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//
// Copyright 2020 gRPC authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
#include <grpc/support/port_platform.h>
#include "src/core/lib/security/credentials/external/aws_request_signer.h"
#include "absl/strings/ascii.h"
#include "absl/strings/escaping.h"
#include "absl/strings/str_format.h"
#include "absl/strings/str_join.h"
#include "absl/strings/str_split.h"
#include "absl/time/clock.h"
#include "absl/time/time.h"
#include <openssl/hmac.h>
#include <openssl/sha.h>
namespace grpc_core {
namespace {
const char kAlgorithm[] = "AWS4-HMAC-SHA256";
const char kDateFormat[] = "%a, %d %b %E4Y %H:%M:%S %Z";
const char kXAmzDateFormat[] = "%Y%m%dT%H%M%SZ";
void SHA256(const std::string& str, unsigned char out[SHA256_DIGEST_LENGTH]) {
SHA256_CTX sha256;
SHA256_Init(&sha256);
SHA256_Update(&sha256, str.c_str(), str.size());
SHA256_Final(out, &sha256);
}
std::string SHA256Hex(const std::string& str) {
unsigned char hash[SHA256_DIGEST_LENGTH];
SHA256(str, hash);
std::string hash_str(reinterpret_cast<char const*>(hash),
SHA256_DIGEST_LENGTH);
return absl::BytesToHexString(hash_str);
}
std::string HMAC(const std::string& key, const std::string& msg) {
unsigned int len;
unsigned char digest[EVP_MAX_MD_SIZE];
HMAC(EVP_sha256(), key.c_str(), key.length(),
reinterpret_cast<const unsigned char*>(msg.c_str()), msg.length(),
digest, &len);
return std::string(digest, digest + len);
}
} // namespace
AwsRequestSigner::AwsRequestSigner(
std::string access_key_id, std::string secret_access_key, std::string token,
std::string method, std::string url, std::string region,
std::string request_payload,
std::map<std::string, std::string> additional_headers,
grpc_error_handle* error)
: access_key_id_(std::move(access_key_id)),
secret_access_key_(std::move(secret_access_key)),
token_(std::move(token)),
method_(std::move(method)),
region_(std::move(region)),
request_payload_(std::move(request_payload)),
additional_headers_(std::move(additional_headers)) {
auto amz_date_it = additional_headers_.find("x-amz-date");
auto date_it = additional_headers_.find("date");
if (amz_date_it != additional_headers_.end() &&
date_it != additional_headers_.end()) {
*error = GRPC_ERROR_CREATE_FROM_STATIC_STRING(
"Only one of {date, x-amz-date} can be specified, not both.");
return;
}
if (amz_date_it != additional_headers_.end()) {
static_request_date_ = amz_date_it->second;
} else if (date_it != additional_headers_.end()) {
absl::Time request_date;
std::string err_str;
if (!absl::ParseTime(kDateFormat, date_it->second, &request_date,
&err_str)) {
*error = GRPC_ERROR_CREATE_FROM_STATIC_STRING(err_str.c_str());
return;
}
static_request_date_ =
absl::FormatTime(kXAmzDateFormat, request_date, absl::UTCTimeZone());
}
absl::StatusOr<URI> tmp_url = URI::Parse(url);
if (!tmp_url.ok()) {
*error = GRPC_ERROR_CREATE_FROM_STATIC_STRING("Invalid Aws request url.");
return;
}
url_ = tmp_url.value();
}
std::map<std::string, std::string> AwsRequestSigner::GetSignedRequestHeaders() {
std::string request_date_full;
if (!static_request_date_.empty()) {
if (!request_headers_.empty()) {
return request_headers_;
}
request_date_full = static_request_date_;
} else {
absl::Time request_date = absl::Now();
request_date_full =
absl::FormatTime(kXAmzDateFormat, request_date, absl::UTCTimeZone());
}
std::string request_date_short = request_date_full.substr(0, 8);
// TASK 1: Create a canonical request for Signature Version 4
// https://docs.aws.amazon.com/general/latest/gr/sigv4-create-canonical-request.html
std::vector<absl::string_view> canonical_request_vector;
// 1. HTTPRequestMethod
canonical_request_vector.emplace_back(method_);
canonical_request_vector.emplace_back("\n");
// 2. CanonicalURI
canonical_request_vector.emplace_back(
url_.path().empty() ? "/" : absl::string_view(url_.path()));
canonical_request_vector.emplace_back("\n");
// 3. CanonicalQueryString
std::vector<std::string> query_vector;
for (const URI::QueryParam& query_kv : url_.query_parameter_pairs()) {
query_vector.emplace_back(absl::StrCat(query_kv.key, "=", query_kv.value));
}
std::string query = absl::StrJoin(query_vector, "&");
canonical_request_vector.emplace_back(query);
canonical_request_vector.emplace_back("\n");
// 4. CanonicalHeaders
if (request_headers_.empty()) {
request_headers_.insert({"host", url_.authority()});
if (!token_.empty()) {
request_headers_.insert({"x-amz-security-token", token_});
}
for (const auto& header : additional_headers_) {
request_headers_.insert(
{absl::AsciiStrToLower(header.first), header.second});
}
}
if (additional_headers_.find("date") == additional_headers_.end()) {
request_headers_["x-amz-date"] = request_date_full;
}
std::vector<absl::string_view> canonical_headers_vector;
for (const auto& header : request_headers_) {
canonical_headers_vector.emplace_back(header.first);
canonical_headers_vector.emplace_back(":");
canonical_headers_vector.emplace_back(header.second);
canonical_headers_vector.emplace_back("\n");
}
std::string canonical_headers = absl::StrJoin(canonical_headers_vector, "");
canonical_request_vector.emplace_back(canonical_headers);
canonical_request_vector.emplace_back("\n");
// 5. SignedHeaders
std::vector<absl::string_view> signed_headers_vector;
for (const auto& header : request_headers_) {
signed_headers_vector.emplace_back(header.first);
}
std::string signed_headers = absl::StrJoin(signed_headers_vector, ";");
canonical_request_vector.emplace_back(signed_headers);
canonical_request_vector.emplace_back("\n");
// 6. RequestPayload
std::string hashed_request_payload = SHA256Hex(request_payload_);
canonical_request_vector.emplace_back(hashed_request_payload);
std::string canonical_request = absl::StrJoin(canonical_request_vector, "");
// TASK 2: Create a string to sign for Signature Version 4
// https://docs.aws.amazon.com/general/latest/gr/sigv4-create-string-to-sign.html
std::vector<absl::string_view> string_to_sign_vector;
// 1. Algorithm
string_to_sign_vector.emplace_back("AWS4-HMAC-SHA256");
string_to_sign_vector.emplace_back("\n");
// 2. RequestDateTime
string_to_sign_vector.emplace_back(request_date_full);
string_to_sign_vector.emplace_back("\n");
// 3. CredentialScope
std::pair<absl::string_view, absl::string_view> host_parts =
absl::StrSplit(url_.authority(), absl::MaxSplits('.', 1));
std::string service_name(host_parts.first);
std::string credential_scope = absl::StrFormat(
"%s/%s/%s/aws4_request", request_date_short, region_, service_name);
string_to_sign_vector.emplace_back(credential_scope);
string_to_sign_vector.emplace_back("\n");
// 4. HashedCanonicalRequest
std::string hashed_canonical_request = SHA256Hex(canonical_request);
string_to_sign_vector.emplace_back(hashed_canonical_request);
std::string string_to_sign = absl::StrJoin(string_to_sign_vector, "");
// TASK 3: Task 3: Calculate the signature for AWS Signature Version 4
// https://docs.aws.amazon.com/general/latest/gr/sigv4-calculate-signature.html
// 1. Derive your signing key.
std::string date = HMAC("AWS4" + secret_access_key_, request_date_short);
std::string region = HMAC(date, region_);
std::string service = HMAC(region, service_name);
std::string signing = HMAC(service, "aws4_request");
// 2. Calculate the signature.
std::string signature_str = HMAC(signing, string_to_sign);
std::string signature = absl::BytesToHexString(signature_str);
// TASK 4: Add the signature to the HTTP request
// https://docs.aws.amazon.com/general/latest/gr/sigv4-add-signature-to-request.html
std::string authorization_header = absl::StrFormat(
"%s Credential=%s/%s, SignedHeaders=%s, Signature=%s", kAlgorithm,
access_key_id_, credential_scope, signed_headers, signature);
request_headers_["Authorization"] = authorization_header;
return request_headers_;
}
} // namespace grpc_core
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