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Add strict validation mode to ssh_config_parse_uri in config_parser

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Signed-off-by: Rui Li <ruili3422@gmail.com>
Reviewed-by: Jakub Jelen <jjelen@redhat.com>
This commit is contained in:
Rui Li
2026-03-06 21:31:44 -08:00
committed by Jakub Jelen
parent 8782fcec18
commit 1ab8a35c5d
5 changed files with 68 additions and 16 deletions
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8
include/libssh/config_parser.h
View File

@@ -54,6 +54,11 @@ int ssh_config_get_yesno(char **str, int notfound);
* be stored or NULL if we do not care about the result.
* @param[in] ignore_port Set to true if we should not attempt to parse
* port number.
* @param[in] strict Set to true to validate hostname against RFC1035
* (for resolving to a real host).
* Set to false to only reject shell metacharacters
* (allowing config aliases with non-RFC1035 chars
* like underscores, resolved later via Hostname).
*
* @returns SSH_OK if the provided string is in format of SSH URI,
* SSH_ERROR on failure
@@ -62,7 +67,8 @@ int ssh_config_parse_uri(const char *tok,
char **username,
char **hostname,
char **port,
bool ignore_port);
bool ignore_port,
bool strict);
/**
* @brief: Parse the ProxyJump configuration line and if parsing,

5
src/config.c
View File

@@ -544,6 +544,7 @@ ssh_config_parse_proxy_jump(ssh_session session, const char *s, bool do_parsing)
&jump_host->username,
&jump_host->hostname,
&port,
false,
false);
if (rv != SSH_OK) {
ssh_set_error_invalid(session);
@@ -566,7 +567,7 @@ ssh_config_parse_proxy_jump(ssh_session session, const char *s, bool do_parsing)
}
} else if (parse_entry) {
/* We actually care only about the first item */
rv = ssh_config_parse_uri(cp, &username, &hostname, &port, false);
rv = ssh_config_parse_uri(cp, &username, &hostname, &port, false, false);
if (rv != SSH_OK) {
ssh_set_error_invalid(session);
goto out;
@@ -582,7 +583,7 @@ ssh_config_parse_proxy_jump(ssh_session session, const char *s, bool do_parsing)
}
} else {
/* The rest is just sanity-checked to avoid failures later */
rv = ssh_config_parse_uri(cp, NULL, NULL, NULL, false);
rv = ssh_config_parse_uri(cp, NULL, NULL, NULL, false, false);
if (rv != SSH_OK) {
ssh_set_error_invalid(session);
goto out;

31
src/config_parser.c
View File

@@ -172,7 +172,8 @@ int ssh_config_parse_uri(const char *tok,
char **username,
char **hostname,
char **port,
bool ignore_port)
bool ignore_port,
bool strict)
{
char *endp = NULL;
long port_n;
@@ -243,13 +244,31 @@ int ssh_config_parse_uri(const char *tok,
if (*hostname == NULL) {
goto error;
}
/* if not an ip, check syntax */
rc = ssh_is_ipaddr(*hostname);
if (rc == 0) {
rc = ssh_check_hostname_syntax(*hostname);
if (rc != SSH_OK) {
if (strict) {
/* if not an ip, check syntax */
rc = ssh_is_ipaddr(*hostname);
if (rc == 0) {
rc = ssh_check_hostname_syntax(*hostname);
if (rc != SSH_OK) {
goto error;
}
}
} else {
/* Reject shell metacharacters to allow config aliases with
* non-RFC1035 chars (e.g. %, _). Modeled on OpenSSH's
* valid_hostname() in ssh.c. */
const char *c = NULL;
if ((*hostname)[0] == '-') {
goto error;
}
for (c = *hostname; *c != '\0'; c++) {
char *is_meta = strchr("'`\"$\\;&<>|(){},", *c);
int is_space = isspace((unsigned char)*c);
int is_ctrl = iscntrl((unsigned char)*c);
if (is_meta != NULL || is_space || is_ctrl) {
goto error;
}
}
}
}
/* Skip also the closing bracket */

2
src/options.c
View File

@@ -718,7 +718,7 @@ int ssh_options_set(ssh_session session, enum ssh_options_e type,
return -1;
} else {
char *username = NULL, *hostname = NULL;
rc = ssh_config_parse_uri(value, &username, &hostname, NULL, true);
rc = ssh_config_parse_uri(value, &username, &hostname, NULL, true, true);
if (rc != SSH_OK) {
ssh_set_error_invalid(session);
return -1;

38
tests/unittests/torture_config.c
View File

@@ -2762,21 +2762,21 @@ static void torture_config_parse_uri(void **state)
(void)state; /* unused */
rc = ssh_config_parse_uri("localhost", &username, &hostname, &port, false);
rc = ssh_config_parse_uri("localhost", &username, &hostname, &port, false, true);
assert_return_code(rc, errno);
assert_null(username);
assert_string_equal(hostname, "localhost");
SAFE_FREE(hostname);
assert_null(port);
rc = ssh_config_parse_uri("1.2.3.4", &username, &hostname, &port, false);
rc = ssh_config_parse_uri("1.2.3.4", &username, &hostname, &port, false, true);
assert_return_code(rc, errno);
assert_null(username);
assert_string_equal(hostname, "1.2.3.4");
SAFE_FREE(hostname);
assert_null(port);
rc = ssh_config_parse_uri("1.2.3.4:2222", &username, &hostname, &port, false);
rc = ssh_config_parse_uri("1.2.3.4:2222", &username, &hostname, &port, false, true);
assert_return_code(rc, errno);
assert_null(username);
assert_string_equal(hostname, "1.2.3.4");
@@ -2784,7 +2784,7 @@ static void torture_config_parse_uri(void **state)
assert_string_equal(port, "2222");
SAFE_FREE(port);
rc = ssh_config_parse_uri("[1:2:3::4]:2222", &username, &hostname, &port, false);
rc = ssh_config_parse_uri("[1:2:3::4]:2222", &username, &hostname, &port, false, true);
assert_return_code(rc, errno);
assert_null(username);
assert_string_equal(hostname, "1:2:3::4");
@@ -2793,13 +2793,39 @@ static void torture_config_parse_uri(void **state)
SAFE_FREE(port);
/* do not want port */
rc = ssh_config_parse_uri("1:2:3::4", &username, &hostname, NULL, true);
rc = ssh_config_parse_uri("1:2:3::4", &username, &hostname, NULL, true, true);
assert_return_code(rc, errno);
assert_null(username);
assert_string_equal(hostname, "1:2:3::4");
SAFE_FREE(hostname);
rc = ssh_config_parse_uri("user -name@", &username, NULL, NULL, true);
rc = ssh_config_parse_uri("user -name@", &username, NULL, NULL, true, true);
assert_int_equal(rc, SSH_ERROR);
/* Non-strict accepts non-RFC1035 chars (e.g. _, %) */
rc = ssh_config_parse_uri("customer_1", &username, &hostname, NULL, true, false);
assert_return_code(rc, errno);
assert_null(username);
assert_string_equal(hostname, "customer_1");
SAFE_FREE(hostname);
rc = ssh_config_parse_uri("admin@%prod", &username, &hostname, NULL, true, false);
assert_return_code(rc, errno);
assert_string_equal(username, "admin");
assert_string_equal(hostname, "%prod");
SAFE_FREE(username);
SAFE_FREE(hostname);
/* Strict rejects what non-strict accepts */
rc = ssh_config_parse_uri("customer_1", &username, &hostname, NULL, true, true);
assert_int_equal(rc, SSH_ERROR);
/* Non-strict rejects shell metacharacters */
rc = ssh_config_parse_uri("host;cmd", &username, &hostname, NULL, true, false);
assert_int_equal(rc, SSH_ERROR);
/* Non-strict rejects leading dash */
rc = ssh_config_parse_uri("-host", &username, &hostname, NULL, true, false);
assert_int_equal(rc, SSH_ERROR);
}