lines
2.3 KiB
Rust
pub fn extract_sni(data: &[u8]) -> Option<String> {
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// Basic TLS ClientHello parser
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// Must be at least 43 bytes to contain anything useful
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if data.len() < 43 {
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return None;
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}
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// TLS Record layer: Handshake (22)
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if data[0] != 0x16 {
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return None;
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}
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// Record layer version: 0x0301 (TLS 1.0) or 0x0303 (TLS 1.2)
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if data[1] != 0x03 {
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return None;
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}
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// Handshake type: ClientHello (1)
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if data[5] != 0x01 {
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return None;
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}
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let mut pos = 43; // Skip fixed ClientHello header
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// Skip Session ID
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if pos >= data.len() { return None; }
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let session_id_len = data[pos] as usize;
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pos += 1 + session_id_len;
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// Skip Cipher Suites
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if pos + 2 > data.len() { return None; }
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let cipher_suites_len = ((data[pos] as usize) << 8) | (data[pos + 1] as usize);
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pos += 2 + cipher_suites_len;
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// Skip Compression Methods
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if pos >= data.len() { return None; }
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let comp_methods_len = data[pos] as usize;
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pos += 1 + comp_methods_len;
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// Extensions
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if pos + 2 > data.len() { return None; }
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let extensions_len = ((data[pos] as usize) << 8) | (data[pos + 1] as usize);
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pos += 2;
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let extensions_end = pos + extensions_len;
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if extensions_end > data.len() { return None; }
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while pos + 4 <= extensions_end {
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let ext_type = ((data[pos] as usize) << 8) | (data[pos + 1] as usize);
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let ext_len = ((data[pos + 2] as usize) << 8) | (data[pos + 3] as usize);
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pos += 4;
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if ext_type == 0x0000 { // Server Name Indication (SNI)
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if pos + 5 <= extensions_end {
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let _list_len = ((data[pos] as usize) << 8) | (data[pos + 1] as usize);
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let name_type = data[pos + 2];
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if name_type == 0 { // Hostname
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let name_len = ((data[pos + 3] as usize) << 8) | (data[pos + 4] as usize);
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if pos + 5 + name_len <= extensions_end {
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let sni_bytes = &data[pos + 5..pos + 5 + name_len];
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if let Ok(sni) = std::str::from_utf8(sni_bytes) {
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return Some(sni.to_string());
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}
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}
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}
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}
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break;
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}
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pos += ext_len;
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}
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None
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}
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