curl auth proposal example

#include <curl/curl.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <time.h>

char *gPromptUsername = 0;
char *gPromptPassword = 0;
CURL *gPausedHandle = 0;
curl_auth_type gPausedType = CURLAUTH_TYPE_NONE;

void loginPrompt(int sig)
{
    if (gPromptUsername) {
        free(gPromptUsername);
        gPromptUsername = NULL;
    }
    if (gPromptPassword) {
        free(gPromptPassword);
        gPromptPassword = NULL;
    }

    printf("Username for %s: ", gPausedType == CURLAUTH_TYPE_HTTP ? "host" : "proxy");
    size_t bufSize;
    ssize_t len = getline(&gPromptUsername, &bufSize, stdin);

    // Delete trailing newline
    char* c;
    for (c = gPromptUsername + len - 1; c > gPromptUsername && *c == '\n'; c--)
        *c = '\0';

    printf("Password: ");
    len = getline(&gPromptPassword, &bufSize, stdin);

    // Delete trailing newline
    for (c = gPromptPassword + len - 1; c > gPromptPassword && *c == '\n'; c--)
        *c = '\0';

    curl_easy_resume_auth(gPausedHandle, gPromptUsername, gPromptPassword);
}

curl_auth_result authCallback(
        curl_auth_type type,
        curl_auth_scheme scheme,
        const char *realm,
        unsigned retryCount,
        const char **usernamePtr,
        const char **passwordPtr,
        void *userdata)
{
    CURL *handle = (CURL *) userdata;

    const char *schemeStr;
    switch (scheme) {
        case CURLAUTH_BASIC: schemeStr = "Basic"; break;
        case CURLAUTH_DIGEST: schemeStr = "Digest"; break;
        case CURLAUTH_NTLM: schemeStr = "NTLM"; break;
        default: schemeStr = "unknown"; break;
    }

    printf("Got %s auth: scheme %s (%d), realm %s, retries %d, last username %s, last password %s\n",
            type == CURLAUTH_TYPE_HTTP ? "HTTP" : "proxy",
            schemeStr,
            scheme,
            realm ? realm : "(null)",
            retryCount,
            *usernamePtr ? *usernamePtr : "(null)",
            *passwordPtr ? *passwordPtr : "(null)");

    if (retryCount > 3) {
        // give up after 3 tries
        return CURLAUTH_RESULT_CANCEL;
    } else if (!*usernamePtr && !*passwordPtr) {
        // on the first attempt, try an autogenerated password based on the current timestamp
        char password[1024];
        snprintf(password, 1024, "timestamp%d", time(NULL));
        *usernamePtr = "guest";
        *passwordPtr = password;;
        return CURLAUTH_RESULT_CONTINUE;
    } else {
        // prompt the user for the username and password
        // normally this would happen in a dedicated UI thread - simulate this with an alarm)
        gPausedHandle = handle;
        gPausedType = type;
        signal(SIGALRM, loginPrompt);
        alarm(1);
        return CURLAUTH_RESULT_PAUSE;
    }
}

int main(int argc, char** argv)
{
    if (argc < 2 || argc > 3) {
        fprintf(stderr, "Usage: curlauthtest url [proxy-address]\n");
        exit(1);
    }

    const char *url = argv[1];
    const char *proxyAddress = argc > 2 ? argv[2] : 0;

    curl_global_init(CURL_GLOBAL_ALL);
    CURL *handle = curl_easy_init();

    curl_easy_setopt(handle, CURLOPT_URL, url);
    curl_easy_setopt(handle, CURLOPT_HTTP_AUTH_FUNCTION, authCallback);
    curl_easy_setopt(handle, CURLOPT_HTTP_AUTH_DATA, handle);
    curl_easy_setopt(handle, CURLOPT_HTTPAUTH, CURLAUTH_ANY);
    if (proxyAddress) {
        curl_easy_setopt(handle, CURLOPT_PROXY, proxyAddress);
        curl_easy_setopt(handle, CURLOPT_PROXYTYPE, CURLPROXY_HTTP);
        curl_easy_setopt(handle, CURLOPT_PROXYAUTH, CURLAUTH_ANY);
    }

    curl_easy_perform(handle);

    curl_easy_cleanup(handle);
    curl_global_cleanup();

    if (gPromptUsername) {
        free(gPromptUsername);
    }
    if (gPromptPassword) {
        free(gPromptPassword);
    }
}