Class: SSHData::PublicKey::RSA

Inherits:
Base
  • Object
show all
Defined in:
lib/ssh_data/public_key/rsa.rb

Constant Summary collapse

ALGO_DIGESTS = 
{
  ALGO_RSA          => OpenSSL::Digest::SHA1,
  ALGO_RSA_SHA2_256 => OpenSSL::Digest::SHA256,
  ALGO_RSA_SHA2_512 => OpenSSL::Digest::SHA512
}

Instance Attribute Summary collapse

Attributes inherited from Base

#algo

Instance Method Summary collapse

Methods inherited from Base

#fingerprint, #openssh, #sign

Constructor Details

#initialize(algo:, e:, n:) ⇒ RSA

Returns a new instance of RSA.



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# File 'lib/ssh_data/public_key/rsa.rb', line 12

def initialize(algo:, e:, n:)
  unless algo == ALGO_RSA
    raise DecodeError, "bad algorithm: #{algo.inspect}"
  end

  @algo = algo
  @e = e
  @n = n

  @openssl = OpenSSL::PKey::RSA.new(asn1.to_der)

  super(algo: algo)
end

Instance Attribute Details

#e ⇒ Object (readonly)

Returns the value of attribute e.



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# File 'lib/ssh_data/public_key/rsa.rb', line 4

def e
  @e
end

#n ⇒ Object (readonly)

Returns the value of attribute n.



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# File 'lib/ssh_data/public_key/rsa.rb', line 4

def n
  @n
end

#openssl ⇒ Object (readonly)

Returns the value of attribute openssl.



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# File 'lib/ssh_data/public_key/rsa.rb', line 4

def openssl
  @openssl
end

Instance Method Details

#==(other) ⇒ Object

Is this public key equal to another public key?

other - Another SSHData::PublicKey::Base instance to compare with.

Returns boolean.



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# File 'lib/ssh_data/public_key/rsa.rb', line 65

def ==(other)
  super && other.e == e && other.n == n
end

#rfc4253 ⇒ Object

RFC4253 binary encoding of the public key.

Returns a binary String.



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# File 'lib/ssh_data/public_key/rsa.rb', line 52

def rfc4253
  Encoding.encode_fields(
    [:string, algo],
    [:mpint,  e],
    [:mpint,  n]
  )
end

#verify(signed_data, signature) ⇒ Object

Verify an SSH signature.

signed_data - The String message that the signature was calculated over. signature - The binary String signature with SSH encoding.

Returns boolean.



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# File 'lib/ssh_data/public_key/rsa.rb', line 32

def verify(signed_data, signature)
  sig_algo, raw_sig, _ = Encoding.decode_signature(signature)
  digest = ALGO_DIGESTS[sig_algo]

  if digest.nil?
    raise DecodeError, "bad signature algorithm: #{sig_algo.inspect}"
  end

  # OpenSSH compatibility: if a the number of bytes in the signature is less than the number of bytes of the RSA
  # modulus, prepend the signature with zeros.
  # See https://github.com/openssh/openssh-portable/blob/ac383f3a5c6f529a2e8a5bc44af79a08c7da294e/ssh-rsa.c#L531
  difference = n.num_bytes - raw_sig.bytesize
  raw_sig = "\0" * difference + raw_sig if difference.positive?

  openssl.verify(digest.new, raw_sig, signed_data)
end