Why is this an issue?
This rule raises an issue when an insecure TLS protocol version (i.e. a protocol different from "TLSv1.2", "TLSv1.3", "DTLSv1.2", or "DTLSv1.3") is
used or allowed.
It is recommended to enforce TLS 1.2 as the minimum protocol version and to disallow older versions like TLS 1.0. Failure to do so could open the
door to downgrade attacks: a malicious actor who is able to intercept the connection could modify the requested protocol version and downgrade it to a
less secure version.
In most cases, using the default system configuration is not compliant. Indeed, an application might get deployed on a wide range of systems with
different configurations. While using a system’s default value might be safe on modern up-to-date systems, this might not be the case on older
systems. It is therefore recommended to explicitly set a safe configuration in every case.
Noncompliant code example
libcurl
#include <curl/curl.h>
CURL *curl;
curl_global_init(CURL_GLOBAL_DEFAULT);
// CURL_SSLVERSION_DEFAULT is the default option for CURLOPT_SSLVERSION
// It means legacy version TLSv1 and TLSv1.1 are enabled
curl = curl_easy_init(); // Noncompliant
curl_easy_setopt(curl, CURLOPT_URL, "https://example.com/");
// Perform the request
curl_easy_perform(curl);
#include <curl/curl.h>
CURL *curl;
curl_global_init(CURL_GLOBAL_DEFAULT);
curl = curl_easy_init();
curl_easy_setopt(curl, CURLOPT_URL, "https://example.com/");
curl_easy_setopt(curl, CURLOPT_SSLVERSION, CURL_SSLVERSION_TLSv1); // Noncompliant; legacy version TLSv1 and TLSv1.1 are enabled
//Perform the request
curl_easy_perform(curl);
OpenSSL
#include <openssl/ssl.h>
const SSL_METHOD *method = TLS_method(); // Noncompliant; legacy version TLSv1 and TLSv1.1 are enabled
SSL_CTX *ctx = SSL_CTX_new(method);
SSL *ssl = SSL_new(ctx);
// ...
SSL_connect(ssl);
botan
#include <botan/tls_client.h>
#include <botan/tls_callbacks.h>
#include <botan/tls_session_manager.h>
#include <botan/tls_policy.h>
#include <botan/auto_rng.h>
#include <botan/certstor.h>
#include <botan/certstor_system.h>
class Callbacks : public Botan::TLS::Callbacks
{
// ...
};
class Client_Credentials : public Botan::Credentials_Manager
{
// ...
};
Callbacks callbacks;
Botan::AutoSeeded_RNG rng;
Botan::TLS::Session_Manager_In_Memory session_mgr(rng);
Client_Credentials creds;
Botan::TLS::Policy policy; // Noncompliant: Default Policy has TLSv1.0 and DLTv1.0 as minimal versions
// open the tls connection
Botan::TLS::Client client(callbacks, session_mgr, creds, policy, rng,
Botan::TLS::Server_Information("example.com", 443),
Botan::TLS::Protocol_Version::TLS_V12);
Compliant solution
libcurl
#include <curl/curl.h>
CURL *curl;
curl_global_init(CURL_GLOBAL_DEFAULT);
curl = curl_easy_init();
curl_easy_setopt(curl, CURLOPT_URL, "https://example.com/");
curl_easy_setopt(curl, CURLOPT_SSLVERSION, CURL_SSLVERSION_TLSv1_2); // Compliant; enables TLSv1.2 / TLSv1.3 version only
// Perform the request
curl_easy_perform(curl);
OpenSSL
#include <openssl/ssl.h>
const SSL_METHOD *method = TLS_method();
SSL_CTX *ctx = SSL_CTX_new(method);
SSL_CTX_set_min_proto_version(ctx, TLS1_2_VERSION); // Compliant; enables TLSv1.2 / TLSv1.3 version only
SSL *ssl = SSL_new(ctx);
// ...
SSL_connect(ssl);
botan
#include <botan/tls_client.h>
#include <botan/tls_callbacks.h>
#include <botan/tls_session_manager.h>
#include <botan/tls_policy.h>
#include <botan/auto_rng.h>
#include <botan/certstor.h>
#include <botan/certstor_system.h>
class Callbacks : public Botan::TLS::Callbacks
{
// ...
};
class Client_Credentials : public Botan::Credentials_Manager
{
// ...
};
Callbacks callbacks;
Botan::AutoSeeded_RNG rng;
Botan::TLS::Session_Manager_In_Memory session_mgr(rng);
Client_Credentials creds;
Botan::TLS::Strict_Policy policy; // Compliant: Strict_Policy has TLSv1.2 and TLSv1.2 as minimal versions
// open the tls connection
Botan::TLS::Client client(callbacks, session_mgr, creds, policy, rng,
Botan::TLS::Server_Information("example.com", 443),
Botan::TLS::Protocol_Version::TLS_V12);
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