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libnetconf2/src/session_server_ssh.c
Daniel Baumann 6af28b7e8e
Merging upstream version 3.5.5 (Closes: #1098233). 
Signed-off-by: Daniel Baumann <daniel@debian.org>
2025-02-18 11:33:30 +01:00

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/**
* @file session_server_ssh.c
* @author Michal Vasko <mvasko@cesnet.cz>
* @brief libnetconf2 SSH server session manipulation functions
*
* @copyright
* Copyright (c) 2017 - 2021 CESNET, z.s.p.o.
*
* This source code is licensed under BSD 3-Clause License (the "License").
* You may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* https://opensource.org/licenses/BSD-3-Clause
*/
#define _GNU_SOURCE
#include "config.h" /* Expose HAVE_LIBPAM and HAVE_SHADOW */
#ifdef HAVE_LIBPAM
# include <security/pam_appl.h>
#endif
#ifdef HAVE_SHADOW
# include <shadow.h>
#endif
#include <arpa/inet.h>
#include <assert.h>
#include <ctype.h>
#include <errno.h>
#include <libssh/libssh.h>
#include <libssh/server.h>
#include <libyang/libyang.h>
#include <pwd.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <time.h>
#include <unistd.h>
#include "compat.h"
#include "log_p.h"
#include "nc_version.h"
#include "session.h"
#include "session_p.h"
#include "session_wrapper.h"
/**
* @brief Stores the private key data as a temporary file.
*
* @param[in] in Private key data.
* @param[in] privkey_format String representation of the private key format.
* @return Path to the created temporary file or NULL on fail.
*/
static char *
nc_server_ssh_privkey_data_to_tmp_file(const char *in, const char *privkey_format)
{
char path[12] = "/tmp/XXXXXX";
int fd, written;
unsigned len;
mode_t umode;
FILE *file;
NC_CHECK_ARG_RET(NULL, in, NULL);
umode = umask(0177);
fd = mkstemp(path);
umask(umode);
if (fd == -1) {
return NULL;
}
file = fdopen(fd, "w");
if (!file) {
close(fd);
return NULL;
}
/* write header */
written = fwrite("-----BEGIN", 1, 10, file);
if (privkey_format) {
written += fwrite(privkey_format, 1, strlen(privkey_format), file);
written += fwrite("PRIVATE KEY-----\n", 1, 17, file);
} else {
written += fwrite(" PRIVATE KEY-----\n", 1, 18, file);
}
/* write data */
written += fwrite(in, 1, strlen(in), file);
/* write footer */
written += fwrite("\n-----END", 1, 9, file);
if (privkey_format) {
written += fwrite(privkey_format, 1, strlen(privkey_format), file);
written += fwrite("PRIVATE KEY-----", 1, 16, file);
} else {
written += fwrite(" PRIVATE KEY-----", 1, 17, file);
}
fclose(file);
/* checksum */
if (privkey_format) {
len = 10 + strlen(privkey_format) + 17 + strlen(in) + 9 + strlen(privkey_format) + 16;
} else {
len = 10 + 18 + strlen(in) + 9 + 17;
}
if ((unsigned)written != len) {
unlink(path);
return NULL;
}
return strdup(path);
}
/**
* @brief Get asymmetric key from the keystore.
*
* @param[in] referenced_name Name of the asymmetric key in the keystore.
* @param[out] askey Referenced asymmetric key.
* @return 0 on success, 1 on error.
*/
static int
nc_server_ssh_ks_ref_get_key(const char *referenced_name, struct nc_asymmetric_key **askey)
{
uint16_t i;
struct nc_keystore *ks = &server_opts.keystore;
*askey = NULL;
/* lookup name */
for (i = 0; i < ks->asym_key_count; i++) {
if (!strcmp(referenced_name, ks->asym_keys[i].name)) {
break;
}
}
if (i == ks->asym_key_count) {
ERR(NULL, "Keystore entry \"%s\" not found.", referenced_name);
return 1;
}
*askey = &ks->asym_keys[i];
/* check if the referenced public key is SubjectPublicKeyInfo */
if ((*askey)->pubkey_data && nc_is_pk_subject_public_key_info((*askey)->pubkey_data)) {
ERR(NULL, "The public key of the referenced hostkey \"%s\" is in the SubjectPublicKeyInfo format, "
"which is not allowed in the SSH!", referenced_name);
return 1;
}
return 0;
}
/**
* @brief Get public keys from the truststore.
*
* @param[in] referenced_name Name of the public key bag in the truststore.
* @param[out] pubkeys Referenced public keys.
* @param[out] pubkey_count Referenced public key count.
* @return 0 on success, 1 on error.
*/
static int
nc_server_ssh_ts_ref_get_keys(const char *referenced_name, struct nc_public_key **pubkeys, uint16_t *pubkey_count)
{
uint16_t i, j;
struct nc_truststore *ts = &server_opts.truststore;
*pubkeys = NULL;
*pubkey_count = 0;
/* lookup name */
for (i = 0; i < ts->pub_bag_count; i++) {
if (!strcmp(referenced_name, ts->pub_bags[i].name)) {
break;
}
}
if (i == ts->pub_bag_count) {
ERR(NULL, "Truststore entry \"%s\" not found.", referenced_name);
return 1;
}
/* check if any of the referenced public keys is SubjectPublicKeyInfo */
for (j = 0; j < ts->pub_bags[i].pubkey_count; j++) {
if (nc_is_pk_subject_public_key_info(ts->pub_bags[i].pubkeys[j].data)) {
ERR(NULL, "A public key of the referenced public key bag \"%s\" is in the SubjectPublicKeyInfo format, "
"which is not allowed in the SSH!", referenced_name);
return 1;
}
}
*pubkeys = ts->pub_bags[i].pubkeys;
*pubkey_count = ts->pub_bags[i].pubkey_count;
return 0;
}
/**
* @brief Convert UID to string.
*
* @param[in] uid UID to convert.
* @return UID converted to string or NULL on fail.
*/
static char *
nc_server_ssh_uid_to_str(uid_t uid)
{
int buf_len;
char *uid_str;
/* get the number of digits and alloc */
buf_len = snprintf(NULL, 0, "%u", uid);
uid_str = malloc(buf_len + 1);
NC_CHECK_ERRMEM_RET(!uid_str, NULL);
/* convert to string */
sprintf(uid_str, "%u", uid);
uid_str[buf_len] = '\0';
return uid_str;
}
/**
* @brief Append a character or a string to a string.
*
* @param[in] src_c Source character.
* @param[in] src_str Source string.
* @param[in,out] size Size of the destination string.
* @param[out] idx Index of the next character to write.
* @param[out] dst Destination string.
* @return 0 on success, 1 on error.
*/
static int
nc_server_ssh_str_append(const char src_c, const char *src_str, int *size, int *idx, char **dst)
{
int src_size, allocate = 0, ret;
/* get size of char/string we want to append */
if (src_str) {
src_size = strlen(src_str);
} else {
src_size = 1;
}
/* check if we have enough space, if not realloc */
while ((src_size + *idx) >= *size) {
(*size) += 16;
allocate = 1;
}
if (allocate) {
*dst = nc_realloc(*dst, *size);
NC_CHECK_ERRMEM_RET(!*dst, 1);
}
/* append the char/string */
if (src_str) {
ret = sprintf(*dst + *idx, "%s", src_str);
} else {
ret = sprintf(*dst + *idx, "%c", src_c);
}
if (ret < 0) {
return 1;
}
*idx += ret;
return 0;
}
/**
* @brief Get the path to the system public keys from format set by an API.
*
* @param[in] username Username.
* @param[out] out_path Path to the system public keys.
* @return 0 on success, 1 on error.
*/
static int
nc_server_ssh_get_system_keys_path(const char *username, char **out_path)
{
int ret = 0, i, have_percent = 0, size = 0, idx = 0;
const char *path_fmt = server_opts.authkey_path_fmt;
char *path = NULL, *buf = NULL, *uid = NULL;
struct passwd *pw, pw_buf;
size_t buf_len = 0;
if (!path_fmt) {
ERR(NULL, "System public keys path format not set.");
return 1;
}
/* check if the path format contains any tokens */
if (strstr(path_fmt, "%h") || strstr(path_fmt, "%U") || strstr(path_fmt, "%u") || strstr(path_fmt, "%%")) {
/* get pw */
pw = nc_getpw(0, username, &pw_buf, &buf, &buf_len);
if (!pw) {
ERR(NULL, "Unable to get passwd entry for user \"%s\".", username);
ret = 1;
goto cleanup;
}
/* convert UID to a string */
uid = nc_server_ssh_uid_to_str(pw->pw_uid);
if (!uid) {
ret = 1;
goto cleanup;
}
} else {
/* no tokens, just copy the path and return */
*out_path = strdup(path_fmt);
NC_CHECK_ERRMEM_RET(!*out_path, 1);
goto cleanup;
}
/* go over characters from format, copy them to path and interpret tokens correctly */
for (i = 0; path_fmt[i]; i++) {
if (have_percent) {
/* special token, need to convert it */
if (path_fmt[i] == '%') {
ret = nc_server_ssh_str_append('%', NULL, &size, &idx, &path);
} else if (path_fmt[i] == 'h') {
/* user home */
ret = nc_server_ssh_str_append(0, pw->pw_dir, &size, &idx, &path);
} else if (path_fmt[i] == 'u') {
/* username */
ret = nc_server_ssh_str_append(0, username, &size, &idx, &path);
} else if (path_fmt[i] == 'U') {
/* UID */
ret = nc_server_ssh_str_append(0, uid, &size, &idx, &path);
} else {
ERR(NULL, "Failed to parse system public keys path format \"%s\".", server_opts.authkey_path_fmt);
ret = 1;
}
have_percent = 0;
} else {
if (path_fmt[i] == '%') {
have_percent = 1;
} else {
/* ordinary character with no meaning */
ret = nc_server_ssh_str_append(path_fmt[i], NULL, &size, &idx, &path);
}
}
if (ret) {
free(path);
goto cleanup;
}
}
*out_path = path;
cleanup:
free(uid);
free(buf);
return ret;
}
/**
* @brief Read public keys from the authorized keys file.
*
* @param[in] path Path to the authorized keys file.
* @param[out] pubkeys Public keys.
* @param[out] pubkey_count Public key count.
* @return 0 on success, 1 on error.
*/
static int
nc_server_ssh_read_authorized_keys_file(const char *path, struct nc_public_key **pubkeys, uint16_t *pubkey_count)
{
int ret = 0, rc, line_num = 0;
FILE *f = NULL;
char *line = NULL, *ptr, *ptr2;
size_t n;
enum ssh_keytypes_e ktype;
NC_CHECK_ARG_RET(NULL, path, pubkeys, 1);
*pubkeys = NULL;
*pubkey_count = 0;
f = fopen(path, "r");
if (!f) {
ERR(NULL, "Unable to open \"%s\" (%s).", path, strerror(errno));
ret = 1;
goto cleanup;
}
while (getline(&line, &n, f) > -1) {
++line_num;
if ((line[0] == '#') || (line[0] == '\n')) {
/* comment or empty line */
continue;
}
/* separate key type */
ptr = line;
for (ptr2 = ptr; ptr2[0] && !isspace(ptr2[0]); ptr2++) {}
if (!ptr2[0]) {
ERR(NULL, "Invalid format of authorized keys file \"%s\" on line %d.", path, line_num);
ret = 1;
goto cleanup;
}
ptr2[0] = '\0';
/* detect key type */
ktype = ssh_key_type_from_name(ptr);
if ((ktype != SSH_KEYTYPE_RSA) && (ktype != SSH_KEYTYPE_ECDSA_P256) && (ktype != SSH_KEYTYPE_ECDSA_P384) &&
(ktype != SSH_KEYTYPE_ECDSA_P521) && (ktype != SSH_KEYTYPE_ED25519)) {
WRN(NULL, "Unsupported key type \"%s\" in authorized keys file \"%s\" on line %d.", ptr, path, line_num);
continue;
}
/* get key data */
ptr = ptr2 + 1;
for (ptr2 = ptr; ptr2[0] && !isspace(ptr2[0]); ptr2++) {}
ptr2[0] = '\0';
/* add the key */
*pubkeys = nc_realloc(*pubkeys, (*pubkey_count + 1) * sizeof **pubkeys);
NC_CHECK_ERRMEM_GOTO(!(*pubkeys), ret = 1, cleanup);
rc = asprintf(&(*pubkeys)[*pubkey_count].name, "authorized_key_%" PRIu16, *pubkey_count);
NC_CHECK_ERRMEM_GOTO(rc == -1, (*pubkeys)[*pubkey_count].name = NULL; ret = 1, cleanup);
(*pubkeys)[*pubkey_count].type = NC_PUBKEY_FORMAT_SSH;
(*pubkeys)[*pubkey_count].data = strdup(ptr);
NC_CHECK_ERRMEM_GOTO(!(*pubkeys)[*pubkey_count].data, ret = 1, cleanup);
(*pubkey_count)++;
}
/* ok */
ret = 0;
cleanup:
if (f) {
fclose(f);
}
free(line);
return ret;
}
/**
* @brief Get user's public keys from the system.
*
* @param[in] username Username.
* @param[out] pubkeys User's public keys.
* @param[out] pubkey_count Public key count.
* @return 0 on success, non-zero on error.
*/
static int
nc_server_ssh_get_system_keys(const char *username, struct nc_public_key **pubkeys, uint16_t *pubkey_count)
{
int ret = 0;
char *path = NULL;
/* convert the path format to get the actual path */
ret = nc_server_ssh_get_system_keys_path(username, &path);
if (ret) {
ERR(NULL, "Getting system keys path failed.");
goto cleanup;
}
/* get the keys */
ret = nc_server_ssh_read_authorized_keys_file(path, pubkeys, pubkey_count);
if (ret) {
ERR(NULL, "Reading system keys failed.");
goto cleanup;
}
cleanup:
free(path);
return ret;
}
#ifdef HAVE_SHADOW
/**
* @brief Get the user's /etc/passwd entry.
*
* @param[in] username Username.
* @param[out] pwd_buf Buffer for the passwd structure.
* @param[out] buf Buffer for the pwd's strings.
* @param[out] buf_size Size of the buffer.
* @return User's passwd entry or NULL on error.
*/
static struct passwd *
nc_server_ssh_getpwnam(const char *username, struct passwd *pwd_buf, char **buf, size_t *buf_size)
{
struct passwd *pwd = NULL;
char *mem;
int r = 0;
do {
r = getpwnam_r(username, pwd_buf, *buf, *buf_size, &pwd);
if (pwd) {
/* entry found */
break;
}
if (r == ERANGE) {
/* small buffer, enlarge */
*buf_size <<= 2;
mem = realloc(*buf, *buf_size);
if (!mem) {
ERRMEM;
return NULL;
}
*buf = mem;
}
} while (r == ERANGE);
return pwd;
}
/**
* @brief Get the user's /etc/shadow entry.
*
* @param[in] username Username.
* @param[out] spwd_buf Buffer for the spwd structure.
* @param[out] buf Buffer for the spwd's strings.
* @param[out] buf_size Size of the buffer.
* @return User's shadow entry or NULL on error.
*/
static struct spwd *
nc_server_ssh_getspnam(const char *username, struct spwd *spwd_buf, char **buf, size_t *buf_size)
{
struct spwd *spwd = NULL;
char *mem;
int r = 0;
do {
# ifndef __QNXNTO__
r = getspnam_r(username, spwd_buf, *buf, *buf_size, &spwd);
# else
spwd = getspnam_r(username, spwd_buf, *buf, *buf_size);
r = errno;
# endif
if (spwd) {
/* entry found */
break;
}
if (r == ERANGE) {
/* small buffer, enlarge */
*buf_size <<= 2;
mem = realloc(*buf, *buf_size);
if (!mem) {
ERRMEM;
return NULL;
}
*buf = mem;
}
} while (r == ERANGE);
return spwd;
}
/**
* @brief Get the user's hashed password from the system.
*
* @param[in] username Username.
* @return User's hashed password or NULL on error.
*/
static char *
nc_server_ssh_get_pwd_hash(const char *username)
{
struct passwd *pwd, pwd_buf;
struct spwd *spwd, spwd_buf;
char *pass_hash = NULL, *buf = NULL;
size_t buf_size = 256;
buf = malloc(buf_size);
NC_CHECK_ERRMEM_GOTO(!buf, , error);
pwd = nc_server_ssh_getpwnam(username, &pwd_buf, &buf, &buf_size);
if (!pwd) {
VRB(NULL, "User \"%s\" not found in the system.", username);
goto error;
}
if (!strcmp(pwd->pw_passwd, "x")) {
spwd = nc_server_ssh_getspnam(username, &spwd_buf, &buf, &buf_size);
if (!spwd) {
VRB(NULL, "Failed to retrieve the shadow entry for \"%s\".", username);
goto error;
} else if ((spwd->sp_expire > -1) && (spwd->sp_expire <= (time(NULL) / (60 * 60 * 24)))) {
WRN(NULL, "User \"%s\" account has expired.", username);
goto error;
}
pass_hash = spwd->sp_pwdp;
} else {
pass_hash = pwd->pw_passwd;
}
if (!pass_hash) {
ERR(NULL, "No password could be retrieved for \"%s\".", username);
goto error;
}
/* check the hash structure for special meaning */
if (!strcmp(pass_hash, "*") || !strcmp(pass_hash, "!")) {
VRB(NULL, "User \"%s\" is not allowed to authenticate using a password.", username);
goto error;
}
if (!strcmp(pass_hash, "*NP*")) {
VRB(NULL, "Retrieving password for \"%s\" from a NIS+ server not supported.", username);
goto error;
}
pass_hash = strdup(pass_hash);
free(buf);
return pass_hash;
error:
free(buf);
return NULL;
}
#endif
/**
* @brief Compare stored hashed password with a cleartext received password.
*
* @param[in] stored_pw Hashed stored password.
* @param[in] received_pw Cleartext received password.
* @return 0 on match, non-zero otherwise.
*/
static int
nc_server_ssh_compare_password(const char *stored_pw, const char *received_pw)
{
char *received_pw_hash = NULL;
struct crypt_data cdata = {0};
NC_CHECK_ARG_RET(NULL, stored_pw, received_pw, 1);
if (!stored_pw[0]) {
if (!received_pw[0]) {
WRN(NULL, "User authentication successful with an empty password!");
return 0;
} else {
/* the user did now know he does not need any password,
* (which should not be used) so deny authentication */
return 1;
}
}
if (!strncmp(stored_pw, "$0$", 3)) {
/* cleartext password, simply compare the values */
return strcmp(stored_pw + 3, received_pw);
}
received_pw_hash = crypt_r(received_pw, stored_pw, &cdata);
if (!received_pw_hash) {
ERR(NULL, "Hashing the password failed (%s).", strerror(errno));
return 1;
}
return strcmp(received_pw_hash, stored_pw);
}
API int
nc_server_ssh_kbdint_get_nanswers(const struct nc_session *session, ssh_session libssh_session)
{
int ret = 0;
struct timespec ts_timeout = {0};
ssh_message reply = NULL;
uint16_t auth_timeout = *((uint16_t *)session->data);
NC_CHECK_ARG_RET(NULL, session, libssh_session, -1);
if (auth_timeout) {
nc_timeouttime_get(&ts_timeout, auth_timeout * 1000);
}
/* wait for answers from the client */
do {
if (!nc_session_is_connected(session)) {
ERR(NULL, "SSH communication socket unexpectedly closed.");
ret = -1;
goto cleanup;
}
reply = ssh_message_get(libssh_session);
if (reply) {
break;
}
usleep(NC_TIMEOUT_STEP);
} while (auth_timeout && (nc_timeouttime_cur_diff(&ts_timeout) >= 1));
if (!reply) {
ERR(NULL, "Authentication timeout.");
ret = -1;
goto cleanup;
}
ret = ssh_userauth_kbdint_getnanswers(libssh_session);
cleanup:
ssh_message_free(reply);
return ret;
}
#ifdef HAVE_LIBPAM
/**
* @brief PAM conversation function, which serves as a callback for exchanging messages between the client and a PAM module.
*
* @param[in] n_messages Number of messages.
* @param[in] msg PAM module's messages.
* @param[out] resp User responses.
* @param[in] appdata_ptr Callback's data.
* @return PAM_SUCCESS on success, PAM_BUF_ERR on memory allocation error, PAM_CONV_ERR otherwise.
*/
static int
nc_pam_conv_clb(int n_messages, const struct pam_message **msg, struct pam_response **resp, void *appdata_ptr)
{
int i, j, t, r = PAM_SUCCESS, n_answers, n_requests = n_messages;
const char **prompts = NULL;
char *echo = NULL;
const char *name = "Keyboard-Interactive Authentication";
const char *instruction = "Please enter your authentication token";
ssh_message reply = NULL;
struct nc_pam_thread_arg *clb_data = appdata_ptr;
ssh_session libssh_session;
libssh_session = clb_data->session->ti.libssh.session;
/* PAM_MAX_NUM_MSG == 32 by default */
if ((n_messages <= 0) || (n_messages >= PAM_MAX_NUM_MSG)) {
ERR(clb_data->session, "Bad number of PAM messages (#%d).", n_messages);
r = PAM_CONV_ERR;
goto cleanup;
}
/* only accepting these 4 types of messages */
for (i = 0; i < n_messages; i++) {
t = msg[i]->msg_style;
if ((t != PAM_PROMPT_ECHO_OFF) && (t != PAM_PROMPT_ECHO_ON) && (t != PAM_TEXT_INFO) && (t != PAM_ERROR_MSG)) {
ERR(clb_data->session, "PAM conversation callback received an unexpected type of message.");
r = PAM_CONV_ERR;
goto cleanup;
}
}
/* display messages with errors and/or some information and count the amount of actual authentication challenges */
for (i = 0; i < n_messages; i++) {
if (msg[i]->msg_style == PAM_TEXT_INFO) {
VRB(clb_data->session, "PAM conversation callback received a message with some information for the client (%s).", msg[i]->msg);
n_requests--;
}
if (msg[i]->msg_style == PAM_ERROR_MSG) {
ERR(clb_data->session, "PAM conversation callback received an error message (%s).", msg[i]->msg);
r = PAM_CONV_ERR;
goto cleanup;
}
}
/* there are no requests left for the user, only messages with some information for the client were sent */
if (n_requests <= 0) {
r = PAM_SUCCESS;
goto cleanup;
}
/* it is the PAM module's responsibility to release both, this array and the responses themselves */
*resp = calloc(n_requests, sizeof **resp);
prompts = calloc(n_requests, sizeof *prompts);
echo = calloc(n_requests, sizeof *echo);
NC_CHECK_ERRMEM_GOTO(!(*resp) || !prompts || !echo, r = PAM_BUF_ERR, cleanup);
/* set the prompts for the user */
j = 0;
for (i = 0; i < n_messages; i++) {
if ((msg[i]->msg_style == PAM_PROMPT_ECHO_ON) || (msg[i]->msg_style == PAM_PROMPT_ECHO_OFF)) {
prompts[j++] = msg[i]->msg;
}
}
/* iterate over all the messages and adjust the echo array accordingly */
j = 0;
for (i = 0; i < n_messages; i++) {
if (msg[i]->msg_style == PAM_PROMPT_ECHO_ON) {
echo[j++] = 1;
}
if (msg[i]->msg_style == PAM_PROMPT_ECHO_OFF) {
/* no need to set to 0 because of calloc */
j++;
}
}
/* print all the keyboard-interactive challenges to the user */
r = ssh_message_auth_interactive_request(clb_data->msg, name, instruction, n_requests, prompts, echo);
if (r != SSH_OK) {
ERR(clb_data->session, "Failed to send an authentication request.");
r = PAM_CONV_ERR;
goto cleanup;
}
n_answers = nc_server_ssh_kbdint_get_nanswers(clb_data->session, libssh_session);
if (n_answers < 0) {
/* timeout or dc */
r = PAM_CONV_ERR;
goto cleanup;
} else if (n_answers != n_requests) {
/* check if the number of answers and requests matches */
ERR(clb_data->session, "Expected %d response(s), got %d.", n_requests, n_answers);
r = PAM_CONV_ERR;
goto cleanup;
}
/* give the replies to a PAM module */
for (i = 0; i < n_answers; i++) {
(*resp)[i].resp = strdup(ssh_userauth_kbdint_getanswer(libssh_session, i));
/* it should be the caller's responsibility to free this, however if mem alloc fails,
* it is safer to free the responses here and set them to NULL */
if ((*resp)[i].resp == NULL) {
for (j = 0; j < i; j++) {
free((*resp)[j].resp);
(*resp)[j].resp = NULL;
}
ERRMEM;
r = PAM_BUF_ERR;
goto cleanup;
}
}
cleanup:
ssh_message_free(reply);
free(prompts);
free(echo);
return r;
}
/**
* @brief Handles authentication via Linux PAM.
*
* @param[in] session NETCONF session.
* @param[in] username Username of the client to auhtenticate.
* @param[in] ssh_msg SSH message with a keyboard-interactive authentication request.
* @return PAM_SUCCESS on success;
* @return PAM error otherwise.
*/
static int
nc_server_ssh_auth_kbdint_pam(struct nc_session *session, const char *username, ssh_message ssh_msg)
{
pam_handle_t *pam_h = NULL;
int ret;
struct nc_pam_thread_arg clb_data;
struct pam_conv conv;
/* structure holding callback's data */
clb_data.msg = ssh_msg;
clb_data.session = session;
/* PAM conversation structure holding the callback and it's data */
conv.conv = nc_pam_conv_clb;
conv.appdata_ptr = &clb_data;
if (!server_opts.pam_config_name) {
ERR(session, "PAM configuration filename not set.");
ret = 1;
goto cleanup;
}
/* initialize PAM and see if the given configuration file exists */
ret = pam_start(server_opts.pam_config_name, username, &conv, &pam_h);
if (ret != PAM_SUCCESS) {
ERR(session, "PAM error occurred (%s).", pam_strerror(pam_h, ret));
goto cleanup;
}
/* authentication based on the modules listed in the configuration file */
ret = pam_authenticate(pam_h, 0);
if (ret != PAM_SUCCESS) {
if (ret == PAM_ABORT) {
ERR(session, "PAM error occurred (%s).", pam_strerror(pam_h, ret));
goto cleanup;
} else {
VRB(session, "PAM error occurred (%s).", pam_strerror(pam_h, ret));
goto cleanup;
}
}
/* correct token entered, check other requirements(the time of the day, expired token, ...) */
ret = pam_acct_mgmt(pam_h, 0);
if ((ret != PAM_SUCCESS) && (ret != PAM_NEW_AUTHTOK_REQD)) {
VRB(session, "PAM error occurred (%s).", pam_strerror(pam_h, ret));
goto cleanup;
}
/* if a token has expired a new one will be generated */
if (ret == PAM_NEW_AUTHTOK_REQD) {
VRB(session, "PAM warning occurred (%s).", pam_strerror(pam_h, ret));
ret = pam_chauthtok(pam_h, PAM_CHANGE_EXPIRED_AUTHTOK);
if (ret == PAM_SUCCESS) {
VRB(session, "The authentication token of user \"%s\" updated successfully.", username);
} else {
ERR(session, "PAM error occurred (%s).", pam_strerror(pam_h, ret));
goto cleanup;
}
}
cleanup:
/* destroy the PAM context */
if (pam_h && (pam_end(pam_h, ret) != PAM_SUCCESS)) {
ERR(NULL, "PAM error occurred (%s).", pam_strerror(pam_h, ret));
}
return ret;
}
#elif defined (HAVE_SHADOW)
/**
* @brief Authenticate using credentials stored in the system.
*
* @param[in] session Session to authenticate on.
* @param[in] username Username of the client to authenticate.
* @param[in] msg SSH message that originally requested kbdint authentication.
*
* @return 0 on success, non-zero otherwise.
*/
static int
nc_server_ssh_auth_kbdint_system(struct nc_session *session, const char *username, ssh_message msg)
{
int ret = 0, n_answers;
const char *name = "Keyboard-Interactive Authentication";
const char *instruction = "Please enter your authentication token";
char *prompt = NULL, *pw = NULL, *received_pw = NULL;
char echo[] = {0};
/* try to get the client's pw hash from the system */
pw = nc_server_ssh_get_pwd_hash(username);
if (!pw) {
ret = 1;
goto cleanup;
}
ret = asprintf(&prompt, "%s's password:", username);
NC_CHECK_ERRMEM_GOTO(ret == -1, prompt = NULL; ret = 1, cleanup);
/* send the password prompt to the client */
ret = ssh_message_auth_interactive_request(msg, name, instruction, 1, (const char **) &prompt, echo);
if (ret) {
ERR(session, "Failed to send an authentication request to client \"%s\".", username);
goto cleanup;
}
/* get the reply */
n_answers = nc_server_ssh_kbdint_get_nanswers(session, session->ti.libssh.session);
if (n_answers < 0) {
/* timeout or dc */
ret = 1;
goto cleanup;
} else if (n_answers != 1) {
/* only expecting a single answer */
ERR(session, "Unexpected amount of answers in system auth. Expected 1, got \"%d\".", n_answers);
ret = 1;
goto cleanup;
}
received_pw = strdup(ssh_userauth_kbdint_getanswer(session->ti.libssh.session, 0));
NC_CHECK_ERRMEM_GOTO(!received_pw, ret = 1, cleanup);
/* cmp the passwords */
ret = nc_server_ssh_compare_password(pw, received_pw);
cleanup:
free(pw);
free(received_pw);
free(prompt);
return ret;
}
#endif
API void
nc_server_ssh_set_interactive_auth_clb(int (*interactive_auth_clb)(const struct nc_session *session, ssh_session ssh_sess, ssh_message msg, void *user_data),
void *user_data, void (*free_user_data)(void *user_data))
{
/* CONFIG LOCK */
pthread_rwlock_wrlock(&server_opts.config_lock);
server_opts.interactive_auth_clb = interactive_auth_clb;
server_opts.interactive_auth_data = user_data;
server_opts.interactive_auth_data_free = free_user_data;
/* CONFIG UNLOCK */
pthread_rwlock_unlock(&server_opts.config_lock);
}
#ifdef HAVE_LIBPAM
API int
nc_server_ssh_set_pam_conf_filename(const char *filename)
{
int ret = 0;
NC_CHECK_ARG_RET(NULL, filename, 1);
/* CONFIG LOCK */
pthread_rwlock_wrlock(&server_opts.config_lock);
free(server_opts.pam_config_name);
server_opts.pam_config_name = strdup(filename);
if (!server_opts.pam_config_name) {
ERRMEM;
ret = 1;
}
/* CONFIG UNLOCK */
pthread_rwlock_unlock(&server_opts.config_lock);
return ret;
}
#else
API int
nc_server_ssh_set_pam_conf_filename(const char *filename)
{
/* LibPAM not supported */
(void) filename;
return 1;
}
#endif /* HAVE_LIBPAM */
API int
nc_server_ssh_set_authkey_path_format(const char *path)
{
int ret = 0;
NC_CHECK_ARG_RET(NULL, path, 1);
/* CONFIG LOCK */
pthread_rwlock_wrlock(&server_opts.config_lock);
free(server_opts.authkey_path_fmt);
server_opts.authkey_path_fmt = strdup(path);
if (!server_opts.authkey_path_fmt) {
ERRMEM;
ret = 1;
}
/* CONFIG UNLOCK */
pthread_rwlock_unlock(&server_opts.config_lock);
return ret;
}
/**
* @brief Get the public key type from binary data.
*
* @param[in] buffer Binary key data, which is in the form of: 4 bytes = data length, then data of data length.
* Data is in network byte order. The key has to be in the SSH2 format.
* @param[out] len Length of the key type.
* @return Pointer to where the key type starts in the buffer and is of the length @p len .
*/
static const char *
nc_server_ssh_get_pubkey_type(const unsigned char *buffer, uint32_t *len)
{
uint32_t type_len;
/* copy the 4 bytes */
memcpy(&type_len, buffer, sizeof type_len);
/* type_len now stores the length of the key type */
type_len = ntohl(type_len);
*len = type_len;
/* move 4 bytes in the buffer, this is where the type should be */
buffer += sizeof type_len;
return (const char *)buffer;
}
/**
* @brief Create ssh key from base64 pubkey data.
*
* @param[in] base64 base64 encoded public key.
* @param[out] key created ssh key.
* @return 0 on success, 1 otherwise.
*/
static int
nc_server_ssh_create_ssh_pubkey(const char *base64, ssh_key *key)
{
int ret = 0;
unsigned char *bin = NULL;
const char *pub_type = NULL;
uint32_t pub_type_len = 0;
NC_CHECK_ARG_RET(NULL, base64, key, 1);
*key = NULL;
/* convert base64 to binary */
if (nc_base64_decode_wrap(base64, &bin) == -1) {
ret = 1;
goto cleanup;
}
/* get the key type and try to import it if possible */
pub_type = nc_server_ssh_get_pubkey_type(bin, &pub_type_len);
if (!pub_type) {
ret = 1;
goto cleanup;
} else if (!strncmp(pub_type, "ssh-dss", pub_type_len)) {
ERR(NULL, "DSA keys are not supported.");
ret = 1;
goto cleanup;
} else if (!strncmp(pub_type, "ssh-rsa", pub_type_len)) {
ret = ssh_pki_import_pubkey_base64(base64, SSH_KEYTYPE_RSA, key);
} else if (!strncmp(pub_type, "ecdsa-sha2-nistp256", pub_type_len)) {
ret = ssh_pki_import_pubkey_base64(base64, SSH_KEYTYPE_ECDSA_P256, key);
} else if (!strncmp(pub_type, "ecdsa-sha2-nistp384", pub_type_len)) {
ret = ssh_pki_import_pubkey_base64(base64, SSH_KEYTYPE_ECDSA_P384, key);
} else if (!strncmp(pub_type, "ecdsa-sha2-nistp521", pub_type_len)) {
ret = ssh_pki_import_pubkey_base64(base64, SSH_KEYTYPE_ECDSA_P521, key);
} else if (!strncmp(pub_type, "ssh-ed25519", pub_type_len)) {
ret = ssh_pki_import_pubkey_base64(base64, SSH_KEYTYPE_ED25519, key);
} else {
ERR(NULL, "Public key type not recognised.");
ret = 1;
goto cleanup;
}
cleanup:
if (ret != SSH_OK) {
ERR(NULL, "Error importing public key.");
}
free(bin);
return ret;
}
/**
* @brief Compare SSH key with configured authorized keys and return the username of the matching one, if any.
*
* @param[in] key Presented SSH key to compare.
* @return Authorized key username, NULL if no match was found.
*/
static int
nc_server_ssh_auth_pubkey_compare_key(ssh_key key, struct nc_public_key *pubkeys, uint16_t pubkey_count)
{
uint16_t i;
int ret = 0;
ssh_key new_key = NULL;
/* try to compare all of the client's keys with the key received in the SSH message */
for (i = 0; i < pubkey_count; i++) {
/* create the SSH key from the data */
if (nc_server_ssh_create_ssh_pubkey(pubkeys[i].data, &new_key)) {
/* skip */
ssh_key_free(new_key);
continue;
}
/* compare the keys */
ret = ssh_key_cmp(key, new_key, SSH_KEY_CMP_PUBLIC);
ssh_key_free(new_key);
if (!ret) {
/* found a match */
break;
}
}
if (i == pubkey_count) {
ret = 1;
}
return ret;
}
/**
* @brief Handle authentication request for the None method.
*
* @param[in] local_users_supported Whether the server supports local users.
* @param[in] auth_client Configured client's authentication data.
* @param[in] msg libssh message.
* @return 0 if the authentication was successful, -1 if not (@p msg already replied to).
*/
static int
nc_server_ssh_auth_none(int local_users_supported, struct nc_auth_client *auth_client, ssh_message msg)
{
assert(!local_users_supported || auth_client);
if (local_users_supported && auth_client->none_enabled) {
/* success */
return 0;
}
/* reply and return -1 so that this does not get counted as an unsuccessful authentication attempt */
ssh_message_reply_default(msg);
return -1;
}
/**
* @brief Handle authentication request for the Password method.
*
* @param[in] session NETCONF session.
* @param[in] local_users_supported Whether the server supports local users.
* @param[in] auth_client Configured client's authentication data.
* @param[in] msg libssh message.
* @return 0 if the authentication was successful, 1 if not (@p msg not yet replied to).
*/
static int
nc_server_ssh_auth_password(struct nc_session *session, int local_users_supported,
struct nc_auth_client *auth_client, ssh_message msg)
{
int rc;
char *password = NULL;
assert(!local_users_supported || auth_client);
if (local_users_supported) {
/* obtain pw from config */
password = auth_client->password;
if (!password) {
VRB(session, "User \"%s\" does not have password method configured, but a request was received.", session->username);
return 1;
}
} else {
#ifdef HAVE_SHADOW
/* obtain pw from system, this one needs to be free'd */
password = nc_server_ssh_get_pwd_hash(session->username);
if (!password) {
return 1;
}
#else
ERR(session, "Obtaining password from system not supported.");
return 1;
#endif
}
/* compare the passwords */
rc = nc_server_ssh_compare_password(password, ssh_message_auth_password(msg));
if (!local_users_supported) {
free(password);
}
return rc ? 1 : 0;
}
/**
* @brief Handle authentication request for the Publickey method.
*
* @param[in] session NETCONF session.
* @param[in] local_users_supported Whether the server supports local users.
* @param[in] auth_client Configured client's authentication data.
* @param[in] msg libssh message.
* @return 0 if the authentication was successful, 1 if not and the @p msg not yet replied to, -1 if not and @p msg was replied to.
*/
static int
nc_server_ssh_auth_pubkey(struct nc_session *session, int local_users_supported,
struct nc_auth_client *auth_client, ssh_message msg)
{
int signature_state, ret = 0;
struct nc_public_key *pubkeys = NULL;
uint16_t pubkey_count = 0, i;
assert(!local_users_supported || auth_client);
/* get the public keys */
if (!local_users_supported || (auth_client->store == NC_STORE_SYSTEM)) {
/* system user or the user has 'use system keys' configured, these need to be free'd */
ret = nc_server_ssh_get_system_keys(session->username, &pubkeys, &pubkey_count);
if (ret) {
goto cleanup;
}
} else if (auth_client->store == NC_STORE_LOCAL) {
pubkeys = auth_client->pubkeys;
pubkey_count = auth_client->pubkey_count;
} else if (auth_client->store == NC_STORE_TRUSTSTORE) {
ret = nc_server_ssh_ts_ref_get_keys(auth_client->ts_ref, &pubkeys, &pubkey_count);
if (ret) {
goto cleanup;
}
} else {
ERRINT;
return 1;
}
/* compare the received pubkey with the authorized ones */
if (nc_server_ssh_auth_pubkey_compare_key(ssh_message_auth_pubkey(msg), pubkeys, pubkey_count)) {
VRB(session, "User \"%s\" tried to use an unknown (unauthorized) public key.", session->username);
ret = 1;
goto cleanup;
}
signature_state = ssh_message_auth_publickey_state(msg);
if (signature_state == SSH_PUBLICKEY_STATE_NONE) {
/* accepting only the use of a public key */
ssh_message_auth_reply_pk_ok_simple(msg);
ret = -1;
}
cleanup:
if (!local_users_supported || (auth_client->store == NC_STORE_SYSTEM)) {
for (i = 0; i < pubkey_count; i++) {
free(pubkeys[i].name);
free(pubkeys[i].data);
}
free(pubkeys);
}
return ret;
}
/**
* @brief Handle authentication request for the Keyboard-interactive method.
*
* @param[in] session NETCONF session.
* @param[in] local_users_supported Whether the server supports local users.
* @param[in] auth_client Configured client's authentication data.
* @param[in] msg libssh message.
* @return 0 if the authentication was successful, 1 if not.
*/
static int
nc_server_ssh_auth_kbdint(struct nc_session *session, int local_users_supported, struct nc_auth_client *auth_client, ssh_message msg)
{
int rc = 0;
assert(!local_users_supported || auth_client);
if (local_users_supported && !auth_client->kb_int_enabled) {
VRB(session, "User \"%s\" does not have Keyboard-interactive method configured, but a request was received.", session->username);
return 1;
} else if (server_opts.interactive_auth_clb) {
rc = server_opts.interactive_auth_clb(session, session->ti.libssh.session, msg, server_opts.interactive_auth_data);
} else {
#ifdef HAVE_LIBPAM
/* authenticate using PAM */
rc = nc_server_ssh_auth_kbdint_pam(session, session->username, msg);
#elif defined (HAVE_SHADOW)
/* authenticate using the system */
rc = nc_server_ssh_auth_kbdint_system(session, session->username, msg);
#else
ERR(NULL, "Keyboard-interactive method not supported.");
return 1;
#endif
}
return rc ? 1 : 0;
}
/**
* @brief Handle SSH channel open request.
*
* @param[in] session NETCONF session.
* @param[in] msg libssh message.
* @return 0 on success, -1 on failure.
*/
static int
nc_server_ssh_channel_open(struct nc_session *session, ssh_message msg)
{
ssh_channel chan;
/* first channel request */
if (!session->ti.libssh.channel) {
if (session->status != NC_STATUS_STARTING) {
ERRINT;
return -1;
}
chan = ssh_message_channel_request_open_reply_accept(msg);
if (!chan) {
ERR(session, "Failed to create a new SSH channel.");
return -1;
}
session->ti.libssh.channel = chan;
/* additional channel request */
} else {
chan = ssh_message_channel_request_open_reply_accept(msg);
if (!chan) {
ERR(session, "Session %u: failed to create a new SSH channel.", session->id);
return -1;
}
/* channel was created and libssh stored it internally in the ssh_session structure, good enough */
}
return 0;
}
/**
* @brief Handle SSH channel request subsystem request.
*
* @param[in] session NETCONF session.
* @param[in] channel Requested SSH channel.
* @param[in] subsystem Name of the requested subsystem.
* @return 0 on success, -1 on failure.
*/
static int
nc_server_ssh_channel_subsystem(struct nc_session *session, ssh_channel channel, const char *subsystem)
{
struct nc_session *new_session;
if (strcmp(subsystem, "netconf")) {
WRN(session, "Received an unknown subsystem \"%s\" request.", subsystem);
return -1;
}
if (session->ti.libssh.channel == channel) {
/* first channel requested */
if (session->ti.libssh.next || (session->status != NC_STATUS_STARTING)) {
ERRINT;
return -1;
}
if (session->flags & NC_SESSION_SSH_SUBSYS_NETCONF) {
ERR(session, "Subsystem \"netconf\" requested for the second time.");
return -1;
}
session->flags |= NC_SESSION_SSH_SUBSYS_NETCONF;
} else {
/* additional channel subsystem request, new session is ready as far as SSH is concerned */
new_session = nc_new_session(NC_SERVER, 1);
NC_CHECK_ERRMEM_RET(!new_session, -1);
/* insert the new session */
if (!session->ti.libssh.next) {
new_session->ti.libssh.next = session;
} else {
new_session->ti.libssh.next = session->ti.libssh.next;
}
session->ti.libssh.next = new_session;
new_session->status = NC_STATUS_STARTING;
new_session->ti_type = NC_TI_SSH;
new_session->io_lock = session->io_lock;
new_session->ti.libssh.channel = channel;
new_session->ti.libssh.session = session->ti.libssh.session;
new_session->username = strdup(session->username);
new_session->host = strdup(session->host);
new_session->port = session->port;
new_session->ctx = (struct ly_ctx *)session->ctx;
new_session->flags = NC_SESSION_SSH_AUTHENTICATED | NC_SESSION_SSH_SUBSYS_NETCONF | NC_SESSION_SHAREDCTX;
}
return 0;
}
/**
* @brief Handle NETCONF SSH authentication.
*
* @param[in] session NETCONF session.
* @param[in] opts SSH server options.
* @param[in] msg libssh message.
* @param[in] method Type of the authentication method.
* @param[in] str_method String representation of the authentication method.
* @param[in] local_users_supported Whether the server supports local users.
* @param[in,out] auth_state Authentication state.
* @return 1 in case of a fatal error, 0 otherwise.
*/
static int
nc_server_ssh_auth(struct nc_session *session, struct nc_server_ssh_opts *opts, ssh_message msg,
int method, const char *str_method, int local_users_supported, struct nc_auth_state *auth_state)
{
const char *username;
int ret = 0;
uint16_t i;
struct nc_auth_client *auth_client = NULL;
struct nc_endpt *referenced_endpt;
/* save the username, do not let the client change it */
username = ssh_message_auth_user(msg);
assert(username);
if (local_users_supported) {
/* get the locally configured user */
for (i = 0; i < opts->client_count; i++) {
if (!strcmp(opts->auth_clients[i].username, username)) {
auth_client = &opts->auth_clients[i];
break;
}
}
if (!auth_client) {
if (opts->referenced_endpt_name) {
/* client not known by the endpt, but it references another one so try it */
if (nc_server_get_referenced_endpt(opts->referenced_endpt_name, &referenced_endpt)) {
ERRINT;
return 1;
}
return nc_server_ssh_auth(session, referenced_endpt->opts.ssh, msg, method,
str_method, local_users_supported, auth_state);
}
/* user not known, set his authentication methods to public key only so that
* there is no interaction and it will simply be denied */
ERR(NULL, "User \"%s\" not known by the server.", username);
ssh_set_auth_methods(session->ti.libssh.session, SSH_AUTH_METHOD_PUBLICKEY);
ssh_message_reply_default(msg);
return 0;
}
}
if (!session->username) {
session->username = strdup(username);
NC_CHECK_ERRMEM_RET(!session->username, 1);
/* configure and count accepted auth methods */
if (local_users_supported) {
if (((auth_client->store == NC_STORE_LOCAL) && (auth_client->pubkey_count)) ||
(auth_client->store == NC_STORE_TRUSTSTORE) || (auth_client->store == NC_STORE_SYSTEM)) {
/* either locally configured pubkeys, or truststore or system (need to check for
* pubkey count, because NC_STORE_LOCAL is the default enum value) */
auth_state->methods |= SSH_AUTH_METHOD_PUBLICKEY;
auth_state->method_count++;
}
if (auth_client->password) {
auth_state->methods |= SSH_AUTH_METHOD_PASSWORD;
auth_state->method_count++;
}
if (auth_client->kb_int_enabled) {
auth_state->methods |= SSH_AUTH_METHOD_INTERACTIVE;
auth_state->method_count++;
}
if (auth_client->none_enabled) {
auth_state->methods |= SSH_AUTH_METHOD_NONE;
auth_state->method_count++;
}
} else {
/* no local users meaning pw, pubkey and kbdint methods are supported, method count is set to 1,
* because only one method is needed for successful auth */
auth_state->methods = SSH_AUTH_METHOD_PUBLICKEY | SSH_AUTH_METHOD_PASSWORD | SSH_AUTH_METHOD_INTERACTIVE;
auth_state->method_count = 1;
}
ssh_set_auth_methods(session->ti.libssh.session, auth_state->methods);
} else {
if (strcmp(username, session->username)) {
/* changing username not allowed */
ERR(session, "User \"%s\" changed its username to \"%s\".", session->username, username);
session->status = NC_STATUS_INVALID;
session->term_reason = NC_SESSION_TERM_OTHER;
return 1;
}
}
/* try authenticating, if local users are supported, then the configured user must authenticate via all of his
* configured auth methods, otherwise for system users just one is needed,
* 0 return indicates success, 1 fail (msg not yet replied to), -1 fail (msg was replied to) */
if (method == SSH_AUTH_METHOD_NONE) {
ret = nc_server_ssh_auth_none(local_users_supported, auth_client, msg);
} else if (method == SSH_AUTH_METHOD_PASSWORD) {
ret = nc_server_ssh_auth_password(session, local_users_supported, auth_client, msg);
} else if (method == SSH_AUTH_METHOD_PUBLICKEY) {
ret = nc_server_ssh_auth_pubkey(session, local_users_supported, auth_client, msg);
} else if (method == SSH_AUTH_METHOD_INTERACTIVE) {
ret = nc_server_ssh_auth_kbdint(session, local_users_supported, auth_client, msg);
} else {
++session->opts.server.ssh_auth_attempts;
VRB(session, "Authentication method \"%s\" not supported.", str_method);
ssh_message_reply_default(msg);
return 0;
}
if (!ret) {
auth_state->success_methods |= method;
auth_state->success_count++;
if (auth_state->success_count < auth_state->method_count) {
/* success, but he needs to do another method */
VRB(session, "User \"%s\" partially authenticated, but still needs to authenticate via the rest of his configured methods.", username);
ssh_set_auth_methods(session->ti.libssh.session, auth_state->methods & ~auth_state->success_methods);
ssh_message_auth_reply_success(msg, 1);
} else {
/* authenticated */
ssh_message_auth_reply_success(msg, 0);
session->flags |= NC_SESSION_SSH_AUTHENTICATED;
VRB(session, "User \"%s\" authenticated.", username);
}
} else if (ret == 1) {
/* failed attempt, msg wasnt yet replied to */
++session->opts.server.ssh_auth_attempts;
VRB(session, "Failed user \"%s\" authentication attempt (#%d).", session->username,
session->opts.server.ssh_auth_attempts);
ssh_message_reply_default(msg);
}
return 0;
}
int
nc_session_ssh_msg(struct nc_session *session, struct nc_server_ssh_opts *opts, ssh_message msg, struct nc_auth_state *auth_state)
{
const char *str_type, *str_subtype = NULL;
int subtype, type, rc, local_users_supported;
const struct ly_ctx *ctx;
struct lys_module *mod;
type = ssh_message_type(msg);
subtype = ssh_message_subtype(msg);
switch (type) {
case SSH_REQUEST_AUTH:
str_type = "request-auth";
switch (subtype) {
case SSH_AUTH_METHOD_NONE:
str_subtype = "none";
break;
case SSH_AUTH_METHOD_PASSWORD:
str_subtype = "password";
break;
case SSH_AUTH_METHOD_PUBLICKEY:
str_subtype = "publickey";
break;
case SSH_AUTH_METHOD_HOSTBASED:
str_subtype = "hostbased";
break;
case SSH_AUTH_METHOD_INTERACTIVE:
str_subtype = "interactive";
break;
case SSH_AUTH_METHOD_GSSAPI_MIC:
str_subtype = "gssapi-mic";
break;
}
break;
case SSH_REQUEST_CHANNEL_OPEN:
str_type = "request-channel-open";
switch (subtype) {
case SSH_CHANNEL_SESSION:
str_subtype = "session";
break;
case SSH_CHANNEL_DIRECT_TCPIP:
str_subtype = "direct-tcpip";
break;
case SSH_CHANNEL_FORWARDED_TCPIP:
str_subtype = "forwarded-tcpip";
break;
case (int)SSH_CHANNEL_X11:
str_subtype = "channel-x11";
break;
case SSH_CHANNEL_UNKNOWN:
/* fallthrough */
default:
str_subtype = "unknown";
break;
}
break;
case SSH_REQUEST_CHANNEL:
str_type = "request-channel";
switch (subtype) {
case SSH_CHANNEL_REQUEST_PTY:
str_subtype = "pty";
break;
case SSH_CHANNEL_REQUEST_EXEC:
str_subtype = "exec";
break;
case SSH_CHANNEL_REQUEST_SHELL:
str_subtype = "shell";
break;
case SSH_CHANNEL_REQUEST_ENV:
str_subtype = "env";
break;
case SSH_CHANNEL_REQUEST_SUBSYSTEM:
str_subtype = "subsystem";
break;
case SSH_CHANNEL_REQUEST_WINDOW_CHANGE:
str_subtype = "window-change";
break;
case SSH_CHANNEL_REQUEST_X11:
str_subtype = "x11";
break;
case SSH_CHANNEL_REQUEST_UNKNOWN:
/* fallthrough */
default:
str_subtype = "unknown";
break;
}
break;
case SSH_REQUEST_SERVICE:
str_type = "request-service";
str_subtype = ssh_message_service_service(msg);
break;
case SSH_REQUEST_GLOBAL:
str_type = "request-global";
switch (subtype) {
case SSH_GLOBAL_REQUEST_TCPIP_FORWARD:
str_subtype = "tcpip-forward";
break;
case SSH_GLOBAL_REQUEST_CANCEL_TCPIP_FORWARD:
str_subtype = "cancel-tcpip-forward";
break;
case SSH_GLOBAL_REQUEST_UNKNOWN:
/* fallthrough */
default:
str_subtype = "unknown";
break;
}
break;
default:
str_type = "unknown";
str_subtype = "unknown";
break;
}
VRB(session, "Received an SSH message \"%s\" of subtype \"%s\".", str_type, str_subtype);
if (!session || (session->status == NC_STATUS_CLOSING) || (session->status == NC_STATUS_INVALID)) {
/* "valid" situation if, for example, receiving some auth or channel request timeouted,
* but we got it now, during session free */
VRB(session, "SSH message arrived on a %s session, the request will be denied.",
(session && session->status == NC_STATUS_CLOSING ? "closing" : "invalid"));
ssh_message_reply_default(msg);
return 0;
}
/*
* process known messages
*/
if (type == SSH_REQUEST_AUTH) {
if (session->flags & NC_SESSION_SSH_AUTHENTICATED) {
ERR(session, "User \"%s\" authenticated, but requested another authentication.", session->username);
ssh_message_reply_default(msg);
return 0;
} else if (!auth_state || !opts) {
/* these two parameters should always be set during an authentication,
* however do a check just in case something goes really wrong, since they
* are not needed for other types of messages
*/
ERRINT;
return 1;
}
/* get libyang ctx from session and ietf-ssh-server yang model from the ctx */
ctx = nc_session_get_ctx(session);
mod = ly_ctx_get_module_latest(ctx, "ietf-ssh-server");
if (!mod) {
ERRINT;
return 1;
}
/* check if local-users-supported feature is enabled */
rc = lys_feature_value(mod, "local-users-supported");
if (!rc) {
/* using users from the YANG data */
local_users_supported = 1;
} else if (rc == LY_ENOT) {
/* using users from the system */
local_users_supported = 0;
} else {
ERRINT;
return 1;
}
/* authenticate */
return nc_server_ssh_auth(session, opts, msg, subtype, str_subtype, local_users_supported, auth_state);
} else if (session->flags & NC_SESSION_SSH_AUTHENTICATED) {
if ((type == SSH_REQUEST_CHANNEL_OPEN) && ((enum ssh_channel_type_e)subtype == SSH_CHANNEL_SESSION)) {
if (nc_server_ssh_channel_open(session, msg)) {
ssh_message_reply_default(msg);
}
return 0;
} else if ((type == SSH_REQUEST_CHANNEL) && ((enum ssh_channel_requests_e)subtype == SSH_CHANNEL_REQUEST_SUBSYSTEM)) {
if (nc_server_ssh_channel_subsystem(session, ssh_message_channel_request_channel(msg),
ssh_message_channel_request_subsystem(msg))) {
ssh_message_reply_default(msg);
} else {
ssh_message_channel_request_reply_success(msg);
}
return 0;
}
}
/* we did not process it */
return 1;
}
/* ret 1 on success, 0 on timeout, -1 on error */
static int
nc_accept_ssh_session_open_netconf_channel(struct nc_session *session, struct nc_server_ssh_opts *opts, int timeout)
{
struct timespec ts_timeout;
ssh_message msg;
DBG(session, "Waiting for \"netconf\" SSH subsystem request...");
if (timeout) {
nc_timeouttime_get(&ts_timeout, timeout * 1000);
}
while (1) {
if (!nc_session_is_connected(session)) {
ERR(session, "Communication SSH socket unexpectedly closed.");
return -1;
}
msg = ssh_message_get(session->ti.libssh.session);
if (msg) {
if (nc_session_ssh_msg(session, opts, msg, NULL)) {
ssh_message_reply_default(msg);
}
ssh_message_free(msg);
}
if (session->ti.libssh.channel && session->flags & NC_SESSION_SSH_SUBSYS_NETCONF) {
return 1;
}
usleep(NC_TIMEOUT_STEP);
if (timeout && (nc_timeouttime_cur_diff(&ts_timeout) < 1)) {
/* timeout */
ERR(session, "Failed to start \"netconf\" SSH subsystem for too long, disconnecting.");
break;
}
}
return 0;
}
/**
* @brief Set hostkeys to be used for an SSH bind.
*
* @param[in] sbind SSH bind to use.
* @param[in] hostkeys Array of hostkeys.
* @param[in] hostkey_count Count of @p hostkeys.
* @return 0 on success.
* @return -1 on error.
*/
static int
nc_ssh_bind_add_hostkeys(ssh_bind sbind, struct nc_server_ssh_opts *opts, uint16_t hostkey_count)
{
uint16_t i;
char *privkey_path;
int ret;
struct nc_asymmetric_key *key = NULL;
for (i = 0; i < hostkey_count; ++i) {
privkey_path = NULL;
/* get the asymmetric key */
if (opts->hostkeys[i].store == NC_STORE_LOCAL) {
/* stored locally */
key = &opts->hostkeys[i].key;
} else {
/* keystore reference, need to get it */
if (nc_server_ssh_ks_ref_get_key(opts->hostkeys[i].ks_ref, &key)) {
return -1;
}
}
privkey_path = nc_server_ssh_privkey_data_to_tmp_file(key->privkey_data, nc_privkey_format_to_str(key->privkey_type));
if (!privkey_path) {
ERR(NULL, "Temporarily storing a host key into a file failed (%s).", strerror(errno));
return -1;
}
ret = ssh_bind_options_set(sbind, SSH_BIND_OPTIONS_HOSTKEY, privkey_path);
/* cleanup */
if (unlink(privkey_path)) {
WRN(NULL, "Removing a temporary host key file \"%s\" failed (%s).", privkey_path, strerror(errno));
}
if (ret != SSH_OK) {
ERR(NULL, "Failed to set hostkey \"%s\" (%s).", opts->hostkeys[i].name, privkey_path);
}
free(privkey_path);
if (ret != SSH_OK) {
return -1;
}
}
return 0;
}
static int
nc_accept_ssh_session_auth(struct nc_session *session, struct nc_server_ssh_opts *opts)
{
struct timespec ts_timeout;
ssh_message msg;
struct nc_auth_state auth_state = {0};
DBG(session, "SSH authentication...");
/* authenticate */
if (opts->auth_timeout) {
nc_timeouttime_get(&ts_timeout, opts->auth_timeout * 1000);
}
while (1) {
if (!nc_session_is_connected(session)) {
ERR(session, "Communication SSH socket unexpectedly closed.");
return -1;
}
msg = ssh_message_get(session->ti.libssh.session);
if (msg) {
if (nc_session_ssh_msg(session, opts, msg, &auth_state)) {
ssh_message_reply_default(msg);
}
ssh_message_free(msg);
}
if (session->flags & NC_SESSION_SSH_AUTHENTICATED) {
break;
}
usleep(NC_TIMEOUT_STEP);
if (opts->auth_timeout && (nc_timeouttime_cur_diff(&ts_timeout) < 1)) {
/* timeout */
break;
}
}
if (!(session->flags & NC_SESSION_SSH_AUTHENTICATED)) {
/* timeout */
if (session->username) {
ERR(session, "User \"%s\" failed to authenticate for too long, disconnecting.", session->username);
} else {
ERR(session, "User failed to authenticate for too long, disconnecting.");
}
return 0;
}
return 1;
}
int
nc_accept_ssh_session(struct nc_session *session, struct nc_server_ssh_opts *opts, int sock, int timeout)
{
ssh_bind sbind = NULL;
int rc = 1, r;
struct timespec ts_timeout;
const char *err_msg, *banner;
/* other transport-specific data */
session->ti_type = NC_TI_SSH;
session->ti.libssh.session = ssh_new();
if (!session->ti.libssh.session) {
ERR(NULL, "Failed to initialize a new SSH session.");
rc = -1;
goto cleanup;
}
sbind = ssh_bind_new();
if (!sbind) {
ERR(session, "Failed to create an SSH bind.");
rc = -1;
goto cleanup;
}
/* configure host keys */
if (nc_ssh_bind_add_hostkeys(sbind, opts, opts->hostkey_count)) {
rc = -1;
goto cleanup;
}
/* configure supported algorithms */
if (opts->hostkey_algs && ssh_bind_options_set(sbind, SSH_BIND_OPTIONS_HOSTKEY_ALGORITHMS, opts->hostkey_algs)) {
rc = -1;
goto cleanup;
}
if (opts->encryption_algs && ssh_bind_options_set(sbind, SSH_BIND_OPTIONS_CIPHERS_S_C, opts->encryption_algs)) {
rc = -1;
goto cleanup;
}
if (opts->kex_algs && ssh_bind_options_set(sbind, SSH_BIND_OPTIONS_KEY_EXCHANGE, opts->kex_algs)) {
rc = -1;
goto cleanup;
}
if (opts->mac_algs && ssh_bind_options_set(sbind, SSH_BIND_OPTIONS_HMAC_S_C, opts->mac_algs)) {
rc = -1;
goto cleanup;
}
/* configure the ssh banner */
if (opts->banner) {
banner = opts->banner;
} else {
banner = "libnetconf2-" NC_VERSION;
}
if (ssh_bind_options_set(sbind, SSH_BIND_OPTIONS_BANNER, banner)) {
rc = -1;
goto cleanup;
}
/* accept new connection on the bind */
if (ssh_bind_accept_fd(sbind, session->ti.libssh.session, sock) == SSH_ERROR) {
ERR(session, "SSH failed to accept a new connection (%s).", ssh_get_error(sbind));
rc = -1;
goto cleanup;
}
sock = -1;
/* set to non-blocking */
ssh_set_blocking(session->ti.libssh.session, 0);
DBG(session, "Performing SSH key exchange...");
if (timeout > -1) {
nc_timeouttime_get(&ts_timeout, timeout);
}
while ((r = ssh_handle_key_exchange(session->ti.libssh.session)) == SSH_AGAIN) {
/* this tends to take longer */
usleep(NC_TIMEOUT_STEP * 20);
if ((timeout > -1) && (nc_timeouttime_cur_diff(&ts_timeout) < 1)) {
break;
}
}
if (r == SSH_AGAIN) {
ERR(session, "SSH key exchange timeout.");
rc = 0;
goto cleanup;
} else if (r != SSH_OK) {
err_msg = ssh_get_error(session->ti.libssh.session);
if (err_msg[0] == '\0') {
err_msg = "hostkey algorithm generated from the hostkey most likely not found in the set of configured hostkey algorithms";
}
ERR(session, "SSH key exchange error (%s).", err_msg);
rc = -1;
goto cleanup;
}
/* authenticate, store auth_timeout in session so we can retrieve it in kb interactive API */
session->data = &opts->auth_timeout;
rc = nc_accept_ssh_session_auth(session, opts);
session->data = NULL;
if (rc != 1) {
goto cleanup;
}
/* open channel and request 'netconf' subsystem */
if ((rc = nc_accept_ssh_session_open_netconf_channel(session, opts, timeout)) != 1) {
goto cleanup;
}
cleanup:
if (sock > -1) {
close(sock);
}
ssh_bind_free(sbind);
return rc;
}
API NC_MSG_TYPE
nc_session_accept_ssh_channel(struct nc_session *orig_session, struct nc_session **session)
{
NC_MSG_TYPE msgtype;
struct nc_session *new_session = NULL;
struct timespec ts_cur;
NC_CHECK_ARG_RET(orig_session, orig_session, session, NC_MSG_ERROR);
if ((orig_session->status == NC_STATUS_RUNNING) && (orig_session->ti_type == NC_TI_SSH) &&
orig_session->ti.libssh.next) {
for (new_session = orig_session->ti.libssh.next;
new_session != orig_session;
new_session = new_session->ti.libssh.next) {
if ((new_session->status == NC_STATUS_STARTING) && new_session->ti.libssh.channel &&
(new_session->flags & NC_SESSION_SSH_SUBSYS_NETCONF)) {
/* we found our session */
break;
}
}
if (new_session == orig_session) {
new_session = NULL;
}
}
if (!new_session) {
ERR(orig_session, "Session does not have a NETCONF SSH channel ready.");
return NC_MSG_ERROR;
}
/* assign new SID atomically */
new_session->id = ATOMIC_INC_RELAXED(server_opts.new_session_id);
/* NETCONF handshake */
msgtype = nc_handshake_io(new_session);
if (msgtype != NC_MSG_HELLO) {
return msgtype;
}
nc_realtime_get(&ts_cur);
new_session->opts.server.session_start = ts_cur;
nc_timeouttime_get(&ts_cur, 0);
new_session->opts.server.last_rpc = ts_cur.tv_sec;
new_session->status = NC_STATUS_RUNNING;
*session = new_session;
return msgtype;
}
API NC_MSG_TYPE
nc_ps_accept_ssh_channel(struct nc_pollsession *ps, struct nc_session **session)
{
uint8_t q_id;
NC_MSG_TYPE msgtype;
struct nc_session *new_session = NULL, *cur_session;
struct timespec ts_cur;
uint16_t i;
NC_CHECK_ARG_RET(NULL, ps, session, NC_MSG_ERROR);
/* LOCK */
if (nc_ps_lock(ps, &q_id, __func__)) {
return NC_MSG_ERROR;
}
for (i = 0; i < ps->session_count; ++i) {
cur_session = ps->sessions[i]->session;
if ((cur_session->status == NC_STATUS_RUNNING) && (cur_session->ti_type == NC_TI_SSH) &&
cur_session->ti.libssh.next) {
/* an SSH session with more channels */
for (new_session = cur_session->ti.libssh.next;
new_session != cur_session;
new_session = new_session->ti.libssh.next) {
if ((new_session->status == NC_STATUS_STARTING) && new_session->ti.libssh.channel &&
(new_session->flags & NC_SESSION_SSH_SUBSYS_NETCONF)) {
/* we found our session */
break;
}
}
if (new_session != cur_session) {
break;
}
new_session = NULL;
}
}
/* UNLOCK */
nc_ps_unlock(ps, q_id, __func__);
if (!new_session) {
ERR(NULL, "No session with a NETCONF SSH channel ready was found.");
return NC_MSG_ERROR;
}
/* assign new SID atomically */
new_session->id = ATOMIC_INC_RELAXED(server_opts.new_session_id);
/* NETCONF handshake */
msgtype = nc_handshake_io(new_session);
if (msgtype != NC_MSG_HELLO) {
return msgtype;
}
nc_realtime_get(&ts_cur);
new_session->opts.server.session_start = ts_cur;
nc_timeouttime_get(&ts_cur, 0);
new_session->opts.server.last_rpc = ts_cur.tv_sec;
new_session->status = NC_STATUS_RUNNING;
*session = new_session;
return msgtype;
}
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