+/* 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"
#define AUTHFILE_ID_STRING "SSH PRIVATE KEY FILE FORMAT 1.1\n"
+#define mpp(s,n) do { char *p = mpz_get_str(NULL,16,n); printf("%s 0x%sL\n", s, p); free(p); } while (0)
+
struct rsapriv {
closure_t cl;
struct rsaprivkey_if ops;
struct cloc loc;
- MP_INT d;
MP_INT n;
+ MP_INT p, dp;
+ MP_INT q, dq;
+ MP_INT w;
};
struct rsapub {
closure_t cl;
};
/* Sign data. NB data must be smaller than modulus */
-static char *hexchars="0123456789abcdef";
+#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;
- char buff[2048];
+ char buff[2*RSA_MAX_MODBYTES + 1];
int msize, i;
- string_t signature;
-
- mpz_init(&a);
- mpz_init(&b);
-
- msize=mpz_sizeinbase(&st->n, 16);
- if (datalen*2+4>=msize) {
+ /* 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(n, 16);
+
+ 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);
+}
- mpz_powm(&b, &a, &st->d, &st->n);
+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
+ * Remainder Theorem. We compute:
+ *
+ * u = a^dp mod p (== a^d mod p, since dp == d mod (p-1))
+ * v = a^dq mod q (== a^d mod q, similarly)
+ *
+ * We also know w == iqmp * q, which has the property that w ==
+ * 0 mod q and w == 1 mod p. So (1-w) has the reverse property
+ * (congruent to 0 mod p and to 1 mod q). Hence we now compute
+ *
+ * b = w * u + (1-w) * v
+ * = w * (u-v) + v
+ *
+ * so that b is congruent to a^d both mod p and mod q. Hence b,
+ * reduced mod n, is the required signature.
+ */
+ mpz_init(&tmp);
+ mpz_init(&tmp2);
+ mpz_init(&u);
+ mpz_init(&v);
+
+ mpz_powm(&u, &a, &st->dp, &st->p);
+ mpz_powm(&v, &a, &st->dq, &st->q);
+ mpz_sub(&tmp, &u, &v);
+ mpz_mul(&tmp2, &tmp, &st->w);
+ mpz_add(&tmp, &tmp2, &v);
+ mpz_mod(&b, &tmp, &st->n);
+
+ mpz_clear(&tmp);
+ mpz_clear(&tmp2);
+ mpz_clear(&u);
+ mpz_clear(&v);
signature=write_mpstring(&b);
return signature;
}
-static bool_t rsa_sig_check(void *sst, uint8_t *data, uint32_t datalen,
- string_t signature)
+static rsa_checksig_fn rsa_sig_check;
+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);
}
{
struct rsapriv *st;
FILE *f;
- string_t filename;
+ cstring_t filename;
item_t *i;
long length;
uint8_t *b, *c;
int cipher_type;
- MP_INT e,sig,plain,check;
+ 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 {
- filename=""; /* Make compiler happy */
+ filename=NULL; /* Make compiler happy */
cfgfatal(loc,"rsa-private","you must provide a filename\n");
}
/* 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);
}
cfgfatal_maybefile(f,loc,"rsa-private",
"error reading decryption key\n");
}
- mpz_init(&st->d);
- read_mpbin(&st->d,b,length);
+ mpz_init(&d);
+ read_mpbin(&d,b,length);
+ free(b);
+ /* Read iqmp (inverse of q mod p) */
+ length=(keyfile_get_short(loc,f)+7)/8;
+ if (length>RSA_MAX_MODBYTES) {
+ cfgfatal(loc,"rsa-private","implausibly long (%ld)"
+ " iqmp auxiliary value\n", length);
+ }
+ b=safe_malloc(length,"rsapriv_apply");
+ if (fread(b,length,1,f)!=1) {
+ cfgfatal_maybefile(f,loc,"rsa-private",
+ "error reading decryption key\n");
+ }
+ mpz_init(&iqmp);
+ read_mpbin(&iqmp,b,length);
+ free(b);
+ /* Read q (the smaller of the two primes) */
+ length=(keyfile_get_short(loc,f)+7)/8;
+ if (length>RSA_MAX_MODBYTES) {
+ cfgfatal(loc,"rsa-private","implausibly long (%ld) q value\n",
+ length);
+ }
+ b=safe_malloc(length,"rsapriv_apply");
+ if (fread(b,length,1,f)!=1) {
+ cfgfatal_maybefile(f,loc,"rsa-private",
+ "error reading q value\n");
+ }
+ mpz_init(&st->q);
+ read_mpbin(&st->q,b,length);
+ free(b);
+ /* Read p (the larger of the two primes) */
+ length=(keyfile_get_short(loc,f)+7)/8;
+ if (length>RSA_MAX_MODBYTES) {
+ cfgfatal(loc,"rsa-private","implausibly long (%ld) p value\n",
+ length);
+ }
+ b=safe_malloc(length,"rsapriv_apply");
+ if (fread(b,length,1,f)!=1) {
+ cfgfatal_maybefile(f,loc,"rsa-private",
+ "error reading p value\n");
+ }
+ mpz_init(&st->p);
+ read_mpbin(&st->p,b,length);
free(b);
if (fclose(f)!=0) {
fatal_perror("rsa-private (%s:%d): fclose",loc.file,loc.line);
}
- /* Now do trial signature/check to make sure it's a real keypair:
- sign the comment string! */
+ /*
+ * 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 {
- mpz_init(&sig);
- mpz_init(&plain);
- mpz_init(&check);
- read_mpbin(&plain,c,strlen(c));
- mpz_powm(&sig, &plain, &st->d, &st->n);
- mpz_powm(&check, &sig, &e, &st->n);
- if (mpz_cmp(&plain,&check)!=0) {
- cfgfatal(loc,"rsa-private","file \"%s\" does not contain a "
- "valid RSA key!\n",filename);
- }
- mpz_clear(&sig);
- mpz_clear(&plain);
- mpz_clear(&check);
+ /* Verify that p*q is equal to n. */
+ mpz_mul(&tmp, &st->p, &st->q);
+ if (mpz_cmp(&tmp, &st->n) != 0)
+ goto done_checks;
+
+ /*
+ * 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
+ * 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(&tmp3, &tmp, &tmp2);
+ if (mpz_cmp_si(&tmp3, 1) != 0)
+ goto done_checks;
+ mpz_sub_ui(&tmp2, &st->q, 1);
+ mpz_mod(&tmp3, &tmp, &tmp2);
+ if (mpz_cmp_si(&tmp3, 1) != 0)
+ goto done_checks;
+
+ /* Verify that q*iqmp is congruent to 1 mod p. */
+ mpz_mul(&tmp, &st->q, &iqmp);
+ mpz_mod(&tmp2, &tmp, &st->p);
+ if (mpz_cmp_si(&tmp2, 1) != 0)
+ goto done_checks;
+ }
+ /* 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);
+ mpz_clear(&d);
+ mpz_clear(&iqmp);
assume_valid:
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