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Handle oversized homedir paths safely #695

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Handle oversized homedir paths safely #695

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95 changes: 64 additions & 31 deletions src/unix/system.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -178,39 +178,72 @@ Sys_Init
*/
void Sys_Init(void)
{
const char *homedir;

signal(SIGTERM, term_handler);
signal(SIGINT, term_handler);
signal(SIGTTIN, SIG_IGN);
signal(SIGTTOU, SIG_IGN);
signal(SIGPIPE, SIG_IGN);
signal(SIGHUP, term_handler);
signal(SIGUSR1, usr1_handler);

// basedir <path>
// allows the game to run from outside the data tree
sys_basedir = Cvar_Get("basedir", DATADIR, CVAR_NOSET);

// homedir <path>
// specifies per-user writable directory for demos, screenshots, etc
if (HOMEDIR[0] == '~') {
char *s = getenv("HOME");
if (s && strlen(s) >= MAX_OSPATH - MAX_QPATH)
Sys_Error("HOME path too long");
if (s && *s) {
homedir = va("%s%s", s, &HOMEDIR[1]);
} else {
homedir = "";
}
} else {
homedir = HOMEDIR;
}
const char *homedir;

signal(SIGTERM, term_handler);
signal(SIGINT, term_handler);
signal(SIGTTIN, SIG_IGN);
signal(SIGTTOU, SIG_IGN);
signal(SIGPIPE, SIG_IGN);
signal(SIGHUP, term_handler);
signal(SIGUSR1, usr1_handler);

// basedir <path>
// allows the game to run from outside the data tree
sys_basedir = Cvar_Get("basedir", DATADIR, CVAR_NOSET);

// homedir <path>
// specifies per-user writable directory for demos, screenshots, etc
if (HOMEDIR[0] == '~') {
static char homedir_buffer[MAX_OSPATH];
char *s = getenv("HOME");
const char *suffix = &HOMEDIR[1];

if (s && *s) {
size_t home_len = strlen(s);
size_t suffix_len = strlen(suffix);
size_t max_total = MAX_OSPATH - 1;
size_t available_suffix = 0;

if (home_len < max_total) {
available_suffix = max_total - home_len;
}

if (home_len >= max_total) {
Q_strlcpy(homedir_buffer, s, sizeof(homedir_buffer));
Com_Printf("HOME (%s) exceeds %zu characters, truncating to fit limit\n", s, max_total);
homedir = homedir_buffer;
} else if (suffix_len > available_suffix) {
Q_strlcpy(homedir_buffer, s, sizeof(homedir_buffer));
if (available_suffix > 0) {
char truncated_suffix[MAX_OSPATH];

Q_strlcpy(truncated_suffix, suffix, available_suffix + 1);
Q_strlcat(homedir_buffer, truncated_suffix, sizeof(homedir_buffer));
Com_Printf(
"Combined HOME (%s) and HOMEDIR (%s) exceed %zu characters, truncating HOMEDIR to \"%s\"\n",
s, suffix, max_total, homedir_buffer);
} else {
Com_Printf(
"HOME (%s) length leaves no room for HOMEDIR (%s); using HOME only\n",
s, suffix);
}

homedir = homedir_buffer;
} else {
homedir = va("%s%s", s, suffix);
}
} else {
homedir = "";
}
} else {
homedir = HOMEDIR;
}

sys_homedir = Cvar_Get("homedir", homedir, CVAR_NOSET);
sys_libdir = Cvar_Get("libdir", LIBDIR, CVAR_NOSET);
sys_homedir = Cvar_Get("homedir", homedir, CVAR_NOSET);
sys_libdir = Cvar_Get("libdir", LIBDIR, CVAR_NOSET);

tty_init_input();
tty_init_input();
}

/*
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