Fix global hotkeys not working on some systems (filesystem is mounted with nosuid

1 files changed, 163 insertions, 38 deletions

diff --git a/main.c b/main.c
index 314d274..68bb4c2 100644
--- a/main.c
+++ b/main.c
@@ -32,16 +32,23 @@ static bool readlink_realpath(const char *filepath, char *buffer) {
     return true;
 }
 
-static bool file_has_sys_admin_capability(const char *filepath) {
+static bool file_has_capabilities(const char *filepath, const cap_value_t *caps, int num_caps) {
     cap_t cap = cap_get_file(filepath);
     if(!cap)
         return false;
 
-    cap_flag_value_t res = CAP_CLEAR;
-    cap_get_flag(cap, CAP_SYS_ADMIN, CAP_PERMITTED, &res);
-    bool cap_set = res == CAP_SET;
+    bool has_caps = true;
+    for(int i = 0; i < num_caps; ++i) {
+        cap_flag_value_t res = CAP_CLEAR;
+        cap_get_flag(cap, caps[i], CAP_PERMITTED, &res);
+        if(res != CAP_SET) {
+            has_caps = false;
+            break;
+        }
+    }
+
     cap_free(cap);
-    return cap_set;
+    return has_caps;
 }
 
 static bool file_set_capabilities(const char *filepath, const cap_value_t *caps_to_set, int num_caps_to_set) {
@@ -64,6 +71,89 @@ static bool file_set_capabilities(const char *filepath, const cap_value_t *caps_
     return res == 0;
 }
 
+static const char* get_column(const char *str, int size, int *column_size, int column) {
+    *column_size = 0;
+    int current_column = 0;
+    int i = 0;
+    for(; column > 0 && i < size; ++i) {
+        if(str[i] == ' ') {
+            ++current_column;
+            if(current_column == column) {
+                ++i;
+                break;
+            }
+        }
+    }
+
+    const int column_start = i;
+    for(; i < size; ++i) {
+        if(str[i] == ' ') {
+            *column_size = i - column_start;
+            return str + column_start;
+        }
+    }
+
+    *column_size = size;
+    return str;
+}
+
+static bool mount_has_flag(const char *flags, int flags_size, const char *flag_to_find) {
+    if(flags_size == 0)
+        return false;
+
+    const int flag_to_find_size = strlen(flag_to_find);
+    int offset = 0;
+    for(;;) {
+        const char *p = memmem(flags + offset, flags_size - offset, flag_to_find, flag_to_find_size);
+        if(!p)
+            return false;
+
+        offset = p - flags;
+        const char prev_char = offset > 0 ? flags[offset - 1] : ',';
+        const char next_char = offset + flag_to_find_size < flags_size ? flags[offset + flag_to_find_size] : ',';
+        if((prev_char == ',' || prev_char == '\n') && (next_char == ',' || next_char == '\n'))
+            return true;
+    }
+
+    return false;
+}
+
+static bool mount_has_setuid_permission(const char *path) {
+    FILE *f = fopen("/proc/mounts", "rb");
+    if(!f) {
+        fprintf(stderr, "Error: failed to open /proc/mounts\n");
+        // Assume it's ok and just continue
+        return true;
+    }
+
+    // Assume there is permission if it can't be found
+    bool has_permission = true;
+    const int path_size = strlen(path);
+    char line[1024];
+    while(fgets(line, sizeof(line), f)) {
+        const int line_size = strlen(line);
+        int mount_point_size = 0;
+        const char *mount_point = get_column(line, line_size, &mount_point_size, 1);
+        if(!mount_point)
+            continue;
+
+        if(mount_point && mount_point_size == path_size && memcmp(mount_point, path, mount_point_size) == 0) {
+            int flags_size = 0;
+            const char *flags = get_column(line, line_size, &flags_size, 3);
+            if(!flags)
+                continue;
+
+            const bool has_rw = mount_has_flag(flags, flags_size, "rw");
+            const bool has_nosuid = mount_has_flag(flags, flags_size, "nosuid");
+            has_permission = has_rw && !has_nosuid;
+            break;
+        }
+    }
+
+    fclose(f);
+    return has_permission;
+}
+
 static bool create_local_kms_server_proxy_directory(const char *home) {
     char path[PATH_MAX];
     int err;
@@ -139,14 +229,7 @@ static bool copy_file_atomic(const char *source_path, const char *dest_path) {
     return res;
 }
 
-static void usage(void) {
-    fprintf(stderr, "usage alt.1: kms-server-proxy <initial_socket_path> <card_path> <user_homepath>\n");
-    fprintf(stderr, "usage alt.2: kms-server-proxy setup-gsr-ui [user_homepath]\n");
-    fprintf(stderr, "usage alt.3: kms-server-proxy launch-gsr-global-hotkeys <user_homepath> [args...]\n");
-    exit(1);
-}
-
-static bool set_gsr_files_set_permissions_and_capabilities(const char *kms_server_proxy_local_filepath) {
+static bool gsr_files_set_permissions_and_capabilities(const char *kms_server_proxy_local_filepath) {
     /* owner: read/write/execute, group: read/execute, public: read/execute */
     if(chmod(kms_server_proxy_local_filepath, 0755) != 0) {
         fprintf(stderr, "Error: failed to set %s permissions\n", kms_server_proxy_local_filepath);
@@ -158,7 +241,7 @@ static bool set_gsr_files_set_permissions_and_capabilities(const char *kms_serve
         return false;
     }
 
-    if(!file_set_capabilities(kms_server_proxy_local_filepath, (const cap_value_t[]){ CAP_SYS_ADMIN, CAP_SETFCAP, CAP_SETUID }, 3)) {
+    if(!file_set_capabilities(kms_server_proxy_local_filepath, (const cap_value_t[]){ CAP_SYS_ADMIN, CAP_SETUID }, 2)) {
         fprintf(stderr, "Error: failed to set kms-server-proxy capabilities\n");
         return false;
     }
@@ -167,17 +250,13 @@ static bool set_gsr_files_set_permissions_and_capabilities(const char *kms_serve
 }
 
 /* |gsr_global_hotkeys_local_filepath| can be NULL */
-static bool setup_local_gsr_files(const char *user_homepath, const char *kms_server_proxy_local_filepath, const char *kms_server_proxy_home) {
+static bool setup_local_gsr_files(const char *user_homepath, const char *kms_server_proxy_home) {
     if(!create_local_kms_server_proxy_directory(user_homepath)) {
         fprintf(stderr, "Error: failed to create ~/.local/share/gpu-screen-recorder directory\n");
         return false;
     }
 
-    if(!copy_file_atomic(KMS_SERVER_PROXY_FILEPATH, kms_server_proxy_local_filepath)) {
-        fprintf(stderr, "Error: failed to copy kms-server-proxy to %s\n", kms_server_proxy_local_filepath);
-        return false;
-    }
-
+    remove(kms_server_proxy_home);
     if(!copy_file_atomic(KMS_SERVER_PROXY_FILEPATH, kms_server_proxy_home)) {
         fprintf(stderr, "Error: failed to copy kms-server-proxy to %s\n", kms_server_proxy_home);
         return false;
@@ -186,13 +265,20 @@ static bool setup_local_gsr_files(const char *user_homepath, const char *kms_ser
     return true;
 }
 
-static int setup_gsr_ui(const char *user_homepath) {
-    char self_path[PATH_MAX];
-    if(!readlink_realpath("/proc/self/exe", self_path)) {
-        fprintf(stderr, "failed to resolve /proc/self/exe\n");
-        return 1;
+static bool get_local_kms_server_proxy_filepath(char *output, size_t output_size, const char *user_homepath) {
+    if(mount_has_setuid_permission(user_homepath)) {
+        snprintf(output, output_size, "%s/.local/share/gpu-screen-recorder/kms-server-proxy-2", user_homepath);
+        return true;
+    } else if(mount_has_setuid_permission("/")) {
+        snprintf(output, output_size, "/usr/bin/kms-server-proxy-2");
+        return true;
+    } else {
+        fprintf(stderr, "Error: neither %s nor / has both read-write permission and setuid permission\n", user_homepath);
+        return false;
     }
+}
 
+static int setup_gsr_ui(const char *user_homepath) {
     if(!user_homepath) {
         user_homepath = getenv("HOME");
         if(!user_homepath)
@@ -200,8 +286,7 @@ static int setup_gsr_ui(const char *user_homepath) {
     }
 
     char kms_server_proxy_local_filepath[PATH_MAX];
-    /* Update kms-server-proxy-N to kms-server-proxy-N+1 on update (update that needs to run before this program launches itself) */
-    snprintf(kms_server_proxy_local_filepath, sizeof(kms_server_proxy_local_filepath), "%s/.local/share/gpu-screen-recorder/kms-server-proxy-2", user_homepath);
+    get_local_kms_server_proxy_filepath(kms_server_proxy_local_filepath, sizeof(kms_server_proxy_local_filepath), user_homepath);
 
     /* Weird-ass distros like openSUSE only allow pkexec for files in $HOME!!! */
     char kms_server_proxy_home[PATH_MAX];
@@ -209,12 +294,18 @@ static int setup_gsr_ui(const char *user_homepath) {
 
     if(geteuid() == 0) { /* is current user root? */
         remove(kms_server_proxy_home);
-        if(!set_gsr_files_set_permissions_and_capabilities(kms_server_proxy_local_filepath))
+        remove(kms_server_proxy_local_filepath);
+        if(!copy_file_atomic(KMS_SERVER_PROXY_FILEPATH, kms_server_proxy_local_filepath)) {
+            fprintf(stderr, "Error: failed to copy kms-server-proxy to %s\n", kms_server_proxy_local_filepath);
+            return 1;
+        }
+
+        if(!gsr_files_set_permissions_and_capabilities(kms_server_proxy_local_filepath))
             return 1;
 
         return 0;
     } else {
-        if(!setup_local_gsr_files(user_homepath, kms_server_proxy_local_filepath, kms_server_proxy_home))
+        if(!setup_local_gsr_files(user_homepath, kms_server_proxy_home))
             return 1;
 
         const char *args[] = { "pkexec", kms_server_proxy_home, "setup-gsr-ui", user_homepath, NULL };
@@ -225,6 +316,24 @@ static int setup_gsr_ui(const char *user_homepath) {
     }
 }
 
+static bool is_setup(const char *user_homepath) {
+    if(!user_homepath) {
+        user_homepath = getenv("HOME");
+        if(!user_homepath)
+            user_homepath = "/tmp";
+    }
+
+    char kms_server_proxy_local_filepath[PATH_MAX];
+    get_local_kms_server_proxy_filepath(kms_server_proxy_local_filepath, sizeof(kms_server_proxy_local_filepath), user_homepath);
+
+    if(!file_has_capabilities(kms_server_proxy_local_filepath, (const cap_value_t[]){ CAP_SYS_ADMIN, CAP_SETUID }, 2)) {
+        fprintf(stderr, "Error: kms-server-proxy (%s) is either not installed or is missing capabilities\n", kms_server_proxy_local_filepath);
+        return false;
+    }
+
+    return true;
+}
+
 static int launch_gsr_kms_server(const char *initial_socket_path, const char *card_path, const char *user_homepath) {
     char self_path[PATH_MAX];
     if(!readlink_realpath("/proc/self/exe", self_path)) {
@@ -233,14 +342,13 @@ static int launch_gsr_kms_server(const char *initial_socket_path, const char *ca
     }
 
     char kms_server_proxy_local_filepath[PATH_MAX];
-    /* Update kms-server-proxy-N to kms-server-proxy-N+1 on update (update that needs to run before this program launches itself) */
-    snprintf(kms_server_proxy_local_filepath, sizeof(kms_server_proxy_local_filepath), "%s/.local/share/gpu-screen-recorder/kms-server-proxy-2", user_homepath);
+    get_local_kms_server_proxy_filepath(kms_server_proxy_local_filepath, sizeof(kms_server_proxy_local_filepath), user_homepath);
 
     /* Weird-ass distros like openSUSE only allow pkexec for files in $HOME!!! */
     char kms_server_proxy_home[PATH_MAX];
     snprintf(kms_server_proxy_home, sizeof(kms_server_proxy_home), "%s/kms-server-proxy", user_homepath);
 
-    if(file_has_sys_admin_capability(kms_server_proxy_local_filepath)) {
+    if(file_has_capabilities(kms_server_proxy_local_filepath, (const cap_value_t[]){ CAP_SYS_ADMIN }, 1)) {
         /* Need to resolve kms_server_proxy_local_filepath because /home can be a symlink to another location */
         char kms_server_proxy_local_filepath_full[PATH_MAX];
         if(!readlink_realpath(kms_server_proxy_local_filepath, kms_server_proxy_local_filepath_full)) {
@@ -266,13 +374,19 @@ static int launch_gsr_kms_server(const char *initial_socket_path, const char *ca
         return execvp(args[0], (char *const*)args);
     } else if(geteuid() == 0) { /* is current user root? */
         remove(kms_server_proxy_home);
-        if(!set_gsr_files_set_permissions_and_capabilities(kms_server_proxy_local_filepath))
+        remove(kms_server_proxy_local_filepath);
+        if(!copy_file_atomic(KMS_SERVER_PROXY_FILEPATH, kms_server_proxy_local_filepath)) {
+            fprintf(stderr, "Error: failed to copy kms-server-proxy to %s\n", kms_server_proxy_local_filepath);
+            return 1;
+        }
+
+        if(!gsr_files_set_permissions_and_capabilities(kms_server_proxy_local_filepath))
             return 1;
 
         const char *args[] = { GSR_KMS_SERVER_FILEPATH, initial_socket_path, card_path, NULL };
         return execv(args[0], (char *const*)args);
     } else {
-        if(!setup_local_gsr_files(user_homepath, kms_server_proxy_local_filepath, kms_server_proxy_home))
+        if(!setup_local_gsr_files(user_homepath, kms_server_proxy_home))
             return 1;
 
         const char *args[] = { "pkexec", kms_server_proxy_home, initial_socket_path, card_path, user_homepath, NULL };
@@ -293,11 +407,10 @@ static int launch_gsr_global_hotkeys(char **argv) {
     const char *user_homepath = argv[2];
 
     char kms_server_proxy_local_filepath[PATH_MAX];
-    /* Update kms-server-proxy-N to kms-server-proxy-N+1 on update (update that needs to run before this program launches itself) */
-    snprintf(kms_server_proxy_local_filepath, sizeof(kms_server_proxy_local_filepath), "%s/.local/share/gpu-screen-recorder/kms-server-proxy-2", user_homepath);
+    get_local_kms_server_proxy_filepath(kms_server_proxy_local_filepath, sizeof(kms_server_proxy_local_filepath), user_homepath);
 
-    if(!file_has_sys_admin_capability(kms_server_proxy_local_filepath)) {
-        fprintf(stderr, "Error: kms-server-proxy is missing cap sys admin capability\n");
+    if(!file_has_capabilities(kms_server_proxy_local_filepath, (const cap_value_t[]){ CAP_SETUID }, 1)) {
+        fprintf(stderr, "Error: kms-server-proxy (%s) is either not installed or is missing capabilities\n", kms_server_proxy_local_filepath);
         return 1;
     }
 
@@ -328,6 +441,14 @@ static int launch_gsr_global_hotkeys(char **argv) {
     return result;
 }
 
+static void usage(void) {
+    fprintf(stderr, "usage alt.1: kms-server-proxy <initial_socket_path> <card_path> <user_homepath>\n");
+    fprintf(stderr, "usage alt.2: kms-server-proxy setup-gsr-ui [user_homepath]\n");
+    fprintf(stderr, "usage alt.3: kms-server-proxy launch-gsr-global-hotkeys <user_homepath> [args...]\n");
+    fprintf(stderr, "usage alt.4: kms-server-proxy is-setup [user_homepath]\n");
+    exit(1);
+}
+
 int main(int argc, char **argv) {
     if(argc < 2)
         usage();
@@ -342,6 +463,10 @@ int main(int argc, char **argv) {
             fprintf(stderr, "Error: missing user_homepath argument to launch-gsr-global-hotkeys\n");
             usage();
         }
+    } else if(strcmp(argv[1], "is-setup") == 0) {
+        const char *user_homepath = argc == 3 ? argv[2] : NULL;
+        const bool s = is_setup(user_homepath);
+        return s ? 0 : 1;
     } else if(argc == 4) {
         return launch_gsr_kms_server(argv[1], argv[2], argv[3]);
     } else {