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knownhosts: Use ssh_mkdirs() instead of ssh_mkdir()

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Previously, if the path to known_hosts file set through
SSH_OPTIONS_KNOWNHOSTS included missing directories,
ssh_session_update_known_hosts() would fail.  The added test case checks
that this is not the case anymore.

The logic of checking if the directory is accessible before creating it
was replaced by creating the directory if opening the file failed.  This
is to minimize the risk of TOCTOU race conditions.

Fixes: T166

Signed-off-by: Anderson Toshiyuki Sasaki <ansasaki@redhat.com>
Reviewed-by: Andreas Schneider <asn@cryptomilk.org>
This commit is contained in:
Anderson Toshiyuki Sasaki
2019-07-31 15:48:48 +02:00
committed by Andreas Schneider
parent 742918cb1c
commit 5b18bcb0ac
3 changed files with 109 additions and 47 deletions
Download Patch File Download Diff File Expand all files Collapse all files

55
src/known_hosts.c
View File

@@ -496,6 +496,7 @@ int ssh_write_knownhost(ssh_session session) {
FILE *file;
char *buffer;
char *dir;
int rc;
if (session->opts.knownhosts == NULL) {
if (ssh_options_apply(session) < 0) {
@@ -504,29 +505,41 @@ int ssh_write_knownhost(ssh_session session) {
}
}
/* Check if directory exists and create it if not */
dir = ssh_dirname(session->opts.knownhosts);
if (dir == NULL) {
ssh_set_error(session, SSH_FATAL, "%s", strerror(errno));
return SSH_ERROR;
}
if (!ssh_file_readaccess_ok(dir)) {
if (ssh_mkdir(dir, 0700) < 0) {
ssh_set_error(session, SSH_FATAL,
"Cannot create %s directory.", dir);
SAFE_FREE(dir);
return SSH_ERROR;
}
}
SAFE_FREE(dir);
errno = 0;
file = fopen(session->opts.knownhosts, "a");
if (file == NULL) {
ssh_set_error(session, SSH_FATAL,
"Couldn't open known_hosts file %s for appending: %s",
session->opts.knownhosts, strerror(errno));
return SSH_ERROR;
if (errno == ENOENT) {
dir = ssh_dirname(session->opts.knownhosts);
if (dir == NULL) {
ssh_set_error(session, SSH_FATAL, "%s", strerror(errno));
return SSH_ERROR;
}
rc = ssh_mkdirs(dir, 0700);
if (rc < 0) {
ssh_set_error(session, SSH_FATAL,
"Cannot create %s directory: %s",
dir, strerror(errno));
SAFE_FREE(dir);
return SSH_ERROR;
}
SAFE_FREE(dir);
errno = 0;
file = fopen(session->opts.knownhosts, "a");
if (file == NULL) {
ssh_set_error(session, SSH_FATAL,
"Couldn't open known_hosts file %s"
" for appending: %s",
session->opts.knownhosts, strerror(errno));
return SSH_ERROR;
}
} else {
ssh_set_error(session, SSH_FATAL,
"Couldn't open known_hosts file %s for appending: %s",
session->opts.knownhosts, strerror(errno));
return SSH_ERROR;
}
}
buffer = ssh_dump_knownhost(session);

59
src/knownhosts.c
View File

@@ -979,34 +979,41 @@ int ssh_session_update_known_hosts(ssh_session session)
}
}
/* Check if directory exists and create it if not */
dir = ssh_dirname(session->opts.knownhosts);
if (dir == NULL) {
ssh_set_error(session, SSH_FATAL, "%s", strerror(errno));
return SSH_ERROR;
}
rc = ssh_file_readaccess_ok(dir);
if (rc == 0) {
rc = ssh_mkdir(dir, 0700);
} else {
rc = 0;
}
if (rc != 0) {
ssh_set_error(session, SSH_FATAL,
"Cannot create %s directory.", dir);
SAFE_FREE(dir);
return SSH_ERROR;
}
SAFE_FREE(dir);
errno = 0;
fp = fopen(session->opts.knownhosts, "a");
if (fp == NULL) {
ssh_set_error(session, SSH_FATAL,
"Couldn't open known_hosts file %s for appending: %s",
session->opts.knownhosts, strerror(errno));
return SSH_ERROR;
if (errno == ENOENT) {
dir = ssh_dirname(session->opts.knownhosts);
if (dir == NULL) {
ssh_set_error(session, SSH_FATAL, "%s", strerror(errno));
return SSH_ERROR;
}
rc = ssh_mkdirs(dir, 0700);
if (rc < 0) {
ssh_set_error(session, SSH_FATAL,
"Cannot create %s directory: %s",
dir, strerror(errno));
SAFE_FREE(dir);
return SSH_ERROR;
}
SAFE_FREE(dir);
errno = 0;
fp = fopen(session->opts.knownhosts, "a");
if (fp == NULL) {
ssh_set_error(session, SSH_FATAL,
"Couldn't open known_hosts file %s"
" for appending: %s",
session->opts.knownhosts, strerror(errno));
return SSH_ERROR;
}
} else {
ssh_set_error(session, SSH_FATAL,
"Couldn't open known_hosts file %s for appending: %s",
session->opts.knownhosts, strerror(errno));
return SSH_ERROR;
}
}
rc = ssh_session_export_known_hosts_entry(session, &entry);

42
tests/client/torture_knownhosts_verify.c
View File

@@ -35,6 +35,8 @@
#define BAD_RSA "AAAAB3NzaC1yc2EAAAADAQABAAABAQDXvXuawzaArEwkLIXTz/EWywLOCtqQL3P9yKkrhz6AplXP2PhOh5pyxa1VfGKe453jNeYBJ0ROto3BshXgZXbo86oLXTkbe0gO5xi3r5WjXxjOFvRRTLot5fPLNDOv9+TnsPmkNn0iIeyPnfrcPIyjWt5zSWUfkNC8oNHxsiSshjpbJvTXSDipukpUy41d7jg4uWGuonMTF7yu7HfuHqq7lhb0WlwSpfbqAbfYARBddcdcARyhix4RMWZZqVY20H3Vsjq8bjKC+NJXFce1PRg+qcOWQdlXEei4dkzAvHvfQRx1TjzkrBZ6B6thmZtyeb9IsiB0tg2g0JN2VTAGkxqp"
const char template[] = "temp_dir_XXXXXX";
static int sshd_group_setup(void **state)
{
torture_setup_sshd_server(state, false);
@@ -414,6 +416,43 @@ static void torture_knownhosts_conflict(void **state)
/* session will be freed by session_teardown() */
}
static void torture_knownhosts_new_file(void **state)
{
struct torture_state *s = *state;
ssh_session session = s->ssh.session;
enum ssh_known_hosts_e found;
int rc;
char new_known_hosts[256];
char *tmp_dir = NULL;
ssize_t count = 0;
/* Create a disposable directory */
tmp_dir = torture_make_temp_dir(template);
assert_non_null(tmp_dir);
count = snprintf(new_known_hosts, sizeof(new_known_hosts),
"%s/a/b/c/d/known_hosts", tmp_dir);
assert_return_code(count, errno);
rc = ssh_options_set(session, SSH_OPTIONS_KNOWNHOSTS, new_known_hosts);
assert_ssh_return_code(session, rc);
rc = ssh_connect(session);
assert_ssh_return_code(session, rc);
rc = ssh_session_update_known_hosts(session);
assert_ssh_return_code(session, rc);
found = ssh_session_is_known_server(session);
assert_int_equal(found, SSH_KNOWN_HOSTS_OK);
/* Cleanup */
torture_rmdirs(tmp_dir);
SAFE_FREE(tmp_dir);
}
int torture_run_tests(void) {
int rc;
struct CMUnitTest tests[] = {
@@ -438,6 +477,9 @@ int torture_run_tests(void) {
cmocka_unit_test_setup_teardown(torture_knownhosts_duplicate,
session_setup,
session_teardown),
cmocka_unit_test_setup_teardown(torture_knownhosts_new_file,
session_setup,
session_teardown),
};
ssh_init();