Session.cc

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/*
 * Copyright (C) 1996-2023 The Squid Software Foundation and contributors
 *
 * Squid software is distributed under GPLv2+ license and includes
 * contributions from numerous individuals and organizations.
 * Please see the COPYING and CONTRIBUTORS files for details.
 */
 
/* DEBUG: section 83    TLS session management */
 
#include "squid.h"
#include "anyp/PortCfg.h"
#include "base/RunnersRegistry.h"
#include "CachePeer.h"
#include "debug/Stream.h"
#include "fd.h"
#include "fde.h"
#include "ipc/MemMap.h"
#include "security/Session.h"
#include "SquidConfig.h"
#include "ssl/bio.h"
 
#define SSL_SESSION_ID_SIZE 32
#define SSL_SESSION_MAX_SIZE 10*1024
 
#if USE_OPENSSL
static Ipc::MemMap *SessionCache = nullptr;
static const char *SessionCacheName = "tls_session_cache";
#endif
 
#if USE_OPENSSL || HAVE_LIBGNUTLS
static int
tls_read_method(int fd, char *buf, int len)
{
    auto session = fd_table[fd].ssl.get();
    debugs(83, 3, "started for session=" << (void*)session);
 
#if USE_OPENSSL
    int i = SSL_read(session, buf, len);
#elif HAVE_LIBGNUTLS
    int i = gnutls_record_recv(session, buf, len);
#endif
 
    if (i > 0) {
        debugs(83, 8, "TLS FD " << fd << " session=" << (void*)session << " " << i << " bytes");
        (void)VALGRIND_MAKE_MEM_DEFINED(buf, i);
    }
 
#if USE_OPENSSL
    if (i > 0 && SSL_pending(session) > 0) {
#elif HAVE_LIBGNUTLS
    if (i > 0 && gnutls_record_check_pending(session) > 0) {
#endif
        debugs(83, 2, "TLS FD " << fd << " is pending");
        fd_table[fd].flags.read_pending = true;
    } else
        fd_table[fd].flags.read_pending = false;
 
    return i;
}
 
static int
tls_write_method(int fd, const char *buf, int len)
{
    auto session = fd_table[fd].ssl.get();
    debugs(83, 3, "started for session=" << (void*)session);
 
#if USE_OPENSSL
    if (!SSL_is_init_finished(session)) {
        errno = ENOTCONN;
        return -1;
    }
#endif
 
#if USE_OPENSSL
    int i = SSL_write(session, buf, len);
#elif HAVE_LIBGNUTLS
    int i = gnutls_record_send(session, buf, len);
#endif
 
    if (i > 0) {
        debugs(83, 8, "TLS FD " << fd << " session=" << (void*)session << " " << i << " bytes");
    }
    return i;
}
#endif
 
#if USE_OPENSSL
Security::SessionPointer
Security::NewSessionObject(const Security::ContextPointer &ctx)
{
    Security::SessionPointer session(SSL_new(ctx.get()), [](SSL *p) {
        debugs(83, 5, "SSL_free session=" << (void*)p);
        SSL_free(p);
    });
    debugs(83, 5, "SSL_new session=" << (void*)session.get());
    return session;
}
#endif
 
static bool
CreateSession(const Security::ContextPointer &ctx, const Comm::ConnectionPointer &conn, Security::PeerOptions &opts, Security::Io::Type type, const char *squidCtx)
{
    if (!Comm::IsConnOpen(conn)) {
        debugs(83, DBG_IMPORTANT, "Gone connection");
        return false;
    }
 
#if USE_OPENSSL || HAVE_LIBGNUTLS
 
    const char *errAction = "with no TLS/SSL library";
    Security::LibErrorCode errCode = 0;
#if USE_OPENSSL
    Security::SessionPointer session(Security::NewSessionObject(ctx));
    if (!session) {
        errCode = ERR_get_error();
        errAction = "failed to allocate handle";
        debugs(83, DBG_IMPORTANT, "ERROR: TLS failure: " << errAction << ": " << Security::ErrorString(errCode));
    }
#elif HAVE_LIBGNUTLS
    gnutls_session_t tmp;
    errCode = gnutls_init(&tmp, static_cast<unsigned int>(type) | GNUTLS_NONBLOCK);
    Security::SessionPointer session(tmp, [](gnutls_session_t p) {
        debugs(83, 5, "gnutls_deinit session=" << (void*)p);
        gnutls_deinit(p);
    });
    debugs(83, 5, "gnutls_init " << (type == Security::Io::BIO_TO_SERVER ? "client" : "server" )<< " session=" << (void*)session.get());
    if (errCode != GNUTLS_E_SUCCESS) {
        session.reset();
        errAction = "failed to initialize session";
        debugs(83, DBG_IMPORTANT, "ERROR: TLS failure: " << errAction << ": " << Security::ErrorString(errCode));
    }
#endif /* HAVE_LIBGNUTLS */
 
    if (session) {
        const int fd = conn->fd;
 
#if USE_OPENSSL
        // without BIO, we would call SSL_set_fd(ssl.get(), fd) instead
        if (BIO *bio = Ssl::Bio::Create(fd, type)) {
            Ssl::Bio::Link(session.get(), bio); // cannot fail
#elif HAVE_LIBGNUTLS
        errCode = gnutls_credentials_set(session.get(), GNUTLS_CRD_CERTIFICATE, ctx.get());
        if (errCode == GNUTLS_E_SUCCESS) {
 
            opts.updateSessionOptions(session);
 
            // NP: GnuTLS does not yet support the BIO operations
            //     this does the equivalent of SSL_set_fd() for now.
            gnutls_transport_set_int(session.get(), fd);
            gnutls_handshake_set_timeout(session.get(), GNUTLS_DEFAULT_HANDSHAKE_TIMEOUT);
#endif /* HAVE_LIBGNUTLS */
 
            debugs(83, 5, "link FD " << fd << " to TLS session=" << (void*)session.get());
 
            fd_table[fd].ssl = session;
            fd_table[fd].useBufferedIo(&tls_read_method, &tls_write_method);
            fd_note(fd, squidCtx);
            return true;
        }
 
#if USE_OPENSSL
        errCode = ERR_get_error();
        errAction = "failed to initialize I/O";
        (void)opts;
#elif HAVE_LIBGNUTLS
        errAction = "failed to assign credentials";
#endif
    }
 
    debugs(83, DBG_IMPORTANT, "ERROR: " << squidCtx << ' ' << errAction <<
           ": " << (errCode != 0 ? Security::ErrorString(errCode) : ""));
#else
    (void)ctx;
    (void)opts;
    (void)type;
    (void)squidCtx;
#endif /* USE_OPENSSL || HAVE_LIBGNUTLS */
    return false;
}
 
bool
Security::CreateClientSession(FuturePeerContext &ctx, const Comm::ConnectionPointer &c, const char *squidCtx)
{
    // TODO: We cannot make ctx constant because CreateSession() takes
    // non-constant ctx.options (PeerOptions). It does that because GnuTLS
    // needs to call PeerOptions::updateSessionOptions(), which is not constant
    // because it compiles options (just in case) every time. To achieve
    // const-correctness, we should compile PeerOptions once, not every time.
    return CreateSession(ctx.raw, c, ctx.options, Security::Io::BIO_TO_SERVER, squidCtx);
}
 
bool
Security::CreateServerSession(const Security::ContextPointer &ctx, const Comm::ConnectionPointer &c, Security::PeerOptions &o, const char *squidCtx)
{
    return CreateSession(ctx, c, o, Security::Io::BIO_TO_CLIENT, squidCtx);
}
 
void
Security::SessionSendGoodbye(const Security::SessionPointer &s)
{
    debugs(83, 5, "session=" << (void*)s.get());
    if (s) {
#if USE_OPENSSL
        SSL_shutdown(s.get());
#elif HAVE_LIBGNUTLS
        gnutls_bye(s.get(), GNUTLS_SHUT_RDWR);
#endif
    }
}
 
bool
Security::SessionIsResumed(const Security::SessionPointer &s)
{
    bool result = false;
#if USE_OPENSSL
    result = SSL_session_reused(s.get()) == 1;
#elif HAVE_LIBGNUTLS
    result = gnutls_session_is_resumed(s.get()) != 0;
#endif
    debugs(83, 7, "session=" << (void*)s.get() << ", query? answer: " << (result ? 'T' : 'F') );
    return result;
}
 
void
Security::MaybeGetSessionResumeData(const Security::SessionPointer &s, Security::SessionStatePointer &data)
{
    if (!SessionIsResumed(s)) {
#if USE_OPENSSL
        // nil is valid for SSL_get1_session(), it cannot fail.
        data.reset(SSL_get1_session(s.get()));
#elif HAVE_LIBGNUTLS
        gnutls_datum_t *tmp = nullptr;
        const auto x = gnutls_session_get_data2(s.get(), tmp);
        if (x != GNUTLS_E_SUCCESS) {
            debugs(83, 3, "session=" << (void*)s.get() << " error: " << Security::ErrorString(x));
        }
        data.reset(tmp);
#endif
        debugs(83, 5, "session=" << (void*)s.get() << " data=" << (void*)data.get());
    } else {
        debugs(83, 5, "session=" << (void*)s.get() << " data=" << (void*)data.get() << ", do nothing.");
    }
}
 
void
Security::SetSessionResumeData(const Security::SessionPointer &s, const Security::SessionStatePointer &data)
{
    if (data) {
#if USE_OPENSSL
        if (!SSL_set_session(s.get(), data.get())) {
            const auto ssl_error = ERR_get_error();
            debugs(83, 3, "session=" << (void*)s.get() << " data=" << (void*)data.get() <<
                   " resume error: " << Security::ErrorString(ssl_error));
        }
#elif HAVE_LIBGNUTLS
        const auto x = gnutls_session_set_data(s.get(), data->data, data->size);
        if (x != GNUTLS_E_SUCCESS) {
            debugs(83, 3, "session=" << (void*)s.get() << " data=" << (void*)data.get() <<
                   " resume error: " << Security::ErrorString(x));
        }
#else
        // critical because, how did it get here?
        debugs(83, DBG_CRITICAL, "no TLS library. session=" << (void*)s.get() << " data=" << (void*)data.get());
#endif
        debugs(83, 5, "session=" << (void*)s.get() << " data=" << (void*)data.get());
    } else {
        debugs(83, 5, "session=" << (void*)s.get() << " no resume data");
    }
}
 
static bool
isTlsServer()
{
    for (AnyP::PortCfgPointer s = HttpPortList; s != nullptr; s = s->next) {
        if (s->secure.encryptTransport)
            return true;
        if (s->flags.tunnelSslBumping)
            return true;
    }
 
    return false;
}
 
#if USE_OPENSSL
static int
store_session_cb(SSL *, SSL_SESSION *session)
{
    if (!SessionCache)
        return 0;
 
    debugs(83, 5, "Request to store SSL_SESSION");
 
    SSL_SESSION_set_timeout(session, Config.SSL.session_ttl);
 
    unsigned int idlen;
    const unsigned char *id = SSL_SESSION_get_id(session, &idlen);
    // XXX: the other calls [to openForReading()] do not copy the sessionId to a char buffer, does this really have to?
    unsigned char key[MEMMAP_SLOT_KEY_SIZE];
    // Session ids are of size 32bytes. They should always fit to a
    // MemMap::Slot::key
    assert(idlen <= MEMMAP_SLOT_KEY_SIZE);
    memset(key, 0, sizeof(key));
    memcpy(key, id, idlen);
    int pos;
    if (auto slotW = SessionCache->openForWriting(static_cast<const cache_key*>(key), pos)) {
        int lenRequired = i2d_SSL_SESSION(session, nullptr);
        if (lenRequired <  MEMMAP_SLOT_DATA_SIZE) {
            unsigned char *p = static_cast<unsigned char *>(slotW->p);
            lenRequired = i2d_SSL_SESSION(session, &p);
            slotW->set(key, nullptr, lenRequired, squid_curtime + Config.SSL.session_ttl);
        }
        SessionCache->closeForWriting(pos);
        debugs(83, 5, "wrote an SSL_SESSION entry of size " << lenRequired << " at pos " << pos);
    }
    return 0;
}
 
static void
remove_session_cb(SSL_CTX *, SSL_SESSION *sessionID)
{
    if (!SessionCache)
        return;
 
    debugs(83, 5, "Request to remove corrupted or not valid SSL_SESSION");
    int pos;
    if (SessionCache->openForReading(reinterpret_cast<const cache_key*>(sessionID), pos)) {
        SessionCache->closeForReading(pos);
        // TODO:
        // What if we are not able to remove the session?
        // Maybe schedule a job to remove it later?
        // For now we just have an invalid entry in cache until will be expired
        // The OpenSSL library will reject it when we try to use it
        SessionCache->free(pos);
    }
}
 
static SSL_SESSION *
#if SQUID_USE_CONST_SSL_SESSION_CBID
get_session_cb(SSL *, const unsigned char *sessionID, int len, int *copy)
#else
get_session_cb(SSL *, unsigned char *sessionID, int len, int *copy)
#endif
{
    if (!SessionCache)
        return nullptr;
 
    const unsigned int *p = reinterpret_cast<const unsigned int *>(sessionID);
    debugs(83, 5, "Request to search for SSL_SESSION of len: " <<
           len << p[0] << ":" << p[1]);
 
    SSL_SESSION *session = nullptr;
    int pos;
    if (const auto slot = SessionCache->openForReading(static_cast<const cache_key*>(sessionID), pos)) {
        if (slot->expire > squid_curtime) {
            const unsigned char *ptr = slot->p;
            session = d2i_SSL_SESSION(nullptr, &ptr, slot->pSize);
            debugs(83, 5, "SSL_SESSION retrieved from cache at pos " << pos);
        } else
            debugs(83, 5, "SSL_SESSION in cache expired");
        SessionCache->closeForReading(pos);
    }
 
    if (!session)
        debugs(83, 5, "Failed to retrieve SSL_SESSION from cache");
 
    // With the parameter copy the callback can require the SSL engine
    // to increment the reference count of the SSL_SESSION object, Normally
    // the reference count is not incremented and therefore the session must
    // not be explicitly freed with SSL_SESSION_free(3).
    *copy = 0;
    return session;
}
 
void
Security::SetSessionCacheCallbacks(Security::ContextPointer &ctx)
{
    if (SessionCache) {
        SSL_CTX_set_session_cache_mode(ctx.get(), SSL_SESS_CACHE_SERVER|SSL_SESS_CACHE_NO_INTERNAL);
        SSL_CTX_sess_set_new_cb(ctx.get(), store_session_cb);
        SSL_CTX_sess_set_remove_cb(ctx.get(), remove_session_cb);
        SSL_CTX_sess_set_get_cb(ctx.get(), get_session_cb);
    }
}
#endif /* USE_OPENSSL */
 
#if USE_OPENSSL
static void
initializeSessionCache()
{
    // Check if the MemMap keys and data are enough big to hold
    // session ids and session data
    assert(SSL_SESSION_ID_SIZE >= MEMMAP_SLOT_KEY_SIZE);
    assert(SSL_SESSION_MAX_SIZE >= MEMMAP_SLOT_DATA_SIZE);
 
    int configuredItems = ::Config.SSL.sessionCacheSize / sizeof(Ipc::MemMap::Slot);
    if (IamWorkerProcess() && configuredItems)
        SessionCache = new Ipc::MemMap(SessionCacheName);
    else {
        SessionCache = nullptr;
        return;
    }
 
    for (AnyP::PortCfgPointer s = HttpPortList; s != nullptr; s = s->next) {
        if (s->secure.staticContext)
            Security::SetSessionCacheCallbacks(s->secure.staticContext);
    }
}
#endif
 
class SharedSessionCacheRr: public Ipc::Mem::RegisteredRunner
{
public:
    /* RegisteredRunner API */
    SharedSessionCacheRr(): owner(nullptr) {}
    void useConfig() override;
    ~SharedSessionCacheRr() override;
 
protected:
    void create() override;
 
private:
    Ipc::MemMap::Owner *owner;
};
 
DefineRunnerRegistrator(SharedSessionCacheRr);
 
void
SharedSessionCacheRr::useConfig()
{
#if USE_OPENSSL
    if (SessionCache || !isTlsServer()) // no need to configure SSL_SESSION* cache.
        return;
 
    Ipc::Mem::RegisteredRunner::useConfig();
    initializeSessionCache();
#endif
}
 
void
SharedSessionCacheRr::create()
{
    if (!isTlsServer()) // no need to configure SSL_SESSION* cache.
        return;
 
#if USE_OPENSSL
    if (int items = Config.SSL.sessionCacheSize / sizeof(Ipc::MemMap::Slot))
        owner = Ipc::MemMap::Init(SessionCacheName, items);
#endif
}
 
SharedSessionCacheRr::~SharedSessionCacheRr()
{
    // XXX: Enable after testing to reduce at-exit memory "leaks".
    // delete SessionCache;
 
    delete owner;
}