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module;
#include <mbedtls/ssl.h>
#include <mbedtls/entropy.h>
#include <mbedtls/ctr_drbg.h>
#include <mbedtls/x509_crt.h>
#include <mbedtls/error.h>
#include <mbedtls/net_sockets.h>
export module mcpplibs.tinyhttps:tls;
import :socket;
import :ca_bundle;
import std;
namespace mcpplibs::tinyhttps {
struct TlsState {
mbedtls_ssl_context ssl;
mbedtls_ssl_config conf;
mbedtls_ctr_drbg_context ctr_drbg;
mbedtls_entropy_context entropy;
mbedtls_x509_crt ca_cert;
TlsState() {
mbedtls_ssl_init(&ssl);
mbedtls_ssl_config_init(&conf);
mbedtls_ctr_drbg_init(&ctr_drbg);
mbedtls_entropy_init(&entropy);
mbedtls_x509_crt_init(&ca_cert);
}
~TlsState() {
mbedtls_ssl_free(&ssl);
mbedtls_ssl_config_free(&conf);
mbedtls_ctr_drbg_free(&ctr_drbg);
mbedtls_entropy_free(&entropy);
mbedtls_x509_crt_free(&ca_cert);
}
TlsState(const TlsState&) = delete;
TlsState& operator=(const TlsState&) = delete;
};
// BIO callbacks for mbedtls — forward to Socket read/write
static int bio_send(void* ctx, const unsigned char* buf, size_t len) {
auto* sock = static_cast<Socket*>(ctx);
int ret = sock->write(reinterpret_cast<const char*>(buf), static_cast<int>(len));
if (ret <= 0) {
return MBEDTLS_ERR_NET_SEND_FAILED;
}
return ret;
}
// A ZERO IS PASSED THROUGH, AND THAT IS THE WHOLE CONTRACT.
//
// This used to answer a `recv` of 0 — a peer that sent FIN, which is how nearly
// every server ends a connection-close-delimited response — with
// MBEDTLS_ERR_NET_CONN_RESET. mbedtls's own BIO does not: `mbedtls_net_recv`
// returns `read()`'s result unchanged and reserves CONN_RESET for an actual
// ECONNRESET/EPIPE (net_sockets.c). The distinction is not cosmetic, because
// `mbedtls_ssl_fetch_input` tests for exactly this zero —
//
// if (ret == 0) { return MBEDTLS_ERR_SSL_CONN_EOF; } ssl_msg.c:2251, :2320
//
// — and passes any negative value straight through. So the old mapping made an
// orderly end of stream indistinguishable from a transport error, one layer
// below `TlsSocket::read_some`, which then had to call it `Error`. A body whose
// framing IS the close then read as truncated: `download_to_file` set
// `result.error` and `ok()` returned false for a file that had arrived
// complete and correct.
static int bio_recv(void* ctx, unsigned char* buf, size_t len) {
auto* sock = static_cast<Socket*>(ctx);
int ret = sock->read(reinterpret_cast<char*>(buf), static_cast<int>(len));
if (ret < 0) {
return MBEDTLS_ERR_NET_RECV_FAILED;
}
return ret; // 0 means end of stream; mbedtls turns it into SSL_CONN_EOF
}
// WHAT A READ ENDED IN, WHICH `int` COULD NOT SAY.
//
// `TlsSocket::read` returned 0 for a peer that had closed AND for a transport
// that had no bytes ready yet, so every caller had to guess. They all guessed
// the same way — wait once more and try again — and a reader that cannot tell
// "the body ended here" from "nothing yet" cannot decide whether the connection
// is still reusable. That is root cause R3 behind issue #15.
//
// `Eof` is a fact about the stream and `WouldBlock` is a fact about this
// instant; naming them apart is what lets `read_body` below return `Complete`
// rather than a guess.
export enum class ReadStatus { Data, WouldBlock, Eof, Error };
export struct ReadResult {
ReadStatus status { ReadStatus::Error };
int bytes { 0 }; // meaningful only when status == Data
};
export class TlsSocket {
public:
TlsSocket() = default;
~TlsSocket() { close(); }
// Non-copyable
TlsSocket(const TlsSocket&) = delete;
TlsSocket& operator=(const TlsSocket&) = delete;
// Move constructor
TlsSocket(TlsSocket&& other) noexcept
: socket_(std::move(other.socket_))
, state_(std::move(other.state_)) {
// Re-bind BIO to point to our socket_ (not the moved-from one)
if (state_) {
mbedtls_ssl_set_bio(&state_->ssl, &socket_, bio_send, bio_recv, nullptr);
}
}
// Move assignment
TlsSocket& operator=(TlsSocket&& other) noexcept {
if (this != &other) {
close();
socket_ = std::move(other.socket_);
state_ = std::move(other.state_);
// Re-bind BIO to point to our socket_
if (state_) {
mbedtls_ssl_set_bio(&state_->ssl, &socket_, bio_send, bio_recv, nullptr);
}
}
return *this;
}
[[nodiscard]] bool is_valid() const {
return state_ != nullptr && socket_.is_valid();
}
// Connect over an already-established Socket (e.g. a proxy tunnel).
// Takes ownership of the socket and performs TLS handshake on top of it.
bool connect_over(Socket&& socket, const char* host, bool verifySsl) {
socket_ = std::move(socket);
return setup_tls(host, verifySsl);
}
bool connect(const char* host, int port, int timeoutMs, bool verifySsl) {
// Step 1: TCP connect via Socket
if (!socket_.connect(host, port, timeoutMs)) {
return false;
}
return setup_tls(host, verifySsl);
}
// The read that says which of the four things happened. Prefer it over
// `read` below wherever the answer changes what the caller does.
ReadResult read_some(char* buf, int len) {
if (!is_valid()) return { ReadStatus::Error, 0 };
int ret = mbedtls_ssl_read(&state_->ssl,
reinterpret_cast<unsigned char*>(buf), static_cast<size_t>(len));
// Three spellings of "there is nothing more coming", and all three are
// an end of stream rather than a failure: the peer shut the session
// down politely, the transport reached its end (what `bio_recv`'s zero
// becomes), or mbedtls had nothing left to hand back. Most servers do
// NOT send close_notify before closing, so the middle one is the common
// case rather than the exotic one.
if (ret == MBEDTLS_ERR_SSL_PEER_CLOSE_NOTIFY
|| ret == MBEDTLS_ERR_SSL_CONN_EOF
|| ret == 0) {
return { ReadStatus::Eof, 0 };
}
if (ret == MBEDTLS_ERR_SSL_WANT_READ || ret == MBEDTLS_ERR_SSL_WANT_WRITE) {
return { ReadStatus::WouldBlock, 0 };
}
if (ret < 0) return { ReadStatus::Error, 0 };
return { ReadStatus::Data, ret };
}
// The older shape, kept because it is exported and callers outside this
// repository use it. It collapses Eof and WouldBlock back into 0, which is
// the ambiguity `read_some` exists to remove.
int read(char* buf, int len) {
auto r = read_some(buf, len);
switch (r.status) {
case ReadStatus::Data: return r.bytes;
case ReadStatus::Eof:
case ReadStatus::WouldBlock: return 0;
case ReadStatus::Error: return -1;
}
return -1;
}
// Returns 0 for "the transport is not ready", which `write_all` answers by
// waiting on the socket rather than by retrying immediately.
int write(const char* buf, int len) {
if (!is_valid()) return -1;
int ret = mbedtls_ssl_write(&state_->ssl,
reinterpret_cast<const unsigned char*>(buf), static_cast<size_t>(len));
if (ret < 0) {
if (ret == MBEDTLS_ERR_SSL_WANT_READ || ret == MBEDTLS_ERR_SSL_WANT_WRITE) {
return 0;
}
return -1;
}
return ret;
}
void close() {
if (state_) {
mbedtls_ssl_close_notify(&state_->ssl);
state_.reset();
}
socket_.close();
}
bool wait_readable(int timeoutMs) {
// Check if mbedtls has already buffered decrypted data
if (state_ && mbedtls_ssl_get_bytes_avail(&state_->ssl) > 0) {
return true;
}
return socket_.wait_readable(timeoutMs);
}
// TLS back-pressure is a wait, not a failure. `mbedtls_ssl_write` reports
// WANT_WRITE when the record layer cannot flush, and `write` above turns
// that into 0; without something to wait on, `write_all` could only retry
// at once and then give up, which reached the caller as "Write failed".
bool wait_writable(int timeoutMs) {
return socket_.wait_writable(timeoutMs);
}
private:
Socket socket_;
std::unique_ptr<TlsState> state_;
bool setup_tls(const char* host, bool verifySsl) {
state_ = std::make_unique<TlsState>();
int ret = mbedtls_ctr_drbg_seed(
&state_->ctr_drbg, mbedtls_entropy_func, &state_->entropy,
nullptr, 0);
if (ret != 0) {
state_.reset();
socket_.close();
return false;
}
ret = mbedtls_ssl_config_defaults(
&state_->conf,
MBEDTLS_SSL_IS_CLIENT,
MBEDTLS_SSL_TRANSPORT_STREAM,
MBEDTLS_SSL_PRESET_DEFAULT);
if (ret != 0) {
state_.reset();
socket_.close();
return false;
}
mbedtls_ssl_conf_rng(&state_->conf, mbedtls_ctr_drbg_random, &state_->ctr_drbg);
// mbedTLS 3.6 TLS 1.3 key derivation can fail in statically-linked
// builds; cap at TLS 1.2 which works reliably everywhere.
mbedtls_ssl_conf_max_tls_version(&state_->conf, MBEDTLS_SSL_VERSION_TLS1_2);
// Load CA certs
auto ca_pem = load_ca_certs();
if (!ca_pem.empty()) {
ret = mbedtls_x509_crt_parse(
&state_->ca_cert,
reinterpret_cast<const unsigned char*>(ca_pem.c_str()),
ca_pem.size() + 1); // +1 for null terminator required by mbedtls
// ret > 0 means some certs failed to parse but others succeeded — acceptable
if (ret < 0) {
state_.reset();
socket_.close();
return false;
}
mbedtls_ssl_conf_ca_chain(&state_->conf, &state_->ca_cert, nullptr);
}
// Certificate verification
// Use OPTIONAL (not REQUIRED) so handshake succeeds even if the CA
// bundle is incomplete; callers that need strict verification can
// inspect the verification result after handshake.
if (verifySsl) {
mbedtls_ssl_conf_authmode(&state_->conf, MBEDTLS_SSL_VERIFY_OPTIONAL);
} else {
mbedtls_ssl_conf_authmode(&state_->conf, MBEDTLS_SSL_VERIFY_NONE);
}
ret = mbedtls_ssl_setup(&state_->ssl, &state_->conf);
if (ret != 0) {
state_.reset();
socket_.close();
return false;
}
// Set hostname for SNI
ret = mbedtls_ssl_set_hostname(&state_->ssl, host);
if (ret != 0) {
state_.reset();
socket_.close();
return false;
}
// Set BIO callbacks using our Socket
mbedtls_ssl_set_bio(&state_->ssl, &socket_, bio_send, bio_recv, nullptr);
// Perform TLS handshake
while ((ret = mbedtls_ssl_handshake(&state_->ssl)) != 0) {
if (ret != MBEDTLS_ERR_SSL_WANT_READ && ret != MBEDTLS_ERR_SSL_WANT_WRITE) {
state_.reset();
socket_.close();
return false;
}
}
return true;
}
};
} // namespace mcpplibs::tinyhttps
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