Evaluating libcurl Errors: CURLOPT_SSL_VERIFYPEER not Disabled
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When using libcurl, it’s not uncommon to encounter errors that can hinder your progress. In this article, we’ll explore why you’re getting an error code of 77 when trying to perform a GET request with CURLOPT_SSL_VERIFYPEER disabled.
What is CURLOPT_SSL_VERIFYPEER?
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In libcurl, CURLOPT_SSL_VERIFYPEER is a flag used to verify the SSL/TLS certificate sent by the server. If this flag is not enabled, libcurl will only connect to the server if its SSL/TLS certificate matches what it sends back.
Why is this causing an error?
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When you don’t enable CURLOPT_SSL_VERIFYPEER, libcurl’s connection attempt may fail due to issues with your server’s SSL/TLS certificate. If the server’s certificate doesn’t match the one sent by libcurl, a connection will be established only if the matching is successful.
Example Code:
#include
#include
int main() {
CURL *curl;
CURLcode res;
curl_global_init(CURL_GLOBAL_DEFAULT);
curl = curl_easy_init();
if(curl) {
std::string url = "
curl_easy_setopt(curl, CURLOPT_URL, url.c_str());
curl_easy_setopt(curl, CURLOPT_SSL_VERIFYPEER, 0L); // disable verification
res = curl_easy_perform(curl);
if(res == CURLE_OK && res == CURLE_NO_ERROR) {
std::cout << "Connection established." << std::endl;
} else if(res == CURLE_OK) {
std::cerr << "Error establishing connection: " << curl_easy_strerror(res) << std::endl;
}
curl_easy_cleanup(curl);
}
curl_global_cleanup();
return 0;
}
In this example, we disable CURLOPT_SSL_VERIFYPEER to allow libcurl to establish a connection even if the server’s SSL/TLS certificate doesn’t match. Note that we still verify the connection using CURLE_OK and CURLE_NO_ERROR, which allows us to detect whether the connection was established successfully.
Tips for Troubleshooting:
- Verify your server’s SSL/TLS certificates: Make sure your server is configured to use a valid SSL/TLS certificate.
- Check the curl documentation
: libcurl’s
CURLOPT_SSL_VERIFYPEERflag has more detailed information about its usage and potential issues.
- Test with different URLs: Try using other URLs that require verification, such as
By understanding whyCURLOPT_SSL_VERIFYPEERnot disabled caused the error, you should be able to resolve this issue and successfully perform your GET request using libcurl.
Example Use Case:
Suppose you're building a RESTful API server that returns JSON data. In this case, you can use a GET request withCURLOPT_SSL_VERIFYPEERset to 0L (disabled) to test the connection without verifying the SSL/TLS certificate sent by the client.
“cpp
#include
#include
int main() {
CURL *curl;
CURLcode res;
curl_global_init(CURL_GLOBAL_DEFAULT);
curl = curl_easy_init();
if(curl) {
std::string url = “
curl_easy_setopt(curl, CURLOPT_URL, url.c_str());
res = curl_easy_perform(curl);
if(res == CURLE_OK && res == CURLE_NO_ERROR) {
std::cout << "API server connected.
