Class: HTTPX::Plugins::AWSSigV4::Signer

Inherits:
Object
  • Object
show all
Defined in:
lib/httpx/plugins/aws_sigv4.rb

Overview

Signs requests using the AWS sigv4 signing.

Instance Method Summary collapse

Constructor Details

#initialize(service:, region:, credentials: nil, username: nil, password: nil, security_token: nil, provider_prefix: "aws", header_provider_field: "amz", unsigned_headers: [], apply_checksum_header: true, algorithm: "SHA256") ⇒ Signer

Returns a new instance of Signer.



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# File 'lib/httpx/plugins/aws_sigv4.rb', line 17

def initialize(
  service:,
  region:,
  credentials: nil,
  username: nil,
  password: nil,
  security_token: nil,
  provider_prefix: "aws",
  header_provider_field: "amz",
  unsigned_headers: [],
  apply_checksum_header: true,
  algorithm: "SHA256"
)
  @credentials = credentials || Credentials.new(username, password, security_token)
  @service = service
  @region = region

  @unsigned_headers = Set.new(unsigned_headers.map(&:downcase))
  @unsigned_headers << "authorization"
  @unsigned_headers << "x-amzn-trace-id"
  @unsigned_headers << "expect"

  @apply_checksum_header = apply_checksum_header
  @provider_prefix = provider_prefix
  @header_provider_field = header_provider_field

  @algorithm = algorithm
end

Instance Method Details

#sign!(request) ⇒ Object 



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# File 'lib/httpx/plugins/aws_sigv4.rb', line 46

def sign!(request)
  lower_provider_prefix = "#{@provider_prefix}4"
  upper_provider_prefix = lower_provider_prefix.upcase

  downcased_algorithm = @algorithm.downcase

  datetime = (request.headers["x-#{@header_provider_field}-date"] ||= Time.now.utc.strftime("%Y%m%dT%H%M%SZ"))
  date = datetime[0, 8]

  content_hashed = request.headers["x-#{@header_provider_field}-content-#{downcased_algorithm}"] || hexdigest(request.body)

  request.headers["x-#{@header_provider_field}-content-#{downcased_algorithm}"] ||= content_hashed if @apply_checksum_header
  request.headers["x-#{@header_provider_field}-security-token"] ||= @credentials.security_token if @credentials.security_token

  signature_headers = request.headers.each.reject do |k, _|
    @unsigned_headers.include?(k)
  end
  # aws sigv4 needs to declare the host, regardless of protocol version
  signature_headers << ["host", request.authority] unless request.headers.key?("host")
  signature_headers.sort_by!(&:first)

  signed_headers = signature_headers.map(&:first).join(";")

  canonical_headers = signature_headers.map do |k, v|
    # eliminate whitespace between value fields, unless it's a quoted value
    "#{k}:#{v.start_with?("\"") && v.end_with?("\"") ? v : v.gsub(/\s+/, " ").strip}\n"
  end.join

  # canonical request
  creq = "#{request.verb}" \
         "\n#{request.canonical_path}" \
         "\n#{request.canonical_query}" \
         "\n#{canonical_headers}" \
         "\n#{signed_headers}" \
         "\n#{content_hashed}"

  credential_scope = "#{date}" \
                     "/#{@region}" \
                     "/#{@service}" \
                     "/#{lower_provider_prefix}_request"

  algo_line = "#{upper_provider_prefix}-HMAC-#{@algorithm}"
  # string to sign
  sts = "#{algo_line}" \
        "\n#{datetime}" \
        "\n#{credential_scope}" \
        "\n#{OpenSSL::Digest.new(@algorithm).hexdigest(creq)}"

  # signature
  k_date = hmac("#{upper_provider_prefix}#{@credentials.password}", date)
  k_region = hmac(k_date, @region)
  k_service = hmac(k_region, @service)
  k_credentials = hmac(k_service, "#{lower_provider_prefix}_request")
  sig = hexhmac(k_credentials, sts)

  credential = "#{@credentials.username}/#{credential_scope}"
  # apply signature
  request.headers["authorization"] =
    "#{algo_line} " \
    "Credential=#{credential}, " \
    "SignedHeaders=#{signed_headers}, " \
    "Signature=#{sig}"
end