/*
 * Copyright (C) 1996-2015 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    SSL accelerator support */

#include "squid.h"

/* MS Visual Studio Projects are monolithic, so we need the following
 * #if to exclude the SSL code from compile process when not needed.
 */
#if USE_OPENSSL

#include "acl/FilledChecklist.h"
#include "anyp/PortCfg.h"
#include "fd.h"
#include "fde.h"
#include "globals.h"
#include "ipc/MemMap.h"
#include "SquidConfig.h"
#include "SquidTime.h"
#include "ssl/bio.h"
#include "ssl/Config.h"
#include "ssl/ErrorDetail.h"
#include "ssl/gadgets.h"
#include "ssl/support.h"
#include "URL.h"

#include <cerrno>

static void setSessionCallbacks(SSL_CTX *ctx);
Ipc::MemMap *SslSessionCache = NULL;
const char *SslSessionCacheName = "ssl_session_cache";

const EVP_MD *Ssl::DefaultSignHash = NULL;

const char *Ssl::BumpModeStr[] = {
    "none",
    "client-first",
    "server-first",
    "peek",
    "stare",
    "bump",
    "splice",
    "terminate",
    /*"err",*/
    NULL
};

/**
 \defgroup ServerProtocolSSLInternal Server-Side SSL Internals
 \ingroup ServerProtocolSSLAPI
 */

/// \ingroup ServerProtocolSSLInternal
static int
ssl_ask_password_cb(char *buf, int size, int rwflag, void *userdata)
{
    FILE *in;
    int len = 0;
    char cmdline[1024];

    snprintf(cmdline, sizeof(cmdline), "\"%s\" \"%s\"", Config.Program.ssl_password, (const char *)userdata);
    in = popen(cmdline, "r");

    if (fgets(buf, size, in))

        len = strlen(buf);

    while (len > 0 && (buf[len - 1] == '\n' || buf[len - 1] == '\r'))
        --len;

    buf[len] = '\0';

    pclose(in);

    return len;
}

/// \ingroup ServerProtocolSSLInternal
static void
ssl_ask_password(SSL_CTX * context, const char * prompt)
{
    if (Config.Program.ssl_password) {
        SSL_CTX_set_default_passwd_cb(context, ssl_ask_password_cb);
        SSL_CTX_set_default_passwd_cb_userdata(context, (void *)prompt);
    }
}

/// \ingroup ServerProtocolSSLInternal
static RSA *
ssl_temp_rsa_cb(SSL * ssl, int anInt, int keylen)
{
    static RSA *rsa_512 = NULL;
    static RSA *rsa_1024 = NULL;
    RSA *rsa = NULL;
    int newkey = 0;

    switch (keylen) {

    case 512:

        if (!rsa_512) {
            rsa_512 = RSA_generate_key(512, RSA_F4, NULL, NULL);
            newkey = 1;
        }

        rsa = rsa_512;
        break;

    case 1024:

        if (!rsa_1024) {
            rsa_1024 = RSA_generate_key(1024, RSA_F4, NULL, NULL);
            newkey = 1;
        }

        rsa = rsa_1024;
        break;

    default:
        debugs(83, DBG_IMPORTANT, "ssl_temp_rsa_cb: Unexpected key length " << keylen);
        return NULL;
    }

    if (rsa == NULL) {
        debugs(83, DBG_IMPORTANT, "ssl_temp_rsa_cb: Failed to generate key " << keylen);
        return NULL;
    }

    if (newkey) {
        if (do_debug(83, 5))
            PEM_write_RSAPrivateKey(debug_log, rsa, NULL, NULL, 0, NULL, NULL);

        debugs(83, DBG_IMPORTANT, "Generated ephemeral RSA key of length " << keylen);
    }

    return rsa;
}

int Ssl::asn1timeToString(ASN1_TIME *tm, char *buf, int len)
{
    BIO *bio;
    int write = 0;
    bio = BIO_new(BIO_s_mem());
    if (bio) {
        if (ASN1_TIME_print(bio, tm))
            write = BIO_read(bio, buf, len-1);
        BIO_free(bio);
    }
    buf[write]='\0';
    return write;
}

int Ssl::matchX509CommonNames(X509 *peer_cert, void *check_data, int (*check_func)(void *check_data,  ASN1_STRING *cn_data))
{
    assert(peer_cert);

    X509_NAME *name = X509_get_subject_name(peer_cert);

    for (int i = X509_NAME_get_index_by_NID(name, NID_commonName, -1); i >= 0; i = X509_NAME_get_index_by_NID(name, NID_commonName, i)) {

        ASN1_STRING *cn_data = X509_NAME_ENTRY_get_data(X509_NAME_get_entry(name, i));

        if ( (*check_func)(check_data, cn_data) == 0)
            return 1;
    }

    STACK_OF(GENERAL_NAME) * altnames;
    altnames = (STACK_OF(GENERAL_NAME)*)X509_get_ext_d2i(peer_cert, NID_subject_alt_name, NULL, NULL);

    if (altnames) {
        int numalts = sk_GENERAL_NAME_num(altnames);
        for (int i = 0; i < numalts; ++i) {
            const GENERAL_NAME *check = sk_GENERAL_NAME_value(altnames, i);
            if (check->type != GEN_DNS) {
                continue;
            }
            ASN1_STRING *cn_data = check->d.dNSName;

            if ( (*check_func)(check_data, cn_data) == 0) {
                sk_GENERAL_NAME_pop_free(altnames, GENERAL_NAME_free);
                return 1;
            }
        }
        sk_GENERAL_NAME_pop_free(altnames, GENERAL_NAME_free);
    }
    return 0;
}

static int check_domain( void *check_data, ASN1_STRING *cn_data)
{
    char cn[1024];
    const char *server = (const char *)check_data;

    if (cn_data->length > (int)sizeof(cn) - 1) {
        return 1; //if does not fit our buffer just ignore
    }
    char *s = reinterpret_cast<char*>(cn_data->data);
    char *d = cn;
    for (int i = 0; i < cn_data->length; ++i, ++d, ++s) {
        if (*s == '\0')
            return 1; // always a domain mismatch. contains 0x00
        *d = *s;
    }
    cn[cn_data->length] = '\0';
    debugs(83, 4, "Verifying server domain " << server << " to certificate name/subjectAltName " << cn);
    return matchDomainName(server, cn[0] == '*' ? cn + 1 : cn);
}

bool Ssl::checkX509ServerValidity(X509 *cert, const char *server)
{
    return matchX509CommonNames(cert, (void *)server, check_domain);
}

/// \ingroup ServerProtocolSSLInternal
static int
ssl_verify_cb(int ok, X509_STORE_CTX * ctx)
{
    // preserve original ctx->error before SSL_ calls can overwrite it
    Ssl::ssl_error_t error_no = ok ? SSL_ERROR_NONE : ctx->error;

    char buffer[256] = "";
    SSL *ssl = (SSL *)X509_STORE_CTX_get_ex_data(ctx, SSL_get_ex_data_X509_STORE_CTX_idx());
    SSL_CTX *sslctx = SSL_get_SSL_CTX(ssl);
    SBuf *server = (SBuf *)SSL_get_ex_data(ssl, ssl_ex_index_server);
    void *dont_verify_domain = SSL_CTX_get_ex_data(sslctx, ssl_ctx_ex_index_dont_verify_domain);
    ACLChecklist *check = (ACLChecklist*)SSL_get_ex_data(ssl, ssl_ex_index_cert_error_check);
    X509 *peeked_cert = (X509 *)SSL_get_ex_data(ssl, ssl_ex_index_ssl_peeked_cert);
    X509 *peer_cert = ctx->cert;

    X509_NAME_oneline(X509_get_subject_name(peer_cert), buffer,
                      sizeof(buffer));

    // detect infinite loops
    uint32_t *validationCounter = static_cast<uint32_t *>(SSL_get_ex_data(ssl, ssl_ex_index_ssl_validation_counter));
    if (!validationCounter) {
        validationCounter = new uint32_t(1);
        SSL_set_ex_data(ssl, ssl_ex_index_ssl_validation_counter, validationCounter);
    } else {
        // overflows allowed if SQUID_CERT_VALIDATION_ITERATION_MAX >= UINT32_MAX
        (*validationCounter)++;
    }

    if ((*validationCounter) >= SQUID_CERT_VALIDATION_ITERATION_MAX) {
        ok = 0; // or the validation loop will never stop
        error_no = SQUID_X509_V_ERR_INFINITE_VALIDATION;
        debugs(83, 2, "SQUID_X509_V_ERR_INFINITE_VALIDATION: " <<
               *validationCounter << " iterations while checking " << buffer);
    }

    if (ok) {
        debugs(83, 5, "SSL Certificate signature OK: " << buffer);

        // Check for domain mismatch only if the current certificate is the peer certificate.
        if (!dont_verify_domain && server && peer_cert == X509_STORE_CTX_get_current_cert(ctx)) {
            if (!Ssl::checkX509ServerValidity(peer_cert, server->c_str())) {
                debugs(83, 2, "SQUID_X509_V_ERR_DOMAIN_MISMATCH: Certificate " << buffer << " does not match domainname " << server);
                ok = 0;
                error_no = SQUID_X509_V_ERR_DOMAIN_MISMATCH;
            }
        }
    }

    if (ok && peeked_cert) {
        // Check whether the already peeked certificate matches the new one.
        if (X509_cmp(peer_cert, peeked_cert) != 0) {
            debugs(83, 2, "SQUID_X509_V_ERR_CERT_CHANGE: Certificate " << buffer << " does not match peeked certificate");
            ok = 0;
            error_no =  SQUID_X509_V_ERR_CERT_CHANGE;
        }
    }

    if (!ok) {
        X509 *broken_cert =  X509_STORE_CTX_get_current_cert(ctx);
        if (!broken_cert)
            broken_cert = peer_cert;

        Ssl::CertErrors *errs = static_cast<Ssl::CertErrors *>(SSL_get_ex_data(ssl, ssl_ex_index_ssl_errors));
        if (!errs) {
            errs = new Ssl::CertErrors(Ssl::CertError(error_no, broken_cert));
            if (!SSL_set_ex_data(ssl, ssl_ex_index_ssl_errors,  (void *)errs)) {
                debugs(83, 2, "Failed to set ssl error_no in ssl_verify_cb: Certificate " << buffer);
                delete errs;
                errs = NULL;
            }
        } else // remember another error number
            errs->push_back_unique(Ssl::CertError(error_no, broken_cert));

        if (const char *err_descr = Ssl::GetErrorDescr(error_no))
            debugs(83, 5, err_descr << ": " << buffer);
        else
            debugs(83, DBG_IMPORTANT, "SSL unknown certificate error " << error_no << " in " << buffer);

        // Check if the certificate error can be bypassed.
        // Infinity validation loop errors can not bypassed.
        if (error_no != SQUID_X509_V_ERR_INFINITE_VALIDATION) {
            if (check) {
                ACLFilledChecklist *filledCheck = Filled(check);
                assert(!filledCheck->sslErrors);
                filledCheck->sslErrors = new Ssl::CertErrors(Ssl::CertError(error_no, broken_cert));
                filledCheck->serverCert.resetAndLock(peer_cert);
                if (check->fastCheck() == ACCESS_ALLOWED) {
                    debugs(83, 3, "bypassing SSL error " << error_no << " in " << buffer);
                    ok = 1;
                } else {
                    debugs(83, 5, "confirming SSL error " << error_no);
                }
                delete filledCheck->sslErrors;
                filledCheck->sslErrors = NULL;
                filledCheck->serverCert.reset(NULL);
            }
            // If the certificate validator is used then we need to allow all errors and
            // pass them to certficate validator for more processing
            else if (Ssl::TheConfig.ssl_crt_validator) {
                ok = 1;
            }
        }
    }

    if (Ssl::TheConfig.ssl_crt_validator) {
        // Check if we have stored certificates chain. Store if not.
        if (!SSL_get_ex_data(ssl, ssl_ex_index_ssl_cert_chain)) {
            STACK_OF(X509) *certStack = X509_STORE_CTX_get1_chain(ctx);
            if (certStack && !SSL_set_ex_data(ssl, ssl_ex_index_ssl_cert_chain, certStack))
                sk_X509_pop_free(certStack, X509_free);
        }
    }

    if (!ok && !SSL_get_ex_data(ssl, ssl_ex_index_ssl_error_detail) ) {

        // Find the broken certificate. It may be intermediate.
        X509 *broken_cert = peer_cert; // reasonable default if search fails
        // Our SQUID_X509_V_ERR_DOMAIN_MISMATCH implies peer_cert is at fault.
        if (error_no != SQUID_X509_V_ERR_DOMAIN_MISMATCH) {
            if (X509 *last_used_cert = X509_STORE_CTX_get_current_cert(ctx))
                broken_cert = last_used_cert;
        }

        Ssl::ErrorDetail *errDetail =
            new Ssl::ErrorDetail(error_no, peer_cert, broken_cert);

        if (!SSL_set_ex_data(ssl, ssl_ex_index_ssl_error_detail,  errDetail)) {
            debugs(83, 2, "Failed to set Ssl::ErrorDetail in ssl_verify_cb: Certificate " << buffer);
            delete errDetail;
        }
    }

    return ok;
}

/// \ingroup ServerProtocolSSLInternal
static struct ssl_option {
    const char *name;
    long value;
}

ssl_options[] = {

#if SSL_OP_MICROSOFT_SESS_ID_BUG
    {
        "MICROSOFT_SESS_ID_BUG", SSL_OP_MICROSOFT_SESS_ID_BUG
    },
#endif
#if SSL_OP_NETSCAPE_CHALLENGE_BUG
    {
        "NETSCAPE_CHALLENGE_BUG", SSL_OP_NETSCAPE_CHALLENGE_BUG
    },
#endif
#if SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG
    {
        "NETSCAPE_REUSE_CIPHER_CHANGE_BUG", SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG
    },
#endif
#if SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG
    {
        "SSLREF2_REUSE_CERT_TYPE_BUG", SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG
    },
#endif
#if SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER
    {
        "MICROSOFT_BIG_SSLV3_BUFFER", SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER
    },
#endif
#if SSL_OP_MSIE_SSLV2_RSA_PADDING
    {
        "MSIE_SSLV2_RSA_PADDING", SSL_OP_MSIE_SSLV2_RSA_PADDING
    },
#endif
#if SSL_OP_SSLEAY_080_CLIENT_DH_BUG
    {
        "SSLEAY_080_CLIENT_DH_BUG", SSL_OP_SSLEAY_080_CLIENT_DH_BUG
    },
#endif
#if SSL_OP_TLS_D5_BUG
    {
        "TLS_D5_BUG", SSL_OP_TLS_D5_BUG
    },
#endif
#if SSL_OP_TLS_BLOCK_PADDING_BUG
    {
        "TLS_BLOCK_PADDING_BUG", SSL_OP_TLS_BLOCK_PADDING_BUG
    },
#endif
#if SSL_OP_TLS_ROLLBACK_BUG
    {
        "TLS_ROLLBACK_BUG", SSL_OP_TLS_ROLLBACK_BUG
    },
#endif
#if SSL_OP_ALL
    {
        "ALL", (long)SSL_OP_ALL
    },
#endif
#if SSL_OP_SINGLE_DH_USE
    {
        "SINGLE_DH_USE", SSL_OP_SINGLE_DH_USE
    },
#endif
#if SSL_OP_EPHEMERAL_RSA
    {
        "EPHEMERAL_RSA", SSL_OP_EPHEMERAL_RSA
    },
#endif
#if SSL_OP_PKCS1_CHECK_1
    {
        "PKCS1_CHECK_1", SSL_OP_PKCS1_CHECK_1
    },
#endif
#if SSL_OP_PKCS1_CHECK_2
    {
        "PKCS1_CHECK_2", SSL_OP_PKCS1_CHECK_2
    },
#endif
#if SSL_OP_NETSCAPE_CA_DN_BUG
    {
        "NETSCAPE_CA_DN_BUG", SSL_OP_NETSCAPE_CA_DN_BUG
    },
#endif
#if SSL_OP_NON_EXPORT_FIRST
    {
        "NON_EXPORT_FIRST", SSL_OP_NON_EXPORT_FIRST
    },
#endif
#if SSL_OP_CIPHER_SERVER_PREFERENCE
    {
        "CIPHER_SERVER_PREFERENCE", SSL_OP_CIPHER_SERVER_PREFERENCE
    },
#endif
#if SSL_OP_NETSCAPE_DEMO_CIPHER_CHANGE_BUG
    {
        "NETSCAPE_DEMO_CIPHER_CHANGE_BUG", SSL_OP_NETSCAPE_DEMO_CIPHER_CHANGE_BUG
    },
#endif
#if SSL_OP_NO_SSLv2
    {
        "NO_SSLv2", SSL_OP_NO_SSLv2
    },
#endif
#if SSL_OP_NO_SSLv3
    {
        "NO_SSLv3", SSL_OP_NO_SSLv3
    },
#endif
#if SSL_OP_NO_TLSv1
    {
        "NO_TLSv1", SSL_OP_NO_TLSv1
    },
#endif
#if SSL_OP_NO_TLSv1_1
    {
        "NO_TLSv1_1", SSL_OP_NO_TLSv1_1
    },
#endif
#if SSL_OP_NO_TLSv1_2
    {
        "NO_TLSv1_2", SSL_OP_NO_TLSv1_2
    },
#endif
#if SSL_OP_NO_COMPRESSION
    {
        "No_Compression", SSL_OP_NO_COMPRESSION
    },
#endif
#if SSL_OP_NO_TICKET
    {
        "NO_TICKET", SSL_OP_NO_TICKET
    },
#endif
    {
        "", 0
    },
    {
        NULL, 0
    }
};

/// \ingroup ServerProtocolSSLInternal
long
Ssl::parse_options(const char *options)
{
    long op = 0;
    char *tmp;
    char *option;

    if (!options)
        goto no_options;

    tmp = xstrdup(options);

    option = strtok(tmp, ":,");

    while (option) {

        struct ssl_option *opt = NULL, *opttmp;
        long value = 0;
        enum {
            MODE_ADD, MODE_REMOVE
        } mode;

        switch (*option) {

        case '!':

        case '-':
            mode = MODE_REMOVE;
            ++option;
            break;

        case '+':
            mode = MODE_ADD;
            ++option;
            break;

        default:
            mode = MODE_ADD;
            break;
        }

        for (opttmp = ssl_options; opttmp->name; ++opttmp) {
            if (strcmp(opttmp->name, option) == 0) {
                opt = opttmp;
                break;
            }
        }

        if (opt)
            value = opt->value;
        else if (strncmp(option, "0x", 2) == 0) {
            /* Special case.. hex specification */
            value = strtol(option + 2, NULL, 16);
        } else {
            fatalf("Unknown SSL option '%s'", option);
            value = 0;      /* Keep GCC happy */
        }

        switch (mode) {

        case MODE_ADD:
            op |= value;
            break;

        case MODE_REMOVE:
            op &= ~value;
            break;
        }

        option = strtok(NULL, ":,");
    }

    safe_free(tmp);

no_options:
    return op;
}

/// \ingroup ServerProtocolSSLInternal
#define SSL_FLAG_NO_DEFAULT_CA      (1<<0)
/// \ingroup ServerProtocolSSLInternal
#define SSL_FLAG_DELAYED_AUTH       (1<<1)
/// \ingroup ServerProtocolSSLInternal
#define SSL_FLAG_DONT_VERIFY_PEER   (1<<2)
/// \ingroup ServerProtocolSSLInternal
#define SSL_FLAG_DONT_VERIFY_DOMAIN (1<<3)
/// \ingroup ServerProtocolSSLInternal
#define SSL_FLAG_NO_SESSION_REUSE   (1<<4)
/// \ingroup ServerProtocolSSLInternal
#define SSL_FLAG_VERIFY_CRL     (1<<5)
/// \ingroup ServerProtocolSSLInternal
#define SSL_FLAG_VERIFY_CRL_ALL     (1<<6)

/// \ingroup ServerProtocolSSLInternal
long
Ssl::parse_flags(const char *flags)
{
    long fl = 0;
    char *tmp;
    char *flag;

    if (!flags)
        return 0;

    tmp = xstrdup(flags);

    flag = strtok(tmp, ":,");

    while (flag) {
        if (strcmp(flag, "NO_DEFAULT_CA") == 0)
            fl |= SSL_FLAG_NO_DEFAULT_CA;
        else if (strcmp(flag, "DELAYED_AUTH") == 0)
            fl |= SSL_FLAG_DELAYED_AUTH;
        else if (strcmp(flag, "DONT_VERIFY_PEER") == 0)
            fl |= SSL_FLAG_DONT_VERIFY_PEER;
        else if (strcmp(flag, "DONT_VERIFY_DOMAIN") == 0)
            fl |= SSL_FLAG_DONT_VERIFY_DOMAIN;
        else if (strcmp(flag, "NO_SESSION_REUSE") == 0)
            fl |= SSL_FLAG_NO_SESSION_REUSE;

#if X509_V_FLAG_CRL_CHECK

        else if (strcmp(flag, "VERIFY_CRL") == 0)
            fl |= SSL_FLAG_VERIFY_CRL;
        else if (strcmp(flag, "VERIFY_CRL_ALL") == 0)
            fl |= SSL_FLAG_VERIFY_CRL_ALL;

#endif

        else
            fatalf("Unknown ssl flag '%s'", flag);

        flag = strtok(NULL, ":,");
    }

    safe_free(tmp);
    return fl;
}

// "dup" function for SSL_get_ex_new_index("cert_err_check")
static int
ssl_dupAclChecklist(CRYPTO_EX_DATA *, CRYPTO_EX_DATA *, void *,
                    int, long, void *)
{
    // We do not support duplication of ACLCheckLists.
    // If duplication is needed, we can count copies with cbdata.
    assert(false);
    return 0;
}

// "free" function for SSL_get_ex_new_index("cert_err_check")
static void
ssl_freeAclChecklist(void *, void *ptr, CRYPTO_EX_DATA *,
                     int, long, void *)
{
    delete static_cast<ACLChecklist *>(ptr); // may be NULL
}

// "free" function for SSL_get_ex_new_index("ssl_error_detail")
static void
ssl_free_ErrorDetail(void *, void *ptr, CRYPTO_EX_DATA *,
                     int, long, void *)
{
    Ssl::ErrorDetail  *errDetail = static_cast <Ssl::ErrorDetail *>(ptr);
    delete errDetail;
}

static void
ssl_free_SslErrors(void *, void *ptr, CRYPTO_EX_DATA *,
                   int, long, void *)
{
    Ssl::CertErrors *errs = static_cast <Ssl::CertErrors*>(ptr);
    delete errs;
}

// "free" function for SSL_get_ex_new_index("ssl_ex_index_ssl_validation_counter")
static void
ssl_free_int(void *, void *ptr, CRYPTO_EX_DATA *,
             int, long, void *)
{
    uint32_t *counter = static_cast <uint32_t *>(ptr);
    delete counter;
}

/// \ingroup ServerProtocolSSLInternal
/// Callback handler function to release STACK_OF(X509) "ex" data stored
/// in an SSL object.
static void
ssl_free_CertChain(void *, void *ptr, CRYPTO_EX_DATA *,
                   int, long, void *)
{
    STACK_OF(X509) *certsChain = static_cast <STACK_OF(X509) *>(ptr);
    sk_X509_pop_free(certsChain,X509_free);
}

// "free" function for X509 certificates
static void
ssl_free_X509(void *, void *ptr, CRYPTO_EX_DATA *,
              int, long, void *)
{
    X509  *cert = static_cast <X509 *>(ptr);
    X509_free(cert);
}

// "free" function for SBuf
static void
ssl_free_SBuf(void *, void *ptr, CRYPTO_EX_DATA *,
              int, long, void *)
{
    SBuf  *buf = static_cast <SBuf *>(ptr);
    delete buf;
}

/// \ingroup ServerProtocolSSLInternal
static void
ssl_initialize(void)
{
    static bool initialized = false;
    if (initialized)
        return;
    initialized = true;

    SSL_load_error_strings();
    SSLeay_add_ssl_algorithms();

#if HAVE_OPENSSL_ENGINE_H
    if (Config.SSL.ssl_engine) {
        ENGINE *e;
        if (!(e = ENGINE_by_id(Config.SSL.ssl_engine)))
            fatalf("Unable to find SSL engine '%s'\n", Config.SSL.ssl_engine);

        if (!ENGINE_set_default(e, ENGINE_METHOD_ALL)) {
            int ssl_error = ERR_get_error();
            fatalf("Failed to initialise SSL engine: %s\n", ERR_error_string(ssl_error, NULL));
        }
    }
#else
    if (Config.SSL.ssl_engine)
        fatalf("Your OpenSSL has no SSL engine support\n");
#endif

    const char *defName = Config.SSL.certSignHash ? Config.SSL.certSignHash : SQUID_SSL_SIGN_HASH_IF_NONE;
    Ssl::DefaultSignHash = EVP_get_digestbyname(defName);
    if (!Ssl::DefaultSignHash)
        fatalf("Sign hash '%s' is not supported\n", defName);

    ssl_ex_index_server = SSL_get_ex_new_index(0, (void *) "server", NULL, NULL, ssl_free_SBuf);
    ssl_ctx_ex_index_dont_verify_domain = SSL_CTX_get_ex_new_index(0, (void *) "dont_verify_domain", NULL, NULL, NULL);
    ssl_ex_index_cert_error_check = SSL_get_ex_new_index(0, (void *) "cert_error_check", NULL, &ssl_dupAclChecklist, &ssl_freeAclChecklist);
    ssl_ex_index_ssl_error_detail = SSL_get_ex_new_index(0, (void *) "ssl_error_detail", NULL, NULL, &ssl_free_ErrorDetail);
    ssl_ex_index_ssl_peeked_cert  = SSL_get_ex_new_index(0, (void *) "ssl_peeked_cert", NULL, NULL, &ssl_free_X509);
    ssl_ex_index_ssl_errors =  SSL_get_ex_new_index(0, (void *) "ssl_errors", NULL, NULL, &ssl_free_SslErrors);
    ssl_ex_index_ssl_cert_chain = SSL_get_ex_new_index(0, (void *) "ssl_cert_chain", NULL, NULL, &ssl_free_CertChain);
    ssl_ex_index_ssl_validation_counter = SSL_get_ex_new_index(0, (void *) "ssl_validation_counter", NULL, NULL, &ssl_free_int);
}

/// \ingroup ServerProtocolSSLInternal
static int
ssl_load_crl(SSL_CTX *sslContext, const char *CRLfile)
{
    X509_STORE *st = SSL_CTX_get_cert_store(sslContext);
    X509_CRL *crl;
    BIO *in = BIO_new_file(CRLfile, "r");
    int count = 0;

    if (!in) {
        debugs(83, 2, "WARNING: Failed to open CRL file '" << CRLfile << "'");
        return 0;
    }

    while ((crl = PEM_read_bio_X509_CRL(in,NULL,NULL,NULL))) {
        if (!X509_STORE_add_crl(st, crl))
            debugs(83, 2, "WARNING: Failed to add CRL from file '" << CRLfile << "'");
        else
            ++count;

        X509_CRL_free(crl);
    }

    BIO_free(in);
    return count;
}

STACK_OF(X509_CRL) *
Ssl::loadCrl(const char *CRLFile, long &flags)
{
    X509_CRL *crl;
    BIO *in = BIO_new_file(CRLFile, "r");
    if (!in) {
        debugs(83, 2, "WARNING: Failed to open CRL file '" << CRLFile << "'");
        return NULL;
    }

    STACK_OF(X509_CRL) *CRLs = sk_X509_CRL_new_null();
    if (!CRLs) {
        debugs(83, 2, "WARNING: Failed to allocate X509_CRL stack  to load file '" << CRLFile << "'");
        return NULL;
    }

    int count = 0;
    while ((crl = PEM_read_bio_X509_CRL(in,NULL,NULL,NULL))) {
        if (!sk_X509_CRL_push(CRLs, crl))
            debugs(83, 2, "WARNING: Failed to add CRL from file '" << CRLFile << "'");
        else
            ++count;
    }
    BIO_free(in);

    if (count)
        flags |= SSL_FLAG_VERIFY_CRL;

    return CRLs;
}

DH *
Ssl::readDHParams(const char *dhfile)
{
    FILE *in = fopen(dhfile, "r");
    DH *dh = NULL;
    int codes;

    if (in) {
        dh = PEM_read_DHparams(in, NULL, NULL, NULL);
        fclose(in);
    }

    if (!dh)
        debugs(83, DBG_IMPORTANT, "WARNING: Failed to read DH parameters '" << dhfile << "'");
    else if (dh && DH_check(dh, &codes) == 0) {
        if (codes) {
            debugs(83, DBG_IMPORTANT, "WARNING: Failed to verify DH parameters '" << dhfile  << "' (" << std::hex << codes  << ")");
            DH_free(dh);
            dh = NULL;
        }
    }
    return dh;
}

#if defined(SSL3_FLAGS_NO_RENEGOTIATE_CIPHERS)
static void
ssl_info_cb(const SSL *ssl, int where, int ret)
{
    (void)ret;
    if ((where & SSL_CB_HANDSHAKE_DONE) != 0) {
        // disable renegotiation (CVE-2009-3555)
        ssl->s3->flags |= SSL3_FLAGS_NO_RENEGOTIATE_CIPHERS;
    }
}
#endif

static bool
configureSslContext(SSL_CTX *sslContext, AnyP::PortCfg &port)
{
    int ssl_error;
    SSL_CTX_set_options(sslContext, port.sslOptions);

#if defined(SSL3_FLAGS_NO_RENEGOTIATE_CIPHERS)
    SSL_CTX_set_info_callback(sslContext, ssl_info_cb);
#endif

    if (port.sslContextSessionId)
        SSL_CTX_set_session_id_context(sslContext, (const unsigned char *)port.sslContextSessionId, strlen(port.sslContextSessionId));

    if (port.sslContextFlags & SSL_FLAG_NO_SESSION_REUSE) {
        SSL_CTX_set_session_cache_mode(sslContext, SSL_SESS_CACHE_OFF);
    }

    if (Config.SSL.unclean_shutdown) {
        debugs(83, 5, "Enabling quiet SSL shutdowns (RFC violation).");

        SSL_CTX_set_quiet_shutdown(sslContext, 1);
    }

    if (port.cipher) {
        debugs(83, 5, "Using chiper suite " << port.cipher << ".");

        if (!SSL_CTX_set_cipher_list(sslContext, port.cipher)) {
            ssl_error = ERR_get_error();
            debugs(83, DBG_CRITICAL, "ERROR: Failed to set SSL cipher suite '" << port.cipher << "': " << ERR_error_string(ssl_error, NULL));
            return false;
        }
    }

    debugs(83, 9, "Setting RSA key generation callback.");
    SSL_CTX_set_tmp_rsa_callback(sslContext, ssl_temp_rsa_cb);

    debugs(83, 9, "Setting CA certificate locations.");

    const char *cafile = port.cafile ? port.cafile : port.clientca;
    if ((cafile || port.capath) && !SSL_CTX_load_verify_locations(sslContext, cafile, port.capath)) {
        ssl_error = ERR_get_error();
        debugs(83, DBG_IMPORTANT, "WARNING: Ignoring error setting CA certificate locations: " << ERR_error_string(ssl_error, NULL));
    }

    if (!(port.sslContextFlags & SSL_FLAG_NO_DEFAULT_CA) &&
            !SSL_CTX_set_default_verify_paths(sslContext)) {
        ssl_error = ERR_get_error();
        debugs(83, DBG_IMPORTANT, "WARNING: Ignoring error setting default CA certificate location: " << ERR_error_string(ssl_error, NULL));
    }

    if (port.clientCA.get()) {
        ERR_clear_error();
        if (STACK_OF(X509_NAME) *clientca = SSL_dup_CA_list(port.clientCA.get())) {
            SSL_CTX_set_client_CA_list(sslContext, clientca);
        } else {
            ssl_error = ERR_get_error();
            debugs(83, DBG_CRITICAL, "ERROR: Failed to dupe the client CA list: " << ERR_error_string(ssl_error, NULL));
            return false;
        }

        if (port.sslContextFlags & SSL_FLAG_DELAYED_AUTH) {
            debugs(83, 9, "Not requesting client certificates until acl processing requires one");
            SSL_CTX_set_verify(sslContext, SSL_VERIFY_NONE, NULL);
        } else {
            debugs(83, 9, "Requiring client certificates.");
            SSL_CTX_set_verify(sslContext, SSL_VERIFY_PEER | SSL_VERIFY_FAIL_IF_NO_PEER_CERT, ssl_verify_cb);
        }

        if (port.clientVerifyCrls.get()) {
            X509_STORE *st = SSL_CTX_get_cert_store(sslContext);
            for (int i = 0; i < sk_X509_CRL_num(port.clientVerifyCrls.get()); ++i) {
                X509_CRL *crl = sk_X509_CRL_value(port.clientVerifyCrls.get(), i);
                if (!X509_STORE_add_crl(st, crl))
                    debugs(83, 2, "WARNING: Failed to add CRL");
            }
        }

#if X509_V_FLAG_CRL_CHECK
        if (port.sslContextFlags & SSL_FLAG_VERIFY_CRL_ALL)
            X509_STORE_set_flags(SSL_CTX_get_cert_store(sslContext), X509_V_FLAG_CRL_CHECK|X509_V_FLAG_CRL_CHECK_ALL);
        else if (port.sslContextFlags & SSL_FLAG_VERIFY_CRL)
            X509_STORE_set_flags(SSL_CTX_get_cert_store(sslContext), X509_V_FLAG_CRL_CHECK);
#endif

    } else {
        debugs(83, 9, "Not requiring any client certificates");
        SSL_CTX_set_verify(sslContext, SSL_VERIFY_NONE, NULL);
    }

    if (port.dhParams.get()) {
        SSL_CTX_set_tmp_dh(sslContext, port.dhParams.get());
    }

    if (port.sslContextFlags & SSL_FLAG_DONT_VERIFY_DOMAIN)
        SSL_CTX_set_ex_data(sslContext, ssl_ctx_ex_index_dont_verify_domain, (void *) -1);

    setSessionCallbacks(sslContext);

    return true;
}

SSL_CTX *
sslCreateServerContext(AnyP::PortCfg &port)
{
    int ssl_error;
    SSL_CTX *sslContext;
    const char *keyfile, *certfile;
    certfile = port.cert;
    keyfile = port.key;

    ssl_initialize();

    if (!keyfile)
        keyfile = certfile;

    if (!certfile)
        certfile = keyfile;

    sslContext = SSL_CTX_new(port.contextMethod);

    if (sslContext == NULL) {
        ssl_error = ERR_get_error();
        debugs(83, DBG_CRITICAL, "ERROR: Failed to allocate SSL context: " << ERR_error_string(ssl_error, NULL));
        return NULL;
    }

    if (!SSL_CTX_use_certificate(sslContext, port.signingCert.get())) {
        ssl_error = ERR_get_error();
        debugs(83, DBG_CRITICAL, "ERROR: Failed to acquire SSL certificate '" << certfile << "': " << ERR_error_string(ssl_error, NULL));
        SSL_CTX_free(sslContext);
        return NULL;
    }

    if (!SSL_CTX_use_PrivateKey(sslContext, port.signPkey.get())) {
        ssl_error = ERR_get_error();
        debugs(83, DBG_CRITICAL, "ERROR: Failed to acquire SSL private key '" << keyfile << "': " << ERR_error_string(ssl_error, NULL));
        SSL_CTX_free(sslContext);
        return NULL;
    }

    Ssl::addChainToSslContext(sslContext, port.certsToChain.get());

    /* Alternate code;
        debugs(83, DBG_IMPORTANT, "Using certificate in " << certfile);

        if (!SSL_CTX_use_certificate_chain_file(sslContext, certfile)) {
            ssl_error = ERR_get_error();
            debugs(83, DBG_CRITICAL, "ERROR: Failed to acquire SSL certificate '" << certfile << "': " << ERR_error_string(ssl_error, NULL));
            SSL_CTX_free(sslContext);
            return NULL;
        }

        debugs(83, DBG_IMPORTANT, "Using private key in " << keyfile);
        ssl_ask_password(sslContext, keyfile);

        if (!SSL_CTX_use_PrivateKey_file(sslContext, keyfile, SSL_FILETYPE_PEM)) {
            ssl_error = ERR_get_error();
            debugs(83, DBG_CRITICAL, "ERROR: Failed to acquire SSL private key '" << keyfile << "': " << ERR_error_string(ssl_error, NULL));
            SSL_CTX_free(sslContext);
            return NULL;
        }

        debugs(83, 5, "Comparing private and public SSL keys.");

        if (!SSL_CTX_check_private_key(sslContext)) {
            ssl_error = ERR_get_error();
            debugs(83, DBG_CRITICAL, "ERROR: SSL private key '" << certfile << "' does not match public key '" <<
                   keyfile << "': " << ERR_error_string(ssl_error, NULL));
            SSL_CTX_free(sslContext);
            return NULL;
        }
    */

    if (!configureSslContext(sslContext, port)) {
        debugs(83, DBG_CRITICAL, "ERROR: Configuring static SSL context");
        SSL_CTX_free(sslContext);
        return NULL;
    }

    return sslContext;
}

int Ssl::OpenSSLtoSquidSSLVersion(int sslVersion)
{
    if (sslVersion == SSL2_VERSION)
        return 2;
    else if (sslVersion == SSL3_VERSION)
        return 3;
    else if (sslVersion == TLS1_VERSION)
        return 4;
#if OPENSSL_VERSION_NUMBER >= 0x10001000L
    else if (sslVersion == TLS1_1_VERSION)
        return 5;
    else if (sslVersion == TLS1_2_VERSION)
        return 6;
#endif
    else
        return 1;
}

#if OPENSSL_VERSION_NUMBER < 0x00909000L
SSL_METHOD *
#else
const SSL_METHOD *
#endif
Ssl::method(int version)
{
    switch (version) {

    case 2:
#if !defined(OPENSSL_NO_SSL2)
        debugs(83, 5, "Using SSLv2.");
        return SSLv2_client_method();
#else
        debugs(83, DBG_IMPORTANT, "SSLv2 is not available in this Proxy.");
        return NULL;
#endif
        break;

    case 3:
#if !defined(OPENSSL_NO_SSL3)
        debugs(83, 5, "Using SSLv3.");
        return SSLv3_client_method();
#else
        debugs(83, DBG_IMPORTANT, "SSLv3 is not available in this Proxy.");
        return NULL;
#endif
        break;

    case 4:
        debugs(83, 5, "Using TLSv1.");
        return TLSv1_client_method();
        break;

    case 5:
#if OPENSSL_VERSION_NUMBER >= 0x10001000L  // NP: not sure exactly which sub-version yet.
        debugs(83, 5, "Using TLSv1.1.");
        return TLSv1_1_client_method();
#else
        debugs(83, DBG_IMPORTANT, "TLSv1.1 is not available in this Proxy.");
        return NULL;
#endif
        break;

    case 6:
#if OPENSSL_VERSION_NUMBER >= 0x10001000L // NP: not sure exactly which sub-version yet.
        debugs(83, 5, "Using TLSv1.2");
        return TLSv1_2_client_method();
#else
        debugs(83, DBG_IMPORTANT, "TLSv1.2 is not available in this Proxy.");
        return NULL;
#endif
        break;

    case 1:

    default:
        debugs(83, 5, "Using SSLv2/SSLv3.");
        return SSLv23_client_method();
        break;
    }

    //Not reached
    return NULL;
}

const SSL_METHOD *
Ssl::serverMethod(int version)
{
    switch (version) {

    case 2:
#if !defined(OPENSSL_NO_SSL2)
        debugs(83, 5, "Using SSLv2.");
        return SSLv2_server_method();
#else
        debugs(83, DBG_IMPORTANT, "SSLv2 is not available in this Proxy.");
        return NULL;
#endif
        break;

    case 3:
#if !defined(OPENSSL_NO_SSL3)
        debugs(83, 5, "Using SSLv3.");
        return SSLv3_server_method();
#else
        debugs(83, DBG_IMPORTANT, "SSLv3 is not available in this Proxy.");
        return NULL;
#endif
        break;

    case 4:
        debugs(83, 5, "Using TLSv1.");
        return TLSv1_server_method();
        break;

    case 5:
#if OPENSSL_VERSION_NUMBER >= 0x10001000L  // NP: not sure exactly which sub-version yet.
        debugs(83, 5, "Using TLSv1.1.");
        return TLSv1_1_server_method();
#else
        debugs(83, DBG_IMPORTANT, "TLSv1.1 is not available in this Proxy.");
        return NULL;
#endif
        break;

    case 6:
#if OPENSSL_VERSION_NUMBER >= 0x10001000L // NP: not sure exactly which sub-version yet.
        debugs(83, 5, "Using TLSv1.2");
        return TLSv1_2_server_method();
#else
        debugs(83, DBG_IMPORTANT, "TLSv1.2 is not available in this Proxy.");
        return NULL;
#endif
        break;

    case 1:

    default:
        debugs(83, 5, "Using SSLv2/SSLv3.");
        return SSLv23_server_method();
        break;
    }

    //Not reached
    return NULL;
}

#if defined(TLSEXT_TYPE_next_proto_neg)
//Dummy next_proto_neg callback
static int
ssl_next_proto_cb(SSL *s, unsigned char **out, unsigned char *outlen, const unsigned char *in, unsigned int inlen, void *arg)
{
    static const unsigned char supported_protos[] = {8, 'h','t','t', 'p', '/', '1', '.', '1'};
    (void)SSL_select_next_proto(out, outlen, in, inlen, supported_protos, sizeof(supported_protos));
    return SSL_TLSEXT_ERR_OK;
}
#endif

SSL_CTX *
sslCreateClientContext(const char *certfile, const char *keyfile, int version, const char *cipher, const char *options, const char *flags, const char *CAfile, const char *CApath, const char *CRLfile)
{
    int ssl_error;
    Ssl::ContextMethod method;
    SSL_CTX * sslContext;
    long fl = Ssl::parse_flags(flags);

    ssl_initialize();

    if (!keyfile)
        keyfile = certfile;

    if (!certfile)
        certfile = keyfile;

    if (!(method = Ssl::method(version)))
        return NULL;

    sslContext = SSL_CTX_new(method);

    if (sslContext == NULL) {
        ssl_error = ERR_get_error();
        fatalf("Failed to allocate SSL context: %s\n",
               ERR_error_string(ssl_error, NULL));
    }

    SSL_CTX_set_options(sslContext, Ssl::parse_options(options));

#if defined(SSL3_FLAGS_NO_RENEGOTIATE_CIPHERS)
    SSL_CTX_set_info_callback(sslContext, ssl_info_cb);
#endif

    if (cipher) {
        debugs(83, 5, "Using chiper suite " << cipher << ".");

        if (!SSL_CTX_set_cipher_list(sslContext, cipher)) {
            ssl_error = ERR_get_error();
            fatalf("Failed to set SSL cipher suite '%s': %s\n",
                   cipher, ERR_error_string(ssl_error, NULL));
        }
    }

    if (certfile) {
        debugs(83, DBG_IMPORTANT, "Using certificate in " << certfile);

        if (!SSL_CTX_use_certificate_chain_file(sslContext, certfile)) {
            ssl_error = ERR_get_error();
            fatalf("Failed to acquire SSL certificate '%s': %s\n",
                   certfile, ERR_error_string(ssl_error, NULL));
        }

        debugs(83, DBG_IMPORTANT, "Using private key in " << keyfile);
        ssl_ask_password(sslContext, keyfile);

        if (!SSL_CTX_use_PrivateKey_file(sslContext, keyfile, SSL_FILETYPE_PEM)) {
            ssl_error = ERR_get_error();
            fatalf("Failed to acquire SSL private key '%s': %s\n",
                   keyfile, ERR_error_string(ssl_error, NULL));
        }

        debugs(83, 5, "Comparing private and public SSL keys.");

        if (!SSL_CTX_check_private_key(sslContext)) {
            ssl_error = ERR_get_error();
            fatalf("SSL private key '%s' does not match public key '%s': %s\n",
                   certfile, keyfile, ERR_error_string(ssl_error, NULL));
        }
    }

    debugs(83, 9, "Setting RSA key generation callback.");
    SSL_CTX_set_tmp_rsa_callback(sslContext, ssl_temp_rsa_cb);

    if (fl & SSL_FLAG_DONT_VERIFY_PEER) {
        debugs(83, 2, "NOTICE: Peer certificates are not verified for validity!");
        SSL_CTX_set_verify(sslContext, SSL_VERIFY_NONE, NULL);
    } else {
        debugs(83, 9, "Setting certificate verification callback.");
        SSL_CTX_set_verify(sslContext, SSL_VERIFY_PEER | SSL_VERIFY_FAIL_IF_NO_PEER_CERT, ssl_verify_cb);
    }

    debugs(83, 9, "Setting CA certificate locations.");

    if ((CAfile || CApath) && !SSL_CTX_load_verify_locations(sslContext, CAfile, CApath)) {
        ssl_error = ERR_get_error();
        debugs(83, DBG_IMPORTANT, "WARNING: Ignoring error setting CA certificate locations: " << ERR_error_string(ssl_error, NULL));
    }

    if (CRLfile) {
        ssl_load_crl(sslContext, CRLfile);
        fl |= SSL_FLAG_VERIFY_CRL;
    }

#if X509_V_FLAG_CRL_CHECK
    if (fl & SSL_FLAG_VERIFY_CRL_ALL)
        X509_STORE_set_flags(SSL_CTX_get_cert_store(sslContext), X509_V_FLAG_CRL_CHECK|X509_V_FLAG_CRL_CHECK_ALL);
    else if (fl & SSL_FLAG_VERIFY_CRL)
        X509_STORE_set_flags(SSL_CTX_get_cert_store(sslContext), X509_V_FLAG_CRL_CHECK);

#endif

    if (!(fl & SSL_FLAG_NO_DEFAULT_CA) &&
            !SSL_CTX_set_default_verify_paths(sslContext)) {
        ssl_error = ERR_get_error();
        debugs(83, DBG_IMPORTANT, "WARNING: Ignoring error setting default CA certificate location: " << ERR_error_string(ssl_error, NULL));
    }

#if defined(TLSEXT_TYPE_next_proto_neg)
    SSL_CTX_set_next_proto_select_cb(sslContext, &ssl_next_proto_cb, NULL);
#endif
    return sslContext;
}

/// \ingroup ServerProtocolSSLInternal
int
ssl_read_method(int fd, char *buf, int len)
{
    SSL *ssl = fd_table[fd].ssl;
    int i;

#if DONT_DO_THIS

    if (!SSL_is_init_finished(ssl)) {
        errno = ENOTCONN;
        return -1;
    }

#endif

    i = SSL_read(ssl, buf, len);

    if (i > 0 && SSL_pending(ssl) > 0) {
        debugs(83, 2, "SSL FD " << fd << " is pending");
        fd_table[fd].flags.read_pending = true;
    } else
        fd_table[fd].flags.read_pending = false;

    return i;
}

/// \ingroup ServerProtocolSSLInternal
int
ssl_write_method(int fd, const char *buf, int len)
{
    SSL *ssl = fd_table[fd].ssl;
    int i;

    if (!SSL_is_init_finished(ssl)) {
        errno = ENOTCONN;
        return -1;
    }

    i = SSL_write(ssl, buf, len);

    return i;
}

void
ssl_shutdown_method(SSL *ssl)
{
    SSL_shutdown(ssl);
}

/// \ingroup ServerProtocolSSLInternal
static const char *
ssl_get_attribute(X509_NAME * name, const char *attribute_name)
{
    static char buffer[1024];
    int nid;

    buffer[0] = '\0';

    if (strcmp(attribute_name, "DN") == 0) {
        X509_NAME_oneline(name, buffer, sizeof(buffer));
        goto done;
    }

    nid = OBJ_txt2nid((char *) attribute_name);

    if (nid == 0) {
        debugs(83, DBG_IMPORTANT, "WARNING: Unknown SSL attribute name '" << attribute_name << "'");
        return NULL;
    }

    X509_NAME_get_text_by_NID(name, nid, buffer, sizeof(buffer));

done:
    return *buffer ? buffer : NULL;
}

/// \ingroup ServerProtocolSSLInternal
const char *
Ssl::GetX509UserAttribute(X509 * cert, const char *attribute_name)
{
    X509_NAME *name;
    const char *ret;

    if (!cert)
        return NULL;

    name = X509_get_subject_name(cert);

    ret = ssl_get_attribute(name, attribute_name);

    return ret;
}

const char *
Ssl::GetX509Fingerprint(X509 * cert, const char *)
{
    static char buf[1024];
    if (!cert)
        return NULL;

    unsigned int n;
    unsigned char md[EVP_MAX_MD_SIZE];
    if (!X509_digest(cert, EVP_sha1(), md, &n))
        return NULL;

    assert(3 * n + 1 < sizeof(buf));

    char *s = buf;
    for (unsigned int i=0; i < n; ++i, s += 3) {
        const char term = (i + 1 < n) ? ':' : '\0';
        snprintf(s, 4, "%02X%c", md[i], term);
    }

    return buf;
}

/// \ingroup ServerProtocolSSLInternal
const char *
Ssl::GetX509CAAttribute(X509 * cert, const char *attribute_name)
{

    X509_NAME *name;
    const char *ret;

    if (!cert)
        return NULL;

    name = X509_get_issuer_name(cert);

    ret = ssl_get_attribute(name, attribute_name);

    return ret;
}

const char *sslGetUserAttribute(SSL *ssl, const char *attribute_name)
{
    if (!ssl)
        return NULL;

    X509 *cert = SSL_get_peer_certificate(ssl);

    const char *attr = Ssl::GetX509UserAttribute(cert, attribute_name);

    X509_free(cert);
    return attr;
}

const char *sslGetCAAttribute(SSL *ssl, const char *attribute_name)
{
    if (!ssl)
        return NULL;

    X509 *cert = SSL_get_peer_certificate(ssl);

    const char *attr = Ssl::GetX509CAAttribute(cert, attribute_name);

    X509_free(cert);
    return attr;
}

const char *
sslGetUserEmail(SSL * ssl)
{
    return sslGetUserAttribute(ssl, "emailAddress");
}

const char *
sslGetUserCertificatePEM(SSL *ssl)
{
    X509 *cert;
    BIO *mem;
    static char *str = NULL;
    char *ptr;
    long len;

    safe_free(str);

    if (!ssl)
        return NULL;

    cert = SSL_get_peer_certificate(ssl);

    if (!cert)
        return NULL;

    mem = BIO_new(BIO_s_mem());

    PEM_write_bio_X509(mem, cert);

    len = BIO_get_mem_data(mem, &ptr);

    str = (char *)xmalloc(len + 1);

    memcpy(str, ptr, len);

    str[len] = '\0';

    X509_free(cert);

    BIO_free(mem);

    return str;
}

const char *
sslGetUserCertificateChainPEM(SSL *ssl)
{
    STACK_OF(X509) *chain;
    BIO *mem;
    static char *str = NULL;
    char *ptr;
    long len;
    int i;

    safe_free(str);

    if (!ssl)
        return NULL;

    chain = SSL_get_peer_cert_chain(ssl);

    if (!chain)
        return sslGetUserCertificatePEM(ssl);

    mem = BIO_new(BIO_s_mem());

    for (i = 0; i < sk_X509_num(chain); ++i) {
        X509 *cert = sk_X509_value(chain, i);
        PEM_write_bio_X509(mem, cert);
    }

    len = BIO_get_mem_data(mem, &ptr);

    str = (char *)xmalloc(len + 1);
    memcpy(str, ptr, len);
    str[len] = '\0';

    BIO_free(mem);

    return str;
}

Ssl::ContextMethod
Ssl::contextMethod(int version)
{
    Ssl::ContextMethod method;

    switch (version) {

    case 2:
#if !defined(OPENSSL_NO_SSL2)
        debugs(83, 5, "Using SSLv2.");
        method = SSLv2_server_method();
#else
        debugs(83, DBG_IMPORTANT, "SSLv2 is not available in this Proxy.");
        return NULL;
#endif
        break;

    case 3:
#if !defined(OPENSSL_NO_SSL3)
        debugs(83, 5, "Using SSLv3.");
        method = SSLv3_server_method();
#else
        debugs(83, DBG_IMPORTANT, "SSLv3 is not available in this Proxy.");
        return NULL;
#endif
        break;

    case 4:
        debugs(83, 5, "Using TLSv1.");
        method = TLSv1_server_method();
        break;

    case 5:
#if OPENSSL_VERSION_NUMBER >= 0x10001000L  // NP: not sure exactly which sub-version yet.
        debugs(83, 5, "Using TLSv1.1.");
        method = TLSv1_1_server_method();
#else
        debugs(83, DBG_IMPORTANT, "TLSv1.1 is not available in this Proxy.");
        return NULL;
#endif
        break;

    case 6:
#if OPENSSL_VERSION_NUMBER >= 0x10001000L // NP: not sure exactly which sub-version yet.
        debugs(83, 5, "Using TLSv1.2");
        method = TLSv1_2_server_method();
#else
        debugs(83, DBG_IMPORTANT, "TLSv1.2 is not available in this Proxy.");
        return NULL;
#endif
        break;

    case 1:

    default:
        debugs(83, 5, "Using SSLv2/SSLv3.");
        method = SSLv23_server_method();
        break;
    }
    return method;
}

/// \ingroup ServerProtocolSSLInternal
/// Create SSL context and apply ssl certificate and private key to it.
SSL_CTX *
Ssl::createSSLContext(Ssl::X509_Pointer & x509, Ssl::EVP_PKEY_Pointer & pkey, AnyP::PortCfg &port)
{
    Ssl::SSL_CTX_Pointer sslContext(SSL_CTX_new(port.contextMethod));

    if (!SSL_CTX_use_certificate(sslContext.get(), x509.get()))
        return NULL;

    if (!SSL_CTX_use_PrivateKey(sslContext.get(), pkey.get()))
        return NULL;

    if (!configureSslContext(sslContext.get(), port))
        return NULL;

    return sslContext.release();
}

SSL_CTX *
Ssl::generateSslContextUsingPkeyAndCertFromMemory(const char * data, AnyP::PortCfg &port)
{
    Ssl::X509_Pointer cert;
    Ssl::EVP_PKEY_Pointer pkey;
    if (!readCertAndPrivateKeyFromMemory(cert, pkey, data))
        return NULL;

    if (!cert || !pkey)
        return NULL;

    return createSSLContext(cert, pkey, port);
}

SSL_CTX *
Ssl::generateSslContext(CertificateProperties const &properties, AnyP::PortCfg &port)
{
    Ssl::X509_Pointer cert;
    Ssl::EVP_PKEY_Pointer pkey;
    if (!generateSslCertificate(cert, pkey, properties))
        return NULL;

    if (!cert)
        return NULL;

    if (!pkey)
        return NULL;

    return createSSLContext(cert, pkey, port);
}

bool
Ssl::configureSSL(SSL *ssl, CertificateProperties const &properties, AnyP::PortCfg &port)
{
    Ssl::X509_Pointer cert;
    Ssl::EVP_PKEY_Pointer pkey;
    if (!generateSslCertificate(cert, pkey, properties))
        return false;

    if (!cert)
        return false;

    if (!pkey)
        return false;

    if (!SSL_use_certificate(ssl, cert.get()))
        return false;

    if (!SSL_use_PrivateKey(ssl, pkey.get()))
        return false;

    return true;
}

bool
Ssl::configureSSLUsingPkeyAndCertFromMemory(SSL *ssl, const char *data, AnyP::PortCfg &port)
{
    Ssl::X509_Pointer cert;
    Ssl::EVP_PKEY_Pointer pkey;
    if (!readCertAndPrivateKeyFromMemory(cert, pkey, data))
        return false;

    if (!cert || !pkey)
        return false;

    if (!SSL_use_certificate(ssl, cert.get()))
        return false;

    if (!SSL_use_PrivateKey(ssl, pkey.get()))
        return false;

    return true;
}

bool Ssl::verifySslCertificate(SSL_CTX * sslContext, CertificateProperties const &properties)
{
    // SSL_get_certificate is buggy in openssl versions 1.0.1d and 1.0.1e
    // Try to retrieve certificate directly from SSL_CTX object
#if SQUID_USE_SSLGETCERTIFICATE_HACK
    X509 ***pCert = (X509 ***)sslContext->cert;
    X509 * cert = pCert && *pCert ? **pCert : NULL;
#elif SQUID_SSLGETCERTIFICATE_BUGGY
    X509 * cert = NULL;
    assert(0);
#else
    // Temporary ssl for getting X509 certificate from SSL_CTX.
    Ssl::SSL_Pointer ssl(SSL_new(sslContext));
    X509 * cert = SSL_get_certificate(ssl.get());
#endif
    if (!cert)
        return false;
    ASN1_TIME * time_notBefore = X509_get_notBefore(cert);
    ASN1_TIME * time_notAfter = X509_get_notAfter(cert);
    bool ret = (X509_cmp_current_time(time_notBefore) < 0 && X509_cmp_current_time(time_notAfter) > 0);
    if (!ret)
        return false;

    return certificateMatchesProperties(cert, properties);
}

bool
Ssl::setClientSNI(SSL *ssl, const char *fqdn)
{
    //The SSL_CTRL_SET_TLSEXT_HOSTNAME is a openssl macro which indicates
    // if the TLS servername extension (SNI) is enabled in openssl library.
#if defined(SSL_CTRL_SET_TLSEXT_HOSTNAME)
    if (!SSL_set_tlsext_host_name(ssl, fqdn)) {
        const int ssl_error = ERR_get_error();
        debugs(83, 3,  "WARNING: unable to set TLS servername extension (SNI): " <<
               ERR_error_string(ssl_error, NULL) << "\n");
        return false;
    }
    return true;
#else
    debugs(83, 7,  "no support for TLS servername extension (SNI)\n");
    return false;
#endif
}

void Ssl::addChainToSslContext(SSL_CTX *sslContext, STACK_OF(X509) *chain)
{
    if (!chain)
        return;

    for (int i = 0; i < sk_X509_num(chain); ++i) {
        X509 *cert = sk_X509_value(chain, i);
        if (SSL_CTX_add_extra_chain_cert(sslContext, cert)) {
            // increase the certificate lock
            CRYPTO_add(&(cert->references),1,CRYPTO_LOCK_X509);
        } else {
            const int ssl_error = ERR_get_error();
            debugs(83, DBG_IMPORTANT, "WARNING: can not add certificate to SSL context chain: " << ERR_error_string(ssl_error, NULL));
        }
    }
}

/**
 \ingroup ServerProtocolSSLInternal
 * Read certificate from file.
 * See also: static readSslX509Certificate function, gadgets.cc file
 */
static X509 * readSslX509CertificatesChain(char const * certFilename,  STACK_OF(X509)* chain)
{
    if (!certFilename)
        return NULL;
    Ssl::BIO_Pointer bio(BIO_new(BIO_s_file_internal()));
    if (!bio)
        return NULL;
    if (!BIO_read_filename(bio.get(), certFilename))
        return NULL;
    X509 *certificate = PEM_read_bio_X509(bio.get(), NULL, NULL, NULL);

    if (certificate && chain) {

        if (X509_check_issued(certificate, certificate) == X509_V_OK)
            debugs(83, 5, "Certificate is self-signed, will not be chained");
        else {
            // and add to the chain any other certificate exist in the file
            while (X509 *ca = PEM_read_bio_X509(bio.get(), NULL, NULL, NULL)) {
                if (!sk_X509_push(chain, ca))
                    debugs(83, DBG_IMPORTANT, "WARNING: unable to add CA certificate to cert chain");
            }
        }
    }

    return certificate;
}

void Ssl::readCertChainAndPrivateKeyFromFiles(X509_Pointer & cert, EVP_PKEY_Pointer & pkey, X509_STACK_Pointer & chain, char const * certFilename, char const * keyFilename)
{
    if (keyFilename == NULL)
        keyFilename = certFilename;

    if (certFilename == NULL)
        certFilename = keyFilename;

    debugs(83, DBG_IMPORTANT, "Using certificate in " << certFilename);

    if (!chain)
        chain.reset(sk_X509_new_null());
    if (!chain)
        debugs(83, DBG_IMPORTANT, "WARNING: unable to allocate memory for cert chain");
    // XXX: ssl_ask_password_cb needs SSL_CTX_set_default_passwd_cb_userdata()
    // so this may not fully work iff Config.Program.ssl_password is set.
    pem_password_cb *cb = ::Config.Program.ssl_password ? &ssl_ask_password_cb : NULL;
    pkey.reset(readSslPrivateKey(keyFilename, cb));
    cert.reset(readSslX509CertificatesChain(certFilename, chain.get()));
    if (!pkey || !cert || !X509_check_private_key(cert.get(), pkey.get())) {
        pkey.reset(NULL);
        cert.reset(NULL);
    }
}

bool Ssl::generateUntrustedCert(X509_Pointer &untrustedCert, EVP_PKEY_Pointer &untrustedPkey, X509_Pointer const  &cert, EVP_PKEY_Pointer const & pkey)
{
    // Generate the self-signed certificate, using a hard-coded subject prefix
    Ssl::CertificateProperties certProperties;
    if (const char *cn = CommonHostName(cert.get())) {
        certProperties.commonName = "Not trusted by \"";
        certProperties.commonName += cn;
        certProperties.commonName += "\"";
    } else if (const char *org = getOrganization(cert.get())) {
        certProperties.commonName =  "Not trusted by \"";
        certProperties.commonName += org;
        certProperties.commonName += "\"";
    } else
        certProperties.commonName =  "Not trusted";
    certProperties.setCommonName = true;
    // O, OU, and other CA subject fields will be mimicked
    // Expiration date and other common properties will be mimicked
    certProperties.signAlgorithm = Ssl::algSignSelf;
    certProperties.signWithPkey.resetAndLock(pkey.get());
    certProperties.mimicCert.resetAndLock(cert.get());
    return Ssl::generateSslCertificate(untrustedCert, untrustedPkey, certProperties);
}

SSL *
SslCreate(SSL_CTX *sslContext, const int fd, Ssl::Bio::Type type, const char *squidCtx)
{
    if (fd < 0) {
        debugs(83, DBG_IMPORTANT, "Gone connection");
        return NULL;
    }

    const char *errAction = NULL;
    int errCode = 0;
    if (SSL *ssl = SSL_new(sslContext)) {
        // without BIO, we would call SSL_set_fd(ssl, fd) instead
        if (BIO *bio = Ssl::Bio::Create(fd, type)) {
            Ssl::Bio::Link(ssl, bio); // cannot fail

            fd_table[fd].ssl = ssl;
            fd_table[fd].read_method = &ssl_read_method;
            fd_table[fd].write_method = &ssl_write_method;
            fd_note(fd, squidCtx);

            return ssl;
        }
        errCode = ERR_get_error();
        errAction = "failed to initialize I/O";
        SSL_free(ssl);
    } else {
        errCode = ERR_get_error();
        errAction = "failed to allocate handle";
    }

    debugs(83, DBG_IMPORTANT, "ERROR: " << squidCtx << ' ' << errAction <<
           ": " << ERR_error_string(errCode, NULL));
    return NULL;
}

SSL *
Ssl::CreateClient(SSL_CTX *sslContext, const int fd, const char *squidCtx)
{
    return SslCreate(sslContext, fd, Ssl::Bio::BIO_TO_SERVER, squidCtx);
}

SSL *
Ssl::CreateServer(SSL_CTX *sslContext, const int fd, const char *squidCtx)
{
    return SslCreate(sslContext, fd, Ssl::Bio::BIO_TO_CLIENT, squidCtx);
}

Ssl::CertError::CertError(ssl_error_t anErr, X509 *aCert): code(anErr)
{
    cert.resetAndLock(aCert);
}

Ssl::CertError::CertError(CertError const &err): code(err.code)
{
    cert.resetAndLock(err.cert.get());
}

Ssl::CertError &
Ssl::CertError::operator = (const CertError &old)
{
    code = old.code;
    cert.resetAndLock(old.cert.get());
    return *this;
}

bool
Ssl::CertError::operator == (const CertError &ce) const
{
    return code == ce.code && cert.get() == ce.cert.get();
}

bool
Ssl::CertError::operator != (const CertError &ce) const
{
    return code != ce.code || cert.get() != ce.cert.get();
}

static int
store_session_cb(SSL *ssl, SSL_SESSION *session)
{
    if (!SslSessionCache)
        return 0;

    debugs(83, 5, "Request to store SSL Session ");

    SSL_SESSION_set_timeout(session, Config.SSL.session_ttl);

    unsigned char *id = session->session_id;
    unsigned int idlen = session->session_id_length;
    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;
    Ipc::MemMap::Slot *slotW = SslSessionCache->openForWriting((const cache_key*)key, pos);
    if (slotW) {
        int lenRequired =  i2d_SSL_SESSION(session, NULL);
        if (lenRequired <  MEMMAP_SLOT_DATA_SIZE) {
            unsigned char *p = (unsigned char *)slotW->p;
            lenRequired = i2d_SSL_SESSION(session, &p);
            slotW->set(key, NULL, lenRequired, squid_curtime + Config.SSL.session_ttl);
        }
        SslSessionCache->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 (!SslSessionCache)
        return ;

    debugs(83, 5, "Request to remove corrupted or not valid SSL Session ");
    int pos;
    Ipc::MemMap::Slot const *slot = SslSessionCache->openForReading((const cache_key*)sessionID, pos);
    if (slot == NULL)
        return;
    SslSessionCache->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 will reject it when we try to use it
    SslSessionCache->free(pos);
}

static SSL_SESSION *
get_session_cb(SSL *, unsigned char *sessionID, int len, int *copy)
{
    if (!SslSessionCache)
        return NULL;

    SSL_SESSION *session = NULL;
    const unsigned int *p;
    p = (unsigned int *)sessionID;
    debugs(83, 5, "Request to search for SSL Session of len:" <<
           len << p[0] << ":" << p[1]);

    int pos;
    Ipc::MemMap::Slot const *slot = SslSessionCache->openForReading((const cache_key*)sessionID, pos);
    if (slot != NULL) {
        if (slot->expire > squid_curtime) {
            const unsigned char *ptr = slot->p;
            session = d2i_SSL_SESSION(NULL, &ptr, slot->pSize);
            debugs(83, 5, "Session retrieved from cache at pos " << pos);
        } else
            debugs(83, 5, "Session in cache expired");
        SslSessionCache->closeForReading(pos);
    }

    if (!session)
        debugs(83, 5, "Failed to retrieved from cache\n");

    // 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;
}

static void
setSessionCallbacks(SSL_CTX *ctx)
{
    if (SslSessionCache) {
        SSL_CTX_set_session_cache_mode(ctx, SSL_SESS_CACHE_SERVER|SSL_SESS_CACHE_NO_INTERNAL);
        SSL_CTX_sess_set_new_cb(ctx, store_session_cb);
        SSL_CTX_sess_set_remove_cb(ctx, remove_session_cb);
        SSL_CTX_sess_set_get_cb(ctx, get_session_cb);
    }
}

static bool
isSslServer()
{
    if (HttpsPortList != NULL)
        return true;

    for (AnyP::PortCfgPointer s = HttpPortList; s != NULL; s = s->next) {
        if (s->flags.tunnelSslBumping)
            return true;
    }

    return false;
}

#define SSL_SESSION_ID_SIZE 32
#define SSL_SESSION_MAX_SIZE 10*1024

void
Ssl::initialize_session_cache()
{

    if (!isSslServer()) //no need to configure ssl session cache.
        return;

    // 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)
        SslSessionCache = new Ipc::MemMap(SslSessionCacheName);
    else {
        SslSessionCache = NULL;
        return;
    }

    for (AnyP::PortCfgPointer s = HttpsPortList; s != NULL; s = s->next) {
        if (s->staticSslContext.get() != NULL)
            setSessionCallbacks(s->staticSslContext.get());
    }

    for (AnyP::PortCfgPointer s = HttpPortList; s != NULL; s = s->next) {
        if (s->staticSslContext.get() != NULL)
            setSessionCallbacks(s->staticSslContext.get());
    }
}

void
destruct_session_cache()
{
    delete SslSessionCache;
}

/// initializes shared memory segments used by MemStore
class SharedSessionCacheRr: public Ipc::Mem::RegisteredRunner
{
public:
    /* RegisteredRunner API */
    SharedSessionCacheRr(): owner(NULL) {}
    virtual void useConfig();
    virtual ~SharedSessionCacheRr();

protected:
    virtual void create();

private:
    Ipc::MemMap::Owner *owner;
};

RunnerRegistrationEntry(SharedSessionCacheRr);

void
SharedSessionCacheRr::useConfig()
{
    Ipc::Mem::RegisteredRunner::useConfig();
}

void
SharedSessionCacheRr::create()
{
    if (!isSslServer()) //no need to configure ssl session cache.
        return;

    int items;
    items = Config.SSL.sessionCacheSize / sizeof(Ipc::MemMap::Slot);
    if (items)
        owner =  Ipc::MemMap::Init(SslSessionCacheName, items);
}

SharedSessionCacheRr::~SharedSessionCacheRr()
{
    delete owner;
}

#endif /* USE_OPENSSL */