如何使用curl从私有GitHub仓库下载文件？

问题现象 #

用C++ curl代码从私有GitHub仓库下载文件时，得到的不是目标文件内容，而是GitHub的HTML页面。尝试了Authorization: token和Authorization: Bearer两种授权头格式，均未解决问题。

原代码 #

#include <curl/curl.h>

static size_t WriteMemoryCallback(void* contents, size_t size, size_t nmemb, void* userp) {
    size_t realsize = size * nmemb;
    auto& mem = *static_cast<std::string*>(userp);
    mem.append(static_cast<char*>(contents), realsize);
    return realsize;
}

void Download(std::string& data, char* url)
{
    CURL* curl_handle;
    CURLcode res;
    struct curl_slist* slist{};

    curl_handle = curl_easy_init();

    curl_easy_setopt(curl_handle, CURLOPT_URL, url);
    SecureZeroMemory(url, strlen(url));        

    slist = curl_slist_append(slist, "Authorization: token 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");
    slist = curl_slist_append(slist, "Content-Type: application/json");
    curl_easy_setopt(curl_handle, CURLOPT_HTTPHEADER, slist);

    curl_easy_setopt(curl_handle, CURLOPT_TCP_KEEPALIVE, 0);
    curl_easy_setopt(curl_handle, CURLOPT_WRITEFUNCTION, WriteMemoryCallback);
    curl_easy_setopt(curl_handle, CURLOPT_WRITEDATA, &data);
    curl_easy_setopt(curl_handle, CURLOPT_USERAGENT, "libcurl-agent/1.0");
    curl_easy_setopt(curl_handle, CURLOPT_FOLLOWLOCATION, 1L);  // redirects
   
    //curl_easy_setopt(curl_handle, CURLOPT_VERBOSE, 1L); // only to debug

    res = curl_easy_perform(curl_handle);

    if(res != CURLE_OK)
       std::cerr << "curl_easy_perform() failed: " << curl_easy_strerror(res) << '\n';

    curl_easy_cleanup(curl_handle);
    curl_global_cleanup();
}

int main(int argc, char* argv[]) {
     std::string data;
     Download(data, /* link */);
}

错误返回内容 #

<!DOCTYPE html>
<html lang="en" data-color-mode="auto" data-light-theme="light" data-dark-theme="dark" data-a11y-animated-images="system">
  <head>
    <meta charset="utf-8">
  <link rel="dns-prefetch" href="https://github.githubassets.com">
  <link rel="dns-prefetch" href="https://avatars.githubusercontent.com">
  <link rel="dns-prefetch" href="https://github-cloud.s3.amazonaws.com">
  <link rel="dns-prefetch" href="https://user-images.githubusercontent.com/">
  <link rel="preconnect" href="https://github.githubassets.com" crossorigin>
  <link rel="preconnect" href="https://avatars.githubusercontent.com">
...

解决步骤 #

1. 使用GitHub API专用URL
   不要用浏览器里的网页URL，改用GitHub Contents API的格式：

   https://api.github.com/repos/{用户名}/{仓库名}/contents/{文件路径}
   

   例如下载username/private-repo仓库里的src/main.cpp，URL应为：

   https://api.github.com/repos/username/private-repo/contents/src/main.cpp
   

2. 移除多余请求头
   Content-Type: application/json是POST请求发送JSON数据时用的，GET请求下载文件不需要这个头，直接删除该行：

   // 删掉此行
   // slist = curl_slist_append(slist, "Content-Type: application/json");
   

3. 检查Token权限
   确保你的Personal Access Token（PAT）拥有repo权限，生成Token时必须勾选repo选项，否则无法访问私有仓库。同时确认Token未过期、未被撤销。

4. 启用调试定位问题
   打开CURLOPT_VERBOSE选项，查看请求的详细日志（包括HTTP状态码、重定向地址等），方便快速定位问题：

   curl_easy_setopt(curl_handle, CURLOPT_VERBOSE, 1L);
   

修正后的代码片段 #

void Download(std::string& data, char* url)
{
    CURL* curl_handle;
    CURLcode res;
    struct curl_slist* slist{};

    curl_handle = curl_easy_init();

    curl_easy_setopt(curl_handle, CURLOPT_URL, url);
    SecureZeroMemory(url, strlen(url));        

    // 仅保留正确的授权头
    slist = curl_slist_append(slist, "Authorization: token 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");
    curl_easy_setopt(curl_handle, CURLOPT_HTTPHEADER, slist);

    curl_easy_setopt(curl_handle, CURLOPT_TCP_KEEPALIVE, 0);
    curl_easy_setopt(curl_handle, CURLOPT_WRITEFUNCTION, WriteMemoryCallback);
    curl_easy_setopt(curl_handle, CURLOPT_WRITEDATA, &data);
    curl_easy_setopt(curl_handle, CURLOPT_USERAGENT, "libcurl-agent/1.0");
    curl_easy_setopt(curl_handle, CURLOPT_FOLLOWLOCATION, 1L);
    curl_easy_setopt(curl_handle, CURLOPT_VERBOSE, 1L); // 启用调试日志

    res = curl_easy_perform(curl_handle);

    if(res != CURLE_OK)
       std::cerr << "curl_easy_perform() failed: " << curl_easy_strerror(res) << '\n';

    // 新增：清理请求头链表，避免内存泄漏
    curl_slist_free_all(slist);
    curl_easy_cleanup(curl_handle);
    curl_global_cleanup();
}

内容的提问来源于stack exchange，提问作者Cesar