res_pjsip_stir_shaken.c

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/*
 * Asterisk -- An open source telephony toolkit.
 *
 * Copyright (C) 2020, Sangoma Technologies Corporation
 *
 * Ben Ford <bford@sangoma.com>
 *
 * See http://www.asterisk.org for more information about
 * the Asterisk project. Please do not directly contact
 * any of the maintainers of this project for assistance;
 * the project provides a web site, mailing lists and IRC
 * channels for your use.
 *
 * This program is free software, distributed under the terms of
 * the GNU General Public License Version 2. See the LICENSE file
 * at the top of the source tree.
 */
 
/*** MODULEINFO
    <depend>pjproject</depend>
    <depend>res_pjsip</depend>
    <depend>res_pjsip_session</depend>
    <depend>res_stir_shaken</depend>
    <support_level>core</support_level>
 ***/
 
#include "asterisk.h"
 
#define _TRACE_PREFIX_ "pjss",__LINE__, ""
 
#include "asterisk/callerid.h"
#include "asterisk/res_pjsip.h"
#include "asterisk/res_pjsip_session.h"
#include "asterisk/module.h"
#include "asterisk/rtp_engine.h"
 
#include "asterisk/res_stir_shaken.h"
 
static const pj_str_t identity_hdr_str = { "Identity", 8 };
static const pj_str_t date_hdr_str = { "Date", 4 };
 
/* Response codes from RFC8224 */
enum sip_response_code {
    SIP_RESPONSE_CODE_OK = 200,
    SIP_RESPONSE_CODE_STALE_DATE = 403,
    SIP_RESPONSE_CODE_USE_IDENTITY_HEADER = 428,
    SIP_RESPONSE_CODE_ANONYMITY_DISALLOWED = 433,
    SIP_RESPONSE_CODE_BAD_IDENTITY_INFO = 436,
    SIP_RESPONSE_CODE_UNSUPPORTED_CREDENTIAL = 437,
    SIP_RESPONSE_CODE_INVALID_IDENTITY_HEADER = 438,
    SIP_RESPONSE_CODE_INTERNAL_ERROR = 500,
};
 
#define SIP_RESPONSE_CODE_OK_STR "OK"
/* Response strings from RFC8224 */
#define SIP_RESPONSE_CODE_STALE_DATE_STR "Stale Date"
#define SIP_RESPONSE_CODE_USE_IDENTITY_HEADER_STR "Use Identity Header"
#define SIP_RESPONSE_CODE_ANONYMITY_DISALLOWED_STR "Anonymity Disallowed"
#define SIP_RESPONSE_CODE_BAD_IDENTITY_INFO_STR "Bad Identity Info"
#define SIP_RESPONSE_CODE_UNSUPPORTED_CREDENTIAL_STR "Unsupported Credential"
#define SIP_RESPONSE_CODE_INVALID_IDENTITY_HEADER_STR "Invalid Identity Header"
#define SIP_RESPONSE_CODE_INTERNAL_ERROR_STR "Internal Error"
 
#define response_to_str(_code) \
case _code: \
    return _code ## _STR;
 
static const char *sip_response_code_to_str(enum sip_response_code code)
{
    switch (code) {
    response_to_str(SIP_RESPONSE_CODE_OK)
    response_to_str(SIP_RESPONSE_CODE_STALE_DATE)
    response_to_str(SIP_RESPONSE_CODE_USE_IDENTITY_HEADER)
    response_to_str(SIP_RESPONSE_CODE_ANONYMITY_DISALLOWED)
    response_to_str(SIP_RESPONSE_CODE_BAD_IDENTITY_INFO)
    response_to_str(SIP_RESPONSE_CODE_UNSUPPORTED_CREDENTIAL)
    response_to_str(SIP_RESPONSE_CODE_INVALID_IDENTITY_HEADER)
    default:
        break;
    }
    return "";
}
 
#define translate_code(_vs_rc, _sip_rc) \
case AST_STIR_SHAKEN_VS_ ## _vs_rc: \
    return SIP_RESPONSE_CODE_ ## _sip_rc;
 
static enum sip_response_code vs_code_to_sip_code(
    enum ast_stir_shaken_vs_response_code vs_rc)
{
    /*
     * We want to use a switch/case statement here because
     * it'll spit out an error if VS codes are added to the
     * enum but aren't present here.
     */
    switch (vs_rc) {
    translate_code(SUCCESS,                 OK)
    translate_code(DISABLED,                OK)
    translate_code(INVALID_ARGUMENTS,       INTERNAL_ERROR)
    translate_code(INTERNAL_ERROR,          INTERNAL_ERROR)
    translate_code(NO_IDENTITY_HDR,         USE_IDENTITY_HEADER)
    translate_code(NO_DATE_HDR,             STALE_DATE)
    translate_code(DATE_HDR_PARSE_FAILURE,  STALE_DATE)
    translate_code(DATE_HDR_EXPIRED,        STALE_DATE)
    translate_code(NO_JWT_HDR,              INVALID_IDENTITY_HEADER)
    translate_code(INVALID_OR_NO_X5U,       INVALID_IDENTITY_HEADER)
    translate_code(CERT_CACHE_MISS,         INVALID_IDENTITY_HEADER)
    translate_code(CERT_CACHE_INVALID,      INVALID_IDENTITY_HEADER)
    translate_code(CERT_CACHE_EXPIRED,      INVALID_IDENTITY_HEADER)
    translate_code(CERT_RETRIEVAL_FAILURE,  BAD_IDENTITY_INFO)
    translate_code(CERT_CONTENTS_INVALID,   UNSUPPORTED_CREDENTIAL)
    translate_code(CERT_NOT_TRUSTED,        UNSUPPORTED_CREDENTIAL)
    translate_code(CERT_DATE_INVALID,       UNSUPPORTED_CREDENTIAL)
    translate_code(CERT_NO_TN_AUTH_EXT,     UNSUPPORTED_CREDENTIAL)
    translate_code(CERT_NO_SPC_IN_TN_AUTH_EXT,  UNSUPPORTED_CREDENTIAL)
    translate_code(NO_RAW_KEY,              UNSUPPORTED_CREDENTIAL)
    translate_code(SIGNATURE_VALIDATION,    INVALID_IDENTITY_HEADER)
    translate_code(NO_IAT,                  INVALID_IDENTITY_HEADER)
    translate_code(IAT_EXPIRED,             STALE_DATE)
    translate_code(INVALID_OR_NO_PPT,       INVALID_IDENTITY_HEADER)
    translate_code(INVALID_OR_NO_ALG,       INVALID_IDENTITY_HEADER)
    translate_code(INVALID_OR_NO_TYP,       INVALID_IDENTITY_HEADER)
    translate_code(INVALID_OR_NO_ATTEST,    INVALID_IDENTITY_HEADER)
    translate_code(NO_ORIGID,               INVALID_IDENTITY_HEADER)
    translate_code(NO_ORIG_TN,              INVALID_IDENTITY_HEADER)
    translate_code(NO_DEST_TN,              INVALID_IDENTITY_HEADER)
    translate_code(INVALID_HEADER,          INVALID_IDENTITY_HEADER)
    translate_code(INVALID_GRANT,           INVALID_IDENTITY_HEADER)
    translate_code(INVALID_OR_NO_GRANTS,    INVALID_IDENTITY_HEADER)
    translate_code(CID_ORIG_TN_MISMATCH,    INVALID_IDENTITY_HEADER)
    translate_code(INVALID_OR_NO_CID,       ANONYMITY_DISALLOWED)
    translate_code(RESPONSE_CODE_MAX,       INVALID_IDENTITY_HEADER)
    }
 
    return 500;
}
 
enum process_failure_rc {
    PROCESS_FAILURE_CONTINUE = 0,
    PROCESS_FAILURE_REJECT,
    PROCESS_FAILURE_SYSTEM_FAILURE,
};
 
static void reject_incoming_call(struct ast_sip_session *session,
    enum sip_response_code response_code)
{
    ast_sip_session_terminate(session, response_code);
    ast_hangup(session->channel);
}
 
static enum process_failure_rc process_failure(struct ast_stir_shaken_vs_ctx *ctx,
    const char *caller_id, struct ast_sip_session *session,
    pjsip_rx_data *rdata, enum ast_stir_shaken_vs_response_code vs_rc)
{
    enum sip_response_code response_code = vs_code_to_sip_code(vs_rc);
    pj_str_t response_str;
    const char *response_string =
        sip_response_code_to_str(response_code);
    enum stir_shaken_failure_action_enum failure_action =
        ast_stir_shaken_vs_get_failure_action(ctx);
    const char *tag = ast_sip_session_get_name(session);
    SCOPE_ENTER(1, "%s: FA: %d  RC: %d\n", tag,
        failure_action, response_code);
 
    pj_cstr(&response_str, response_string);
 
    if (failure_action == stir_shaken_failure_action_REJECT_REQUEST) {
        reject_incoming_call(session, response_code);
        SCOPE_EXIT_RTN_VALUE(PROCESS_FAILURE_REJECT,
            "%s: Rejecting request and terminating session\n",
            tag);
    }
 
    ast_stir_shaken_vs_ctx_set_response_code(ctx, vs_rc);
    ast_stir_shaken_add_result_to_channel(ctx);
 
    if (failure_action == stir_shaken_failure_action_CONTINUE_RETURN_REASON) {
        int rc = ast_sip_session_add_reason_header(session,
            ast_stir_shaken_vs_get_use_rfc9410_responses(ctx) ? "STIR" : "SIP",
            response_code, response_str.ptr);
        if (rc != 0) {
            SCOPE_EXIT_RTN_VALUE(PROCESS_FAILURE_SYSTEM_FAILURE,
                "%s: Failed to add Reason header\n", tag);
        }
        SCOPE_EXIT_RTN_VALUE(PROCESS_FAILURE_CONTINUE,
            "%s: Attaching reason code to session\n", tag);
    }
    SCOPE_EXIT_RTN_VALUE(PROCESS_FAILURE_CONTINUE,
        "%s: Continuing\n", tag);
}
 
/*!
 * \internal
 * \brief Session supplement callback on an incoming INVITE request
 *
 * When we receive an INVITE, check it for STIR/SHAKEN information and
 * decide what to do from there
 *
 * \param session The session that has received an INVITE
 * \param rdata The incoming INVITE
 */
static int stir_shaken_incoming_request(struct ast_sip_session *session, pjsip_rx_data *rdata)
{
    RAII_VAR(struct ast_stir_shaken_vs_ctx *, ctx, NULL, ao2_cleanup);
    RAII_VAR(char *, header, NULL, ast_free);
    RAII_VAR(char *, payload, NULL, ast_free);
    char *identity_hdr_val;
    char *date_hdr_val;
    char *caller_id = session->id.number.str;
    const char *session_name = ast_sip_session_get_name(session);
    struct ast_channel *chan = session->channel;
    enum ast_stir_shaken_vs_response_code vs_rc;
    enum process_failure_rc p_rc;
    SCOPE_ENTER(1, "%s: Enter\n", session_name);
 
    if (!session) {
        SCOPE_EXIT_LOG_RTN_VALUE(1, LOG_ERROR, "No session\n");
    }
    if (!session->channel) {
        SCOPE_EXIT_LOG_RTN_VALUE(1, LOG_ERROR, "%s: No channel\n", session_name);
    }
    if (!rdata) {
        SCOPE_EXIT_LOG_RTN_VALUE(1, LOG_ERROR, "%s: No rdata\n", session_name);
    }
 
    /* Check if this is a reinvite. If it is, we don't need to do anything */
    if (rdata->msg_info.to->tag.slen) {
        SCOPE_EXIT_RTN_VALUE(0, "%s: Reinvite. No action needed\n", session_name);
    }
 
    /*
     * Shortcut:  If there's no profile name just bail now.
     */
    if (ast_strlen_zero(session->endpoint->stir_shaken_profile)) {
        SCOPE_EXIT_RTN_VALUE(0, "%s: No profile name on endpoint. No action needed\n", session_name);
    }
 
    vs_rc = ast_stir_shaken_vs_ctx_create(caller_id, chan,
        session->endpoint->stir_shaken_profile,
        session_name, &ctx);
    if (vs_rc == AST_STIR_SHAKEN_VS_DISABLED) {
        SCOPE_EXIT_RTN_VALUE(0, "%s: VS Disabled\n", session_name);
    } else if (vs_rc != AST_STIR_SHAKEN_VS_SUCCESS) {
        reject_incoming_call(session, 500);
        SCOPE_EXIT_RTN_VALUE(1, "%s: Unable to create context.  Call terminated\n",
            session_name);
    }
 
    if (ast_strlen_zero(ast_stir_shaken_vs_get_caller_id(ctx))) {
        p_rc = process_failure(ctx, caller_id, session, rdata,
            AST_STIR_SHAKEN_VS_INVALID_OR_NO_CID);
        if (p_rc == PROCESS_FAILURE_CONTINUE) {
            SCOPE_EXIT_RTN_VALUE(0, "%s: Invalid or no callerid found.  Call continuing\n",
                session_name);
        }
        SCOPE_EXIT_LOG_RTN_VALUE(1, LOG_ERROR, "%s: Invalid or no callerid found.  Call terminated\n",
            session_name);
    }
 
    identity_hdr_val = ast_sip_rdata_get_header_value(rdata, identity_hdr_str);
    if (ast_strlen_zero(identity_hdr_val)) {
        p_rc = process_failure(ctx, caller_id, session, rdata,
            AST_STIR_SHAKEN_VS_NO_IDENTITY_HDR);
        if (p_rc == PROCESS_FAILURE_CONTINUE) {
            SCOPE_EXIT_RTN_VALUE(0, "%s: No Identity header found.  Call continuing\n",
                session_name);
        }
        SCOPE_EXIT_LOG_RTN_VALUE(1, LOG_ERROR, "%s: No Identity header found.  Call terminated\n",
            session_name);
    }
 
    vs_rc = ast_stir_shaken_vs_ctx_add_identity_hdr(ctx, identity_hdr_val);
    if (vs_rc != AST_STIR_SHAKEN_VS_SUCCESS) {
        reject_incoming_call(session, 500);
        SCOPE_EXIT_LOG_RTN_VALUE(1, LOG_ERROR, "%s: Unable to add Identity header.  Call terminated.\n",
            session_name);
    }
 
    date_hdr_val = ast_sip_rdata_get_header_value(rdata, date_hdr_str);
    if (ast_strlen_zero(date_hdr_val)) {
        p_rc = process_failure(ctx, caller_id, session, rdata,
            AST_STIR_SHAKEN_VS_NO_DATE_HDR);
        if (p_rc == PROCESS_FAILURE_CONTINUE) {
            SCOPE_EXIT_RTN_VALUE(0, "%s: No Date header found.  Call continuing\n",
                session_name);
        }
        SCOPE_EXIT_LOG_RTN_VALUE(1, LOG_ERROR, "%s: No Date header found.  Call terminated\n",
            session_name);
    }
 
    ast_stir_shaken_vs_ctx_add_date_hdr(ctx, date_hdr_val);
    if (vs_rc != AST_STIR_SHAKEN_VS_SUCCESS) {
        reject_incoming_call(session, 500);
        SCOPE_EXIT_LOG_RTN_VALUE(1, LOG_ERROR, "%s: Unable to add Date header.  Call terminated.\n",
            session_name);
    }
 
    vs_rc = ast_stir_shaken_vs_verify(ctx);
    if (vs_rc != AST_STIR_SHAKEN_VS_SUCCESS) {
        p_rc = process_failure(ctx, caller_id, session, rdata, vs_rc);
        if (p_rc == PROCESS_FAILURE_CONTINUE) {
            SCOPE_EXIT_RTN_VALUE(0, "%s: Verification failed.  Call continuing\n",
                session_name);
        }
        SCOPE_EXIT_LOG_RTN_VALUE(1, LOG_ERROR, "%s: Verification failed.  Call terminated\n",
            session_name);
 
    }
 
    ast_stir_shaken_add_result_to_channel(ctx);
 
    SCOPE_EXIT_RTN_VALUE(0, "Passed\n");
}
 
static void add_fingerprints_if_present(struct ast_sip_session *session,
    struct ast_stir_shaken_as_ctx *ctx)
{
    struct ast_sip_session_media_state *ms = session->pending_media_state;
    struct ast_sip_session_media *m = NULL;
    struct ast_rtp_engine_dtls *d = NULL;
    enum ast_rtp_dtls_hash h;
    int i;
    const char *tag = ast_sip_session_get_name(session);
    size_t count = AST_VECTOR_SIZE(&ms->sessions);
    SCOPE_ENTER(4, "%s: Check %zu media sessions for fingerprints\n",
        tag, count);
 
    if (!ast_stir_shaken_as_ctx_wants_fingerprints(ctx)) {
        SCOPE_EXIT_RTN("%s: Fingerprints not needed\n", tag);
    }
 
    for (i = 0; i < count; i++) {
        const char *f;
 
        m = AST_VECTOR_GET(&ms->sessions, i);
        if (!m|| !m->rtp) {
            ast_trace(1, "Session: %d: No session or rtp instance\n", i);
            continue;
        }
        d = ast_rtp_instance_get_dtls(m->rtp);
        h = d->get_fingerprint_hash(m->rtp);
        f = d->get_fingerprint(m->rtp);
 
        ast_stir_shaken_as_ctx_add_fingerprint(ctx,
            h == AST_RTP_DTLS_HASH_SHA256 ? "sha-256" : "sha-1", f);
    }
    SCOPE_EXIT_RTN("%s: Done\n", tag);
}
 
static char *get_dest_tn(pjsip_tx_data *tdata, const char *tag)
{
    pjsip_fromto_hdr *to;
    pjsip_sip_uri *uri;
    char *dest_tn = NULL;
    SCOPE_ENTER(4, "%s: Enter\n", tag);
 
    to = pjsip_msg_find_hdr(tdata->msg, PJSIP_H_TO, NULL);
    if (!to) {
        SCOPE_EXIT_RTN_VALUE(NULL, "%s: Failed to find To header\n", tag);
    }
 
    uri = pjsip_uri_get_uri(to->uri);
    if (!uri) {
        SCOPE_EXIT_RTN_VALUE(NULL,
            "%s: Failed to retrieve URI from To header\n", tag);
    }
 
    dest_tn = ast_malloc(uri->user.slen + 1);
    if (!dest_tn) {
        SCOPE_EXIT_RTN_VALUE(NULL,
            "%s: Failed to allocate memory for dest_tn\n", tag);
    }
 
    ast_copy_pj_str(dest_tn, &uri->user, uri->user.slen + 1);
 
    SCOPE_EXIT_RTN_VALUE(dest_tn, "%s: Done\n", tag);
}
 
static void add_date_header(const struct ast_sip_session *session, pjsip_tx_data *tdata)
{
    pjsip_fromto_hdr *old_date;
    const char *session_name = ast_sip_session_get_name(session);
    SCOPE_ENTER(1, "%s: Enter\n", session_name);
 
    old_date = pjsip_msg_find_hdr_by_name(tdata->msg, &date_hdr_str, NULL);
    if (old_date) {
        SCOPE_EXIT_RTN("Found existing Date header, no need to add one\n");
    }
 
    ast_sip_add_date_header(tdata);
    SCOPE_EXIT_RTN("Done\n");
}
 
static void stir_shaken_outgoing_request(struct ast_sip_session *session,
    pjsip_tx_data *tdata)
{
    struct ast_party_id effective_id;
    struct ast_party_id connected_id;
    pjsip_generic_string_hdr *old_identity;
    pjsip_generic_string_hdr *identity_hdr;
    pj_str_t identity_val;
    char *dest_tn;
    char *identity_str;
    struct ast_stir_shaken_as_ctx *ctx = NULL;
    enum ast_stir_shaken_as_response_code as_rc;
    const char *session_name = ast_sip_session_get_name(session);
    SCOPE_ENTER(1, "%s: Enter\n", session_name);
 
    if (!session) {
        SCOPE_EXIT_LOG_RTN(LOG_ERROR, "No session\n");
    }
    if (!session->channel) {
        SCOPE_EXIT_LOG_RTN(LOG_ERROR, "%s: No channel\n", session_name);
    }
    if (!tdata) {
        SCOPE_EXIT_LOG_RTN(LOG_ERROR, "%s: No tdata\n", session_name);
    }
 
    old_identity = pjsip_msg_find_hdr_by_name(tdata->msg, &identity_hdr_str, NULL);
    if (old_identity) {
        SCOPE_EXIT_RTN("Found an existing Identity header\n");
    }
 
    dest_tn = get_dest_tn(tdata, session_name);
    if (!dest_tn) {
        SCOPE_EXIT_LOG_RTN(LOG_ERROR, "%s: Unable to find destination tn\n",
            session_name);
    }
 
    ast_party_id_init(&connected_id);
    ast_channel_lock(session->channel);
    effective_id = ast_channel_connected_effective_id(session->channel);
    ast_party_id_copy(&connected_id, &effective_id);
    ast_channel_unlock(session->channel);
 
    if (!ast_sip_can_present_connected_id(session, &connected_id)) {
        ast_free(dest_tn);
        ast_party_id_free(&connected_id);
        SCOPE_EXIT_RTN("Unable to get caller id\n");
    }
 
    as_rc = ast_stir_shaken_as_ctx_create(connected_id.number.str,
        dest_tn, session->channel,
        session->endpoint->stir_shaken_profile,
        session_name, &ctx);
 
    ast_free(dest_tn);
    ast_party_id_free(&connected_id);
 
    if (as_rc == AST_STIR_SHAKEN_AS_DISABLED) {
        SCOPE_EXIT_RTN("%s: AS Disabled\n", session_name);
    } else if (as_rc != AST_STIR_SHAKEN_AS_SUCCESS) {
        SCOPE_EXIT_RTN("%s: Unable to create context\n",
            session_name);
    }
 
    add_date_header(session, tdata);
    add_fingerprints_if_present(session, ctx);
 
    as_rc = ast_stir_shaken_attest(ctx, &identity_str);
    if (as_rc != AST_STIR_SHAKEN_AS_SUCCESS) {
        ao2_cleanup(ctx);
        SCOPE_EXIT_LOG(LOG_ERROR,
            "%s: Failed to create attestation\n", session_name);
    }
 
    ast_trace(1, "%s: Identity header: %s\n", session_name, identity_str);
    identity_val = pj_str(identity_str);
    identity_hdr = pjsip_generic_string_hdr_create(tdata->pool, &identity_hdr_str, &identity_val);
    ast_free(identity_str);
    if (!identity_hdr) {
        ao2_cleanup(ctx);
        SCOPE_EXIT_LOG_RTN(LOG_ERROR,
            "%s: Unable to create Identity header\n", session_name);
    }
 
    pjsip_msg_add_hdr(tdata->msg, (pjsip_hdr *)identity_hdr);
 
    ao2_cleanup(ctx);
    SCOPE_EXIT_RTN("Done\n");
}
 
static struct ast_sip_session_supplement stir_shaken_supplement = {
    .method = "INVITE",
    .priority = AST_SIP_SUPPLEMENT_PRIORITY_CHANNEL + 1, /* Run AFTER channel creation */
    .incoming_request = stir_shaken_incoming_request,
    .outgoing_request = stir_shaken_outgoing_request,
};
 
static int unload_module(void)
{
    ast_sip_session_unregister_supplement(&stir_shaken_supplement);
    return 0;
}
 
static int load_module(void)
{
    ast_sip_session_register_supplement(&stir_shaken_supplement);
    return AST_MODULE_LOAD_SUCCESS;
}
 
#undef AST_BUILDOPT_SUM
#define AST_BUILDOPT_SUM ""
 
AST_MODULE_INFO(ASTERISK_GPL_KEY, AST_MODFLAG_GLOBAL_SYMBOLS | AST_MODFLAG_LOAD_ORDER, "PJSIP STIR/SHAKEN Module for Asterisk",
    .support_level = AST_MODULE_SUPPORT_CORE,
    .load = load_module,
    .unload = unload_module,
    .load_pri = AST_MODPRI_DEFAULT,
    .requires = "res_pjsip,res_pjsip_session,res_stir_shaken",
);