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res_stir_shaken: Add inbound INVITE support. 

Integrated STIR/SHAKEN support with incoming INVITES. Upon receiving an
INVITE, the Identity header is retrieved, parsing the message to verify
the signature. If any of the parsing fails,
AST_STIR_SHAKEN_VERIFY_NOT_PRESENT will be added to the channel for this
caller ID. If verification itself fails,
AST_STIR_SHAKEN_VERIFY_SIGNATURE_FAILED will be added. If anything in
the payload does not line up with the SIP signaling,
AST_STIR_SHAKEN_VERIFY_MISMATCH will be added. If all of the above steps
pass, then AST_STIR_SHAKEN_VERIFY_PASSED will be added, completing the
verification process.

A new config option has been added to the general section for
stir_shaken.conf. "signature_timeout" is the amount of time a signature
will be considered valid. If an INVITE is received and the amount of
time between when it was received and when it was signed is greater than
signature_timeout, verification will fail.

Some changes were also made to signing and verification. There was an
error where the whole JSON string was being signed rather than the
header combined with the payload. This has been changed to sign the
correct thing. Verification has been changed to do this as well, and the
unit tests have been updated to reflect these changes.

A couple of utility functions have also been added. One decodes a BASE64
string and returns the decoded string, doing all the length calculations
for you. The other retrieves a string value from a header in a rdata
object.

Change-Id: I855f857be3d1c63b64812ac35d9ce0534085b913
This commit is contained in:
Ben Ford 2020-05-19 14:46:45 -05:00 committed by Joshua Colp
parent 1fcb6b1b21
commit 3927f79cb5
10 changed files with 344 additions and 34 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

13
include/asterisk/res_pjsip.h
View File

@ -2218,6 +2218,19 @@ int ast_sip_create_request_with_auth(const struct ast_sip_auth_vector *auths, pj
*/
struct ast_sip_endpoint *ast_sip_identify_endpoint(pjsip_rx_data *rdata);
/*!
* \brief Get a specific header value from rdata
*
* \note The returned value does not need to be freed since it's from the rdata pool
*
* \param rdata The rdata
* \param str The header to find
*
* \retval NULL on failure
* \retval The header value on success
*/
char *ast_sip_rdata_get_header_value(pjsip_rx_data *rdata, const pj_str_t str);
/*!
* \brief Set the outbound proxy for an outbound SIP message
*

7
include/asterisk/res_stir_shaken.h
View File

@ -32,6 +32,13 @@ struct ast_stir_shaken_payload;
struct ast_json;
/*!
* \brief Retrieve the value for 'signature_timeout' from 'general' config object
*
* \retval The signature timeout
*/
unsigned int ast_stir_shaken_get_signature_timeout(void);
/*!
* \brief Add a STIR/SHAKEN verification result to a channel
*

13
include/asterisk/utils.h
View File

@ -250,6 +250,19 @@ int ast_base64encode(char *dst, const unsigned char *src, int srclen, int max);
*/
int ast_base64decode(unsigned char *dst, const char *src, int max);
/*!
* \brief Same as ast_base64decode, but does the math for you and returns
* a decoded string
*
* \note The returned string will need to be freed later
*
* \param src The source buffer
*
* \retval NULL on failure
* \retval Decoded string on success
*/
char *ast_base64decode_string(const char *src);
#define AST_URI_ALPHANUM (1 << 0)
#define AST_URI_MARK (1 << 1)
#define AST_URI_UNRESERVED (AST_URI_ALPHANUM | AST_URI_MARK)

31
main/utils.c
View File

@ -310,6 +310,37 @@ int ast_base64decode(unsigned char *dst, const char *src, int max)
return cnt;
}
/*! \brief Decode BASE64 encoded text and return the string */
char *ast_base64decode_string(const char *src)
{
size_t encoded_len;
size_t decoded_len;
int padding = 0;
unsigned char *decoded_string;
if (ast_strlen_zero(src)) {
return NULL;
}
encoded_len = strlen(src);
if (encoded_len > 2 && src[encoded_len - 1] == '=') {
padding++;
if (src[encoded_len - 2] == '=') {
padding++;
}
}
decoded_len = (encoded_len / 4 * 3) - padding;
decoded_string = ast_calloc(1, decoded_len);
if (!decoded_string) {
return NULL;
}
ast_base64decode(decoded_string, src, decoded_len);
return (char *)decoded_string;
}
/*! \brief encode text to BASE64 coding */
int ast_base64encode_full(char *dst, const unsigned char *src, int srclen, int max, int linebreaks)
{

15
res/res_pjsip.c
View File

@ -3183,6 +3183,21 @@ struct ast_sip_endpoint *ast_sip_identify_endpoint(pjsip_rx_data *rdata)
return endpoint;
}
char *ast_sip_rdata_get_header_value(pjsip_rx_data *rdata, const pj_str_t str)
{
pjsip_generic_string_hdr *hdr;
pj_str_t hdr_val;
hdr = pjsip_msg_find_hdr_by_name(rdata->msg_info.msg, &str, NULL);
if (!hdr) {
return NULL;
}
pj_strdup_with_null(rdata->tp_info.pool, &hdr_val, &hdr->hvalue);
return hdr_val.ptr;
}
static int do_cli_dump_endpt(void *v_a)
{
struct ast_cli_args *a = v_a;

177
res/res_pjsip_stir_shaken.c
View File

@ -3,7 +3,7 @@
*
* Copyright (C) 2020, Sangoma Technologies Corporation
*
* Kevin Harwell <kharwell@digium.com>
* Ben Ford <bford@sangoma.com>
*
* See http://www.asterisk.org for more information about
* the Asterisk project. Please do not directly contact
@ -18,22 +18,197 @@
/*** MODULEINFO
<depend>crypto</depend>
<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"
#include "asterisk/res_pjsip.h"
#include "asterisk/res_pjsip_session.h"
#include "asterisk/module.h"
#include "asterisk/res_stir_shaken.h"
/*!
* \brief Get the attestation from the payload
*
* \param json_str The JSON string representation of the payload
*
* \retval Empty string on failure
* \retval The attestation on success
*/
static char *get_attestation_from_payload(const char *json_str)
{
RAII_VAR(struct ast_json *, json, NULL, ast_json_free);
char *attestation;
json = ast_json_load_string(json_str, NULL);
attestation = (char *)ast_json_string_get(ast_json_object_get(json, "attest"));
if (!ast_strlen_zero(attestation)) {
return attestation;
}
return "";
}
/*!
* \brief Compare the caller ID from the INVITE with the one in the payload
*
* \param json_str The JSON string represntation of the payload
*
* \retval -1 on failure
* \retval 0 on success
*/
static int compare_caller_id(char *caller_id, const char *json_str)
{
RAII_VAR(struct ast_json *, json, NULL, ast_json_free);
char *caller_id_other;
json = ast_json_load_string(json_str, NULL);
caller_id_other = (char *)ast_json_string_get(ast_json_object_get(
ast_json_object_get(json, "orig"), "tn"));
if (strcmp(caller_id, caller_id_other)) {
return -1;
}
return 0;
}
/*!
* \brief Compare the current timestamp with the one in the payload. If the difference
* is greater than the signature timeout, it's not valid anymore
*
* \param json_str The JSON string representation of the payload
*
* \retval -1 on failure
* \retval 0 on success
*/
static int compare_timestamp(const char *json_str)
{
RAII_VAR(struct ast_json *, json, NULL, ast_json_free);
long int timestamp;
struct timeval now = ast_tvnow();
json = ast_json_load_string(json_str, NULL);
timestamp = ast_json_integer_get(ast_json_object_get(json, "iat"));
if (now.tv_sec - timestamp > ast_stir_shaken_get_signature_timeout()) {
return -1;
}
return 0;
}
/*!
* \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)
{
static const pj_str_t identity_str = { "Identity", 8 };
char *identity_hdr_val;
char *encoded_val;
struct ast_channel *chan = session->channel;
char *caller_id = session->id.number.str;
RAII_VAR(char *, header, NULL, ast_free);
RAII_VAR(char *, payload, NULL, ast_free);
char *signature;
char *algorithm;
char *public_key_url;
char *attestation;
int mismatch = 0;
struct ast_stir_shaken_payload *ss_payload;
identity_hdr_val = ast_sip_rdata_get_header_value(rdata, identity_str);
if (ast_strlen_zero(identity_hdr_val)) {
ast_stir_shaken_add_verification(chan, caller_id, "", AST_STIR_SHAKEN_VERIFY_NOT_PRESENT);
return 0;
}
encoded_val = strtok_r(identity_hdr_val, ".", &identity_hdr_val);
header = ast_base64decode_string(encoded_val);
if (ast_strlen_zero(header)) {
ast_stir_shaken_add_verification(chan, caller_id, "", AST_STIR_SHAKEN_VERIFY_SIGNATURE_FAILED);
return 0;
}
encoded_val = strtok_r(identity_hdr_val, ".", &identity_hdr_val);
payload = ast_base64decode_string(encoded_val);
if (ast_strlen_zero(payload)) {
ast_stir_shaken_add_verification(chan, caller_id, "", AST_STIR_SHAKEN_VERIFY_SIGNATURE_FAILED);
return 0;
}
/* It's fine to leave the signature encoded */
signature = strtok_r(identity_hdr_val, ";", &identity_hdr_val);
if (ast_strlen_zero(signature)) {
ast_stir_shaken_add_verification(chan, caller_id, "", AST_STIR_SHAKEN_VERIFY_SIGNATURE_FAILED);
return 0;
}
/* Trim "info=<" to get public key URL */
strtok_r(identity_hdr_val, "<", &identity_hdr_val);
public_key_url = strtok_r(identity_hdr_val, ">", &identity_hdr_val);
if (ast_strlen_zero(public_key_url)) {
ast_stir_shaken_add_verification(chan, caller_id, "", AST_STIR_SHAKEN_VERIFY_SIGNATURE_FAILED);
return 0;
}
algorithm = strtok_r(identity_hdr_val, ";", &identity_hdr_val);
if (ast_strlen_zero(algorithm)) {
ast_stir_shaken_add_verification(chan, caller_id, "", AST_STIR_SHAKEN_VERIFY_SIGNATURE_FAILED);
return 0;
}
attestation = get_attestation_from_payload(payload);
ss_payload = ast_stir_shaken_verify(header, payload, signature, algorithm, public_key_url);
if (!ss_payload) {
ast_stir_shaken_add_verification(chan, caller_id, attestation, AST_STIR_SHAKEN_VERIFY_SIGNATURE_FAILED);
return 0;
}
ast_stir_shaken_payload_free(ss_payload);
mismatch |= compare_caller_id(caller_id, payload);
mismatch |= compare_timestamp(payload);
if (mismatch) {
ast_stir_shaken_add_verification(chan, caller_id, attestation, AST_STIR_SHAKEN_VERIFY_MISMATCH);
return 0;
}
ast_stir_shaken_add_verification(chan, caller_id, attestation, AST_STIR_SHAKEN_VERIFY_PASSED);
return 0;
}
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,
};
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;
}

94
res/res_stir_shaken.c
View File

@ -65,6 +65,9 @@
<configOption name="curl_timeout" default="2">
<synopsis>Maximum time to wait to CURL certificates</synopsis>
</configOption>
<configOption name="signature_timeout" default="15">
<synopsis>Amount of time a signature is valid for</synopsis>
</configOption>
</configObject>
<configObject name="store">
<synopsis>STIR/SHAKEN certificate store options</synopsis>
@ -181,6 +184,11 @@ void ast_stir_shaken_payload_free(struct ast_stir_shaken_payload *payload)
ast_free(payload);
}
unsigned int ast_stir_shaken_get_signature_timeout(void)
{
return ast_stir_shaken_signature_timeout(stir_shaken_general_get());
}
/*!
* \brief Convert an ast_stir_shaken_verification_result to string representation
*
@ -270,8 +278,8 @@ int ast_stir_shaken_add_verification(struct ast_channel *chan, const char *ident
return -1;
}
if (ast_strlen_zero(attestation)) {
ast_log(LOG_ERROR, "No attestation to add STIR/SHAKEN verification to "
if (!attestation) {
ast_log(LOG_ERROR, "Attestation cannot be NULL to add STIR/SHAKEN verification to "
"channel %s\n", chan_name);
return -1;
}
@ -593,8 +601,9 @@ struct ast_stir_shaken_payload *ast_stir_shaken_verify(const char *header, const
EVP_PKEY *public_key;
char *filename;
int curl = 0;
struct ast_json_error err;
RAII_VAR(char *, file_path, NULL, ast_free);
RAII_VAR(char *, combined_str, NULL, ast_free);
size_t combined_size;
if (ast_strlen_zero(header)) {
ast_log(LOG_ERROR, "'header' is required for STIR/SHAKEN verification\n");
@ -697,7 +706,16 @@ struct ast_stir_shaken_payload *ast_stir_shaken_verify(const char *header, const
}
}
if (stir_shaken_verify_signature(payload, signature, public_key)) {
/* Combine the header and payload to get the original signed message: header.payload */
combined_size = strlen(header) + strlen(payload) + 2;
combined_str = ast_calloc(1, combined_size);
if (!combined_str) {
ast_log(LOG_ERROR, "Failed to allocate space for message to verify\n");
EVP_PKEY_free(public_key);
return NULL;
}
snprintf(combined_str, combined_size, "%s.%s", header, payload);
if (stir_shaken_verify_signature(combined_str, signature, public_key)) {
ast_log(LOG_ERROR, "Failed to verify signature\n");
EVP_PKEY_free(public_key);
return NULL;
@ -712,14 +730,14 @@ struct ast_stir_shaken_payload *ast_stir_shaken_verify(const char *header, const
return NULL;
}
ret_payload->header = ast_json_load_string(header, &err);
ret_payload->header = ast_json_load_string(header, NULL);
if (!ret_payload->header) {
ast_log(LOG_ERROR, "Failed to create JSON from header\n");
ast_stir_shaken_payload_free(ret_payload);
return NULL;
}
ret_payload->payload = ast_json_load_string(payload, &err);
ret_payload->payload = ast_json_load_string(payload, NULL);
if (!ret_payload->payload) {
ast_log(LOG_ERROR, "Failed to create JSON from payload\n");
ast_stir_shaken_payload_free(ret_payload);
@ -1000,14 +1018,18 @@ static int stir_shaken_add_iat(struct ast_json *json)
struct ast_stir_shaken_payload *ast_stir_shaken_sign(struct ast_json *json)
{
struct ast_stir_shaken_payload *payload;
struct ast_stir_shaken_payload *ss_payload;
unsigned char *signature;
const char *caller_id_num;
char *json_str = NULL;
const char *header;
const char *payload;
struct ast_json *tmp_json;
char *msg = NULL;
size_t msg_len;
struct stir_shaken_certificate *cert = NULL;
payload = stir_shaken_verify_json(json);
if (!payload) {
ss_payload = stir_shaken_verify_json(json);
if (!ss_payload) {
return NULL;
}
@ -1052,27 +1074,34 @@ struct ast_stir_shaken_payload *ast_stir_shaken_sign(struct ast_json *json)
goto cleanup;
}
json_str = ast_json_dump_string(json);
if (!json_str) {
ast_log(LOG_ERROR, "Failed to convert JSON to string\n");
/* Get the header and the payload. Combine them to get the message to sign */
tmp_json = ast_json_object_get(json, "header");
header = ast_json_dump_string(tmp_json);
tmp_json = ast_json_object_get(json, "payload");
payload = ast_json_dump_string(tmp_json);
msg_len = strlen(header) + strlen(payload) + 2;
msg = ast_calloc(1, msg_len);
if (!msg) {
ast_log(LOG_ERROR, "Failed to allocate space for message to sign\n");
goto cleanup;
}
snprintf(msg, msg_len, "%s.%s", header, payload);
signature = stir_shaken_sign(json_str, stir_shaken_certificate_get_private_key(cert));
signature = stir_shaken_sign(msg, stir_shaken_certificate_get_private_key(cert));
if (!signature) {
goto cleanup;
}
payload->signature = signature;
ss_payload->signature = signature;
ao2_cleanup(cert);
ast_json_free(json_str);
ast_free(msg);
return payload;
return ss_payload;
cleanup:
ao2_cleanup(cert);
ast_stir_shaken_payload_free(payload);
ast_json_free(json_str);
ast_stir_shaken_payload_free(ss_payload);
ast_free(msg);
return NULL;
}
@ -1424,12 +1453,13 @@ AST_TEST_DEFINE(test_stir_shaken_verify)
{
char *caller_id_number = "1234567";
char *public_key_url = "http://testing123";
char *header = "{\"header\": \"placeholder\"}";
char *header;
char *payload;
struct ast_json *tmp_json;
char public_path[] = "/tmp/stir_shaken_public.XXXXXX";
char private_path[] = "/tmp/stir_shaken_public.XXXXXX";
RAII_VAR(char *, rm_on_exit_public, public_path, unlink);
RAII_VAR(char *, rm_on_exit_private, private_path, unlink);
RAII_VAR(char *, json_str, NULL, ast_json_free);
RAII_VAR(struct ast_json *, json, NULL, ast_json_free);
RAII_VAR(struct ast_stir_shaken_payload *, signed_payload, NULL, ast_stir_shaken_payload_free);
RAII_VAR(struct ast_stir_shaken_payload *, returned_payload, NULL, ast_stir_shaken_payload_free);
@ -1463,16 +1493,14 @@ AST_TEST_DEFINE(test_stir_shaken_verify)
return AST_TEST_FAIL;
}
/* Get the message to use for verification */
json_str = ast_json_dump_string(json);
if (!json_str) {
ast_test_status_update(test, "Failed to create string from JSON\n");
test_stir_shaken_cleanup_cert(caller_id_number);
return AST_TEST_FAIL;
}
/* Get the header and payload for ast_stir_shaken_verify */
tmp_json = ast_json_object_get(json, "header");
header = ast_json_dump_string(tmp_json);
tmp_json = ast_json_object_get(json, "payload");
payload = ast_json_dump_string(tmp_json);
/* Test empty header parameter */
returned_payload = ast_stir_shaken_verify("", json_str, (const char *)signed_payload->signature,
returned_payload = ast_stir_shaken_verify("", payload, (const char *)signed_payload->signature,
STIR_SHAKEN_ENCRYPTION_ALGORITHM, public_key_url);
if (returned_payload) {
ast_test_status_update(test, "Verified a signature with missing 'header'\n");
@ -1490,7 +1518,7 @@ AST_TEST_DEFINE(test_stir_shaken_verify)
}
/* Test empty signature parameter */
returned_payload = ast_stir_shaken_verify(header, json_str, "",
returned_payload = ast_stir_shaken_verify(header, payload, "",
STIR_SHAKEN_ENCRYPTION_ALGORITHM, public_key_url);
if (returned_payload) {
ast_test_status_update(test, "Verified a signature with missing 'signature'\n");
@ -1499,7 +1527,7 @@ AST_TEST_DEFINE(test_stir_shaken_verify)
}
/* Test empty algorithm parameter */
returned_payload = ast_stir_shaken_verify(header, json_str, (const char *)signed_payload->signature,
returned_payload = ast_stir_shaken_verify(header, payload, (const char *)signed_payload->signature,
"", public_key_url);
if (returned_payload) {
ast_test_status_update(test, "Verified a signature with missing 'algorithm'\n");
@ -1508,7 +1536,7 @@ AST_TEST_DEFINE(test_stir_shaken_verify)
}
/* Test empty public key URL */
returned_payload = ast_stir_shaken_verify(header, json_str, (const char *)signed_payload->signature,
returned_payload = ast_stir_shaken_verify(header, payload, (const char *)signed_payload->signature,
STIR_SHAKEN_ENCRYPTION_ALGORITHM, "");
if (returned_payload) {
ast_test_status_update(test, "Verified a signature with missing 'public key URL'\n");
@ -1520,7 +1548,7 @@ AST_TEST_DEFINE(test_stir_shaken_verify)
test_stir_shaken_add_fake_astdb_entry(public_key_url, public_path);
/* Verify a valid signature */
returned_payload = ast_stir_shaken_verify(header, json_str, (const char *)signed_payload->signature,
returned_payload = ast_stir_shaken_verify(header, payload, (const char *)signed_payload->signature,
STIR_SHAKEN_ENCRYPTION_ALGORITHM, public_key_url);
if (!returned_payload) {
ast_test_status_update(test, "Failed to verify a valid signature\n");

6
res/res_stir_shaken.exports.in Normal file
View File

@ -0,0 +1,6 @@
{
global:
LINKER_SYMBOL_PREFIXast_stir_*;
local:
*;
};

11
res/res_stir_shaken/general.c
View File

@ -31,6 +31,7 @@
#define DEFAULT_CA_PATH ""
#define DEFAULT_CACHE_MAX_SIZE 1000
#define DEFAULT_CURL_TIMEOUT 2
#define DEFAULT_SIGNATURE_TIMEOUT 15
struct stir_shaken_general {
SORCERY_OBJECT(details);
@ -44,6 +45,8 @@ struct stir_shaken_general {
unsigned int cache_max_size;
/*! Maximum time to wait to CURL certificates */
unsigned int curl_timeout;
/*! Amount of time a signature is valid for */
unsigned int signature_timeout;
};
static struct stir_shaken_general *default_config = NULL;
@ -86,6 +89,11 @@ unsigned int ast_stir_shaken_curl_timeout(const struct stir_shaken_general *cfg)
return cfg ? cfg->curl_timeout : DEFAULT_CURL_TIMEOUT;
}
unsigned int ast_stir_shaken_signature_timeout(const struct stir_shaken_general *cfg)
{
return cfg ? cfg->signature_timeout : DEFAULT_SIGNATURE_TIMEOUT;
}
static void stir_shaken_general_destructor(void *obj)
{
struct stir_shaken_general *cfg = obj;
@ -261,6 +269,9 @@ int stir_shaken_general_load(void)
ast_sorcery_object_field_register(sorcery, CONFIG_TYPE, "curl_timeout",
__stringify(DEFAULT_CURL_TIMEOUT), OPT_UINT_T, 0,
FLDSET(struct stir_shaken_general, curl_timeout));
ast_sorcery_object_field_register(sorcery, CONFIG_TYPE, "signature_timeout",
__stringify(DEFAULT_SIGNATURE_TIMEOUT), OPT_UINT_T, 0,
FLDSET(struct stir_shaken_general, signature_timeout));
if (ast_sorcery_instance_observer_add(sorcery, &stir_shaken_general_observer)) {
ast_log(LOG_ERROR, "stir/shaken - failed to register loaded observer for '%s' "

11
res/res_stir_shaken/general.h
View File

@ -83,6 +83,17 @@ unsigned int ast_stir_shaken_cache_max_size(const struct stir_shaken_general *cf
*/
unsigned int ast_stir_shaken_curl_timeout(const struct stir_shaken_general *cfg);
/*!
* \brief Retrieve the 'signature_timeout' general configuration option value
*
* \note if a NULL configuration is given, then the default value is returned
*
* \param cfg A 'general' configuration object
*
* \retval The 'signature_timeout' value
*/
unsigned int ast_stir_shaken_signature_timeout(const struct stir_shaken_general *cfg);
/*!
* \brief Load time initialization for the stir/shaken 'general' configuration
*