draft-ietf-secsh-transport-17.2.ps
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PS
2,068 行
/fdir () def/ftail () def/user_header_p false def%%EndPageSetup5 723 M(Internet-Draft SSH Transport Layer Protocol Oct 2003) s5 690 M( way that is compatible with the installed SSH clients and servers) s5 679 M( that use an older version of the protocol. Information in this) s5 668 M( section is only relevant for implementations supporting compatibility) s5 657 M( with SSH versions 1.x. There is no standards track or informational) s5 646 M( draft available that defines the SSH 1.x protocol. The only known) s5 635 M( documentation of the 1.x protocol is contained in README files that) s5 624 M( are shipped along with the source code.) s5 602 M(4.3.1 Old Client, New Server) s5 580 M( Server implementations MAY support a configurable "compatibility") s5 569 M( flag that enables compatibility with old versions. When this flag is) s5 558 M( on, the server SHOULD identify its protocol version as "1.99".) s5 547 M( Clients using protocol 2.0 MUST be able to identify this as identical) s5 536 M( to "2.0". In this mode the server SHOULD NOT send the carriage) s5 525 M( return character \(ASCII 13\) after the version identification string.) s5 503 M( In the compatibility mode the server SHOULD NOT send any further data) s5 492 M( after its initialization string until it has received an) s5 481 M( identification string from the client. The server can then determine) s5 470 M( whether the client is using an old protocol, and can revert to the) s5 459 M( old protocol if required. In the compatibility mode, the server MUST) s5 448 M( NOT send additional data before the version string.) s5 426 M( When compatibility with old clients is not needed, the server MAY) s5 415 M( send its initial key exchange data immediately after the) s5 404 M( identification string.) s5 382 M(4.3.2 New Client, Old Server) s5 360 M( Since the new client MAY immediately send additional data after its) s5 349 M( identification string \(before receiving server's identification\), the) s5 338 M( old protocol may already have been corrupted when the client learns) s5 327 M( that the server is old. When this happens, the client SHOULD close) s5 316 M( the connection to the server, and reconnect using the old protocol.) s5 294 M(5. Binary Packet Protocol) s5 272 M( Each packet is in the following format:) s5 250 M( uint32 packet_length) s5 239 M( byte padding_length) s5 228 M( byte[n1] payload; n1 = packet_length - padding_length - 1) s5 217 M( byte[n2] random padding; n2 = padding_length) s5 206 M( byte[m] mac \(message authentication code\); m = mac_length) s5 184 M( packet_length) s5 129 M(Ylonen & Moffat, Editor Expires March 31, 2004 [Page 5]) s_RSPStoPSsaved restoreuserdict/PStoPSsaved save putPStoPSmatrix setmatrix595.000000 421.271378 translate90 rotate0.706651 dup scaleuserdict/PStoPSmatrix matrix currentmatrix putuserdict/PStoPSclip{0 0 moveto 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto closepath}put initclipPStoPSxform concat%%BeginPageSetup_S75 0 translate/pagenum 6 def/fname () def/fdir () def/ftail () def/user_header_p false def%%EndPageSetup5 723 M(Internet-Draft SSH Transport Layer Protocol Oct 2003) s5 690 M( The length of the packet \(bytes\), not including MAC or the) s5 679 M( packet_length field itself.) s5 657 M( padding_length) s5 646 M( Length of padding \(bytes\).) s5 624 M( payload) s5 613 M( The useful contents of the packet. If compression has been) s5 602 M( negotiated, this field is compressed. Initially, compression) s5 591 M( MUST be "none".) s5 569 M( random padding) s5 558 M( Arbitrary-length padding, such that the total length of) s5 547 M( \(packet_length || padding_length || payload || padding\) is a) s5 536 M( multiple of the cipher block size or 8, whichever is larger.) s5 525 M( There MUST be at least four bytes of padding. The padding) s5 514 M( SHOULD consist of random bytes. The maximum amount of padding) s5 503 M( is 255 bytes.) s5 481 M( mac) s5 470 M( Message authentication code. If message authentication has) s5 459 M( been negotiated, this field contains the MAC bytes. Initially,) s5 448 M( the MAC algorithm MUST be "none".) s5 415 M( Note that length of the concatenation of packet length, padding) s5 404 M( length, payload, and padding MUST be a multiple of the cipher block) s5 393 M( size or 8, whichever is larger. This constraint MUST be enforced) s5 382 M( even when using stream ciphers. Note that the packet length field is) s5 371 M( also encrypted, and processing it requires special care when sending) s5 360 M( or receiving packets.) s5 338 M( The minimum size of a packet is 16 \(or the cipher block size,) s5 327 M( whichever is larger\) bytes \(plus MAC\); implementations SHOULD decrypt) s5 316 M( the length after receiving the first 8 \(or cipher block size,) s5 305 M( whichever is larger\) bytes of a packet.) s5 283 M(5.1 Maximum Packet Length) s5 261 M( All implementations MUST be able to process packets with uncompressed) s5 250 M( payload length of 32768 bytes or less and total packet size of 35000) s5 239 M( bytes or less \(including length, padding length, payload, padding,) s5 228 M( and MAC.\). The maximum of 35000 bytes is an arbitrary chosen value) s5 217 M( larger than uncompressed size. Implementations SHOULD support longer) s5 206 M( packets, where they might be needed, e.g. if an implementation wants) s5 195 M( to send a very large number of certificates. Such packets MAY be) s5 184 M( sent if the version string indicates that the other party is able to) s5 173 M( process them. However, implementations SHOULD check that the packet) s5 129 M(Ylonen & Moffat, Editor Expires March 31, 2004 [Page 6]) s_RSPStoPSsaved restore%%Page: (6,7) 4userdict/PStoPSsaved save putPStoPSmatrix setmatrix595.000000 0.271378 translate90 rotate0.706651 dup scaleuserdict/PStoPSmatrix matrix currentmatrix putuserdict/PStoPSclip{0 0 moveto 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto closepath}put initclip/showpage{}def/copypage{}def/erasepage{}defPStoPSxform concat%%BeginPageSetup_S75 0 translate/pagenum 7 def/fname () def/fdir () def/ftail () def/user_header_p false def%%EndPageSetup5 723 M(Internet-Draft SSH Transport Layer Protocol Oct 2003) s5 690 M( length is reasonable for the implementation to avoid) s5 679 M( denial-of-service and/or buffer overflow attacks.) s5 657 M(5.2 Compression) s5 635 M( If compression has been negotiated, the payload field \(and only it\)) s5 624 M( will be compressed using the negotiated algorithm. The length field) s5 613 M( and MAC will be computed from the compressed payload. Encryption will) s5 602 M( be done after compression.) s5 580 M( Compression MAY be stateful, depending on the method. Compression) s5 569 M( MUST be independent for each direction, and implementations MUST) s5 558 M( allow independently choosing the algorithm for each direction.) s5 536 M( The following compression methods are currently defined:) s5 514 M( none REQUIRED no compression) s5 503 M( zlib OPTIONAL ZLIB \(LZ77\) compression) s5 481 M( The "zlib" compression is described in [RFC1950] and in [RFC1951].) s5 470 M( The compression context is initialized after each key exchange, and) s5 459 M( is passed from one packet to the next with only a partial flush being) s5 448 M( performed at the end of each packet. A partial flush means that the) s5 437 M( current compressed block is ended and all data will be output. If the) s5 426 M( current block is not a stored block, one or more empty blocks are) s5 415 M( added after the current block to ensure that there are at least 8) s5 404 M( bits counting from the start of the end-of-block code of the current) s5 393 M( block to the end of the packet payload.) s5 371 M( Additional methods may be defined as specified in [SSH-ARCH].) s5 349 M(5.3 Encryption) s5 327 M( An encryption algorithm and a key will be negotiated during the key) s5 316 M( exchange. When encryption is in effect, the packet length, padding) s5 305 M( length, payload and padding fields of each packet MUST be encrypted) s5 294 M( with the given algorithm.) s5 272 M( The encrypted data in all packets sent in one direction SHOULD be) s5 261 M( considered a single data stream. For example, initialization vectors) s5 250 M( SHOULD be passed from the end of one packet to the beginning of the) s5 239 M( next packet. All ciphers SHOULD use keys with an effective key length) s5 228 M( of 128 bits or more.) s5 206 M( The ciphers in each direction MUST run independently of each other,) s5 195 M( and implementations MUST allow independently choosing the algorithm) s5 184 M( for each direction \(if multiple algorithms are allowed by local) s5 173 M( policy\).) s5 129 M(Ylonen & Moffat, Editor Expires March 31, 2004 [Page 7]) s_RSPStoPSsaved restoreuserdict/PStoPSsaved save putPStoPSmatrix setmatrix595.000000 421.271378 translate90 rotate0.706651 dup scaleuserdict/PStoPSmatrix matrix currentmatrix putuserdict/PStoPSclip{0 0 moveto 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto closepath}put initclipPStoPSxform concat%%BeginPageSetup_S75 0 translate/pagenum 8 def/fname () def/fdir () def/ftail () def/user_header_p false def%%EndPageSetup5 723 M(Internet-Draft SSH Transport Layer Protocol Oct 2003) s5 690 M( The following ciphers are currently defined:) s5 668 M( 3des-cbc REQUIRED three-key 3DES in CBC mode) s5 657 M( blowfish-cbc OPTIONALi Blowfish in CBC mode) s5 646 M( twofish256-cbc OPTIONAL Twofish in CBC mode,) s5 635 M( with 256-bit key) s5 624 M( twofish-cbc OPTIONAL alias for "twofish256-cbc" \(this) s5 613 M( is being retained for) s5 602 M( historical reasons\)) s5 591 M( twofish192-cbc OPTIONAL Twofish with 192-bit key) s5 580 M( twofish128-cbc OPTIONAL Twofish with 128-bit key) s5 569 M( aes256-cbc OPTIONAL AES \(Rijndael\) in CBC mode,) s5 558 M( with 256-bit key) s5 547 M( aes192-cbc OPTIONAL AES with 192-bit key) s5 536 M( aes128-cbc RECOMMENDED AES with 128-bit key) s5 525 M( serpent256-cbc OPTIONAL Serpent in CBC mode, with) s5 514 M( 256-bit key) s5 503 M( serpent192-cbc OPTIONAL Serpent with 192-bit key) s5 492 M( serpent128-cbc OPTIONAL Serpent with 128-bit key) s5 481 M( arcfour OPTIONAL the ARCFOUR stream cipher) s5 470 M( idea-cbc OPTIONAL IDEA in CBC mode) s5 459 M( cast128-cbc OPTIONAL CAST-128 in CBC mode) s5 448 M( none OPTIONAL no encryption; NOT RECOMMENDED) s5 426 M( The "3des-cbc" cipher is three-key triple-DES) s5 415 M( \(encrypt-decrypt-encrypt\), where the first 8 bytes of the key are) s5 404 M( used for the first encryption, the next 8 bytes for the decryption,) s5 393 M( and the following 8 bytes for the final encryption. This requires 24) s5 382 M( bytes of key data \(of which 168 bits are actually used\). To) s5 371 M( implement CBC mode, outer chaining MUST be used \(i.e., there is only) s5 360 M( one initialization vector\). This is a block cipher with 8 byte) s5 349 M( blocks. This algorithm is defined in [FIPS-46-3]) s5 327 M( The "blowfish-cbc" cipher is Blowfish in CBC mode, with 128 bit keys) s5 316 M( [SCHNEIER]. This is a block cipher with 8 byte blocks.) s5 294 M( The "twofish-cbc" or "twofish256-cbc" cipher is Twofish in CBC mode,) s5 283 M( with 256 bit keys as described [TWOFISH]. This is a block cipher with) s5 272 M( 16 byte blocks.) s5 250 M( The "twofish192-cbc" cipher. Same as above but with 192-bit key.) s5 228 M( The "twofish128-cbc" cipher. Same as above but with 128-bit key.) s5 206 M( The "aes256-cbc" cipher is AES \(Advanced Encryption Standard\)) s5 195 M( [FIPS-197], formerly Rijndael, in CBC mode. This version uses 256-bit) s5 184 M( key.) s5 129 M(Ylonen & Moffat, Editor Expires March 31, 2004 [Page 8]) s_RSPStoPSsaved restore%%Page: (8,9) 5userdict/PStoPSsaved save putPStoPSmatrix setmatrix595.000000 0.271378 translate90 rotate0.706651 dup scaleuserdict/PStoPSmatrix matrix currentmatrix putuserdict/PStoPSclip{0 0 moveto 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto closepath}put initclip/showpage{}def/copypage{}def/erasepage{}defPStoPSxform concat%%BeginPageSetup_S75 0 translate/pagenum 9 def/fname () def⌨️ 快捷键说明
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