pairs.c

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/*
 *   This program is free software; you can redistribute it and/or modify
 *   it under the terms of the GNU General Public License as published by
 *   the Free Software Foundation; either version 2 of the License, or
 *   (at your option) any later version.
 *
 *   This program is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *   GNU General Public License for more details.
 *
 *   You should have received a copy of the GNU General Public License
 *   along with this program; if not, write to the Free Software
 *   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA
 */
 
/**
 * $Id: 4fa71237698596e98c0b2849f86be943ac2defea $
 *
 * @file tls/pairs.c
 * @brief Functions to convert certificate OIDs to attribute pairs
 *
 * @copyright 2021 Arran Cudbard-Bell (a.cudbardb@freeradius.org)
 */
RCSID("$Id: 4fa71237698596e98c0b2849f86be943ac2defea $")
USES_APPLE_DEPRECATED_API       /* OpenSSL API has been deprecated by Apple */
 
#ifdef WITH_TLS
#define LOG_PREFIX "tls"
 
#include <freeradius-devel/tls/openssl_user_macros.h>
#include <freeradius-devel/util/pair.h>
#include <freeradius-devel/server/request.h>
#include <freeradius-devel/server/pair.h>
#include <freeradius-devel/der/der.h>
 
#include "attrs.h"
#include "bio.h"
#include "log.h"
#include "session.h"
#include "utils.h"
 
#include <openssl/x509v3.h>
#include <openssl/ssl.h>
 
DIAG_OFF(DIAG_UNKNOWN_PRAGMAS)
DIAG_OFF(used-but-marked-unused)        /* fix spurious warnings for sk macros */
/** Extract session pairs from the Subject Alternate Name extension
 *
 */
static bool tls_session_pairs_from_san(fr_pair_list_t *pair_list, TALLOC_CTX *ctx, request_t *request, X509_EXTENSION *ext)
{
        GENERAL_NAMES   *names = NULL;
        int             i;
        fr_pair_t       *vp;
 
        if (!(names = X509V3_EXT_d2i(ext))) return false;
 
        for (i = 0; i < sk_GENERAL_NAME_num(names); i++) {
                GENERAL_NAME *name = sk_GENERAL_NAME_value(names, i);
 
                switch (name->type) {
#ifdef GEN_EMAIL
                case GEN_EMAIL:
                        MEM(fr_pair_append_by_da(ctx, &vp, pair_list,
                                                 attr_tls_certificate_subject_alt_name_email) == 0);
                        MEM(fr_pair_value_bstrndup(vp,
                                                   (char const *)ASN1_STRING_get0_data(name->d.rfc822Name),
                                                   ASN1_STRING_length(name->d.rfc822Name), true) == 0);
                        break;
#endif  /* GEN_EMAIL */
#ifdef GEN_DNS
                case GEN_DNS:
                        MEM(fr_pair_append_by_da(ctx, &vp, pair_list,
                                                 attr_tls_certificate_subject_alt_name_dns) == 0);
                        MEM(fr_pair_value_bstrndup(vp,
                                                   (char const *)ASN1_STRING_get0_data(name->d.dNSName),
                                                   ASN1_STRING_length(name->d.dNSName), true) == 0);
                        break;
#endif  /* GEN_DNS */
#ifdef GEN_OTHERNAME
                case GEN_OTHERNAME:
                        /* look for a MS UPN */
                        if (NID_ms_upn != OBJ_obj2nid(name->d.otherName->type_id)) break;
 
                        /* we've got a UPN - Must be ASN1-encoded UTF8 string */
                        if (name->d.otherName->value->type == V_ASN1_UTF8STRING) {
                                MEM(fr_pair_append_by_da(ctx, &vp, pair_list,
                                                         attr_tls_certificate_subject_alt_name_upn) == 0);
                                MEM(fr_pair_value_bstrndup(vp,
                                                           (char const *)ASN1_STRING_get0_data(name->d.otherName->value->value.utf8string),
                                                           ASN1_STRING_length(name->d.otherName->value->value.utf8string),
                                                           true) == 0);
                                break;
                        }
                        RWARN("Invalid UPN in Subject Alt Name (should be UTF-8)");
                                break;
#endif  /* GEN_OTHERNAME */
                        default:
                                /* XXX TODO handle other SAN types */
                                break;
                }
        }
        if (names != NULL) GENERAL_NAMES_free(names);
 
        return true;
}
 
/** Extract session pairs from the X509v3-CRL-Distribution-Points extension
 *
 */
static bool tls_session_pairs_from_crl(fr_pair_list_t *pair_list, TALLOC_CTX *ctx, UNUSED request_t *request, X509_EXTENSION *ext)
{
        ASN1_STRING             *s = X509_EXTENSION_get_data(ext);
        char unsigned const     *data = ASN1_STRING_get0_data(s);
        STACK_OF(DIST_POINT)    *dps;
        DIST_POINT              *dp;
        STACK_OF(GENERAL_NAME)  *names;
        GENERAL_NAME            *name;
        fr_pair_t               *vp;
        int                     i, j;
 
        if (!(dps = d2i_CRL_DIST_POINTS(NULL, &data, ASN1_STRING_length(s)))) return false;
 
        for (i = 0; i < sk_DIST_POINT_num(dps); i++) {
                dp = sk_DIST_POINT_value(dps, i);
 
                /*
                 *      RFC 5280 Section 4.2.1.13 says that the distpoint is optional.
                 */
                if (!dp->distpoint) {
                        CRL_DIST_POINTS_free(dps);
                        return false;
                }
 
                names = dp->distpoint->name.fullname;
 
                /*
                 *      We only want CRL distribution points that cover all reasons,
                 *      so ignore any where reasons are set.
                 */
                if (dp->reasons) continue;
 
                for (j = 0; j < sk_GENERAL_NAME_num(names); j++) {
                        name = sk_GENERAL_NAME_value(names, j);
 
                        if (name->type != GEN_URI) continue;
                        MEM(fr_pair_append_by_da(ctx, &vp, pair_list,
                                                 attr_tls_certificate_x509v3_crl_distribution_points) == 0);
                        MEM(fr_pair_value_strdup(vp,
                                                 (char const *)ASN1_STRING_get0_data(name->d.uniformResourceIdentifier),
                                                 true) == 0);
                }
        }
 
        CRL_DIST_POINTS_free(dps);
 
        return true;
}
 
/** Extract attributes from an X509 certificate
 *
 * @param[out] pair_list        to copy attributes to.
 * @param[in] ctx               to allocate attributes in.
 * @param[in] request           the current request.
 * @param[in] cert              to validate.
 * @param[in] der_decode        should the certificate be parsed with the DER decoder.
 * @return
 *      - 1 already exists.
 *      - 0 on success.
 *      - < 0 on failure.
 */
int fr_tls_session_pairs_from_x509_cert(fr_pair_list_t *pair_list, TALLOC_CTX *ctx, request_t *request, X509 *cert,
#if OPENSSL_VERSION_NUMBER >= 0x30400000L
                                        bool der_decode
#else
                                        UNUSED bool der_decode
#endif
                                )
{
        int             loc;
        char            buff[1024];
 
        ASN1_TIME const *asn_time;
        time_t          time;
 
        STACK_OF(X509_EXTENSION) const *ext_list = NULL;
 
        fr_pair_t       *vp = NULL;
        ssize_t         slen;
        bool            san_found = false, crl_found = false;
 
        /*
         *      We require OpenSSL >= 3.4 to call the DER decoder due to the stack size
         *      needed to handle the recursive calls involved in certificate decoding.
         */
#if OPENSSL_VERSION_NUMBER >= 0x30400000L
        if (der_decode) {
                uint8_t                 *cert_der;
                uint8_t                 *cd;
                int                     der_len;
                fr_der_decode_ctx_t     der_ctx;
                fr_pair_list_t          tmp_list;
 
                der_len = i2d_X509(cert, NULL);
                if (der_len < 0) {
                        fr_tls_log(request, "Failed retrieving certificate");
                        return -1;
                }
                der_ctx = (fr_der_decode_ctx_t) {
                        .tmp_ctx = talloc_new(ctx),
                        .root = attr_der_certificate,
                };
                cert_der = cd = talloc_array(der_ctx.tmp_ctx, uint8_t, der_len);
                i2d_X509(cert, &cd);
                fr_pair_list_init(&tmp_list);
                slen = fr_der_decode_pair_dbuff(request->session_state_ctx, &tmp_list,
                                                attr_der_certificate, &FR_DBUFF_TMP(cert_der, (size_t)der_len), &der_ctx);
                talloc_free(der_ctx.tmp_ctx);
                if (slen < 0) {
                        fr_tls_log(request, "Failed decoding certificate");
                        fr_pair_list_free(&tmp_list);
                        return -1;
                }
                /*
                 *  Certificates are decoded in CA .. intermediate .. client sequence
                 *  so, prepend each decoded one to get the client cert first.
                 */
                fr_pair_list_prepend(&request->session_state_pairs, &tmp_list);
        }
#endif
 
        /*
         *      Subject
         */
        MEM(fr_pair_append_by_da(ctx, &vp, pair_list, attr_tls_certificate_subject) == 0);
        if (unlikely(X509_NAME_print_ex(fr_tls_bio_dbuff_thread_local(vp, 256, 0),
                                        X509_get_subject_name(cert), 0, XN_FLAG_ONELINE) < 0)) {
                fr_tls_bio_dbuff_thread_local_clear();
                fr_tls_log(request, "Failed retrieving certificate subject");
        error:
                fr_pair_list_free(pair_list);
                return -1;
        }
        fr_pair_value_bstrdup_buffer_shallow(vp, fr_tls_bio_dbuff_thread_local_finalise_bstr(), true);
 
        RDEBUG3("Creating attributes for \"%pV\":", fr_box_strvalue_buffer(vp->vp_strvalue));
 
        /*
         *      Common name
         */
        slen = X509_NAME_get_text_by_NID(X509_get_subject_name(cert),
                                         NID_commonName, NULL, 0);
        if (slen > 0) {
                char *cn;
 
                MEM(fr_pair_append_by_da(ctx, &vp, pair_list, attr_tls_certificate_common_name) == 0);
                MEM(fr_pair_value_bstr_alloc(vp, &cn, (size_t)slen, true) == 0); /* Allocs \0 byte in addition to len */
 
                slen = X509_NAME_get_text_by_NID(X509_get_subject_name(cert), NID_commonName, cn, (size_t)slen + 1);
                if (slen < 0) {
                        fr_tls_log(request, "Failed retrieving certificate common name");
                        goto error;
                }
        }
 
        /*
         *      Signature
         */
        {
                ASN1_BIT_STRING const *sig;
                X509_ALGOR const *alg;
 
                X509_get0_signature(&sig, &alg, cert);
 
                MEM(fr_pair_append_by_da(ctx, &vp, pair_list, attr_tls_certificate_signature) == 0);
                MEM(fr_pair_value_memdup(vp,
                                         (uint8_t const *)ASN1_STRING_get0_data(sig),
                                         ASN1_STRING_length(sig), true) == 0);
 
                OBJ_obj2txt(buff, sizeof(buff), alg->algorithm, 0);
                MEM(fr_pair_append_by_da(ctx, &vp, pair_list, attr_tls_certificate_signature_algorithm) == 0);
                fr_pair_value_strdup(vp, buff, false);
        }
 
        /*
         *      Issuer
         */
        MEM(fr_pair_append_by_da(ctx, &vp, pair_list, attr_tls_certificate_issuer) == 0);
        if (unlikely(X509_NAME_print_ex(fr_tls_bio_dbuff_thread_local(vp, 256, 0),
                                        X509_get_issuer_name(cert), 0, XN_FLAG_ONELINE) < 0)) {
                fr_tls_bio_dbuff_thread_local_clear();
                fr_tls_log(request, "Failed retrieving certificate issuer");
                goto error;
        }
        fr_pair_value_bstrdup_buffer_shallow(vp, fr_tls_bio_dbuff_thread_local_finalise_bstr(), true);
 
        /*
         *      Serial number
         */
        {
                ASN1_INTEGER const *serial = NULL;
                unsigned char *der;
                int len;
 
                serial = X509_get0_serialNumber(cert);
                if (!serial) {
                        fr_tls_log(request, "Failed retrieving certificate serial");
                        goto error;
                }
 
                len = i2d_ASN1_INTEGER(serial, NULL);   /* get length */
                MEM(fr_pair_append_by_da(ctx, &vp, pair_list, attr_tls_certificate_serial) == 0);
                MEM(fr_pair_value_mem_alloc(vp, &der, len, false) == 0);
                i2d_ASN1_INTEGER(serial, &der);
        }
 
        /*
         *      Not valid before
         */
        asn_time = X509_get0_notBefore(cert);
 
        if (fr_tls_utils_asn1time_to_epoch(&time, asn_time) < 0) {
                RPWDEBUG("Failed parsing certificate not-before");
                goto error;
        }
 
        MEM(fr_pair_append_by_da(ctx, &vp, pair_list, attr_tls_certificate_not_before) == 0);
        vp->vp_date = fr_unix_time_from_time(time);
 
        /*
         *      Not valid after
         */
        asn_time = X509_get0_notAfter(cert);
 
        if (fr_tls_utils_asn1time_to_epoch(&time, asn_time) < 0) {
                RPWDEBUG("Failed parsing certificate not-after");
                goto error;
        }
 
        MEM(fr_pair_append_by_da(ctx, &vp, pair_list, attr_tls_certificate_not_after) == 0);
        vp->vp_date = fr_unix_time_from_time(time);
 
        /*
         *      Get the RFC822 Subject Alternative Name
         */
        loc = X509_get_ext_by_NID(cert, NID_subject_alt_name, 0);
        if (loc >= 0) {
                X509_EXTENSION  *ext = X509_get_ext(cert, loc);
                if (ext) san_found = tls_session_pairs_from_san(pair_list, ctx, request, ext);
        }
 
        loc = X509_get_ext_by_NID(cert, NID_crl_distribution_points, 0);
        if (loc >= 0) {
                X509_EXTENSION  *ext = X509_get_ext(cert, loc);
                if (ext) crl_found = tls_session_pairs_from_crl(pair_list, ctx, request, ext);
        }
 
        /*
         *      Only add extensions for the actual client certificate
         */
        ext_list = X509_get0_extensions(cert);
        if (unlikely(!ext_list)) {
                RWDEBUG("Failed retrieving extensions");
                goto done;
        }
 
        /*
         *      Grab the X509 extensions, and create attributes out of them.
         *      For laziness, we reuse the OpenSSL names
         */
        if (sk_X509_EXTENSION_num(ext_list) > 0) {
                int                     i;
                BIO                     *bio;
                fr_tls_bio_dbuff_t      *bd;
                fr_dbuff_t              *in, *out;
 
                bio = fr_tls_bio_dbuff_alloc(&bd, NULL, NULL, 257, 4097, true);
                in = fr_tls_bio_dbuff_in(bd);
                out = fr_tls_bio_dbuff_out(bd);
 
                for (i = 0; i < sk_X509_EXTENSION_num(ext_list); i++) {
                        ASN1_OBJECT             *obj;
                        X509_EXTENSION          *ext;
                        fr_dict_attr_t const    *da;
                        char                    *p;
 
                        ext = sk_X509_EXTENSION_value(ext_list, i);
 
                        obj = X509_EXTENSION_get_object(ext);
 
                        /*
                         *      If this is extension is Subject Alternate Name have we already
                         *      handled it?  If not, do that now.
                         *
                         *      Some certificate encodings have been observed where the SAN extension
                         *      was not found by X509_get_ext_by_NID() but then seen when the list
                         *      of extensions is handled here.
                         */
                        if (OBJ_obj2nid(obj) == NID_subject_alt_name) {
                                if (!san_found) san_found = tls_session_pairs_from_san(pair_list, ctx, request, ext);
                                goto again;
                        }
 
                        if (OBJ_obj2nid(obj) == NID_crl_distribution_points) {
                                if (!crl_found) crl_found = tls_session_pairs_from_crl(pair_list, ctx, request, ext);
                                goto again;
                        }
 
                        if (i2a_ASN1_OBJECT(bio, obj) <= 0) {
                                RPWDEBUG("Skipping X509 Extension (%i) conversion to attribute. "
                                         "Conversion from ASN1 failed...", i);
                        again:
                                fr_tls_bio_dbuff_reset(bd);
                                continue;
                        }
 
                        if (fr_dbuff_remaining(out) == 0) goto again;   /* Nothing written ? */
 
                        /*
                         *      All disallowed chars get mashed to '-'
                         */
                        for (p = (char *)fr_dbuff_current(out);
                             p < (char *)fr_dbuff_end(out);
                             p++) if (!fr_dict_attr_allowed_chars[(uint8_t)*p]) *p = '-';
 
                        /*
                         *      Terminate the buffer (after char replacement,
                         *      so we do don't replace the \0)
                         */
                        if (unlikely(fr_dbuff_in_bytes(in, (uint8_t)'\0') <= 0)) {
                                RWDEBUG("Attribute name too long");
                                goto again;
                        }
 
                        da = fr_dict_attr_by_name(NULL, attr_tls_certificate, (char *)fr_dbuff_current(out));
 
                        fr_dbuff_set(in, fr_dbuff_current(in) - 1);     /* Ensure the \0 isn't counted in remaining */
 
                        if (!da) {
                                RWDEBUG3("Skipping attribute \"%pV\": "
                                         "Add a dictionary definition if you want to access it",
                                         fr_box_strvalue_len((char *)fr_dbuff_current(out),
                                                             fr_dbuff_remaining(out)));
                                fr_strerror_clear();    /* Don't leave spurious errors from failed resolution */
                                goto again;
                        }
 
                        fr_tls_bio_dbuff_reset(bd);     /* 'free' any data used */
 
                        if (X509V3_EXT_print(bio, ext, X509V3_EXT_PARSE_UNKNOWN, 0) != 1) {
                                REDEBUG("Failed extracting data for \"%s\"", da->name);
                                goto again;
                        }
 
                        MEM(vp = fr_pair_afrom_da(ctx, da));
                        if (fr_pair_value_from_str(vp, (char *)fr_dbuff_current(out), fr_dbuff_remaining(out),
                                                   NULL, true) < 0) {
                                RPWDEBUG3("Skipping: %s += \"%pV\"",
                                          da->name, fr_box_strvalue_len((char *)fr_dbuff_current(out),
                                                                        fr_dbuff_remaining(out)));
                                talloc_free(vp);
                                goto again;
                        }
                        fr_tls_bio_dbuff_reset(bd);     /* 'free' any data used */
 
                        fr_pair_append(pair_list, vp);
                }
                talloc_free(bd);
        }
 
done:
        return 0;
}
 
static int fr_tls_extension_decode(request_t *request, fr_pair_t *container, uint8_t const *extension,
                                   size_t hlen, size_t dlen, size_t total_len, fr_dict_attr_t const *da)
{
        size_t i,extension_len;
        uint8_t const *data;
 
        fr_assert((hlen == 1) || (hlen == 2));
        fr_assert((dlen == 1) || (dlen == 2));
 
        if (total_len < hlen) {
                REDEBUG("Missing length in %s extension", da->name);
                return -1;
        }
 
        if (hlen == 1) {
                fr_assert(da->type == FR_TYPE_UINT8);
                extension_len = extension[0];
        } else {
                fr_assert(da->type == FR_TYPE_UINT16);
                extension_len = (extension[0] << 8) + extension[1];
        }
 
        if (extension_len * dlen + hlen > total_len) {
                REDEBUG("Invalid length in %s extension", da->name);
                return -1;
        }
 
        data = extension + hlen;
 
        for (i = 0; i < extension_len; i += dlen) {
                fr_pair_t *vp;
 
                MEM(fr_pair_append_by_da(container, &vp, &container->vp_group, da) >= 0);
 
                switch (dlen) {
                case 1:
                        vp->vp_uint8= data[0];
                        break;
 
                case 2:
                        vp->vp_uint16 = (data[0] << 8) + data[1];
                        break;
                }
 
                data += dlen;
        }
 
        return 0;
}
 
/** Callback to extract pairs from a Client Hello
 *
 */
int fr_tls_session_client_hello_cb(SSL *ssl, UNUSED int *al, UNUSED void *arg)
{
        request_t               *request = SSL_get_ex_data(ssl, FR_TLS_EX_INDEX_REQUEST);
        request_t               *parent = request->parent;
        uint8_t const           *ciphers, *extension;
        int                     i, *extensions = NULL;
        size_t                  data_size, j;
        STACK_OF(SSL_CIPHER)    *sk;
        SSL_CIPHER const        *cipher;
        STACK_OF(SSL_CIPHER)    *scsvs;
        fr_pair_t               *container, *vp;
 
        fr_assert(parent);
 
        container = fr_pair_find_by_da(&parent->session_state_pairs, NULL, attr_tls_client_hello);
        if (container) return SSL_CLIENT_HELLO_SUCCESS;
 
        MEM(container = fr_pair_afrom_da(parent->session_state_ctx, attr_tls_client_hello));
 
        data_size = SSL_client_hello_get0_ciphers(ssl, &ciphers);
        if (SSL_bytes_to_cipher_list(ssl, ciphers, data_size, SSL_client_hello_isv2(ssl), &sk, &scsvs) == 0) {
                RPEDEBUG("Failed to decode cipher list");
        fail:
                if (extensions) OPENSSL_free(extensions);
                talloc_free(container);
                return SSL_CLIENT_HELLO_ERROR;
        }
 
        for (i = 0; i < sk_SSL_CIPHER_num(sk); i++) {
                fr_pair_append_by_da(container, &vp, &container->vp_group, attr_tls_client_hello_cipher);
                cipher = sk_SSL_CIPHER_value(sk, i);
                fr_value_box_strdup(vp, &vp->data, NULL, SSL_CIPHER_get_name(cipher), false);
        }
 
        sk_SSL_CIPHER_free(sk);
        sk_SSL_CIPHER_free(scsvs);
 
        /*
         *      Fetch the extensions and decode the ones we know about
         *      These are the ones which are returned as simple lists
         *      of values of known length which map to enum attributes.
         */
        if (SSL_client_hello_get1_extensions_present(ssl, &extensions, &data_size) == 0) {
                RPEDEBUG("Failed to fetch client hello extensions");
                goto fail;
        }
 
        for (j = 0; j < data_size; j++) {
                size_t total_len;
 
                if (SSL_client_hello_get0_ext(ssl, extensions[j], &extension, &total_len) == 0) {
                        RPDEBUG("Failed getting client hello extension %d", extensions[j]);
                        goto fail;
                }
 
                switch (extensions[j]) {
                case TLSEXT_TYPE_supported_groups: /* length[2] + 2*data */
                        if (fr_tls_extension_decode(request, container, extension, 2, 2, total_len,
                                                    attr_tls_client_hello_supported_group) < 0) goto fail;
                        break;
 
                case TLSEXT_TYPE_ec_point_formats: /* length[1] + data */
                        if (fr_tls_extension_decode(request, container, extension, 1, 1, total_len,
                                                    attr_tls_client_hello_ec_point_format) < 0) goto fail;
                        break;
 
                case TLSEXT_TYPE_signature_algorithms: /* length[2] + 2*data */
                        if (fr_tls_extension_decode(request, container, extension, 2, 2, total_len,
                                                    attr_tls_client_hello_sig_algo) < 0) goto fail;
                        break;
 
                case TLSEXT_TYPE_supported_versions: /* length[1] + 2*data */
                        if (fr_tls_extension_decode(request, container, extension, 1, 2, total_len,
                                                    attr_tls_client_hello_tls_version) < 0) goto fail;
                        break;
 
                case TLSEXT_TYPE_psk_kex_modes: /* length[1] + data */
                        if (fr_tls_extension_decode(request, container, extension, 1, 1, total_len,
                                                    attr_tls_client_hello_psk_key_mode) < 0) goto fail;
                        break;
                }
        }
 
        if (extensions) OPENSSL_free(extensions);
 
        /*
         *      This is the version being negotiated by the client, but tops at 1.2.
         *      After that the supported_versions extension is where the real value is.
         */
        fr_pair_append_by_da(container, &vp, &container->vp_group, attr_tls_client_hello_tls_version);
        vp->vp_uint16 = SSL_client_hello_get0_legacy_version(ssl);
 
        fr_pair_append(&parent->session_state_pairs, container);
 
        return SSL_CLIENT_HELLO_SUCCESS;
}
DIAG_ON(used-but-marked-unused)
DIAG_ON(DIAG_UNKNOWN_PRAGMAS)
#endif