CURLOPT_DO...VERIFYPEER(3)

✨ CURLOPT_DOH_SSL_VERIFYPEER ✨

Okay bestie, so this is from the libcurl manual — like, the actual official one. Let me break it down for you 💅

---

🌸 SYNOPSIS 🌸

#include <curl/curl.h>

CURLcode curl_easy_setopt(CURL *handle, CURLOPT_DOH_SSL_VERIFYPEER,
                          long verify);

---

💖 DESCRIPTION 💖

So you pass a long as the parameter — set it to 1L to enable, or 0L to disable. That's it. That's the whole vibe check.

This option tells curl to verify the authenticity of the DoH (DNS-over-HTTPS) server's certificate. A value of 1 means curl verifies; 0 (zero) means it does not. No cap.

This is literally the DoH equivalent of CURLOPT_SSL_VERIFYPEER(3) and only affects requests to the DoH server. Like, it's not doing anything else, okay? 🎀

When negotiating a TLS or SSL connection, the server sends a certificate indicating its identity. curl verifies whether the certificate is authentic — i.e. that you can trust that the server is who the certificate says it is. This trust is based on a chain of digital signatures, rooted in certification authority (CA) certificates you supply. curl uses a default bundle of CA certificates (the path for that is determined at build time) and you can specify alternate certificates with the CURLOPT_CAINFO(3) option or the CURLOPT_CAPATH(3) option. It's giving ✨trust chain realness✨.

When CURLOPT_DOH_SSL_VERIFYPEER(3) is enabled, and the verification fails to prove that the certificate is authentic, the connection fails. When the option is zero, the peer certificate verification succeeds regardless. Like, it just vibes through. 🦋

Authenticating the certificate is not enough to be sure about the server. You typically also want to ensure that the server is the server you mean to be talking to. Use CURLOPT_DOH_SSL_VERIFYHOST(3) for that. The check that the hostname in the certificate is valid for the hostname you are connecting to is done independently of the CURLOPT_DOH_SSL_VERIFYPEER(3) option. They're separate, bestie. Don't conflate them 🙈

⚠️ WARNING ⚠️ disabling verification of the certificate allows bad guys to man-in-the-middle the communication without you knowing it. Disabling verification makes the communication insecure. Just having encryption on a transfer is not enough as you cannot be sure that you are communicating with the correct end-point. Like, that's literally the whole point of certs, pls don't turn this off unless you know exactly what you're doing 💀

---

🎀 DEFAULT 🎀

1

---

🦋 PROTOCOLS 🦋

This functionality affects all TLS based protocols: HTTPS, FTPS, IMAPS, POP3S, SMTPS etc.

All TLS backends support this option. Every single one. Periodt 👑

---

💅 EXAMPLE 💅

int main(void)
{
  CURL *curl = curl_easy_init();
  if(curl) {
    curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");

    curl_easy_setopt(curl, CURLOPT_DOH_URL,
                     "https://cloudflare-dns.com/dns-query");

    /* Disable certificate verification of the DoH server */
    curl_easy_setopt(curl, CURLOPT_DOH_SSL_VERIFYPEER, 0L);

    curl_easy_perform(curl);
  }
}

---

🌈 AVAILABILITY 🌈

Added in curl 7.76.0 — so like, it's been around for a minute. Not vintage, not brand new. Just right 🫶

---

🍓 RETURN VALUE 🍓

curl_easy_setopt(3) returns a CURLcode indicating success or error.

CURLE_OK (0) means everything was OK, non-zero means an error occurred, see libcurl-errors(3). Standard. You know the drill 😭

---

🔥 SEE ALSO 🔥

• CURLOPT_CAINFO(3)
• CURLOPT_CAPATH(3)
• CURLOPT_DOH_SSL_VERIFYHOST(3)
• CURLOPT_PROXY_SSL_VERIFYHOST(3)
• CURLOPT_PROXY_SSL_VERIFYPEER(3)
• CURLOPT_SSL_VERIFYHOST(3)
• CURLOPT_SSL_VERIFYPEER(3)

---

Alright bestie, that's the whole thing. This page is from libcurl, and the date on it is 2026-10-12. Go forth and verify those DoH certs like the main character you are 👑💖