As mentioned by Erik Tews, calling fchmod() after fopen() leaves a small window
for exploits. As long as tinc is single-threaded, we can use umask() instead to
reduce file permissions. This also works when creating the AF_UNIX control socket.
The umask of the user running tinc(d) is used for most files, except for the
private keys, invitation files, PID file and control socket.
randomize(controlcookie, sizeof controlcookie / 2);
bin2hex(controlcookie, controlcookie, sizeof controlcookie / 2);
randomize(controlcookie, sizeof controlcookie / 2);
bin2hex(controlcookie, controlcookie, sizeof controlcookie / 2);
+ mode_t mask = umask(0);
+ umask(mask | 077);
FILE *f = fopen(pidfilename, "w");
FILE *f = fopen(pidfilename, "w");
if(!f) {
logger(DEBUG_ALWAYS, LOG_ERR, "Cannot write control socket cookie file %s: %s", pidfilename, strerror(errno));
return false;
}
if(!f) {
logger(DEBUG_ALWAYS, LOG_ERR, "Cannot write control socket cookie file %s: %s", pidfilename, strerror(errno));
return false;
}
-#ifdef HAVE_FCHMOD
- fchmod(fileno(f), 0600);
-#else
- chmod(pidfilename, 0600);
-#endif
// Get the address and port of the first listening socket
char *localhost = NULL;
// Get the address and port of the first listening socket
char *localhost = NULL;
- if(mkdir(confbase, 0755) && errno != EEXIST) {
+ if(mkdir(confbase, 0777) && errno != EEXIST) {
fprintf(stderr, "Could not create directory %s: %s\n", confbase, strerror(errno));
return false;
}
fprintf(stderr, "Could not create directory %s: %s\n", confbase, strerror(errno));
return false;
}
- if(mkdir(hosts_dir, 0755) && errno != EEXIST) {
+ if(mkdir(hosts_dir, 0777) && errno != EEXIST) {
fprintf(stderr, "Could not create directory %s: %s\n", hosts_dir, strerror(errno));
return false;
}
fprintf(stderr, "Could not create directory %s: %s\n", hosts_dir, strerror(errno));
return false;
}
return false;
xasprintf(&filename, "%s" SLASH "ecdsa_key.priv", confbase);
return false;
xasprintf(&filename, "%s" SLASH "ecdsa_key.priv", confbase);
- f = fopen(filename, "w");
-
-#ifdef HAVE_FCHMOD
- /* Make it unreadable for others. */
- fchmod(fileno(f), 0600);
-#endif
+ f = fopenmask(filename, "w", 0600);
if(!ecdsa_write_pem_private_key(key, f)) {
fprintf(stderr, "Error writing private key!\n");
if(!ecdsa_write_pem_private_key(key, f)) {
fprintf(stderr, "Error writing private key!\n");
rsa_t *rsa = rsa_generate(2048, 0x1001);
xasprintf(&filename, "%s" SLASH "rsa_key.priv", confbase);
rsa_t *rsa = rsa_generate(2048, 0x1001);
xasprintf(&filename, "%s" SLASH "rsa_key.priv", confbase);
- f = fopen(filename, "w");
-
-#ifdef HAVE_FCHMOD
- /* Make it unreadable for others. */
- fchmod(fileno(f), 0600);
-#endif
+ f = fopenmask(filename, "w", 0600);
rsa_write_pem_private_key(rsa, f);
fclose(f);
rsa_write_pem_private_key(rsa, f);
fclose(f);
}
// Make sure confbase exists and is accessible.
}
// Make sure confbase exists and is accessible.
- if(mkdir(confbase, 0755) && errno != EEXIST) {
+ if(strcmp(confdir, confbase) && mkdir(confdir, 0755) && errno != EEXIST) {
+ fprintf(stderr, "Could not create directory %s: %s\n", confdir, strerror(errno));
+ return 1;
+ }
+
+ if(mkdir(confbase, 0777) && errno != EEXIST) {
fprintf(stderr, "Could not create directory %s: %s\n", confbase, strerror(errno));
return 1;
}
fprintf(stderr, "Could not create directory %s: %s\n", confbase, strerror(errno));
return 1;
}
- if(bind(unix_fd, (struct sockaddr *)&sa, sizeof sa) < 0) {
+ mode_t mask = umask(0);
+ umask(mask | 077);
+ int result = bind(unix_fd, (struct sockaddr *)&sa, sizeof sa);
+ umask(mask);
+
+ if(result < 0) {
logger(DEBUG_ALWAYS, LOG_ERR, "Could not bind UNIX socket to %s: %s", unixsocketname, sockstrerror(errno));
return false;
}
logger(DEBUG_ALWAYS, LOG_ERR, "Could not bind UNIX socket to %s: %s", unixsocketname, sockstrerror(errno));
return false;
}
+/* Open a file with the desired permissions, minus the umask.
+ Also, if we want to create an executable file, we call fchmod()
+ to set the executable bits. */
+
+FILE *fopenmask(const char *filename, const char *mode, mode_t perms) {
+ mode_t mask = umask(0);
+ perms &= ~mask;
+ umask(~perms);
+ FILE *f = fopen(filename, mode);
+#ifdef HAVE_FCHMOD
+ if((perms & 0444) && f)
+ fchmod(fileno(f), perms);
+#endif
+ umask(mask);
+ return f;
+}
+
static void disable_old_keys(const char *filename, const char *what) {
char tmpfile[PATH_MAX] = "";
char buf[1024];
static void disable_old_keys(const char *filename, const char *what) {
char tmpfile[PATH_MAX] = "";
char buf[1024];
snprintf(tmpfile, sizeof tmpfile, "%s.tmp", filename);
snprintf(tmpfile, sizeof tmpfile, "%s.tmp", filename);
- w = fopen(tmpfile, "w");
-
-#ifdef HAVE_FCHMOD
- /* Let the temporary file have the same permissions as the original. */
-
- if(w) {
- struct stat st = {.st_mode = 0600};
- fstat(fileno(r), &st);
- fchmod(fileno(w), st.st_mode);
- }
-#endif
+ struct stat st = {.st_mode = 0600};
+ fstat(fileno(r), &st);
+ w = fopenmask(tmpfile, "w", st.st_mode);
while(fgets(buf, sizeof buf, r)) {
if(!block && !strncmp(buf, "-----BEGIN ", 11)) {
while(fgets(buf, sizeof buf, r)) {
if(!block && !strncmp(buf, "-----BEGIN ", 11)) {
-static FILE *ask_and_open(const char *filename, const char *what, const char *mode, bool ask) {
+static FILE *ask_and_open(const char *filename, const char *what, const char *mode, bool ask, mode_t perms) {
FILE *r;
char *directory;
char buf[PATH_MAX];
FILE *r;
char *directory;
char buf[PATH_MAX];
/* Open it first to keep the inode busy */
/* Open it first to keep the inode busy */
- r = fopen(filename, mode);
+ r = fopenmask(filename, mode, perms);
if(!r) {
fprintf(stderr, "Error opening file `%s': %s\n", filename, strerror(errno));
if(!r) {
fprintf(stderr, "Error opening file `%s': %s\n", filename, strerror(errno));
fprintf(stderr, "Done.\n");
xasprintf(&privname, "%s" SLASH "ecdsa_key.priv", confbase);
fprintf(stderr, "Done.\n");
xasprintf(&privname, "%s" SLASH "ecdsa_key.priv", confbase);
- f = ask_and_open(privname, "private ECDSA key", "a", ask);
+ f = ask_and_open(privname, "private ECDSA key", "a", ask, 0600);
free(privname);
if(!f)
return false;
free(privname);
if(!f)
return false;
-#ifdef HAVE_FCHMOD
- /* Make it unreadable for others. */
- fchmod(fileno(f), 0600);
-#endif
-
if(!ecdsa_write_pem_private_key(key, f)) {
fprintf(stderr, "Error writing private key!\n");
ecdsa_free(key);
if(!ecdsa_write_pem_private_key(key, f)) {
fprintf(stderr, "Error writing private key!\n");
ecdsa_free(key);
else
xasprintf(&pubname, "%s" SLASH "ecdsa_key.pub", confbase);
else
xasprintf(&pubname, "%s" SLASH "ecdsa_key.pub", confbase);
- f = ask_and_open(pubname, "public ECDSA key", "a", ask);
+ f = ask_and_open(pubname, "public ECDSA key", "a", ask, 0666);
fprintf(stderr, "Done.\n");
xasprintf(&privname, "%s" SLASH "rsa_key.priv", confbase);
fprintf(stderr, "Done.\n");
xasprintf(&privname, "%s" SLASH "rsa_key.priv", confbase);
- f = ask_and_open(privname, "private RSA key", "a", ask);
+ f = ask_and_open(privname, "private RSA key", "a", ask, 0600);
free(privname);
if(!f)
return false;
free(privname);
if(!f)
return false;
-#ifdef HAVE_FCHMOD
- /* Make it unreadable for others. */
- fchmod(fileno(f), 0600);
-#endif
-
if(!rsa_write_pem_private_key(key, f)) {
fprintf(stderr, "Error writing private key!\n");
fclose(f);
if(!rsa_write_pem_private_key(key, f)) {
fprintf(stderr, "Error writing private key!\n");
fclose(f);
else
xasprintf(&pubname, "%s" SLASH "rsa_key.pub", confbase);
else
xasprintf(&pubname, "%s" SLASH "rsa_key.pub", confbase);
- f = ask_and_open(pubname, "public RSA key", "a", ask);
+ f = ask_and_open(pubname, "public RSA key", "a", ask, 0666);
- if(mkdir(confdir, 0755) && errno != EEXIST) {
- fprintf(stderr, "Could not create directory %s: %s\n", CONFDIR, strerror(errno));
+ if(strcmp(confdir, confbase) && mkdir(confdir, 0755) && errno != EEXIST) {
+ fprintf(stderr, "Could not create directory %s: %s\n", confdir, strerror(errno));
- if(mkdir(confbase, 0755) && errno != EEXIST) {
+ if(mkdir(confbase, 0777) && errno != EEXIST) {
fprintf(stderr, "Could not create directory %s: %s\n", confbase, strerror(errno));
return 1;
}
fprintf(stderr, "Could not create directory %s: %s\n", confbase, strerror(errno));
return 1;
}
- if(mkdir(hosts_dir, 0755) && errno != EEXIST) {
+ if(mkdir(hosts_dir, 0777) && errno != EEXIST) {
fprintf(stderr, "Could not create directory %s: %s\n", hosts_dir, strerror(errno));
return 1;
}
fprintf(stderr, "Could not create directory %s: %s\n", hosts_dir, strerror(errno));
return 1;
}
char *filename;
xasprintf(&filename, "%s" SLASH "tinc-up", confbase);
if(access(filename, F_OK)) {
char *filename;
xasprintf(&filename, "%s" SLASH "tinc-up", confbase);
if(access(filename, F_OK)) {
- FILE *f = fopen(filename, "w");
+ FILE *f = fopenmask(filename, "w", 0777);
if(!f) {
fprintf(stderr, "Could not create file %s: %s\n", filename, strerror(errno));
return 1;
}
if(!f) {
fprintf(stderr, "Could not create file %s: %s\n", filename, strerror(errno));
return 1;
}
- mode_t mask = umask(0);
- umask(mask);
- fchmod(fileno(f), 0755 & ~mask);
fprintf(f, "#!/bin/sh\n\necho 'Unconfigured tinc-up script, please edit!'\n\n#ifconfig $INTERFACE <your vpn IP address> netmask <netmask of whole VPN>\n");
fclose(f);
}
fprintf(f, "#!/bin/sh\n\necho 'Unconfigured tinc-up script, please edit!'\n\n#ifconfig $INTERFACE <your vpn IP address> netmask <netmask of whole VPN>\n");
fclose(f);
}
extern bool sendline(int fd, char *format, ...);
extern bool recvline(int fd, char *line, size_t len);
extern int check_port(char *name);
extern bool sendline(int fd, char *format, ...);
extern bool recvline(int fd, char *line, size_t len);
extern int check_port(char *name);
+extern FILE *fopenmask(const char *filename, const char *mode, mode_t perms);