Looks like the telnet dissector could go a step farther and break out the IV.
Original added here: "updated the TELNET dissector to dissect encryption negotiation
commands as specified by RFC 2946"
RFC 2952 - "Telnet Encryption: DES 64 bit Cipher Feedback"
1. Command Names and Codes
Encryption Type
DES_CFB64 1
Suboption Commands
CFB64_IV 1
CFB64_IV_OK 2
CFB64_IV_BAD 3
2. Command Meanings
IAC SB ENCRYPT IS DES_CFB64 CFB64_IV <initial vector> IAC SE
The extra byte (01) before the IV in your data: Type-specific data: 011213141516171819 is the Suboption Command to indicate an IV follows.
I don't see any open issues related to this.
Steps to open one here: ReportingBugs
#define TN_ENCTYPE_NULL 0
#define TN_ENCTYPE_DES_CFB64 1 https://tools.ietf.org/html/rfc2952
#define TN_ENCTYPE_DES_OFB64 2 https://tools.ietf.org/html/rfc2953
#define TN_ENCTYPE_DES3_CFB64 3 https://tools.ietf.org/html/rfc2947
#define TN_ENCTYPE_DES3_OFB64 4 https://tools.ietf.org/html/rfc2948
#define TN_ENCTYPE_CAST5_40_CFB64 8 https://tools.ietf.org/html/rfc2950
#define TN_ENCTYPE_CAST5_40_OFB64 9 https://tools.ietf.org/html/rfc2949
#define TN_ENCTYPE_CAST128_CFB64 10 https://tools.ietf.org/html/rfc2950
#define TN_ENCTYPE_CAST128_OFB64 11 https://tools.ietf.org/html/rfc2949
The RFCs for currently supported encryption types use the same verbage:
The sender of this command generates a random 8 byte initial
vector, and sends it to the other side of the connection using the
"encryption type"_IV command.
As per RFC 2946 this depends on the selected type of encryption. These are further referenced in the IANA registry.
These documents don't specify what the telnet.enc.type_data refer to. in my case, the telnet encryption type is DES_CFB64 so the telnet.enc.type_data could be the IV, but the problem is the IV must be 8 bytes and the telnet.enc.type_data is 9 byte (011213141516171819)
here is the entire packet:
Frame 4: 82 bytes on wire (656 bits), 82 bytes captured (656 bits) Ethernet II, Src: xxx, Dst: xxx Internet Protocol Version 4, Src: x.x.x.x, Dst: x.x.x.x Transmission Control Protocol, Src Port: 42818, Dst Port: 23, Seq: 1, Ack: 1, Len: 16 Telnet Suboption Encryption Option Command: Suboption (250) Subcommand: Encryption Option Enc Cmd: IS (0) Enc Type: DES_CFB64 (1) Type-specific data: 011213141516171819 Suboption End Command: Suboption End (240)
any help in what the telnet.enc.type_data ( Type-specific data) refer to?
Asked: 2021-02-02 08:44:04 +0000
Seen: 412 times
Last updated: Feb 02 '21
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