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%% ====================================================================
%% @author Gavin M. Roy <gavinmroy@gmail.com>
%% @copyright 2016, Gavin M. Roy
%% @private
%% @doc rabbitmq_aws request signing methods
%% @end
%% ====================================================================
-module(rabbitmq_aws_sign).
%% API
-export([headers/1, request_hash/5]).
%% Transitional step until we can require Erlang/OTP 22 and
%% use crypto:mac/4 instead of crypto:hmac/3.
-compile(nowarn_deprecated_function).
%% Export all for unit tests
-ifdef(TEST).
-compile(export_all).
-endif.
-ignore_xref([{crypto, hmac, 3}]).
-include("rabbitmq_aws.hrl").
-define(ALGORITHM, "AWS4-HMAC-SHA256").
-define(ISOFORMAT_BASIC, "~4.10.0b~2.10.0b~2.10.0bT~2.10.0b~2.10.0b~2.10.0bZ").
-spec headers(request()) -> headers().
%% @doc Create the signed request headers
%% end
headers(Request) ->
RequestTimestamp = local_time(),
PayloadHash = sha256(Request#request.body),
URI = rabbitmq_aws_urilib:parse(Request#request.uri),
{_, Host, _} = URI#uri.authority,
Headers = append_headers(RequestTimestamp,
length(Request#request.body),
PayloadHash,
Host,
Request#request.security_token,
Request#request.headers),
RequestHash = request_hash(Request#request.method,
URI#uri.path,
URI#uri.query,
Headers,
Request#request.body),
AuthValue = authorization(Request#request.access_key,
Request#request.secret_access_key,
RequestTimestamp,
Request#request.region,
Request#request.service,
Headers,
RequestHash),
sort_headers(lists:merge([{"authorization", AuthValue}], Headers)).
-spec amz_date(AMZTimestamp :: string()) -> string().
%% @doc Extract the date from the AMZ timestamp format.
%% @end
amz_date(AMZTimestamp) ->
[RequestDate, _] = string:tokens(AMZTimestamp, "T"),
RequestDate.
-spec append_headers(AMZDate :: string(),
ContentLength :: integer(),
PayloadHash :: string(),
Hostname :: host(),
SecurityToken :: security_token(),
Headers :: headers()) -> list().
%% @doc Append the headers that need to be signed to the headers passed in with
%% the request
%% @end
append_headers(AMZDate, ContentLength, PayloadHash, Hostname, SecurityToken, Headers) ->
Defaults = default_headers(AMZDate, ContentLength, PayloadHash, Hostname, SecurityToken),
Headers1 = [{string:to_lower(Key), Value} || {Key, Value} <- Headers],
Keys = lists:usort(lists:append([string:to_lower(Key) || {Key, _} <- Defaults],
[Key || {Key, _} <- Headers1])),
sort_headers([{Key, header_value(Key, Headers1, proplists:get_value(Key, Defaults))} || Key <- Keys]).
-spec authorization(AccessKey :: access_key(),
SecretAccessKey :: secret_access_key(),
RequestTimestamp :: string(),
Region :: region(),
Service :: string(),
Headers :: headers(),
RequestHash :: string()) -> string().
%% @doc Return the authorization header value
%% @end
authorization(AccessKey, SecretAccessKey, RequestTimestamp, Region, Service, Headers, RequestHash) ->
RequestDate = amz_date(RequestTimestamp),
Scope = scope(RequestDate, Region, Service),
Credentials = ?ALGORITHM ++ " Credential=" ++ AccessKey ++ "/" ++ Scope,
SignedHeaders = "SignedHeaders=" ++ signed_headers(Headers),
StringToSign = string_to_sign(RequestTimestamp, RequestDate, Region, Service, RequestHash),
SigningKey = signing_key(SecretAccessKey, RequestDate, Region, Service),
Signature = string:join(["Signature", signature(StringToSign, SigningKey)], "="),
string:join([Credentials, SignedHeaders, Signature], ", ").
-spec default_headers(RequestTimestamp :: string(),
ContentLength :: integer(),
PayloadHash :: string(),
Hostname :: host(),
SecurityToken :: security_token()) -> headers().
%% @doc build the base headers that are merged in with the headers for every
%% request.
%% @end
default_headers(RequestTimestamp, ContentLength, PayloadHash, Hostname, undefined) ->
[{"content-length", integer_to_list(ContentLength)},
{"date", RequestTimestamp},
{"host", Hostname},
{"x-amz-content-sha256", PayloadHash}];
default_headers(RequestTimestamp, ContentLength, PayloadHash, Hostname, SecurityToken) ->
[{"content-length", integer_to_list(ContentLength)},
{"date", RequestTimestamp},
{"host", Hostname},
{"x-amz-content-sha256", PayloadHash},
{"x-amz-security-token", SecurityToken}].
-spec canonical_headers(Headers :: headers()) -> string().
%% @doc Convert the headers list to a line-feed delimited string in the AWZ
%% canonical headers format.
%% @end
canonical_headers(Headers) ->
canonical_headers(sort_headers(Headers), []).
-spec canonical_headers(Headers :: headers(), CanonicalHeaders :: list()) -> string().
%% @doc Convert the headers list to a line-feed delimited string in the AWZ
%% canonical headers format.
%% @end
canonical_headers([], CanonicalHeaders) ->
lists:flatten(CanonicalHeaders);
canonical_headers([{Key, Value}|T], CanonicalHeaders) ->
Header = string:join([string:to_lower(Key), Value], ":") ++ "\n",
canonical_headers(T, lists:append(CanonicalHeaders, [Header])).
-spec credential_scope(RequestDate :: string(),
Region :: region(),
Service :: string()) -> string().
%% @doc Return the credential scope string used in creating the request string to sign.
%% @end
credential_scope(RequestDate, Region, Service) ->
lists:flatten(string:join([RequestDate, Region, Service, "aws4_request"], "/")).
-spec header_value(Key :: string(),
Headers :: headers(),
Default :: string()) -> string().
%% @doc Return the the header value or the default value for the header if it
%% is not specified.
%% @end
header_value(Key, Headers, Default) ->
proplists:get_value(Key, Headers, proplists:get_value(string:to_lower(Key), Headers, Default)).
-spec hmac_sign(Key :: string(), Message :: string()) -> string().
%% @doc Return the SHA-256 hash for the specified value.
%% @end
hmac_sign(Key, Message) ->
SignedValue = crypto:hmac(sha256, Key, Message),
binary_to_list(SignedValue).
-spec local_time() -> string().
%% @doc Return the current timestamp in GMT formatted in ISO8601 basic format.
%% @end
local_time() ->
[LocalTime] = calendar:local_time_to_universal_time_dst(calendar:local_time()),
local_time(LocalTime).
-spec local_time(calendar:datetime()) -> string().
%% @doc Return the current timestamp in GMT formatted in ISO8601 basic format.
%% @end
local_time({{Y,M,D},{HH,MM,SS}}) ->
lists:flatten(io_lib:format(?ISOFORMAT_BASIC, [Y, M, D, HH, MM, SS])).
-spec query_string(QueryArgs :: list()) -> string().
%% @doc Return the sorted query string for the specified arguments.
%% @end
query_string(undefined) -> "";
query_string(QueryArgs) ->
rabbitmq_aws_urilib:build_query_string(lists:keysort(1, QueryArgs)).
-spec request_hash(Method :: method(),
Path :: path(),
QArgs :: query_args(),
Headers :: headers(),
Payload :: string()) -> string().
%% @doc Create the request hash value
%% @end
request_hash(Method, Path, QArgs, Headers, Payload) ->
RawPath = case string:slice(Path, 0, 1) of
"/" -> Path;
_ -> "/" ++ Path
end,
EncodedPath = uri_string:recompose(#{path => RawPath}),
CanonicalRequest = string:join([string:to_upper(atom_to_list(Method)),
EncodedPath,
query_string(QArgs),
canonical_headers(Headers),
signed_headers(Headers),
sha256(Payload)], "\n"),
sha256(CanonicalRequest).
-spec scope(AMZDate :: string(),
Region :: region(),
Service :: string()) -> string().
%% @doc Create the Scope string
%% @end
scope(AMZDate, Region, Service) ->
string:join([AMZDate, Region, Service, "aws4_request"], "/").
-spec sha256(Value :: string()) -> string().
%% @doc Return the SHA-256 hash for the specified value.
%% @end
sha256(Value) ->
lists:flatten(io_lib:format("~64.16.0b",
[binary:decode_unsigned(crypto:hash(sha256, Value))])).
-spec signed_headers(Headers :: list()) -> string().
%% @doc Return the signed headers string of delimited header key names
%% @end
signed_headers(Headers) ->
signed_headers(sort_headers(Headers), []).
-spec signed_headers(Headers :: headers(), Values :: list()) -> string().
%% @doc Return the signed headers string of delimited header key names
%% @end
signed_headers([], SignedHeaders) -> string:join(SignedHeaders, ";");
signed_headers([{Key,_}|T], SignedHeaders) ->
signed_headers(T, SignedHeaders ++ [string:to_lower(Key)]).
-spec signature(StringToSign :: string(),
SigningKey :: string()) -> string().
%% @doc Create the request signature.
%% @end
signature(StringToSign, SigningKey) ->
SignedValue = crypto:hmac(sha256, SigningKey, StringToSign),
lists:flatten(io_lib:format("~64.16.0b", [binary:decode_unsigned(SignedValue)])).
-spec signing_key(SecretKey :: secret_access_key(),
AMZDate :: string(),
Region :: region(),
Service :: string()) -> string().
%% @doc Create the signing key
%% @end
signing_key(SecretKey, AMZDate, Region, Service) ->
DateKey = hmac_sign("AWS4" ++ SecretKey, AMZDate),
RegionKey = hmac_sign(DateKey, Region),
ServiceKey = hmac_sign(RegionKey, Service),
hmac_sign(ServiceKey, "aws4_request").
-spec string_to_sign(RequestTimestamp :: string(),
RequestDate :: string(),
Region :: region(),
Service :: string(),
RequestHash :: string()) -> string().
%% @doc Return the string to sign when creating the signed request.
%% @end
string_to_sign(RequestTimestamp, RequestDate, Region, Service, RequestHash) ->
CredentialScope = credential_scope(RequestDate, Region, Service),
lists:flatten(string:join([
?ALGORITHM,
RequestTimestamp,
CredentialScope,
RequestHash
], "\n")).
-spec sort_headers(Headers :: headers()) -> headers().
%% @doc Case-insensitive sorting of the request headers
%% @end
sort_headers(Headers) ->
lists:sort(fun({A,_}, {B, _}) -> string:to_lower(A) =< string:to_lower(B) end, Headers).
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