X-Git-Url: https://git.distorted.org.uk/~mdw/secnet/blobdiff_plain/fe5e9cc422cd72526ccfceffbc7e5af8ac83b407..refs/heads/master:/rsa.c diff --git a/rsa.c b/rsa.c index 55bd24f..01d97c3 100644 --- a/rsa.c +++ b/rsa.c @@ -1,6 +1,37 @@ -/* CRT work by Simon Tatham */ +/* + * 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. + */ + #include +#include #include #include "secnet.h" #include "util.h" @@ -27,39 +58,73 @@ 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 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>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; in, &a, data, datalen); /* * Produce an RSA signature (a^d mod n) using the Chinese @@ -83,8 +148,8 @@ static string_t rsa_sign(void *sst, uint8_t *data, uint32_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); @@ -103,35 +168,18 @@ static string_t rsa_sign(void *sst, uint8_t *data, uint32_t datalen) } 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>4]; - buff[5+i*2]=hexchars[data[i]&0xf]; - } - buff[4+datalen*2]=0; - - for (i=datalen*2+4; in, &a, data, datalen); mpz_set_str(&b, signature, 16); @@ -153,7 +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; @@ -165,7 +213,7 @@ static list_t *rsapub_apply(closure_t *self, struct cloc loc, dict_t *context, 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) { @@ -175,11 +223,14 @@ 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) { 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) { @@ -189,6 +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); } @@ -223,8 +277,9 @@ static list_t *rsapriv_apply(closure_t *self, struct cloc loc, dict_t *context, 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"); + NEW(st); st->cl.description="rsapriv"; st->cl.type=CL_RSAPRIVKEY; st->cl.apply=NULL; @@ -237,7 +292,7 @@ static list_t *rsapriv_apply(closure_t *self, struct cloc loc, dict_t *context, 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-private","first argument must be a string\n"); } filename=i->data.string; } else { @@ -277,19 +332,19 @@ 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); } 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"); @@ -320,7 +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); } @@ -334,7 +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); } @@ -348,7 +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); } @@ -362,7 +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); } @@ -383,16 +438,15 @@ static list_t *rsapriv_apply(closure_t *self, struct cloc loc, dict_t *context, * 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) @@ -401,8 +455,9 @@ static list_t *rsapriv_apply(closure_t *self, struct cloc loc, dict_t *context, /* * 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); @@ -419,33 +474,35 @@ static list_t *rsapriv_apply(closure_t *self, struct cloc loc, dict_t *context, 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); @@ -456,7 +513,6 @@ assume_valid: return new_closure(&st->cl); } -init_module rsa_module; void rsa_module(dict_t *dict) { add_closure(dict,"rsa-private",rsapriv_apply);