j3d1/tinc
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Use umask() to set file and UNIX socket permissions without race conditions.

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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.
This commit is contained in:
Guus Sliepen 2013-08-02 19:27:06 +02:00
parent a1f4f14c6c
commit a38e0d6213
5 changed files with 52 additions and 56 deletions
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25
src/invitation.c
View file

@ -519,12 +519,12 @@ make_names:
goto make_names;
}
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;
}
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;
}
@ -652,12 +652,7 @@ make_names:
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");
@ -676,12 +671,7 @@ make_names:
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);
@ -772,7 +762,12 @@ int cmd_join(int argc, char *argv[]) {
}
// 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;
}