nm: fix filename overflow for WiFi SSIDs with multi-byte characters

src/nm.c

@@ -22,6 +22,7 @@
 #include <sys/stat.h>
 #include <arpa/inet.h>
 #include <net/if.h>
+#include <linux/limits.h>
 
 #include <glib.h>
 #include <glib/gprintf.h>
@@ -1005,7 +1006,16 @@ write_nm_conf_access_point(const NetplanNetDefinition* def, const char* rootdir,
     if (ap) {
         g_autofree char* escaped_ssid = g_uri_escape_string(ap->ssid, NULL, TRUE);
         /* TODO: make use of netplan_netdef_get_output_filename() */
-        conf_path = g_strjoin(NULL, "run/NetworkManager/system-connections/netplan-", escaped_netdef_id, "-", escaped_ssid, ".nmconnection", NULL);
+        g_autofree char* candidate_basename = g_strjoin(NULL, "netplan-", escaped_netdef_id, "-", escaped_ssid, ".nmconnection", NULL);
+        const char* ssid_part = escaped_ssid;
+        g_autofree char* hashed_ssid = NULL;
+        if (strlen(candidate_basename) > NAME_MAX) {
+            /* SSID contains multi-byte chars (e.g. emojis) that percent-encode to too many bytes.
+             * Use SHA-256 of the raw SSID bytes to guarantee a valid-length unique filename. */
+            hashed_ssid = g_compute_checksum_for_string(G_CHECKSUM_SHA256, ap->ssid, -1);
+            ssid_part = hashed_ssid;
+        }
+        conf_path = g_strjoin(NULL, "run/NetworkManager/system-connections/netplan-", escaped_netdef_id, "-", ssid_part, ".nmconnection", NULL);
 
         g_key_file_set_string(kf, "wifi", "ssid", ap->ssid);
         if (ap->mode < NETPLAN_WIFI_MODE_OTHER)

src/util.c

@@ -27,6 +27,7 @@
 #include <sys/stat.h>
 #include <pwd.h>
 #include <grp.h>
+#include <linux/limits.h>
 
 #include <glib.h>
 #include <glib/gprintf.h>
@@ -131,7 +132,7 @@ void _netplan_g_string_free_to_file_with_permissions(GString* s, const char* roo
     if (pw && gr) {
         ret = chown(full_path, pw->pw_uid, gr->gr_gid);
         if (ret != 0) {
-            g_debug("Failed to set owner and group for file %s: %s", full_path, strerror(errno));
+            g_debug("Failed to set owner and group for file %s: %s", full_path, strerror(errno)); // LCOV_EXCL_LINE
         }
     }
 }
@@ -629,7 +630,6 @@ ssize_t
 netplan_get_id_from_nm_filepath(const char* filename, const char* ssid, char* out_buffer, size_t out_buf_size)
 {
     g_autofree gchar* escaped_ssid = NULL;
-    g_autofree gchar* suffix = NULL;
     const char* nm_prefix = "/run/NetworkManager/system-connections/netplan-";
     const char* pos = g_strrstr(filename, nm_prefix);
     const char* start = NULL;
@@ -641,8 +641,15 @@ netplan_get_id_from_nm_filepath(const char* filename, const char* ssid, char* ou
 
     if (ssid) {
         escaped_ssid = g_uri_escape_string(ssid, NULL, TRUE);
-        suffix = g_strdup_printf("-%s.nmconnection", escaped_ssid);
-        end = g_strrstr(filename, suffix);
+        g_autofree char* escaped_suffix = g_strdup_printf("-%s.nmconnection", escaped_ssid);
+        end = g_strrstr(filename, escaped_suffix);
+
+        if (!end) {
+            /* Escaped SSID not found; try SHA-256 hash (used when escaped form exceeded NAME_MAX) */
+            g_autofree char* hashed_ssid = g_compute_checksum_for_string(G_CHECKSUM_SHA256, ssid, -1);
+            g_autofree char* hashed_suffix = g_strdup_printf("-%s.nmconnection", hashed_ssid);
+            end = g_strrstr(filename, hashed_suffix);
+        }
     } else
         end = g_strrstr(filename, ".nmconnection");
 
@@ -673,7 +680,17 @@ netplan_netdef_get_output_filename(const NetplanNetDefinition* netdef, const cha
     if (netdef->backend == NETPLAN_BACKEND_NM) {
         if (ssid) {
             g_autofree char* escaped_ssid = g_uri_escape_string(ssid, NULL, TRUE);
-            conf_path = g_strjoin(NULL, "/run/NetworkManager/system-connections/netplan-", escaped_netdef_id, "-", escaped_ssid, ".nmconnection", NULL);
+            /* Check if the basename would exceed NAME_MAX (255 bytes) */
+            g_autofree char* candidate_basename = g_strjoin(NULL, "netplan-", escaped_netdef_id, "-", escaped_ssid, ".nmconnection", NULL);
+            const char* ssid_part = escaped_ssid;
+            g_autofree char* hashed_ssid = NULL;
+            if (strlen(candidate_basename) > NAME_MAX) {
+                /* SSID contains multi-byte chars (e.g. emojis) that percent-encode to too many bytes.
+                 * Use SHA-256 of the raw SSID bytes to guarantee a valid-length unique filename. */
+                hashed_ssid = g_compute_checksum_for_string(G_CHECKSUM_SHA256, ssid, -1);
+                ssid_part = hashed_ssid;
+            }
+            conf_path = g_strjoin(NULL, "/run/NetworkManager/system-connections/netplan-", escaped_netdef_id, "-", ssid_part, ".nmconnection", NULL);
         } else {
             conf_path = g_strjoin(NULL, "/run/NetworkManager/system-connections/netplan-", escaped_netdef_id, ".nmconnection", NULL);
         }

tests/ctests/test_netplan_misc.c

@@ -3,8 +3,10 @@
 #include <stddef.h>
 #include <setjmp.h>
 
+#include <string.h>
 #include <sys/stat.h>
 #include <netinet/in.h>
+#include <linux/limits.h>
 
 #include <cmocka.h>
 
@@ -185,6 +187,71 @@ test_netplan_netdef_get_output_filename_invalid_backend(__unused void** state)
     assert_int_equal(ret, 0);
 }
 
+void
+test_netplan_netdef_get_output_filename_nm_with_long_ssid(__unused void** state)
+{
+    NetplanNetDefinition netdef;
+    /* NM stores non-ASCII SSIDs as semicolon-delimited decimal bytes.
+     * 20x U+1F600 (😀, UTF-8: F0 9F 98 80) in NM format = "240;159;152;128;" x20
+     * (320 chars, 80 semicolons).  g_uri_escape_string() encodes each ';' as
+     * '%3B', yielding a 480-char encoded SSID.
+     * basename = "netplan-" (8) + "wlan0" (5) + "-" (1) + 480 + ".nmconnection" (13) = 507 > NAME_MAX.
+     * Expects SHA-256 of raw SSID bytes used in filename instead of escaped form. */
+    const char ssid[] =
+        "240;159;152;128;240;159;152;128;240;159;152;128;240;159;152;128;"
+        "240;159;152;128;240;159;152;128;240;159;152;128;240;159;152;128;"
+        "240;159;152;128;240;159;152;128;240;159;152;128;240;159;152;128;"
+        "240;159;152;128;240;159;152;128;240;159;152;128;240;159;152;128;"
+        "240;159;152;128;240;159;152;128;240;159;152;128;240;159;152;128;";
+    char out_buffer[256] = { 0 };
+
+    netdef.backend = NETPLAN_BACKEND_NM;
+    netdef.id = "wlan0";
+
+    ssize_t ret = netplan_netdef_get_output_filename(&netdef, ssid, out_buffer, sizeof(out_buffer) - 1);
+
+    /* Basename must NOT exceed NAME_MAX */
+    const char* basename = strrchr(out_buffer, '/');
+    assert_true(basename != NULL);
+    assert_true(strlen(basename + 1) <= NAME_MAX);
+    /* Must use the expected prefix */
+    assert_true(g_str_has_prefix(out_buffer,
+        "/run/NetworkManager/system-connections/netplan-wlan0-"));
+    /* Must end with .nmconnection */
+    assert_true(g_str_has_suffix(out_buffer, ".nmconnection"));
+    /* Returned size must match string length + 1 */
+    assert_int_equal(ret, (ssize_t)(strlen(out_buffer) + 1));
+    /* Must contain the SHA-256 hash of the raw SSID, not the escaped form */
+    g_autofree char* expected_hash = g_compute_checksum_for_string(G_CHECKSUM_SHA256, ssid, -1);
+    g_autofree char* expected_suffix = g_strdup_printf("-%s.nmconnection", expected_hash);
+    assert_true(g_str_has_suffix(out_buffer, expected_suffix));
+}
+
+void
+test_netplan_get_id_from_nm_filepath_with_hashed_ssid(__unused void** state)
+{
+    /* Same NM decimal-byte SSID as test above; escaped form exceeds NAME_MAX
+     * so netplan_netdef_get_output_filename() uses the SHA-256 hash path.
+     * netplan_get_id_from_nm_filepath() must fall back to the hash when the
+     * escaped suffix is not found in the filename. */
+    const char ssid[] =
+        "240;159;152;128;240;159;152;128;240;159;152;128;240;159;152;128;"
+        "240;159;152;128;240;159;152;128;240;159;152;128;240;159;152;128;"
+        "240;159;152;128;240;159;152;128;240;159;152;128;240;159;152;128;"
+        "240;159;152;128;240;159;152;128;240;159;152;128;240;159;152;128;"
+        "240;159;152;128;240;159;152;128;240;159;152;128;240;159;152;128;";
+    /* Get the hashed filename from the public API */
+    NetplanNetDefinition netdef = { .backend = NETPLAN_BACKEND_NM, .id = "wlan0" };
+    char hashed_path[256] = { 0 };
+    netplan_netdef_get_output_filename(&netdef, ssid, hashed_path, sizeof(hashed_path) - 1);
+
+    char id[16] = { 0 };
+    ssize_t bytes_copied = netplan_get_id_from_nm_filepath(hashed_path, ssid, id, sizeof(id));
+
+    assert_string_equal(id, "wlan0");
+    assert_int_equal(bytes_copied, 6); /* strlen("wlan0") + 1 */
+}
+
 void
 test_netplan_netdef_write_yaml(__unused void** state)
 {
@@ -575,6 +642,8 @@ main()
            cmocka_unit_test(test_netplan_netdef_get_output_filename_networkd),
            cmocka_unit_test(test_netplan_netdef_get_output_filename_buffer_is_too_small),
            cmocka_unit_test(test_netplan_netdef_get_output_filename_invalid_backend),
+           cmocka_unit_test(test_netplan_netdef_get_output_filename_nm_with_long_ssid),
+           cmocka_unit_test(test_netplan_get_id_from_nm_filepath_with_hashed_ssid),
            cmocka_unit_test(test_netplan_netdef_write_yaml),
            cmocka_unit_test(test_netplan_netdef_write_yaml_90NM),
            cmocka_unit_test(test_util_is_route_present),

tests/ctests/test_netplan_nm.c

@@ -2,11 +2,15 @@
 #include <stdarg.h>
 #include <stddef.h>
 #include <setjmp.h>
+#include <string.h>
+#include <sys/stat.h>
+#include <linux/limits.h>
 
 #include <cmocka.h>
 
 #include "netplan.h"
 #include "util-internal.h"
+#include "nm.h"
 
 #include "test_utils.h"
 
@@ -28,6 +32,74 @@ test_write_empty_state(__unused void** state)
     netplan_state_clear(&np_state);
 }
 
+/* A WiFi SSID whose percent-encoded form would make the .nmconnection
+ * basename exceed NAME_MAX (255) must fall back to a SHA-256 digest.
+ *
+ * NM stores non-ASCII SSIDs as semicolon-delimited decimal bytes, e.g.
+ * the emoji U+1F600 (😀, UTF-8: F0 9F 98 80) becomes "240;159;152;128;".
+ * g_uri_escape_string() encodes each ';' as '%3B' (3 chars), so 20 such
+ * emojis → 480-char encoded SSID → 507-byte candidate basename > NAME_MAX.
+ */
+void
+test_write_wifi_long_ssid_uses_hash(__unused void** state)
+{
+    /* 20× U+1F600 (😀) in NM decimal-byte format */
+    const char ssid[] =
+        "240;159;152;128;240;159;152;128;240;159;152;128;240;159;152;128;"
+        "240;159;152;128;240;159;152;128;240;159;152;128;240;159;152;128;"
+        "240;159;152;128;240;159;152;128;240;159;152;128;240;159;152;128;"
+        "240;159;152;128;240;159;152;128;240;159;152;128;240;159;152;128;"
+        "240;159;152;128;240;159;152;128;240;159;152;128;240;159;152;128;";
+
+    g_autofree char* yaml = g_strdup_printf(
+        "network:\n"
+        "  version: 2\n"
+        "  renderer: NetworkManager\n"
+        "  wifis:\n"
+        "    wlan0:\n"
+        "      dhcp4: true\n"
+        "      access-points:\n"
+        "        \"%s\":\n"
+        "          password: \"s0s3kr1t\"\n",
+        ssid);
+
+    NetplanState* np_state = load_string_to_netplan_state(yaml);
+    assert_non_null(np_state);
+    assert_true(netplan_state_get_netdefs_size(np_state) > 0);
+
+    NetplanNetDefinition* netdef = netplan_state_get_netdef(np_state, "wlan0");
+    assert_non_null(netdef);
+
+    char template[] = "/tmp/netplan_nm_test.XXXXXX";
+    char* rootdir = mkdtemp(template);
+    assert_non_null(rootdir);
+
+    gboolean has_been_written = FALSE;
+    GError* error = NULL;
+    assert_true(_netplan_netdef_write_nm(np_state, netdef, rootdir, &has_been_written, &error));
+    assert_null(error);
+    assert_true(has_been_written);
+
+    /* The output filename must use the SHA-256 digest of the raw SSID */
+    g_autofree char* hash = g_compute_checksum_for_string(G_CHECKSUM_SHA256, ssid, -1);
+    g_autofree char* expected = g_strdup_printf(
+        "%s/run/NetworkManager/system-connections/netplan-wlan0-%s.nmconnection",
+        rootdir, hash);
+
+    assert_true(g_file_test(expected, G_FILE_TEST_EXISTS));
+
+    /* Basename must be within NAME_MAX */
+    const char* basename = strrchr(expected, '/');
+    assert_true(strlen(basename + 1) <= NAME_MAX);
+
+    /* Cleanup */
+    const gchar *rm_argv[] = { "/bin/rm", "-rf", rootdir, NULL };
+    g_spawn_sync(NULL, (gchar**)rm_argv, NULL, G_SPAWN_DEFAULT,
+                 NULL, NULL, NULL, NULL, NULL, NULL);
+
+    netplan_state_clear(&np_state);
+}
+
 
 int
 setup(__unused void** state)
@@ -47,6 +119,7 @@ main()
 
     const struct CMUnitTest tests[] = {
         cmocka_unit_test(test_write_empty_state),
+        cmocka_unit_test(test_write_wifi_long_ssid_uses_hash),
     };
 
     return cmocka_run_group_tests(tests, setup, tear_down);