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This probe sends a DTLS 1.2 (RFC 6347) ClientHello and solicits a server response, which should be either ServerHello or HelloVerifyRequest. The standard UDP port for DTLS is 443. Servers that support only DTLS 1.0 should respond as well, although some are buggy and cannot gracefully negotiate a supported version. This includes older Fortinet SSL-VPN servers: https://gitlab.com/openconnect/openconnect/commit/bfbe33bc081e1015805f6c801a2a116a09bba90e This probe packet was generated using gnutls-cli v3.7.1 via `gnutls-cli --udp --priority 'NORMAL:%NO_EXTENSIONS'`. If you want to send a more realistic, or at least less repeated, client random value, then replace the 32 repeating 0xa5 bytes at offset 0x1b with a new random value.
zakird
approved these changes
Jul 15, 2024
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This probe sends a DTLS 1.2 (RFC 6347) ClientHello and solicits a server response, which should be either ServerHello or HelloVerifyRequest. The standard UDP port for DTLS is 443.
Servers that support only DTLS 1.0 should respond as well, although some are buggy and cannot gracefully negotiate a supported version. This includes older Fortinet SSL-VPN servers:
https://gitlab.com/openconnect/openconnect/commit/bfbe33bc081e1015805f6c801a2a116a09bba90e
This probe packet was generated using gnutls-cli v3.7.1 via
gnutls-cli --udp --priority 'NORMAL:%NO_EXTENSIONS'. If you want to send a more realistic, or at least less repeated, client random value, then replace the 32 repeating 0xa5 bytes at offset 0x1b with a new random value.