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require 'base64'
require 'digest'
require 'openssl'
##
# S3URISigner implements AWS SigV4 for S3 Source to avoid a dependency on the aws-sdk-* gems
# More on AWS SigV4: https://docs.aws.amazon.com/AmazonS3/latest/API/sig-v4-authenticating-requests.html
class Gem::S3URISigner
class ConfigurationError < Gem::Exception
def initialize(message)
super message
end
def to_s # :nodoc:
"#{super}"
end
end
class InstanceProfileError < Gem::Exception
def initialize(message)
super message
end
def to_s # :nodoc:
"#{super}"
end
end
attr_accessor :uri
def initialize(uri)
@uri = uri
end
##
# Signs S3 URI using query-params according to the reference: https://docs.aws.amazon.com/AmazonS3/latest/API/sigv4-query-string-auth.html
def sign(expiration = 86400)
s3_config = fetch_s3_config
current_time = Time.now.utc
date_time = current_time.strftime("%Y%m%dT%H%m%SZ")
date = date_time[0,8]
credential_info = "#{date}/#{s3_config.region}/s3/aws4_request"
canonical_host = "#{uri.host}.s3.#{s3_config.region}.amazonaws.com"
query_params = generate_canonical_query_params(s3_config, date_time, credential_info, expiration)
canonical_request = generate_canonical_request(canonical_host, query_params)
string_to_sign = generate_string_to_sign(date_time, credential_info, canonical_request)
signature = generate_signature(s3_config, date, string_to_sign)
URI.parse("https://#{canonical_host}#{uri.path}?#{query_params}&X-Amz-Signature=#{signature}")
end
private
S3Config = Struct.new :access_key_id, :secret_access_key, :security_token, :region
def generate_canonical_query_params(s3_config, date_time, credential_info, expiration)
canonical_params = {}
canonical_params["X-Amz-Algorithm"] = "AWS4-HMAC-SHA256"
canonical_params["X-Amz-Credential"] = "#{s3_config.access_key_id}/#{credential_info}"
canonical_params["X-Amz-Date"] = date_time
canonical_params["X-Amz-Expires"] = expiration.to_s
canonical_params["X-Amz-SignedHeaders"] = "host"
canonical_params["X-Amz-Security-Token"] = s3_config.security_token if s3_config.security_token
# Sorting is required to generate proper signature
canonical_params.sort.to_h.map do |key, value|
"#{base64_uri_escape(key)}=#{base64_uri_escape(value)}"
end.join("&")
end
def generate_canonical_request(canonical_host, query_params)
[
"GET",
uri.path,
query_params,
"host:#{canonical_host}",
"", # empty params
"host",
"UNSIGNED-PAYLOAD",
].join("\n")
end
def generate_string_to_sign(date_time, credential_info, canonical_request)
[
"AWS4-HMAC-SHA256",
date_time,
credential_info,
Digest::SHA256.hexdigest(canonical_request)
].join("\n")
end
def generate_signature(s3_config, date, string_to_sign)
date_key = OpenSSL::HMAC.digest("sha256", "AWS4" + s3_config.secret_access_key, date)
date_region_key = OpenSSL::HMAC.digest("sha256", date_key, s3_config.region)
date_region_service_key = OpenSSL::HMAC.digest("sha256", date_region_key, "s3")
signing_key = OpenSSL::HMAC.digest("sha256", date_region_service_key, "aws4_request")
OpenSSL::HMAC.hexdigest("sha256", signing_key, string_to_sign)
end
##
# Extracts S3 configuration for S3 bucket
def fetch_s3_config
return S3Config.new(uri.user, uri.password, nil, "us-east-1") if uri.user && uri.password
s3_source = Gem.configuration[:s3_source] || Gem.configuration["s3_source"]
host = uri.host
raise ConfigurationError.new("no s3_source key exists in .gemrc") unless s3_source
auth = s3_source[host] || s3_source[host.to_sym]
raise ConfigurationError.new("no key for host #{host} in s3_source in .gemrc") unless auth
provider = auth[:provider] || auth["provider"]
case provider
when "env"
id = ENV["AWS_ACCESS_KEY_ID"]
secret = ENV["AWS_SECRET_ACCESS_KEY"]
security_token = ENV["AWS_SESSION_TOKEN"]
when "instance_profile"
credentials = ec2_metadata_credentials_json
id = credentials["AccessKeyId"]
secret = credentials["SecretAccessKey"]
security_token = credentials["Token"]
else
id = auth[:id] || auth["id"]
secret = auth[:secret] || auth["secret"]
security_token = auth[:security_token] || auth["security_token"]
end
raise ConfigurationError.new("s3_source for #{host} missing id or secret") unless id && secret
region = auth[:region] || auth["region"] || "us-east-1"
S3Config.new(id, secret, security_token, region)
end
def base64_uri_escape(str)
str.gsub(/[\+\/=\n]/, BASE64_URI_TRANSLATE)
end
def ec2_metadata_credentials_json
require 'net/http'
require 'rubygems/request'
require 'rubygems/request/connection_pools'
require 'json'
iam_info = ec2_metadata_request(EC2_IAM_INFO)
# Expected format: arn:aws:iam::<id>:instance-profile/<role_name>
role_name = iam_info['InstanceProfileArn'].split('/').last
ec2_metadata_request(EC2_IAM_SECURITY_CREDENTIALS + role_name)
end
def ec2_metadata_request(url)
uri = URI(url)
@request_pool ||= create_request_pool(uri)
request = Gem::Request.new(uri, Net::HTTP::Get, nil, @request_pool)
response = request.fetch
case response
when Net::HTTPOK then
JSON.parse(response.body)
else
raise InstanceProfileError.new("Unable to fetch AWS metadata from #{uri}: #{response.message} #{response.code}")
end
end
def create_request_pool(uri)
proxy_uri = Gem::Request.proxy_uri(Gem::Request.get_proxy_from_env(uri.scheme))
certs = Gem::Request.get_cert_files
Gem::Request::ConnectionPools.new(proxy_uri, certs).pool_for(uri)
end
BASE64_URI_TRANSLATE = { "+" => "%2B", "/" => "%2F", "=" => "%3D", "\n" => "" }.freeze
EC2_IAM_INFO = "http://169.254.169.254/latest/meta-data/iam/info".freeze
EC2_IAM_SECURITY_CREDENTIALS = "http://169.254.169.254/latest/meta-data/iam/security-credentials/".freeze
end
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