Help Center> API Request Signing Guide> Developer Guide> AK/SK Signing and Authentication Guide> Signing SDKs and Demo> C
Updated on 2024-02-18 GMT+08:00
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C

Preparing the Environment

This section uses Linux Ubuntu as an example. Before calling APIs, install the required SSL tools.

  1. Install the OpenSSL library. 
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    apt-get install libssl-dev
  2. Install the curl library. 
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    apt-get install libcurl4-openssl-dev

Obtaining the SDK

Download the SDK and demo.

Decompress the downloaded package to the current folder. The following table shows the directory structure.

Name

Description

signer_common.c

SDK code

signer_common.h

signer.c

signer.h

Makefile

Makefile file

main.c

Sample code

Request Signing and API Calling

  1. Add the following references to main.c:

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    #include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <curl/curl.h>
#include "signer.h"

  2. Generate a sig_params_t variable, and enter the AK and SK.

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    sig_params_t params;
sig_params_init(&params);
// Directly writing AK/SK in code is risky. For security, encrypt your AK/SK and store them in the configuration file or environment variables.
// In this example, the AK/SK are stored in environment variables for identity authentication. Before running this example, set environment variables HUAWEICLOUD_SDK_AK and HUAWEICLOUD_SDK_SK.
sig_str_t ak = sig_str(getenv("HUAWEICLOUD_SDK_AK"));
sig_str_t sk = sig_str(getenv("HUAWEICLOUD_SDK_SK"));
params.key = ak;
params.secret = sk;

  3. Specify the method, domain name, request URI, query strings, and request body.

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    sig_str_t host = sig_str("service.region.example.com");
sig_str_t method = sig_str("GET");
sig_str_t uri = sig_str("/v1/{project_id}/vpcs");
sig_str_t query_str = sig_str("limit=2");
sig_str_t payload = sig_str("");
params.host = host;
params.method = method;
params.uri = uri;
params.query_str = query_str;
params.payload = payload;

  4. Add header parameters or other headers required for other purposes. For example, add the X-Project-Id header in multi-project scenarios or the X-Domain-Id header for a global service.

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    //Add header parameters, for example, X-Domain-Id for invoking a global service and X-Project-Id for invoking a project-level service.
sig_headers_add(&params.headers, "X-Project-Id", "xxx");

  5. Execute the following function to add the generated headers as request variables.

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    sig_sign(&params);

  6. Use the curl library to access the API and view the access result.

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    static size_t
WriteMemoryCallback(void *contents, size_t size, size_t nmemb, void *userp)
{
    size_t realsize = size * nmemb;
    struct MemoryStruct *mem = (struct MemoryStruct *)userp;

    mem->memory = (char*)realloc(mem->memory, mem->size + realsize + 1);
    if (mem->memory == NULL) {
        /* out of memory! */
        printf("not enough memory (realloc returned NULL)\n");
        return 0;
    }

    memcpy(&(mem->memory[mem->size]), contents, realsize);
    mem->size += realsize;
    mem->memory[mem->size] = 0;

    return realsize;
}

//send http request using curl library
int perform_request(RequestParams* request)
{
    CURL *curl;
    CURLcode res;
    struct MemoryStruct resp_header;
    resp_header.memory = malloc(1);
    resp_header.size = 0;
    struct MemoryStruct resp_body;
    resp_body.memory = malloc(1);
    resp_body.size = 0;

    curl_global_init(CURL_GLOBAL_ALL);
    curl = curl_easy_init();

    curl_easy_setopt(curl, CURLOPT_CUSTOMREQUEST, params.method.data);
    char url[1024];
    sig_snprintf(url, 1024, "http://%V%V?%V", &params.host, &params.uri, &params.query_str);
    curl_easy_setopt(curl, CURLOPT_URL, url);
    struct curl_slist *chunk = NULL;
    for (int i = 0; i < params.headers.len; i++) {
        char header[1024];
        sig_snprintf(header, 1024, "%V: %V", &params.headers.data[i].name, &params.headers.data[i].value);
        printf("%s\n", header);
        chunk = curl_slist_append(chunk, header);
    }
    printf("-------------\n");
    curl_easy_setopt(curl, CURLOPT_HTTPHEADER, chunk);
    curl_easy_setopt(curl, CURLOPT_POSTFIELDS, params.payload.data);
    curl_easy_setopt(curl, CURLOPT_NOBODY, 0L);
    curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, WriteMemoryCallback);
    curl_easy_setopt(curl, CURLOPT_HEADERDATA, (void *)&resp_header);
    curl_easy_setopt(curl, CURLOPT_WRITEDATA, (void *)&resp_body);
    //curl_easy_setopt(curl, CURLOPT_VERBOSE, 1L);
    res = curl_easy_perform(curl);
    if (res != CURLE_OK) {
        fprintf(stderr, "curl_easy_perform() failed: %s\n", curl_easy_strerror(res));
    }
    else {
        long status;
        curl_easy_getinfo(curl, CURLINFO_HTTP_CODE, &status);
        printf("status %d\n", status);
        printf(resp_header.memory);
        printf(resp_body.memory);
    }
    free(resp_header.memory);
    free(resp_body.memory);
    curl_easy_cleanup(curl);

    curl_global_cleanup();

    //free signature params
    sig_params_free(&params);
    return 0;
}

  7. Run the make command to obtain a main executable file, execute the file, and then view the execution result.
Parent topic: Signing SDKs and Demo