Ensure the invitation filenames do not reveal the secret cookie.

[tinc] / src / protocol_auth.c

diff --git a/src/protocol_auth.c b/src/protocol_auth.c
index 1623e75..d69c8ab 100644 (file)
--- a/src/protocol_auth.c
+++ b/src/protocol_auth.c
@@ -190,8 +190,19 @@ static bool receive_invitation_sptps(void *handle, uint8_t type, const char *dat
        if(type != 0 || len != 18 || c->status.invitation_used)
                return false;
 
+       // Recover the filename from the cookie and the key
+       digest_t *digest = digest_open_by_name("sha256", 18);
+       if(!digest)
+               abort();
+       char *fingerprint = ecdsa_get_base64_public_key(invitation_key);
+       char hashbuf[18 + strlen(fingerprint)];
        char cookie[25];
-       b64encode_urlsafe(data, cookie, 18);
+       memcpy(hashbuf, data, 18);
+       memcpy(hashbuf + 18, fingerprint, sizeof hashbuf - 18);
+       digest_create(digest, hashbuf, sizeof hashbuf, cookie);
+       b64encode_urlsafe(cookie, cookie, 18);
+       digest_close(digest);
+       free(fingerprint);
 
        char filename[PATH_MAX], usedname[PATH_MAX];
        snprintf(filename, sizeof filename, "%s" SLASH "invitations" SLASH "%s", confbase, cookie);