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libssh/CVE-2026-0965.patch
Pavol Žáčik 048ffad847
Backport low/medium CVE patches 
Resolves: RHEL-150661
Resolves: CVE-2025-4877
Resolves: CVE-2025-4878
Resolves: CVE-2025-5351
Resolves: CVE-2025-8114
Resolves: CVE-2025-8277
Resolves: CVE-2026-0964
Resolves: CVE-2026-0965
Resolves: CVE-2026-0966
Resolves: CVE-2026-0967
Resolves: CVE-2026-0968
2026-02-19 18:50:28 +01:00

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From 63079a26261b5ea6736fcdf68077135e7f2c991d Mon Sep 17 00:00:00 2001
From: Jakub Jelen <jjelen@redhat.com>
Date: Thu, 11 Dec 2025 17:33:19 +0100
Subject: [PATCH] CVE-2026-0965 config: Do not attempt to read non-regular and
too large configuration files
Changes also the reading of known_hosts to use the new helper function
Signed-off-by: Jakub Jelen <jjelen@redhat.com>
Reviewed-by: Andreas Schneider <asn@cryptomilk.org>
(cherry picked from commit a5eb30dbfd8f3526b2d04bd9f0a3803b665f5798)
---
include/libssh/misc.h | 4 ++
include/libssh/priv.h | 3 ++
src/bind_config.c | 4 +-
src/config.c | 5 ++-
src/dh-gex.c | 4 +-
src/known_hosts.c | 2 +-
src/knownhosts.c | 2 +-
src/misc.c | 74 ++++++++++++++++++++++++++++++++
tests/unittests/torture_config.c | 19 ++++++++
9 files changed, 109 insertions(+), 8 deletions(-)
diff --git a/include/libssh/misc.h b/include/libssh/misc.h
index 47a423f2..3452251d 100644
--- a/include/libssh/misc.h
+++ b/include/libssh/misc.h
@@ -21,6 +21,8 @@
#ifndef MISC_H_
#define MISC_H_
+#include <stdio.h>
+
/* in misc.c */
/* gets the user home dir. */
char *ssh_get_user_home_dir(void);
@@ -102,4 +104,6 @@ char *ssh_strreplace(const char *src, const char *pattern, const char *repl);
int ssh_check_hostname_syntax(const char *hostname);
+FILE *ssh_strict_fopen(const char *filename, size_t max_file_size);
+
#endif /* MISC_H_ */
diff --git a/include/libssh/priv.h b/include/libssh/priv.h
index bab761b0..876ea4ed 100644
--- a/include/libssh/priv.h
+++ b/include/libssh/priv.h
@@ -434,4 +434,7 @@ bool is_ssh_initialized(void);
#define SSH_ERRNO_MSG_MAX 1024
char *ssh_strerror(int err_num, char *buf, size_t buflen);
+/** The default maximum file size for a configuration file */
+#define SSH_MAX_CONFIG_FILE_SIZE 16 * 1024 * 1024
+
#endif /* _LIBSSH_PRIV_H */
diff --git a/src/bind_config.c b/src/bind_config.c
index 9e4a7fd4..c12f1003 100644
--- a/src/bind_config.c
+++ b/src/bind_config.c
@@ -212,7 +212,7 @@ local_parse_file(ssh_bind bind,
return;
}
- f = fopen(filename, "r");
+ f = ssh_strict_fopen(filename, SSH_MAX_CONFIG_FILE_SIZE);
if (f == NULL) {
SSH_LOG(SSH_LOG_RARE, "Cannot find file %s to load",
filename);
@@ -636,7 +636,7 @@ int ssh_bind_config_parse_file(ssh_bind bind, const char *filename)
* option to be redefined later by another file. */
uint8_t seen[BIND_CFG_MAX] = {0};
- f = fopen(filename, "r");
+ f = ssh_strict_fopen(filename, SSH_MAX_CONFIG_FILE_SIZE);
if (f == NULL) {
return 0;
}
diff --git a/src/config.c b/src/config.c
index 94b70d58..bf349812 100644
--- a/src/config.c
+++ b/src/config.c
@@ -215,7 +215,7 @@ local_parse_file(ssh_session session,
return;
}
- f = fopen(filename, "r");
+ f = ssh_strict_fopen(filename, SSH_MAX_CONFIG_FILE_SIZE);
if (f == NULL) {
SSH_LOG(SSH_LOG_RARE, "Cannot find file %s to load",
filename);
@@ -1205,8 +1205,9 @@ int ssh_config_parse_file(ssh_session session, const char *filename)
int parsing, rv;
bool global = 0;
- f = fopen(filename, "r");
+ f = ssh_strict_fopen(filename, SSH_MAX_CONFIG_FILE_SIZE);
if (f == NULL) {
+ /* The underlying function logs the reasons */
return 0;
}
diff --git a/src/dh-gex.c b/src/dh-gex.c
index b022f09e..81219586 100644
--- a/src/dh-gex.c
+++ b/src/dh-gex.c
@@ -520,9 +520,9 @@ static int ssh_retrieve_dhgroup(char *moduli_file,
}
if (moduli_file != NULL)
- moduli = fopen(moduli_file, "r");
+ moduli = ssh_strict_fopen(moduli_file, SSH_MAX_CONFIG_FILE_SIZE);
else
- moduli = fopen(MODULI_FILE, "r");
+ moduli = ssh_strict_fopen(MODULI_FILE, SSH_MAX_CONFIG_FILE_SIZE);
if (moduli == NULL) {
char err_msg[SSH_ERRNO_MSG_MAX] = {0};
diff --git a/src/known_hosts.c b/src/known_hosts.c
index f660a6f3..ba2ae4d5 100644
--- a/src/known_hosts.c
+++ b/src/known_hosts.c
@@ -83,7 +83,7 @@ static struct ssh_tokens_st *ssh_get_knownhost_line(FILE **file,
struct ssh_tokens_st *tokens = NULL;
if (*file == NULL) {
- *file = fopen(filename,"r");
+ *file = ssh_strict_fopen(filename, SSH_MAX_CONFIG_FILE_SIZE);
if (*file == NULL) {
return NULL;
}
diff --git a/src/knownhosts.c b/src/knownhosts.c
index 62777ad2..e4865ac2 100644
--- a/src/knownhosts.c
+++ b/src/knownhosts.c
@@ -232,7 +232,7 @@ static int ssh_known_hosts_read_entries(const char *match,
FILE *fp = NULL;
int rc;
- fp = fopen(filename, "r");
+ fp = ssh_strict_fopen(filename, SSH_MAX_CONFIG_FILE_SIZE);
if (fp == NULL) {
char err_msg[SSH_ERRNO_MSG_MAX] = {0};
SSH_LOG(SSH_LOG_TRACE, "Failed to open the known_hosts file '%s': %s",
diff --git a/src/misc.c b/src/misc.c
index 7bb431b6..6607775e 100644
--- a/src/misc.c
+++ b/src/misc.c
@@ -37,6 +37,7 @@
#endif /* _WIN32 */
#include <errno.h>
+#include <fcntl.h>
#include <limits.h>
#include <stdio.h>
#include <string.h>
@@ -2074,4 +2075,77 @@ int ssh_check_hostname_syntax(const char *hostname)
return SSH_OK;
}
+/**
+ * @internal
+ *
+ * @brief Safely open a file containing some configuration.
+ *
+ * Runs checks if the file can be used as some configuration file (is regular
+ * file and is not too large). If so, returns the opened file (for reading).
+ * Otherwise logs error and returns `NULL`.
+ *
+ * @param filename The path to the file to open.
+ * @param max_file_size Maximum file size that is accepted.
+ *
+ * @returns the opened file or `NULL` on error.
+ */
+FILE *ssh_strict_fopen(const char *filename, size_t max_file_size)
+{
+ FILE *f = NULL;
+ struct stat sb;
+ char err_msg[SSH_ERRNO_MSG_MAX] = {0};
+ int r, fd;
+
+ /* open first to avoid TOCTOU */
+ fd = open(filename, O_RDONLY);
+ if (fd == -1) {
+ SSH_LOG(SSH_LOG_TRACE,
+ "Failed to open a file %s for reading: %s",
+ filename,
+ ssh_strerror(errno, err_msg, SSH_ERRNO_MSG_MAX));
+ return NULL;
+ }
+
+ /* Check the file is sensible for a configuration file */
+ r = fstat(fd, &sb);
+ if (r != 0) {
+ SSH_LOG(SSH_LOG_TRACE,
+ "Failed to stat %s: %s",
+ filename,
+ ssh_strerror(errno, err_msg, SSH_ERRNO_MSG_MAX));
+ close(fd);
+ return NULL;
+ }
+ if ((sb.st_mode & S_IFMT) != S_IFREG) {
+ SSH_LOG(SSH_LOG_TRACE,
+ "The file %s is not a regular file: skipping",
+ filename);
+ close(fd);
+ return NULL;
+ }
+
+ if ((size_t)sb.st_size > max_file_size) {
+ SSH_LOG(SSH_LOG_TRACE,
+ "The file %s is too large (%jd MB > %zu MB): skipping",
+ filename,
+ (intmax_t)sb.st_size / 1024 / 1024,
+ max_file_size / 1024 / 1024);
+ close(fd);
+ return NULL;
+ }
+
+ f = fdopen(fd, "r");
+ if (f == NULL) {
+ SSH_LOG(SSH_LOG_TRACE,
+ "Failed to open a file %s for reading: %s",
+ filename,
+ ssh_strerror(r, err_msg, SSH_ERRNO_MSG_MAX));
+ close(fd);
+ return NULL;
+ }
+
+ /* the flcose() will close also the underlying fd */
+ return f;
+}
+
/** @} */
diff --git a/tests/unittests/torture_config.c b/tests/unittests/torture_config.c
index 995a5213..70ecfb95 100644
--- a/tests/unittests/torture_config.c
+++ b/tests/unittests/torture_config.c
@@ -2237,6 +2237,23 @@ static void torture_config_parse_uri(void **state)
SAFE_FREE(hostname);
}
+/* Invalid configuration files
+ */
+static void torture_config_invalid(void **state)
+{
+ ssh_session session = *state;
+
+ ssh_options_set(session, SSH_OPTIONS_HOST, "Bar");
+
+ /* non-regular file -- ignored (or missing on non-unix) so OK */
+ _parse_config(session, "/dev/random", NULL, SSH_OK);
+
+#ifndef _WIN32
+ /* huge file -- ignored (or missing on non-unix) so OK */
+ _parse_config(session, "/proc/kcore", NULL, SSH_OK);
+#endif
+}
+
int torture_run_tests(void)
{
int rc;
@@ -2323,6 +2340,8 @@ int torture_run_tests(void)
setup_no_sshdir, teardown),
cmocka_unit_test_setup_teardown(torture_config_parse_uri,
setup, teardown),
+ cmocka_unit_test_setup_teardown(torture_config_invalid,
+ setup, teardown),
};
--
2.53.0
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