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Change SSL certificate file list to OpenSSL builtin load_verify_location

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Specifying SSL certificates for peer verification does an exact match,
making it a not-so-obvious alias for the fingerprints option. This
changes the checks to OpenSSL which loads concatenated certificate(s)
from a single file and does a certificate-authority (chain of trust)
check instead. There is no drop in security - a compromised exact match
fingerprint has the same worse case failure. There is increased security
in allowing separate long-term CA key and short-term SSL server keys.

This also removes loading of the system-default CA files if a custom
CA file or certificate fingerprint is specified.
This commit is contained in:
Lee Clagett 2019-03-11 22:01:03 -04:00
parent 5dbcceb664
commit a3b0284837
13 changed files with 92 additions and 134 deletions
Download patch file Download diff file Expand all files Collapse all files

98
contrib/epee/src/net_ssl.cpp
View file

@ -77,6 +77,21 @@ namespace
}
};
using openssl_bignum = std::unique_ptr<BIGNUM, openssl_bignum_free>;
boost::system::error_code load_ca_file(boost::asio::ssl::context& ctx, const std::string& path)
{
SSL_CTX* const ssl_ctx = ctx.native_handle(); // could be moved from context
if (ssl_ctx == nullptr)
return {boost::asio::error::invalid_argument};
if (!SSL_CTX_load_verify_locations(ssl_ctx, path.c_str(), nullptr))
{
return boost::system::error_code{
int(::ERR_get_error()), boost::asio::error::get_ssl_category()
};
}
return boost::system::error_code{};
}
}
namespace epee
@ -84,6 +99,7 @@ namespace epee
namespace net_utils
{
// https://stackoverflow.com/questions/256405/programmatically-create-x509-certificate-using-openssl
bool create_ssl_certificate(EVP_PKEY *&pkey, X509 *&cert)
{
@ -155,9 +171,9 @@ bool create_ssl_certificate(EVP_PKEY *&pkey, X509 *&cert)
return true;
}
ssl_context_t create_ssl_context(const std::pair<std::string, std::string> &private_key_and_certificate_path, std::list<std::string> allowed_certificates, std::vector<std::vector<uint8_t>> allowed_fingerprints, bool allow_any_cert)
ssl_context_t create_ssl_context(const std::pair<std::string, std::string> &private_key_and_certificate_path, const std::string &ca_path, std::vector<std::vector<uint8_t>> allowed_fingerprints, bool allow_any_cert)
{
ssl_context_t ssl_context{boost::asio::ssl::context(boost::asio::ssl::context::tlsv12), std::move(allowed_certificates), std::move(allowed_fingerprints)};
ssl_context_t ssl_context{boost::asio::ssl::context(boost::asio::ssl::context::tlsv12), std::move(ca_path), std::move(allowed_fingerprints)};
// only allow tls v1.2 and up
ssl_context.context.set_options(boost::asio::ssl::context::default_workarounds);
@ -186,7 +202,15 @@ ssl_context_t create_ssl_context(const std::pair<std::string, std::string> &priv
#ifdef SSL_OP_NO_COMPRESSION
SSL_CTX_set_options(ctx, SSL_OP_NO_COMPRESSION);
#endif
ssl_context.context.set_default_verify_paths();
if (!ssl_context.ca_path.empty())
{
const boost::system::error_code err = load_ca_file(ssl_context.context, ssl_context.ca_path);
if (err)
throw boost::system::system_error{err, "Failed to load user CA file at " + ssl_context.ca_path};
}
else if (allowed_fingerprints.empty())
ssl_context.context.set_default_verify_paths(); // only use system-CAs if no user-supplied cert info
CHECK_AND_ASSERT_THROW_MES(private_key_and_certificate_path.first.empty() == private_key_and_certificate_path.second.empty(), "private key and certificate must be either both given or both empty");
if (private_key_and_certificate_path.second.empty())
@ -237,21 +261,21 @@ bool is_ssl(const unsigned char *data, size_t len)
bool is_certificate_allowed(boost::asio::ssl::verify_context &ctx, const ssl_context_t &ssl_context)
{
X509_STORE_CTX *sctx = ctx.native_handle();
if (!sctx)
{
MERROR("Error getting verify_context handle");
return false;
}
X509 *cert =X509_STORE_CTX_get_current_cert(sctx);
if (!cert)
{
MERROR("No certificate found in verify_context");
return false;
}
// can we check the certificate against a list of fingerprints?
if (!ssl_context.allowed_fingerprints.empty()) {
X509_STORE_CTX *sctx = ctx.native_handle();
if (!sctx)
{
MERROR("Error getting verify_context handle");
return false;
}
X509 *cert =X509_STORE_CTX_get_current_cert(sctx);
if (!cert)
{
MERROR("No certificate found in verify_context");
return false;
}
// buffer for the certificate digest and the size of the result
std::vector<uint8_t> digest(EVP_MAX_MD_SIZE);
unsigned int size{ 0 };
@ -270,52 +294,20 @@ bool is_certificate_allowed(boost::asio::ssl::verify_context &ctx, const ssl_con
return true;
}
if (!ssl_context.allowed_certificates.empty()) {
BIO *bio_cert = BIO_new(BIO_s_mem());
bool success = PEM_write_bio_X509(bio_cert, cert);
if (!success)
{
BIO_free(bio_cert);
MERROR("Failed to print certificate");
return false;
}
BUF_MEM *buf = NULL;
BIO_get_mem_ptr(bio_cert, &buf);
if (!buf || !buf->data || !buf->length)
{
BIO_free(bio_cert);
MERROR("Failed to write certificate: " << ERR_get_error());
return false;
}
std::string certificate(std::string(buf->data, buf->length));
BIO_free(bio_cert);
if (std::find(ssl_context.allowed_certificates.begin(), ssl_context.allowed_certificates.end(), certificate) != ssl_context.allowed_certificates.end())
return true;
}
// if either checklist is non-empty we must have failed it
return ssl_context.allowed_fingerprints.empty() && ssl_context.allowed_certificates.empty();
return ssl_context.allowed_fingerprints.empty() && ssl_context.ca_path.empty();
}
bool ssl_handshake(boost::asio::ssl::stream<boost::asio::ip::tcp::socket> &socket, boost::asio::ssl::stream_base::handshake_type type, const epee::net_utils::ssl_context_t &ssl_context)
{
bool verified = false;
socket.next_layer().set_option(boost::asio::ip::tcp::no_delay(true));
socket.set_verify_mode(boost::asio::ssl::verify_peer);
socket.set_verify_callback([&](bool preverified, boost::asio::ssl::verify_context &ctx)
{
if (!preverified)
{
const int err = X509_STORE_CTX_get_error(ctx.native_handle());
const int depth = X509_STORE_CTX_get_error_depth(ctx.native_handle());
if (err != X509_V_ERR_DEPTH_ZERO_SELF_SIGNED_CERT || depth != 0)
{
MERROR("Invalid SSL certificate, error " << err << " at depth " << depth << ", connection dropped");
return false;
}
}
if (!ssl_context.allow_any_cert && !is_certificate_allowed(ctx, ssl_context))
{
// preverified means it passed system or user CA check. System CA is never loaded
// when fingerprints are whitelisted.
if (!preverified && !ssl_context.allow_any_cert && !is_certificate_allowed(ctx, ssl_context)) {
MERROR("Certificate is not in the allowed list, connection droppped");
return false;
}