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Set the TLS security level early and on context
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The existing code does work for cipher negotiation with old
(FortiOS 4?) FortiGate appliances, but not for personal certificates
(SHA-1 certificates).

Two reasons I can see:
* SSL_set_cipher_list() was called after messing with certificates.
* SSL_set_cipher_list() applies only to the SSL connection, not to
  certificates, call SSL_CTX_set_cipher_list() on context instead.

This change addresses both of the above issues.

See SSL(7) man page:
https://www.openssl.org/docs/man1.1.1/man7/ssl.html#DATA-STRUCTURES

SSL_CTX (SSL Context)
This is the global context structure which is created by a server or client once per program life-time and which holds mainly default values for the SSL structures which are later created for the connections.

SSL (SSL Connection)
This is the main SSL/TLS structure which is created by a server or client per established connection. This actually is the core structure in the SSL API. At run-time the application usually deals with this structure which has links to mostly all other structures.
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@DimitriPapadopoulos
DimitriPapadopoulos committed May 4, 2020
1 parent 92392b4 commit fe46c2c
Showing 1 changed file with 59 additions and 58 deletions.
117 changes: 59 additions & 58 deletions src/tunnel.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -836,7 +836,7 @@ int ssl_connect(struct tunnel *tunnel)
return 1;
}

// Load the OS default CA files
/* Load the OS default CA files */
if (!SSL_CTX_set_default_verify_paths(tunnel->ssl_context))
log_error("Could not load OS OpenSSL files.\n");

Expand All @@ -850,6 +850,64 @@ int ssl_connect(struct tunnel *tunnel)
}
}

/* Modify default TLS security levels */
if (!tunnel->config->insecure_ssl) {
long sslctxopt = SSL_OP_NO_SSLv3 | SSL_OP_NO_COMPRESSION;
long checkopt;

checkopt = SSL_CTX_set_options(tunnel->ssl_context, sslctxopt);
if ((checkopt & sslctxopt) != sslctxopt) {
log_error("SSL_CTX_set_options didn't set opt: %s\n",
ERR_error_string(ERR_peek_last_error(), NULL));
return 1;
}
}

if (!tunnel->config->insecure_ssl) {
if (!tunnel->config->cipher_list) {
const char *cipher_list;

if (tunnel->config->seclevel_1)
cipher_list = "HIGH:!aNULL:!kRSA:!PSK:!SRP:!MD5:!RC4@SECLEVEL=1";
else
cipher_list = "HIGH:!aNULL:!kRSA:!PSK:!SRP:!MD5:!RC4";
tunnel->config->cipher_list = strdup(cipher_list);
}
} else {
#if OPENSSL_VERSION_NUMBER >= 0x10100000L
if (tunnel->config->min_tls <= 0)
tunnel->config->min_tls = TLS1_VERSION;
#endif
if (!tunnel->config->cipher_list && tunnel->config->seclevel_1) {
const char *cipher_list = "DEFAULT@SECLEVEL=1";

tunnel->config->cipher_list = strdup(cipher_list);
}
}

if (tunnel->config->cipher_list) {
log_debug("Setting cipher list to: %s\n", tunnel->config->cipher_list);
if (!SSL_CTX_set_cipher_list(tunnel->ssl_context,
tunnel->config->cipher_list)) {
log_error("SSL_CTX_set_cipher_list failed: %s\n",
ERR_error_string(ERR_peek_last_error(), NULL));
return 1;
}
}

#if OPENSSL_VERSION_NUMBER >= 0x10100000L
if (tunnel->config->min_tls > 0) {
log_debug("Setting min proto version to: 0x%x\n",
tunnel->config->min_tls);
if (!SSL_CTX_set_min_proto_version(tunnel->ssl_context,
tunnel->config->min_tls)) {
log_error("SSL_CTX_set_min_proto_version failed: %s\n",
ERR_error_string(ERR_peek_last_error(), NULL));
return 1;
}
}
#endif

/* Use engine for PIV if user-cert config starts with pkcs11 URI: */
if (tunnel->config->use_engine > 0) {

Expand Down Expand Up @@ -942,70 +1000,13 @@ int ssl_connect(struct tunnel *tunnel)
}
}

if (!tunnel->config->insecure_ssl) {
long sslctxopt = SSL_OP_NO_SSLv3 | SSL_OP_NO_COMPRESSION;
long checkopt;

checkopt = SSL_CTX_set_options(tunnel->ssl_context, sslctxopt);
if ((checkopt & sslctxopt) != sslctxopt) {
log_error("SSL_CTX_set_options didn't set opt: %s\n",
ERR_error_string(ERR_peek_last_error(), NULL));
return 1;
}
}

tunnel->ssl_handle = SSL_new(tunnel->ssl_context);
if (tunnel->ssl_handle == NULL) {
log_error("SSL_new: %s\n",
ERR_error_string(ERR_peek_last_error(), NULL));
return 1;
}

if (!tunnel->config->insecure_ssl) {
if (!tunnel->config->cipher_list) {
const char *cipher_list;

if (tunnel->config->seclevel_1)
cipher_list = "HIGH:!aNULL:!kRSA:!PSK:!SRP:!MD5:!RC4@SECLEVEL=1";
else
cipher_list = "HIGH:!aNULL:!kRSA:!PSK:!SRP:!MD5:!RC4";
tunnel->config->cipher_list = strdup(cipher_list);
}
} else {
#if OPENSSL_VERSION_NUMBER >= 0x10100000L
if (tunnel->config->min_tls <= 0)
tunnel->config->min_tls = TLS1_VERSION;
#endif
if (!tunnel->config->cipher_list && tunnel->config->seclevel_1) {
const char *cipher_list = "DEFAULT@SECLEVEL=1";

tunnel->config->cipher_list = strdup(cipher_list);
}
}

if (tunnel->config->cipher_list) {
log_debug("Setting cipher list to: %s\n", tunnel->config->cipher_list);
if (!SSL_set_cipher_list(tunnel->ssl_handle,
tunnel->config->cipher_list)) {
log_error("SSL_set_cipher_list failed: %s\n",
ERR_error_string(ERR_peek_last_error(), NULL));
return 1;
}
}

#if OPENSSL_VERSION_NUMBER >= 0x10100000L
if (tunnel->config->min_tls > 0) {
log_debug("Setting min proto version to: 0x%x\n",
tunnel->config->min_tls);
if (!SSL_set_min_proto_version(tunnel->ssl_handle,
tunnel->config->min_tls)) {
log_error("SSL_set_min_proto_version failed: %s\n",
ERR_error_string(ERR_peek_last_error(), NULL));
return 1;
}
}
#endif

if (!SSL_set_fd(tunnel->ssl_handle, tunnel->ssl_socket)) {
log_error("SSL_set_fd: %s\n",
ERR_error_string(ERR_peek_last_error(), NULL));
Expand Down

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