Merge remote-tracking branch 'mdw/mdw/powm-sec'

[secnet] / rsa.c

diff --git a/rsa.c b/rsa.c
index 0ca5d19..068cf41 100644 (file)
--- a/rsa.c
+++ b/rsa.c
@@ -1,10 +1,34 @@
-/* This file is part of secnet, and is distributed under the terms of
-   the GNU General Public License version 2 or later.
+/*
+ * rsa.c: implementation of RSA with PKCS#1 padding
+ */
+/*
+ * This file is Free Software.  It was originally written for secnet.
+ *
+ * Copyright 1995-2003 Stephen Early
+ * Copyright 2002-2014 Ian Jackson
+ * Copyright 2001      Simon Tatham
+ * Copyright 2013      Mark Wooding
+ *
+ * You may redistribute secnet as a whole and/or modify it under the
+ * terms of the GNU General Public License as published by the Free
+ * Software Foundation; either version 3, or (at your option) any
+ * later version.
+ *
+ * You may redistribute this file and/or modify it under the terms of
+ * the GNU General Public License as published by the Free Software
+ * Foundation; either version 2, or (at your option) any later
+ * version.
+ *
+ * This software is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this software; if not, see
+ * https://www.gnu.org/licenses/gpl.html.
+ */
 
-   Copyright (C) 1995-2002 Stephen Early
-   Copyright (C) 2001 Simon Tatham
-   Copyright (C) 2002 Ian Jackson
-   */
 
 #include <stdio.h>
 #include <string.h>
@@ -34,12 +58,18 @@ struct rsapub {
 };
 /* Sign data. NB data must be smaller than modulus */
 
+#define RSA_MAX_MODBYTES 2048
+/* The largest modulus I've seen is 15360 bits, which works out at 1920
+ * bytes.  Using keys this big is quite implausible, but it doesn't cost us
+ * much to support them.
+ */
+
 static const char *hexchars="0123456789abcdef";
 
 static void emsa_pkcs1(MP_INT *n, MP_INT *m,
                       const uint8_t *data, int32_t datalen)
 {
-    char buff[2048];
+    char buff[2*RSA_MAX_MODBYTES + 1];
     int msize, i;
 
     /* RSA PKCS#1 v1.5 signature padding:
@@ -118,8 +148,8 @@ static string_t rsa_sign(void *sst, uint8_t *data, int32_t datalen)
     mpz_init(&u);
     mpz_init(&v);
 
-    mpz_powm(&u, &a, &st->dp, &st->p);
-    mpz_powm(&v, &a, &st->dq, &st->q);
+    mpz_powm_sec(&u, &a, &st->dp, &st->p);
+    mpz_powm_sec(&v, &a, &st->dq, &st->q);
     mpz_sub(&tmp, &u, &v);
     mpz_mul(&tmp2, &tmp, &st->w);
     mpz_add(&tmp, &tmp2, &v);
@@ -171,7 +201,7 @@ static list_t *rsapub_apply(closure_t *self, struct cloc loc, dict_t *context,
     item_t *i;
     string_t e,n;
 
-    st=safe_malloc(sizeof(*st),"rsapub_apply");
+    NEW(st);
     st->cl.description="rsapub";
     st->cl.type=CL_RSAPUBKEY;
     st->cl.apply=NULL;
@@ -193,6 +223,9 @@ static list_t *rsapub_apply(closure_t *self, struct cloc loc, dict_t *context,
     } else {
        cfgfatal(loc,"rsa-public","you must provide an encryption key\n");
     }
+    if (mpz_sizeinbase(&st->e, 256) > RSA_MAX_MODBYTES) {
+       cfgfatal(loc, "rsa-public", "implausibly large public exponent\n");
+    }
     
     i=list_elem(args,1);
     if (i) {
@@ -207,6 +240,9 @@ static list_t *rsapub_apply(closure_t *self, struct cloc loc, dict_t *context,
     } else {
        cfgfatal(loc,"rsa-public","you must provide a modulus\n");
     }
+    if (mpz_sizeinbase(&st->n, 256) > RSA_MAX_MODBYTES) {
+       cfgfatal(loc, "rsa-public", "implausibly large modulus\n");
+    }
     return new_closure(&st->cl);
 }
 
@@ -243,7 +279,7 @@ static list_t *rsapriv_apply(closure_t *self, struct cloc loc, dict_t *context,
     MP_INT e,d,iqmp,tmp,tmp2,tmp3;
     bool_t valid;
 
-    st=safe_malloc(sizeof(*st),"rsapriv_apply");
+    NEW(st);
     st->cl.description="rsapriv";
     st->cl.type=CL_RSAPRIVKEY;
     st->cl.apply=NULL;
@@ -296,7 +332,7 @@ static list_t *rsapriv_apply(closure_t *self, struct cloc loc, dict_t *context,
     /* Read the public key */
     keyfile_get_int(loc,f); /* Not sure what this is */
     length=(keyfile_get_short(loc,f)+7)/8;
-    if (length>1024) {
+    if (length>RSA_MAX_MODBYTES) {
        cfgfatal(loc,"rsa-private","implausible length %ld for modulus\n",
                 length);
     }
@@ -308,7 +344,7 @@ static list_t *rsapriv_apply(closure_t *self, struct cloc loc, dict_t *context,
     read_mpbin(&st->n,b,length);
     free(b);
     length=(keyfile_get_short(loc,f)+7)/8;
-    if (length>1024) {
+    if (length>RSA_MAX_MODBYTES) {
        cfgfatal(loc,"rsa-private","implausible length %ld for e\n",length);
     }
     b=safe_malloc(length,"rsapriv_apply");
@@ -339,7 +375,7 @@ static list_t *rsapriv_apply(closure_t *self, struct cloc loc, dict_t *context,
 
     /* Read d */
     length=(keyfile_get_short(loc,f)+7)/8;
-    if (length>1024) {
+    if (length>RSA_MAX_MODBYTES) {
        cfgfatal(loc,"rsa-private","implausibly long (%ld) decryption key\n",
                 length);
     }
@@ -353,7 +389,7 @@ static list_t *rsapriv_apply(closure_t *self, struct cloc loc, dict_t *context,
     free(b);
     /* Read iqmp (inverse of q mod p) */
     length=(keyfile_get_short(loc,f)+7)/8;
-    if (length>1024) {
+    if (length>RSA_MAX_MODBYTES) {
        cfgfatal(loc,"rsa-private","implausibly long (%ld)"
                 " iqmp auxiliary value\n", length);
     }
@@ -367,7 +403,7 @@ static list_t *rsapriv_apply(closure_t *self, struct cloc loc, dict_t *context,
     free(b);
     /* Read q (the smaller of the two primes) */
     length=(keyfile_get_short(loc,f)+7)/8;
-    if (length>1024) {
+    if (length>RSA_MAX_MODBYTES) {
        cfgfatal(loc,"rsa-private","implausibly long (%ld) q value\n",
                 length);
     }
@@ -381,7 +417,7 @@ static list_t *rsapriv_apply(closure_t *self, struct cloc loc, dict_t *context,
     free(b);
     /* Read p (the larger of the two primes) */
     length=(keyfile_get_short(loc,f)+7)/8;
-    if (length>1024) {
+    if (length>RSA_MAX_MODBYTES) {
        cfgfatal(loc,"rsa-private","implausibly long (%ld) p value\n",
                 length);
     }