diff --git a/composer.json b/composer.json
index ec4a090d..e1951679 100644
--- a/composer.json
+++ b/composer.json
@@ -32,7 +32,9 @@
             "inc/mod/auth.php",
             "inc/lock.php",
             "inc/queue.php",
-            "inc/functions.php"
+            "inc/functions.php",
+            "inc/driver/http-driver.php",
+            "inc/service/captcha-queries.php"
         ]
     },
     "license": "Tinyboard + vichan",
diff --git a/inc/config.php b/inc/config.php
index 9140201c..23c31990 100644
--- a/inc/config.php
+++ b/inc/config.php
@@ -1231,6 +1231,8 @@
 	$config['error']['captcha']		= _('You seem to have mistyped the verification.');
 	$config['error']['flag_undefined']	= _('The flag %s is undefined, your PHP version is too old!');
 	$config['error']['flag_wrongtype']	= _('defined_flags_accumulate(): The flag %s is of the wrong type!');
+	$config['error']['remote_io_error']	= _('IO error while interacting with a remote service.');
+	$config['error']['local_io_error']	= _('IO error while interacting with a local resource or service.');
 
 
 	// Moderator errors
diff --git a/inc/context.php b/inc/context.php
new file mode 100644
index 00000000..5e540bab
--- /dev/null
+++ b/inc/context.php
@@ -0,0 +1,28 @@
+<?php
+namespace Vichan;
+
+defined('TINYBOARD') or exit;
+
+use Vichan\Driver\{HttpDriver, HttpDrivers};
+
+
+interface Context {
+	public function getHttpDriver(): HttpDriver;
+}
+
+class AppContext implements Context {
+	private array $config;
+	private ?HttpDriver $http;
+
+
+	public function __construct(array $config) {
+		$this->config = $config;
+	}
+
+	public function getHttpDriver(): HttpDriver {
+		if (is_null($this->http)) {
+			$this->http = HttpDrivers::getHttpDriver($this->config['upload_by_url_timeout'], $this->config['max_filesize']);
+		}
+		return $this->http;
+	}
+}
diff --git a/inc/driver/http-driver.php b/inc/driver/http-driver.php
new file mode 100644
index 00000000..cfbedfad
--- /dev/null
+++ b/inc/driver/http-driver.php
@@ -0,0 +1,151 @@
+<?php // Honestly this is just a wrapper for cURL. Still useful to mock it and have an OOP API on PHP 7.
+namespace Vichan\Driver;
+
+use RuntimeException;
+
+defined('TINYBOARD') or exit;
+
+
+class HttpDrivers {
+	private const DEFAULT_USER_AGENT = 'Tinyboard';
+
+
+	public static function getHttpDriver(int $timeout, int $max_file_size): HttpDriver {
+		return new HttpDriver($timeout, self::DEFAULT_USER_AGENT, $max_file_size);
+	}
+}
+
+class HttpDriver {
+	private mixed $inner;
+	private int $timeout;
+	private string $user_agent;
+	private int $max_file_size;
+
+
+	private function resetTowards(string $url, int $timeout): void {
+		curl_reset($this->inner);
+		curl_setopt_array($this->inner, array(
+			CURLOPT_URL => $url,
+			CURLOPT_TIMEOUT => $this->timeout,
+			CURLOPT_USERAGENT => $this->user_agent,
+			CURLOPT_PROTOCOLS => CURLPROTO_HTTP | CURLPROTO_HTTPS,
+		));
+	}
+
+	private function setSizeLimit(): void {
+		// Adapted from: https://stackoverflow.com/a/17642638
+		curl_setopt($this->inner, CURLOPT_NOPROGRESS, false);
+
+		if (PHP_MAJOR_VERSION >= 8 && PHP_MINOR_VERSION >= 2) {
+			curl_setopt($this->inner, CURLOPT_XFERINFOFUNCTION, function($res, $next_dl, $dl, $next_up, $up) {
+				return (int)($dl <= $this->max_file_size);
+			});
+		} else {
+			curl_setopt($this->inner, CURLOPT_PROGRESSFUNCTION, function($res, $next_dl, $dl, $next_up, $up) {
+				return (int)($dl <= $this->max_file_size);
+			});
+		}
+	}
+
+	function __construct($timeout, $user_agent, $max_file_size) {
+		$this->inner = curl_init();
+		$this->timeout = $timeout;
+		$this->user_agent = $user_agent;
+		$this->max_file_size = $max_file_size;
+	}
+
+	function __destruct() {
+		curl_close($this->inner);
+	}
+
+	/**
+	 * Execute a GET request.
+	 *
+	 * @param string $endpoint Uri endpoint.
+	 * @param ?array $data Optional GET parameters.
+	 * @param int $timeout Optional request timeout in seconds. Use the default timeout if 0.
+	 * @return string Returns the body of the response.
+	 * @throws RuntimeException Throws on IO error.
+	 */
+	public function requestGet(string $endpoint, ?array $data, int $timeout = 0): string {
+		if (!empty($data)) {
+			$endpoint .= '?' . http_build_query($data);
+		}
+		if ($timeout == 0) {
+			$timeout = $this->timeout;
+		}
+
+		$this->resetTowards($endpoint, $timeout);
+		curl_setopt($this->inner, CURLOPT_RETURNTRANSFER, true);
+		$ret = curl_exec($this->inner);
+
+		if ($ret === false) {
+			throw new \RuntimeException(curl_error($this->inner));
+		}
+		return $ret;
+	}
+
+	/**
+	 * Execute a POST request.
+	 *
+	 * @param string $endpoint Uri endpoint.
+	 * @param ?array $data Optional POST parameters.
+	 * @param int $timeout Optional request timeout in seconds. Use the default timeout if 0.
+	 * @return string Returns the body of the response.
+	 * @throws RuntimeException Throws on IO error.
+	 */
+	public function requestPost(string $endpoint, ?array $data, int $timeout = 0): string {
+		if ($timeout == 0) {
+			$timeout = $this->timeout;
+		}
+
+		$this->resetTowards($endpoint, $timeout);
+		curl_setopt($this->inner, CURLOPT_POST, true);
+		if (!empty($data)) {
+			curl_setopt($this->inner, CURLOPT_POSTFIELDS, http_build_query($data));
+		}
+		curl_setopt($this->inner, CURLOPT_RETURNTRANSFER, true);
+		$ret = curl_exec($this->inner);
+
+		if ($ret === false) {
+			throw new \RuntimeException(curl_error($this->inner));
+		}
+		return $ret;
+	}
+
+	/**
+	 * Download the url's target with curl.
+	 *
+	 * @param string $url Url to the file to download.
+	 * @param ?array $data Optional GET parameters.
+	 * @param resource $fd File descriptor to save the content to.
+	 * @param int $timeout Optional request timeout in seconds. Use the default timeout if 0.
+	 * @return bool Returns true on success, false if the file was too large.
+	 * @throws RuntimeException Throws on IO error.
+	 */
+	public function requestGetInto(string $endpoint, ?array $data, mixed $fd, int $timeout = 0): bool {
+		if (!empty($data)) {
+			$endpoint .= '?' . http_build_query($data);
+		}
+		if ($timeout == 0) {
+			$timeout = $this->timeout;
+		}
+
+		$this->resetTowards($endpoint, $timeout);
+		curl_setopt($this->inner, CURLOPT_FAILONERROR, true);
+		curl_setopt($this->inner, CURLOPT_FOLLOWLOCATION, false);
+		curl_setopt($this->inner, CURLOPT_FILE, $fd);
+		curl_setopt($this->inner, CURLOPT_IPRESOLVE, CURL_IPRESOLVE_V4);
+		$this->setSizeLimit();
+		$ret = curl_exec($this->inner);
+
+		if ($ret === false) {
+			if (curl_errno($this->inner) === CURLE_ABORTED_BY_CALLBACK) {
+				return false;
+			}
+
+			throw new \RuntimeException(curl_error($this->inner));
+		}
+		return true;
+	}
+}
diff --git a/inc/service/captcha-queries.php b/inc/service/captcha-queries.php
new file mode 100644
index 00000000..d7966501
--- /dev/null
+++ b/inc/service/captcha-queries.php
@@ -0,0 +1,102 @@
+<?php // Verify captchas server side.
+namespace Vichan\Service;
+
+use Vichan\Driver\HttpDriver;
+
+defined('TINYBOARD') or exit;
+
+
+class RemoteCaptchaQuery {
+	private HttpDriver $http;
+	private string $secret;
+	private string $endpoint;
+
+
+	/**
+	 * Creates a new CaptchaRemoteQueries instance using the google recaptcha service.
+	 *
+	 * @param HttpDriver $http The http client.
+	 * @param string $secret Server side secret.
+	 * @return CaptchaRemoteQueries A new captcha query instance.
+	 */
+	public static function withRecaptcha(HttpDriver $http, string $secret): RemoteCaptchaQuery {
+		return new self($http, $secret, 'https://www.google.com/recaptcha/api/siteverify');
+	}
+
+	/**
+	 * Creates a new CaptchaRemoteQueries instance using the hcaptcha service.
+	 *
+	 * @param HttpDriver $http The http client.
+	 * @param string $secret Server side secret.
+	 * @return CaptchaRemoteQueries A new captcha query instance.
+	 */
+	public static function withHCaptcha(HttpDriver $http, string $secret): RemoteCaptchaQuery {
+		return new self($http, $secret, 'https://hcaptcha.com/siteverify');
+	}
+
+	private function __construct(HttpDriver $http, string $secret, string $endpoint) {
+		$this->http = $http;
+		$this->secret = $secret;
+		$this->endpoint = $endpoint;
+	}
+
+	/**
+	 * Checks if the user at the remote ip passed the captcha.
+	 *
+	 * @param string $response User provided response.
+	 * @param string $remote_ip User ip.
+	 * @return bool Returns true if the user passed the captcha.
+	 * @throws RuntimeException|JsonException Throws on IO errors or if it fails to decode the answer.
+	 */
+	public function verify(string $response, string $remote_ip): bool {
+		$data = array(
+			'secret' => $this->secret,
+			'response' => $response,
+			'remoteip' => $remote_ip
+		);
+
+		$ret = $this->http->requestGet($this->endpoint, $data);
+		$resp = json_decode($ret, true, 16, JSON_THROW_ON_ERROR);
+
+		return isset($resp['success']) && $resp['success'];
+	}
+}
+
+class NativeCaptchaQuery {
+	private HttpDriver $http;
+	private string $domain;
+	private string $provider_check;
+
+
+	/**
+	 * @param HttpDriver $http The http client.
+	 * @param string $domain The server's domain.
+	 * @param string $provider_check Path to the endpoint.
+	 */
+	function __construct(HttpDriver $http, string $domain, string $provider_check) {
+		$this->http = $http;
+		$this->domain = $domain;
+		$this->provider_check = $provider_check;
+	}
+
+	/**
+	 * Checks if the user at the remote ip passed the native vichan captcha.
+	 *
+	 * @param string $extra Extra http parameters.
+	 * @param string $user_text Remote user's text input.
+	 * @param string $user_cookie Remote user cookie.
+	 * @return bool Returns true if the user passed the check.
+	 * @throws RuntimeException Throws on IO errors.
+	 */
+	public function verify(string $extra, string $user_text, string $user_cookie): bool {
+		$data = array(
+			'mode' => 'check',
+			'text' => $user_text,
+			'extra' => $extra,
+			'cookie' => $user_cookie
+		);
+
+		$ret = $this->http->requestGet($this->domain . '/' . $this->provider_check, $data);
+		return $ret === '1';
+	}
+}
diff --git a/post.php b/post.php
index e22171ea..d0e30bdc 100644
--- a/post.php
+++ b/post.php
@@ -5,6 +5,10 @@
 
 require_once 'inc/bootstrap.php';
 
+use Vichan\AppContext;
+use Vichan\Driver\HttpDriver;
+use Vichan\Service\{RemoteCaptchaQuery, NativeCaptchaQuery};
+
 /**
  * Utility functions
  */
@@ -61,54 +65,27 @@ function strip_symbols($input) {
 	}
 }
 
-/**
- * Download the url's target with curl.
- *
- * @param string $url Url to the file to download.
- * @param int $timeout Request timeout in seconds.
- * @param File $fd File descriptor to save the content to.
- * @return null|string Returns a string on error.
- */
-function download_file_into($url, $timeout, $fd) {
-	$err = null;
-	$curl = curl_init();
-	curl_setopt($curl, CURLOPT_URL, $url);
-	curl_setopt($curl, CURLOPT_FAILONERROR, true);
-	curl_setopt($curl, CURLOPT_FOLLOWLOCATION, false);
-	curl_setopt($curl, CURLOPT_CONNECTTIMEOUT, 5);
-	curl_setopt($curl, CURLOPT_TIMEOUT, $timeout);
-	curl_setopt($curl, CURLOPT_USERAGENT, 'Tinyboard');
-	curl_setopt($curl, CURLOPT_FILE, $fd);
-	curl_setopt($curl, CURLOPT_PROTOCOLS, CURLPROTO_HTTP | CURLPROTO_HTTPS);
-	curl_setopt($curl, CURLOPT_IPRESOLVE, CURL_IPRESOLVE_V4);
-
-	if (curl_exec($curl) === false) {
-		$err = curl_error($curl);
-	}
-
-	curl_close($curl);
-	return $err;
-}
-
 /**
  * Download a remote file from the given url.
  * The file is deleted at shutdown.
  *
+ * @param HttpDriver $http The http client.
  * @param string $file_url The url to download the file from.
  * @param int $request_timeout Timeout to retrieve the file.
  * @param array $extra_extensions Allowed file extensions.
  * @param string $tmp_dir Temporary directory to save the file into.
  * @param array $error_array An array with error codes, used to create exceptions on failure.
- * @return array Returns an array describing the file on success.
- * @throws Exception on error.
+ * @return array|false Returns an array describing the file on success, or false if the file was too large
+ * @throws InvalidArgumentException|RuntimeException Throws on invalid arguments and IO errors.
  */
-function download_file_from_url($file_url, $request_timeout, $allowed_extensions, $tmp_dir, &$error_array) {
+function download_file_from_url(HttpDriver $http, $file_url, $request_timeout, $allowed_extensions, $tmp_dir, &$error_array) {
 	if (!preg_match('@^https?://@', $file_url)) {
 		throw new InvalidArgumentException($error_array['invalidimg']);
 	}
 
-	if (mb_strpos($file_url, '?') !== false) {
-		$url_without_params = mb_substr($file_url, 0, mb_strpos($file_url, '?'));
+	$param_idx = mb_strpos($file_url, '?');
+	if ($param_idx !== false) {
+		$url_without_params = mb_substr($file_url, 0, $param_idx);
 	} else {
 		$url_without_params = $file_url;
 	}
@@ -128,10 +105,13 @@ function download_file_from_url($file_url, $request_timeout, $allowed_extensions
 
 	$fd = fopen($tmp_file, 'w');
 
-	$dl_err = download_file_into($fd, $request_timeout, $fd);
-	fclose($fd);
-	if ($dl_err !== null) {
-		throw new Exception($error_array['nomove'] . '<br/>Curl says: ' . $dl_err);
+	try {
+		$success = $http->requestGetInto($url_without_params, null, $fd, $request_timeout);
+		if (!$success) {
+			return false;
+		}
+	} finally {
+		fclose($fd);
 	}
 
 	return array(
@@ -165,6 +145,7 @@ function ocr_image(array $config, string $img_path): string {
 	return trim($ret);
 }
 
+
 /**
  * Trim an image's EXIF metadata
  *
@@ -190,6 +171,7 @@ function strip_image_metadata(string $img_path): int {
  */
 
 $dropped_post = false;
+$context = new AppContext($config);
 
 // Is it a post coming from NNTP? Let's extract it and pretend it's a normal post.
 if (isset($_GET['Newsgroups']) && $config['nntpchan']['enabled']) {
@@ -487,22 +469,32 @@ if (isset($_POST['delete'])) {
 	if (count($report) > $config['report_limit'])
 		error($config['error']['toomanyreports']);
 
-	if ($config['report_captcha'] && !isset($_POST['captcha_text'], $_POST['captcha_cookie'])) {
-		error($config['error']['bot']);
-	}
 
 	if ($config['report_captcha']) {
-		$ch = curl_init($config['domain'].'/'.$config['captcha']['provider_check'] . "?" . http_build_query([
-			'mode' => 'check',
-			'text' => $_POST['captcha_text'],
-			'extra' => $config['captcha']['extra'],
-			'cookie' => $_POST['captcha_cookie']
-		]));
-		curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
-		$resp = curl_exec($ch);
+		if (!isset($_POST['captcha_text'], $_POST['captcha_cookie'])) {
+			error($config['error']['bot']);
+		}
 
-		if ($resp !== '1') {
-			error($config['error']['captcha']);
+		try {
+			$query = new NativeCaptchaQuery(
+				$context->getHttpDriver(),
+				$config['domain'],
+				$config['captcha']['provider_check']
+			);
+			$success = $query->verify(
+				$config['captcha']['extra'],
+				$_POST['captcha_text'],
+				$_POST['captcha_cookie']
+			);
+
+			if (!$success) {
+				error($config['error']['captcha']);
+			}
+		} catch (RuntimeException $e) {
+			if ($config['syslog']) {
+				_syslog(LOG_ERR, "Native captcha IO exception: {$e->getMessage()}");
+			}
+			error($config['error']['local_io_error']);
 		}
 	}
 
@@ -592,62 +584,60 @@ if (isset($_POST['delete'])) {
 		// Check if banned
 		checkBan($board['uri']);
 
-		// Check for CAPTCHA right after opening the board so the "return" link is in there
-		if ($config['recaptcha']) {
-			if (!isset($_POST['g-recaptcha-response']))
-				error($config['error']['bot']);
+		// Check for CAPTCHA right after opening the board so the "return" link is in there.
+		try {
+			// With our custom captcha provider
+			if ($config['captcha']['enabled'] || ($post['op'] && $config['new_thread_capt'])) {
+				$query = new NativeCaptchaQuery($context->getHttpDriver(), $config['domain'], $config['captcha']['provider_check']);
+				$success = $query->verify($config['captcha']['extra'], $_POST['captcha_text'], $_POST['captcha_cookie']);
 
-			// Check what reCAPTCHA has to say...
-			$resp = json_decode(file_get_contents(sprintf('https://www.recaptcha.net/recaptcha/api/siteverify?secret=%s&response=%s&remoteip=%s',
-				$config['recaptcha_private'],
-				urlencode($_POST['g-recaptcha-response']),
-				$_SERVER['REMOTE_ADDR'])), true);
-
-			if (!$resp['success']) {
-				error($config['error']['captcha']);
+				if (!$success) {
+					error(
+						$config['error']['captcha']
+						. '<script>if (actually_load_captcha !== undefined) actually_load_captcha("'
+						. $config['captcha']['provider_get']
+						.'", "'
+						. $config['captcha']['extra']
+						. '");</script>'
+					);
+				}
 			}
-		}
-		// hCaptcha
-		if ($config['hcaptcha']) {
-			if (!isset($_POST['h-captcha-response'])) {
-				error($config['error']['bot']);
+			// Remote 3rd party captchas.
+			else {
+				// recaptcha
+				if ($config['recaptcha']) {
+					if (!isset($_POST['g-recaptcha-response'])) {
+						error($config['error']['bot']);
+					}
+					$response = $_POST['g-recaptcha-response'];
+					$query = RemoteCaptchaQuery::withRecaptcha($context->getHttpDriver(), $config['recaptcha_private']);
+				}
+				// hCaptcha
+				elseif ($config['hcaptcha']) {
+					if (!isset($_POST['h-captcha-response'])) {
+						error($config['error']['bot']);
+					}
+					$response = $_POST['g-recaptcha-response'];
+					$query = RemoteCaptchaQuery::withHCaptcha($context->getHttpDriver(), $config['hcaptcha_private']);
+				}
+
+				$success = $query->verify($response, $_SERVER['REMOTE_ADDR']);
+				if (!$success) {
+					error($config['error']['captcha']);
+				}
 			}
-
-			$data = array(
-				'secret' => $config['hcaptcha_private'],
-				'response' => $_POST['h-captcha-response'],
-				'remoteip' => $_SERVER['REMOTE_ADDR']
-			);
-
-			$hcaptchaverify = curl_init();
-			curl_setopt($hcaptchaverify, CURLOPT_URL, "https://hcaptcha.com/siteverify");
-			curl_setopt($hcaptchaverify, CURLOPT_POST, true);
-			curl_setopt($hcaptchaverify, CURLOPT_POSTFIELDS, http_build_query($data));
-			curl_setopt($hcaptchaverify, CURLOPT_RETURNTRANSFER, true);
-			$hcaptcharesponse = curl_exec($hcaptchaverify);
-
-			$resp = json_decode($hcaptcharesponse, true); // Decoding $hcaptcharesponse instead of $response
-
-			if (!$resp['success']) {
-				error($config['error']['captcha']);
+		} catch (RuntimeException $e) {
+			if ($config['syslog']) {
+				_syslog(LOG_ERR, "Captcha IO exception: {$e->getMessage()}");
 			}
+			error($config['error']['remote_io_error']);
+		} catch (JsonException $e) {
+			if ($config['syslog']) {
+				_syslog(LOG_ERR, "Bad JSON reply to captcha: {$e->getMessage()}");
+			}
+			error($config['error']['remote_io_error']);
 		}
-		// Same, but now with our custom captcha provider
- 		if (($config['captcha']['enabled']) || (($post['op']) && ($config['new_thread_capt'])) ) {
-		$ch = curl_init($config['domain'].'/'.$config['captcha']['provider_check'] . "?" . http_build_query([
-			'mode' => 'check',
-			'text' => $_POST['captcha_text'],
-			'extra' => $config['captcha']['extra'],
-			'cookie' => $_POST['captcha_cookie']
-		]));
-		curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
-		$resp = curl_exec($ch);
 
-		if ($resp !== '1') {
-			error($config['error']['captcha'] .
-				'<script>if (actually_load_captcha !== undefined) actually_load_captcha("'.$config['captcha']['provider_get'].'", "'.$config['captcha']['extra'].'");</script>');
-		}
-	}
 
 		if (!(($post['op'] && $_POST['post'] == $config['button_newtopic']) ||
 			(!$post['op'] && $_POST['post'] == $config['button_reply'])))
@@ -751,7 +741,21 @@ if (isset($_POST['delete'])) {
 		}
 
 		try {
-			$_FILES['file'] = download_file_from_url($_POST['file_url'], $config['upload_by_url_timeout'], $allowed_extensions, $config['tmp'], $config['error']);
+			$ret = download_file_from_url(
+				$context->getHttpDriver(),
+				$_POST['file_url'],
+				$config['upload_by_url_timeout'],
+				$allowed_extensions,
+				$config['tmp'],
+				$config['error']
+			);
+			if ($ret === false) {
+				error(sprintf3($config['error']['filesize'], array(
+					'filesz' => 'more than that',
+					'maxsz' => number_format($config['max_filesize'])
+				)));
+			}
+			$_FILES['file'] = $ret;
 		} catch (Exception $e) {
 			error($e->getMessage());
 		}