-/* CRT work by Simon Tatham */
+/* This file is part of secnet, and is distributed under the terms of
+ the GNU General Public License version 2 or later.
+
+ Copyright (C) 1995-2002 Stephen Early
+ Copyright (C) 2001 Simon Tatham
+ Copyright (C) 2002 Ian Jackson
+ */
#include <stdio.h>
+#include <string.h>
#include <gmp.h>
#include "secnet.h"
#include "util.h"
};
/* 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 string_t rsa_sign(void *sst, uint8_t *data, uint32_t datalen)
+static void emsa_pkcs1(MP_INT *n, MP_INT *m,
+ const uint8_t *data, int32_t datalen)
{
- struct rsapriv *st=sst;
- MP_INT a, b, u, v, tmp, tmp2;
- char buff[2048];
+ char buff[2*RSA_MAX_MODBYTES + 1];
int msize, i;
- string_t signature;
- mpz_init(&a);
- mpz_init(&b);
+ /* RSA PKCS#1 v1.5 signature padding:
+ *
+ * <------------ msize hex digits ---------->
+ *
+ * 00 01 ff ff .... ff ff 00 vv vv vv .... vv
+ *
+ * <--- datalen -->
+ * bytes
+ * = datalen*2 hex digits
+ *
+ * NB that according to PKCS#1 v1.5 we're supposed to include a
+ * hash function OID in the data. We don't do that (because we
+ * don't have the hash function OID to hand here), thus violating
+ * the spec in a way that affects interop but not security.
+ *
+ * -iwj 17.9.2002
+ */
- msize=mpz_sizeinbase(&st->n, 16);
+ msize=mpz_sizeinbase(n, 16);
- if (datalen*2+4>=msize) {
+ if (datalen*2+6>=msize) {
fatal("rsa_sign: message too big");
}
strcpy(buff,"0001");
for (i=0; i<datalen; i++) {
- buff[4+i*2]=hexchars[(data[i]&0xf0)>>4];
- buff[5+i*2]=hexchars[data[i]&0xf];
+ buff[msize+(-datalen+i)*2]=hexchars[(data[i]&0xf0)>>4];
+ buff[msize+(-datalen+i)*2+1]=hexchars[data[i]&0xf];
}
- buff[4+datalen*2]=0;
- for (i=datalen*2+4; i<msize; i++)
- buff[i]='f';
+ buff[msize-datalen*2-2]= '0';
+ buff[msize-datalen*2-1]= '0';
+
+ for (i=4; i<msize-datalen*2-2; i++)
+ buff[i]='f';
buff[msize]=0;
- mpz_set_str(&a, buff, 16);
+ mpz_set_str(m, buff, 16);
+}
+
+static string_t rsa_sign(void *sst, uint8_t *data, int32_t datalen)
+{
+ struct rsapriv *st=sst;
+ MP_INT a, b, u, v, tmp, tmp2;
+ string_t signature;
+
+ mpz_init(&a);
+ mpz_init(&b);
+
+ /* Construct the message representative. */
+ emsa_pkcs1(&st->n, &a, data, datalen);
/*
* Produce an RSA signature (a^d mod n) using the Chinese
}
static rsa_checksig_fn rsa_sig_check;
-static bool_t rsa_sig_check(void *sst, uint8_t *data, uint32_t datalen,
+static bool_t rsa_sig_check(void *sst, uint8_t *data, int32_t datalen,
cstring_t signature)
{
struct rsapub *st=sst;
MP_INT a, b, c;
- char buff[2048];
- int msize, i;
bool_t ok;
mpz_init(&a);
mpz_init(&b);
mpz_init(&c);
- msize=mpz_sizeinbase(&st->n, 16);
-
- strcpy(buff,"0001");
-
- for (i=0; i<datalen; i++) {
- buff[4+i*2]=hexchars[(data[i]&0xf0)>>4];
- buff[5+i*2]=hexchars[data[i]&0xf];
- }
- buff[4+datalen*2]=0;
-
- for (i=datalen*2+4; i<msize; i++)
- buff[i]='f';
-
- buff[msize]=0;
-
- mpz_set_str(&a, buff, 16);
+ emsa_pkcs1(&st->n, &a, data, datalen);
mpz_set_str(&b, signature, 16);
i=list_elem(args,0);
if (i) {
if (i->type!=t_string) {
- cfgfatal(i->loc,"rsa-public","first argument must be a string");
+ cfgfatal(i->loc,"rsa-public","first argument must be a string\n");
}
e=i->data.string;
if (mpz_init_set_str(&st->e,e,10)!=0) {
} 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) {
if (i->type!=t_string) {
- cfgfatal(i->loc,"rsa-public","second argument must be a string");
+ cfgfatal(i->loc,"rsa-public","second argument must be a string\n");
}
n=i->data.string;
if (mpz_init_set_str(&st->n,n,10)!=0) {
} 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);
}
uint8_t *b, *c;
int cipher_type;
MP_INT e,d,iqmp,tmp,tmp2,tmp3;
+ bool_t valid;
st=safe_malloc(sizeof(*st),"rsapriv_apply");
st->cl.description="rsapriv";
i=list_elem(args,0);
if (i) {
if (i->type!=t_string) {
- cfgfatal(i->loc,"rsa-public","first argument must be a string");
+ cfgfatal(i->loc,"rsa-public","first argument must be a string\n");
}
filename=i->data.string;
} else {
/* 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);
}
b=safe_malloc(length,"rsapriv_apply");
if (fread(b,length,1,f) != 1) {
- cfgfatal_maybefile(f,loc,"rsa-private","error reading modulus");
+ cfgfatal_maybefile(f,loc,"rsa-private","error reading modulus\n");
}
mpz_init(&st->n);
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");
/* 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);
}
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);
}
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);
}
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);
}
* Now verify the validity of the key, and set up the auxiliary
* values for fast CRT signing.
*/
+ valid=False;
i=list_elem(args,1);
+ mpz_init(&tmp);
+ mpz_init(&tmp2);
+ mpz_init(&tmp3);
if (i && i->type==t_bool && i->data.bool==False) {
Message(M_INFO,"rsa-private (%s:%d): skipping RSA key validity "
"check\n",loc.file,loc.line);
} else {
- int valid = 0;
- mpz_init(&tmp);
- mpz_init(&tmp2);
- mpz_init(&tmp3);
-
/* Verify that p*q is equal to n. */
mpz_mul(&tmp, &st->p, &st->q);
if (mpz_cmp(&tmp, &st->n) != 0)
/*
* Verify that d*e is congruent to 1 mod (p-1), and mod
* (q-1). This is equivalent to it being congruent to 1 mod
- * lcm(p-1,q-1), i.e. congruent to 1 mod phi(n). Note that
- * phi(n) is _not_ simply (p-1)*(q-1).
+ * lambda(n) = lcm(p-1,q-1). The usual `textbook' condition,
+ * that d e == 1 (mod (p-1)(q-1)) is sufficient, but not
+ * actually necessary.
*/
mpz_mul(&tmp, &d, &e);
mpz_sub_ui(&tmp2, &st->p, 1);
mpz_mod(&tmp2, &tmp, &st->p);
if (mpz_cmp_si(&tmp2, 1) != 0)
goto done_checks;
-
- /* Now we know the key is valid. */
- valid = 1;
-
- /*
- * Now we compute auxiliary values dp, dq and w to allow us
- * to use the CRT optimisation when signing.
- *
- * dp == d mod (p-1) so that a^dp == a^d mod p, for all a
- * dq == d mod (q-1) similarly mod q
- * w == iqmp * q so that w == 0 mod q, and w == 1 mod p
- */
- mpz_sub_ui(&tmp, &st->p, 1);
- mpz_mod(&st->dp, &d, &tmp);
- mpz_sub_ui(&tmp, &st->q, 1);
- mpz_mod(&st->dq, &d, &tmp);
- mpz_mul(&st->w, &iqmp, &st->q);
-
- done_checks:
- if (!valid) {
- cfgfatal(loc,"rsa-private","file \"%s\" does not contain a "
- "valid RSA key!\n",filename);
- }
- mpz_clear(&tmp);
- mpz_clear(&tmp2);
- mpz_clear(&tmp3);
}
+ /* Now we know the key is valid (or we don't care). */
+ valid = True;
+
+ /*
+ * Now we compute auxiliary values dp, dq and w to allow us
+ * to use the CRT optimisation when signing.
+ *
+ * dp == d mod (p-1) so that a^dp == a^d mod p, for all a
+ * dq == d mod (q-1) similarly mod q
+ * w == iqmp * q so that w == 0 mod q, and w == 1 mod p
+ */
+ mpz_init(&st->dp);
+ mpz_init(&st->dq);
+ mpz_init(&st->w);
+ mpz_sub_ui(&tmp, &st->p, 1);
+ mpz_mod(&st->dp, &d, &tmp);
+ mpz_sub_ui(&tmp, &st->q, 1);
+ mpz_mod(&st->dq, &d, &tmp);
+ mpz_mul(&st->w, &iqmp, &st->q);
+
+done_checks:
+ if (!valid) {
+ cfgfatal(loc,"rsa-private","file \"%s\" does not contain a "
+ "valid RSA key!\n",filename);
+ }
+ mpz_clear(&tmp);
+ mpz_clear(&tmp2);
+ mpz_clear(&tmp3);
free(c);
mpz_clear(&e);
return new_closure(&st->cl);
}
-init_module rsa_module;
void rsa_module(dict_t *dict)
{
add_closure(dict,"rsa-private",rsapriv_apply);
~ian / secnet.git / blobdiff