C++ でIAM認証用 API Gatewayにアクセスするソースコード

#include
#include
#include
#include
#include
#include
#include
#include
#include
#include

std::string hmac(std::string key, std::string msg){

FILE *fp;
//char *cmdline = "echo -n 'Hello' | openssl dgst -binary -sha256 -hmac 'secret' | base64" ;
char *cmdline = "echo -n 'key' | openssl dgst -binary -sha256 -hmac 'secret'";
if ((fp=popen(cmdline, "r")) == NULL) {
    perror ("popen failed");
    exit(EXIT_FAILURE);
}
char buf[256];
while(fgets(buf, sizeof(buf), fp) != NULL) {
    printf("=> %s", buf);
}

pclose(fp);
std::string signing_key(buf);
return signing_key;

}

std::string hmac_hex(std::string key, std::string msg){

FILE *fp;
//char *cmdline = "echo -n 'Hello' | openssl dgst -binary -sha256 -hmac 'secret' | base64" ;
char *cmdline = "echo -n 'Hello' | openssl dgst -hex  -sha256 -hmac 'secret'";
if ((fp=popen(cmdline, "r")) == NULL) {
    perror ("popen failed");
    exit(EXIT_FAILURE);
}
char buf[256];
while(fgets(buf, sizeof(buf), fp) != NULL) {
    printf("=> %s", buf);
}

pclose(fp);
std::string signing_key(buf);
return signing_key;

}

std::string sha256(const std::string str){
unsigned char hash[SHA256_DIGEST_LENGTH];

SHA256_CTX sha256;
SHA256_Init(&sha256);
SHA256_Update(&sha256, str.c_str(), str.size());
SHA256_Final(hash, &sha256);

std::stringstream ss;

for(int i = 0; i < SHA256_DIGEST_LENGTH; i++){
ss << std::hex << std::setw(2) << std::setfill('0') << static_cast( hash[i] );
}

return ss.str();
}

using namespace std;
int main(int argc, char *argv[])
{

std::cout <<"start"<< std::endl;
string host = "host";
string stage = "dev";
string region = "";
string access_key ="";
string secret_key = "";
string method = "POST";
time_t now;

struct tm *ptm;
char amz_date[128];
now = time(NULL);
ptm = gmtime(&now);
strftime(amz_date, sizeof(amz_date),"%Y%m%d%H%M%SZ",ptm);
char date_stamp[128];
printf("amz_date : %s\n", amz_date);
strftime(date_stamp, sizeof(date_stamp),"%Y%m%d",ptm);
printf("amz_date : %s\n", date_stamp);
string s_date_stamp(date_stamp);
string request_parameters = "\0";
string credential_scope = s_date_stamp + "/ap-northeast-1/execute-api/aws4_request";
printf("credential scope :");
std::cout <<credential_scope<< std::endl;
string signed_headers = "host;x-amz-date";
string s_amz_date(amz_date);
string canonical_headers = "host:"+ host + "\nx-amz-date:" +s_amz_date + "\n";
printf("canonical_headers :\n");
std::cout <<canonical_headers<< std::endl;
string payload_hash(sha256(request_parameters));

printf("payload_hash :\n");
std::cout <<payload_hash<< std::endl;
string canonical_request = method + "\n" + stage + "/\n\n" + canonical_headers + "\n" + signed_headers + "\n" + payload_hash;
printf("canonical_request :\n");
std::cout <<canonical_request<< std::endl;
string canonical_request_hash = sha256(canonical_request);
printf("canonical_request_hash :\n");
std::cout <<canonical_request_hash<< std::endl;
string target_data = "AWS4-HMAC-SHA256\n" + s_amz_date + "\n" + credential_scope +  "\n" + canonical_request_hash;
printf("target_data :\n");
std::cout <<target_data<< std::endl;
string tmp = "AWS4"+ secret_key;
string signing_key = hmac(tmp,s_date_stamp);
printf("signing_key :\n");
std::cout <<signing_key<< std::endl;

signing_key = hmac(signing_key,region);
printf("signing_key :\n");
std::cout <<signing_key<< std::endl;

signing_key = hmac(signing_key,"execute-api");
printf("signing_key :\n");
std::cout <<signing_key<< std::endl;

signing_key = hmac(signing_key,"aws4_request");
printf("signing_key :\n");
std::cout <<signing_key<< std::endl;

string signature = hmac_hex(signing_key,target_data);

printf("signature :\n");
std::cout <<signing_key<< std::endl;

string authorization_header ="AWS4-HMAC-SHA256 Credential="+access_key + "/"+ credential_scope+",SignedHeaders="+ signed_headers+",Signature="+signature;

printf("authorization_header :\n");
std::cout <<authorization_header<< std::endl;

}