Class: Orthrus::SSH::Buffer
- Inherits:
-
Object
- Object
- Orthrus::SSH::Buffer
- Defined in:
- lib/orthrus/ssh/buffer.rb
Overview
Net::SSH::Buffer is a flexible class for building and parsing binary data packets. It provides a stream-like interface for sequentially reading data items from the buffer, as well as a useful helper method for building binary packets given a signature.
Writing to a buffer always appends to the end, regardless of where the read cursor is. Reading, on the other hand, always begins at the first byte of the buffer and increments the read cursor, with subsequent reads taking up where the last left off.
As a consumer of the Net::SSH library, you will rarely come into contact with these buffer objects directly, but it could happen. Also, if you are ever implementing a protocol on top of SSH (e.g. SFTP), this buffer class can be quite handy.
Instance Attribute Summary collapse
-
#content ⇒ Object
readonly
exposes the raw content of the buffer.
-
#position ⇒ Object
the current position of the pointer in the buffer.
Class Method Summary collapse
-
.from(*args) ⇒ Object
This is a convenience method for creating and populating a new buffer from a single command.
Instance Method Summary collapse
-
#==(buffer) ⇒ Object
Compares the contents of the two buffers, returning
true
only if they are identical in size and content. -
#append(text) ⇒ Object
Appends the given text to the end of the buffer.
-
#available ⇒ Object
Returns the number of bytes available to be read (e.g., how many bytes remain between the current position and the end of the buffer).
-
#clear! ⇒ Object
Resets the buffer, making it empty.
-
#consume!(n = position) ⇒ Object
Consumes n bytes from the buffer, where n is the current position unless otherwise specified.
-
#empty? ⇒ Boolean
Returns
true
if the buffer contains no data (e.g., it is of zero length). -
#eof? ⇒ Boolean
Returns true if the pointer is at the end of the buffer.
-
#initialize(content = "") ⇒ Buffer
constructor
Creates a new buffer, initialized to the given content.
-
#length ⇒ Object
Returns the length of the buffer’s content.
-
#read(count = nil) ⇒ Object
Reads and returns the next
count
bytes from the buffer, starting from the read position. -
#read!(count = nil) ⇒ Object
Reads (as #read) and returns the given number of bytes from the buffer, and then consumes (as #consume!) all data up to the new read position.
-
#read_bignum ⇒ Object
Read a bignum (OpenSSL::BN) from the buffer, in SSH2 format.
-
#read_bool ⇒ Object
Read a single byte and convert it into a boolean, using ‘C’ rules (i.e., zero is false, non-zero is true).
-
#read_buffer ⇒ Object
Reads the next string from the buffer, and returns a new Buffer object that wraps it.
-
#read_byte ⇒ Object
Read and return the next byte in the buffer.
-
#read_int64 ⇒ Object
Return the next 8 bytes as a 64-bit integer (in network byte order).
-
#read_key ⇒ Object
Read a key from the buffer.
-
#read_keyblob(type) ⇒ Object
Read a keyblob of the given type from the buffer, and return it as a key.
-
#read_long ⇒ Object
Return the next four bytes as a long integer (in network byte order).
-
#read_string ⇒ Object
Read and return an SSH2-encoded string.
-
#read_to(pattern) ⇒ Object
Reads all data up to and including the given pattern, which may be a String, Fixnum, or Regexp and is interpreted exactly as String#index does.
-
#remainder_as_buffer ⇒ Object
Returns all text from the current pointer to the end of the buffer as a new Net::SSH::Buffer object.
-
#reset! ⇒ Object
Resets the pointer to the start of the buffer.
-
#to_s ⇒ Object
Returns a copy of the buffer’s content.
-
#write(*data) ⇒ Object
Writes the given data literally into the string.
-
#write_bignum(*n) ⇒ Object
Writes each argument to the buffer as a bignum (SSH2-style).
-
#write_bool(*b) ⇒ Object
Writes each argument to the buffer as a (C-style) boolean, with 1 meaning true, and 0 meaning false.
-
#write_byte(*n) ⇒ Object
Writes each argument to the buffer as a byte.
-
#write_int64(*n) ⇒ Object
Writes each argument to the buffer as a network-byte-order-encoded 64-bit integer (8 bytes).
-
#write_key(*key) ⇒ Object
Writes the given arguments to the buffer as SSH2-encoded keys.
-
#write_long(*n) ⇒ Object
Writes each argument to the buffer as a network-byte-order-encoded long (4-byte) integer.
-
#write_string(*text) ⇒ Object
Writes each argument to the buffer as an SSH2-encoded string.
Constructor Details
#initialize(content = "") ⇒ Buffer
Creates a new buffer, initialized to the given content. The position is initialized to the beginning of the buffer.
73 74 75 76 |
# File 'lib/orthrus/ssh/buffer.rb', line 73 def initialize(content="") @content = content.to_s @position = 0 end |
Instance Attribute Details
#content ⇒ Object (readonly)
exposes the raw content of the buffer
66 67 68 |
# File 'lib/orthrus/ssh/buffer.rb', line 66 def content @content end |
#position ⇒ Object
the current position of the pointer in the buffer
69 70 71 |
# File 'lib/orthrus/ssh/buffer.rb', line 69 def position @position end |
Class Method Details
.from(*args) ⇒ Object
This is a convenience method for creating and populating a new buffer from a single command. The arguments must be even in length, with the first of each pair of arguments being a symbol naming the type of the data that follows. If the type is :raw, the value is written directly to the hash.
b = Buffer.from(:byte, 1, :string, "hello", :raw, "\1\2\3\4")
#-> "\1\0\0\0\5hello\1\2\3\4"
The supported data types are:
-
:raw => write the next value verbatim (#write)
-
:int64 => write an 8-byte integer (#write_int64)
-
:long => write a 4-byte integer (#write_long)
-
:byte => write a single byte (#write_byte)
-
:string => write a 4-byte length followed by character data (#write_string)
-
:bool => write a single byte, interpreted as a boolean (#write_bool)
-
:bignum => write an SSH-encoded bignum (#write_bignum)
-
:key => write an SSH-encoded key value (#write_key)
Any of these, except for :raw, accepts an Array argument, to make it easier to write multiple values of the same type in a briefer manner.
46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 |
# File 'lib/orthrus/ssh/buffer.rb', line 46 def self.from(*args) raise ArgumentError, "odd number of arguments given" unless args.length % 2 == 0 buffer = new 0.step(args.length-1, 2) do |index| type = args[index] value = args[index+1] if type == :raw buffer.append(value.to_s) elsif Array === value buffer.send("write_#{type}", *value) else buffer.send("write_#{type}", value) end end buffer end |
Instance Method Details
#==(buffer) ⇒ Object
Compares the contents of the two buffers, returning true
only if they are identical in size and content.
96 97 98 |
# File 'lib/orthrus/ssh/buffer.rb', line 96 def ==(buffer) to_s == buffer.to_s end |
#append(text) ⇒ Object
Appends the given text to the end of the buffer. Does not alter the read position. Returns the buffer object itself.
145 146 147 148 |
# File 'lib/orthrus/ssh/buffer.rb', line 145 def append(text) @content << text self end |
#available ⇒ Object
Returns the number of bytes available to be read (e.g., how many bytes remain between the current position and the end of the buffer).
85 86 87 |
# File 'lib/orthrus/ssh/buffer.rb', line 85 def available length - position end |
#clear! ⇒ Object
Resets the buffer, making it empty. Also, resets the read position to 0.
119 120 121 122 |
# File 'lib/orthrus/ssh/buffer.rb', line 119 def clear! @content = "" @position = 0 end |
#consume!(n = position) ⇒ Object
Consumes n bytes from the buffer, where n is the current position unless otherwise specified. This is useful for removing data from the buffer that has previously been read, when you are expecting more data to be appended. It helps to keep the size of buffers down when they would otherwise tend to grow without bound.
Returns the buffer object itself.
131 132 133 134 135 136 137 138 139 140 141 |
# File 'lib/orthrus/ssh/buffer.rb', line 131 def consume!(n=position) if n >= length # optimize for a fairly common case clear! elsif n > 0 @content = @content[n..-1] || "" @position -= n @position = 0 if @position < 0 end self end |
#empty? ⇒ Boolean
Returns true
if the buffer contains no data (e.g., it is of zero length).
101 102 103 |
# File 'lib/orthrus/ssh/buffer.rb', line 101 def empty? @content.empty? end |
#eof? ⇒ Boolean
Returns true if the pointer is at the end of the buffer. Subsequent reads will return nil, in this case.
113 114 115 |
# File 'lib/orthrus/ssh/buffer.rb', line 113 def eof? @position >= length end |
#length ⇒ Object
Returns the length of the buffer’s content.
79 80 81 |
# File 'lib/orthrus/ssh/buffer.rb', line 79 def length @content.length end |
#read(count = nil) ⇒ Object
Reads and returns the next count
bytes from the buffer, starting from the read position. If count
is nil
, this will return all remaining text in the buffer. This method will increment the pointer.
174 175 176 177 178 179 |
# File 'lib/orthrus/ssh/buffer.rb', line 174 def read(count=nil) count ||= length count = length - @position if @position + count > length @position += count @content[@position-count, count] end |
#read!(count = nil) ⇒ Object
Reads (as #read) and returns the given number of bytes from the buffer, and then consumes (as #consume!) all data up to the new read position.
183 184 185 186 187 |
# File 'lib/orthrus/ssh/buffer.rb', line 183 def read!(count=nil) data = read(count) consume! data end |
#read_bignum ⇒ Object
Read a bignum (OpenSSL::BN) from the buffer, in SSH2 format. It is essentially just a string, which is reinterpreted to be a bignum in binary format.
231 232 233 234 235 |
# File 'lib/orthrus/ssh/buffer.rb', line 231 def read_bignum data = read_string return unless data OpenSSL::BN.new(data, 2) end |
#read_bool ⇒ Object
Read a single byte and convert it into a boolean, using ‘C’ rules (i.e., zero is false, non-zero is true).
223 224 225 226 |
# File 'lib/orthrus/ssh/buffer.rb', line 223 def read_bool b = read_byte or return nil b != 0 end |
#read_buffer ⇒ Object
Reads the next string from the buffer, and returns a new Buffer object that wraps it.
270 271 272 |
# File 'lib/orthrus/ssh/buffer.rb', line 270 def read_buffer Buffer.new(read_string) end |
#read_byte ⇒ Object
Read and return the next byte in the buffer. Returns nil if called at the end of the buffer.
208 209 210 211 |
# File 'lib/orthrus/ssh/buffer.rb', line 208 def read_byte b = read(1) or return nil b.getbyte(0) end |
#read_int64 ⇒ Object
Return the next 8 bytes as a 64-bit integer (in network byte order). Returns nil if there are less than 8 bytes remaining to be read in the buffer.
192 193 194 195 196 |
# File 'lib/orthrus/ssh/buffer.rb', line 192 def read_int64 hi = read_long or return nil lo = read_long or return nil return (hi << 32) + lo end |
#read_key ⇒ Object
Read a key from the buffer. The key will start with a string describing its type. The remainder of the key is defined by the type that was read.
240 241 242 243 |
# File 'lib/orthrus/ssh/buffer.rb', line 240 def read_key type = read_string return (type ? read_keyblob(type) : nil) end |
#read_keyblob(type) ⇒ Object
Read a keyblob of the given type from the buffer, and return it as a key. Only RSA and DSA keys are supported.
247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 |
# File 'lib/orthrus/ssh/buffer.rb', line 247 def read_keyblob(type) case type when "ssh-dss" key = OpenSSL::PKey::DSA.new key.p = read_bignum key.q = read_bignum key.g = read_bignum key.pub_key = read_bignum when "ssh-rsa" key = OpenSSL::PKey::RSA.new key.e = read_bignum key.n = read_bignum else raise NotImplementedError, "unsupported key type `#{type}'" end return key end |
#read_long ⇒ Object
Return the next four bytes as a long integer (in network byte order). Returns nil if there are less than 4 bytes remaining to be read in the buffer.
201 202 203 204 |
# File 'lib/orthrus/ssh/buffer.rb', line 201 def read_long b = read(4) or return nil b.unpack("N").first end |
#read_string ⇒ Object
Read and return an SSH2-encoded string. The string starts with a long integer that describes the number of bytes remaining in the string. Returns nil if there are not enough bytes to satisfy the request.
216 217 218 219 |
# File 'lib/orthrus/ssh/buffer.rb', line 216 def read_string length = read_long or return nil read(length) end |
#read_to(pattern) ⇒ Object
Reads all data up to and including the given pattern, which may be a String, Fixnum, or Regexp and is interpreted exactly as String#index does. Returns nil if nothing matches. Increments the position to point immediately after the pattern, if it does match. Returns all data up to and including the text that matched the pattern.
161 162 163 164 165 166 167 168 169 |
# File 'lib/orthrus/ssh/buffer.rb', line 161 def read_to(pattern) index = @content.index(pattern, @position) or return nil length = case pattern when String then pattern.length when Fixnum then 1 when Regexp then $&.length end index && read(index+length) end |
#remainder_as_buffer ⇒ Object
Returns all text from the current pointer to the end of the buffer as a new Net::SSH::Buffer object.
152 153 154 |
# File 'lib/orthrus/ssh/buffer.rb', line 152 def remainder_as_buffer Buffer.new(@content[@position..-1]) end |
#reset! ⇒ Object
Resets the pointer to the start of the buffer. Subsequent reads will begin at position 0.
107 108 109 |
# File 'lib/orthrus/ssh/buffer.rb', line 107 def reset! @position = 0 end |
#to_s ⇒ Object
Returns a copy of the buffer’s content.
90 91 92 |
# File 'lib/orthrus/ssh/buffer.rb', line 90 def to_s (@content || "").dup end |
#write(*data) ⇒ Object
Writes the given data literally into the string. Does not alter the read position. Returns the buffer object.
276 277 278 279 |
# File 'lib/orthrus/ssh/buffer.rb', line 276 def write(*data) data.each { |datum| @content << datum } self end |
#write_bignum(*n) ⇒ Object
Writes each argument to the buffer as a bignum (SSH2-style). No checking is done to ensure that the arguments are, in fact, bignums. Does not alter the read position. Returns the buffer object.
331 332 333 334 |
# File 'lib/orthrus/ssh/buffer.rb', line 331 def write_bignum(*n) @content << n.map { |b| Utils.write_bignum(b) }.join self end |
#write_bool(*b) ⇒ Object
Writes each argument to the buffer as a (C-style) boolean, with 1 meaning true, and 0 meaning false. Does not alter the read position. Returns the buffer object.
323 324 325 326 |
# File 'lib/orthrus/ssh/buffer.rb', line 323 def write_bool(*b) b.each { |v| @content << (v ? "\1" : "\0") } self end |
#write_byte(*n) ⇒ Object
Writes each argument to the buffer as a byte. Does not alter the read position. Returns the buffer object.
303 304 305 306 |
# File 'lib/orthrus/ssh/buffer.rb', line 303 def write_byte(*n) n.each { |b| @content << b.chr } self end |
#write_int64(*n) ⇒ Object
Writes each argument to the buffer as a network-byte-order-encoded 64-bit integer (8 bytes). Does not alter the read position. Returns the buffer object.
284 285 286 287 288 289 290 291 |
# File 'lib/orthrus/ssh/buffer.rb', line 284 def write_int64(*n) n.each do |i| hi = (i >> 32) & 0xFFFFFFFF lo = i & 0xFFFFFFFF @content << [hi, lo].pack("N2") end self end |
#write_key(*key) ⇒ Object
Writes the given arguments to the buffer as SSH2-encoded keys. Does not alter the read position. Returns the buffer object.
338 339 340 341 |
# File 'lib/orthrus/ssh/buffer.rb', line 338 def write_key(*key) key.each { |k| append(k.public_identity(false)) } self end |
#write_long(*n) ⇒ Object
Writes each argument to the buffer as a network-byte-order-encoded long (4-byte) integer. Does not alter the read position. Returns the buffer object.
296 297 298 299 |
# File 'lib/orthrus/ssh/buffer.rb', line 296 def write_long(*n) @content << n.pack("N*") self end |
#write_string(*text) ⇒ Object
Writes each argument to the buffer as an SSH2-encoded string. Each string is prefixed by its length, encoded as a 4-byte long integer. Does not alter the read position. Returns the buffer object.
311 312 313 314 315 316 317 318 |
# File 'lib/orthrus/ssh/buffer.rb', line 311 def write_string(*text) text.each do |string| s = string.to_s write_long(s.length) write(s) end self end |