2 * rsa.c: implementation of RSA with PKCS#1 padding
5 * This file is Free Software. It was originally written for secnet.
7 * Copyright 1995-2003 Stephen Early
8 * Copyright 2002-2014 Ian Jackson
9 * Copyright 2001 Simon Tatham
10 * Copyright 2013 Mark Wooding
12 * You may redistribute secnet as a whole and/or modify it under the
13 * terms of the GNU General Public License as published by the Free
14 * Software Foundation; either version 3, or (at your option) any
17 * You may redistribute this file and/or modify it under the terms of
18 * the GNU General Public License as published by the Free Software
19 * Foundation; either version 2, or (at your option) any later
22 * This software is distributed in the hope that it will be useful,
23 * but WITHOUT ANY WARRANTY; without even the implied warranty of
24 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
25 * GNU General Public License for more details.
27 * You should have received a copy of the GNU General Public License
28 * along with this software; if not, see
29 * https://www.gnu.org/licenses/gpl.html.
38 #include "unaligned.h"
40 #define AUTHFILE_ID_STRING "SSH PRIVATE KEY FILE FORMAT 1.1\n"
42 #define mpp(s,n) do { char *p = mpz_get_str(NULL,16,n); printf("%s 0x%sL\n", s, p); free(p); } while (0)
48 #define FREE(b) ({ free((b)); (b)=0; })
51 void (*verror)(struct load_ctx *l, struct cloc loc,
53 const char *message, va_list args);
54 bool_t (*postreadcheck)(struct load_ctx *l, FILE *f);
56 dict_t *deprdict; /* used only to look up hash */
65 static void load_err(struct load_ctx *l,
66 const struct cloc *maybe_loc, FILE *maybe_f,
71 l->verror(l, maybe_loc ? *maybe_loc : l->loc, maybe_f,fmt,al);
76 static void verror_tryload(struct load_ctx *l, struct cloc loc,
78 const char *message, va_list args)
81 slilog_part(l->u.tryload.log,class,"%s: ",l->what);
82 vslilog(l->u.tryload.log,class,message,args);
85 static void verror_cfgfatal(struct load_ctx *l, struct cloc loc,
87 const char *message, va_list args)
89 vcfgfatal_maybefile(maybe_f,l->loc,l->what,message,args,"");
94 struct sigprivkey_if ops;
96 struct rsacommon common;
103 #define RSAPUB_BNS(each) \
104 each(0,e,"public exponent") \
107 #define RSAPUB_LOADCORE_PASSBN(ix,en,what) \
110 #define RSAPUB_INIT_ST_BN( ix,en,what) mpz_init (&st->en);
111 #define RSAPUB_CLEAR_ST_BN(ix,en,what) mpz_clear(&st->en);
115 struct sigpubkey_if ops;
117 struct rsacommon common;
121 /* Sign data. NB data must be smaller than modulus */
123 #define RSA_MAX_MODBYTES 2048
124 /* The largest modulus I've seen is 15360 bits, which works out at 1920
125 * bytes. Using keys this big is quite implausible, but it doesn't cost us
126 * much to support them.
129 static const char *hexchars="0123456789abcdef";
131 static void rsa_sethash(struct rsacommon *c, struct hash_if *hash,
132 const struct hash_if **in_ops)
135 c->hashbuf=safe_malloc(hash->hlen, "generate_msg");
138 static void rsa_pub_sethash(void *sst, struct hash_if *hash)
140 struct rsapub *st=sst;
141 rsa_sethash(&st->common, hash, &st->ops.hash);
143 static void rsa_priv_sethash(void *sst, struct hash_if *hash)
145 struct rsapriv *st=sst;
146 rsa_sethash(&st->common, hash, &st->ops.hash);
148 static void rsacommon_dispose(struct rsacommon *c)
153 static void emsa_pkcs1(MP_INT *n, MP_INT *m,
154 const uint8_t *data, int32_t datalen)
156 char buff[2*RSA_MAX_MODBYTES + 1];
159 /* RSA PKCS#1 v1.5 signature padding:
161 * <------------ msize hex digits ---------->
163 * 00 01 ff ff .... ff ff 00 vv vv vv .... vv
167 * = datalen*2 hex digits
169 * NB that according to PKCS#1 v1.5 we're supposed to include a
170 * hash function OID in the data. We don't do that (because we
171 * don't have the hash function OID to hand here), thus violating
172 * the spec in a way that affects interop but not security.
177 msize=mpz_sizeinbase(n, 16);
179 if (datalen*2+6>=msize) {
180 fatal("rsa: message too big");
185 for (i=0; i<datalen; i++) {
186 buff[msize+(-datalen+i)*2]=hexchars[(data[i]&0xf0)>>4];
187 buff[msize+(-datalen+i)*2+1]=hexchars[data[i]&0xf];
190 buff[msize-datalen*2-2]= '0';
191 buff[msize-datalen*2-1]= '0';
193 for (i=4; i<msize-datalen*2-2; i++)
198 mpz_set_str(m, buff, 16);
201 static bool_t rsa_sign(void *sst, uint8_t *data, int32_t datalen,
202 struct buffer_if *msg)
204 struct rsapriv *st=sst;
205 MP_INT a, b, u, v, tmp, tmp2;
206 string_t signature = 0;
212 hash_hash(st->ops.hash,data,datalen,st->common.hashbuf);
213 /* Construct the message representative. */
214 emsa_pkcs1(&st->n, &a, st->common.hashbuf, st->ops.hash->hlen);
217 * Produce an RSA signature (a^d mod n) using the Chinese
218 * Remainder Theorem. We compute:
220 * u = a^dp mod p (== a^d mod p, since dp == d mod (p-1))
221 * v = a^dq mod q (== a^d mod q, similarly)
223 * We also know w == iqmp * q, which has the property that w ==
224 * 0 mod q and w == 1 mod p. So (1-w) has the reverse property
225 * (congruent to 0 mod p and to 1 mod q). Hence we now compute
227 * b = w * u + (1-w) * v
230 * so that b is congruent to a^d both mod p and mod q. Hence b,
231 * reduced mod n, is the required signature.
238 mpz_powm_sec(&u, &a, &st->dp, &st->p);
239 mpz_powm_sec(&v, &a, &st->dq, &st->q);
240 mpz_sub(&tmp, &u, &v);
241 mpz_mul(&tmp2, &tmp, &st->w);
242 mpz_add(&tmp, &tmp2, &v);
243 mpz_mod(&b, &tmp, &st->n);
250 signature=write_mpstring(&b);
252 uint8_t *op = buf_append(msg,2);
253 if (!op) { ok=False; goto out; }
254 size_t l = strlen(signature);
257 op = buf_append(msg,l);
258 if (!op) { ok=False; goto out; }
259 memcpy(op, signature, l);
270 static bool_t rsa_sig_unpick(void *sst, struct buffer_if *msg,
271 struct alg_msg_data *sig)
273 uint8_t *lp = buf_unprepend(msg, 2);
274 if (!lp) return False;
275 sig->len = get_uint16(lp);
276 sig->start = buf_unprepend(msg, sig->len);
277 if (!sig->start) return False;
279 /* In `rsa_sig_check' below, we assume that we can write a nul
280 * terminator following the signature. Make sure there's enough space.
282 if (msg->start >= msg->base + msg->alloclen)
288 static sig_checksig_fn rsa_sig_check;
289 static bool_t rsa_sig_check(void *sst, uint8_t *data, int32_t datalen,
290 const struct alg_msg_data *sig)
292 struct rsapub *st=sst;
300 hash_hash(st->ops.hash,data,datalen,st->common.hashbuf);
301 emsa_pkcs1(&st->n, &a, st->common.hashbuf, st->ops.hash->hlen);
303 /* Terminate signature with a '0' - already checked that this will fit */
304 int save = sig->start[sig->len];
305 sig->start[sig->len] = 0;
306 mpz_set_str(&b, sig->start, 16);
307 sig->start[sig->len] = save;
309 mpz_powm(&c, &b, &st->e, &st->n);
311 ok=(mpz_cmp(&a, &c)==0);
320 static void rsapub_dispose(void *sst) {
321 struct rsapub *st=sst;
324 RSAPUB_BNS(RSAPUB_CLEAR_ST_BN)
325 rsacommon_dispose(&st->common);
329 #define RSAPUB_LOADCORE_DEFBN(ix,en,what) \
330 const char *en##s, struct cloc en##_loc,
332 #define LDPUBFATAL(lc,...) ({ \
333 load_err(l,(lc),0,__VA_ARGS__); \
337 static struct rsapub *rsa_loadpub_core(RSAPUB_BNS(RSAPUB_LOADCORE_DEFBN)
343 st->cl.description="rsapub";
344 st->cl.type=CL_SIGPUBKEY;
346 st->cl.interface=&st->ops;
348 st->ops.sethash=rsa_pub_sethash;
349 st->common.hashbuf=NULL;
350 st->ops.unpick=rsa_sig_unpick;
351 st->ops.check=rsa_sig_check;
353 st->ops.dispose=rsapub_dispose;
355 RSAPUB_BNS(RSAPUB_INIT_ST_BN)
357 #define RSAPUB_LOADCORE_GETBN(ix,en,what) \
358 if (mpz_init_set_str(&st->en,en##s,10)!=0) { \
359 LDPUBFATAL(&en##_loc, what " \"%s\" is not a " \
360 "decimal number string",en##s); \
362 if (mpz_sizeinbase(&st->en, 256) > RSA_MAX_MODBYTES) { \
363 LDPUBFATAL(&en##_loc, "implausibly large " what); \
366 RSAPUB_BNS(RSAPUB_LOADCORE_GETBN)
375 static list_t *rsapub_apply(closure_t *self, struct cloc loc, dict_t *context,
378 struct load_ctx l[1];
379 l->verror=verror_cfgfatal;
381 l->what="rsa-public";
385 #define RSAPUB_APPLY_GETBN(ix,en,what) \
388 en##i=list_elem(args,ix); \
390 cfgfatal(loc,"rsa-public", \
391 "you must provide an encryption key\n"); \
392 struct cloc en##_loc=en##i->loc; \
393 if (en##i->type!=t_string) \
394 cfgfatal(en##_loc,"rsa-public", \
395 "first argument must be a string\n"); \
396 en##s=en##i->data.string;
398 RSAPUB_BNS(RSAPUB_APPLY_GETBN)
400 struct rsapub *st=rsa_loadpub_core(RSAPUB_BNS(RSAPUB_LOADCORE_PASSBN)
403 return new_closure(&st->cl);
406 bool_t rsa1_loadpub(const struct sigscheme_info *algo,
407 struct buffer_if *pubkeydata,
408 struct sigpubkey_if **sigpub_r,
409 closure_t **closure_r,
410 struct log_if *log, struct cloc loc)
414 struct load_ctx l[1];
415 l->verror=verror_tryload;
417 l->what="rsa1_loadpub";
420 l->u.tryload.log=log;
422 char *nul=buf_append(pubkeydata,1);
423 if (!nul) LDPUBFATAL(0,"rsa1 public key data too long for extra nul");
426 const char *delim=" \t\n";
428 /*unused*/ strtok_r(pubkeydata->start,delim,&saveptr);
430 #define RSAPUB_TRYLOAD_GETBN(ix,en,what) \
431 struct cloc en##_loc=loc; \
432 const char *en##s=strtok_r(0,delim,&saveptr); \
433 if (!en##s) LDPUBFATAL(0,"end of pubkey data looking for " what);
435 RSAPUB_BNS(RSAPUB_TRYLOAD_GETBN);
437 st=rsa_loadpub_core(RSAPUB_BNS(RSAPUB_LOADCORE_PASSBN) l);
438 if (!st) goto error_out;
449 #define LDFATAL(...) ({ load_err(l,0,0,__VA_ARGS__); goto error_out; })
450 #define LDFATAL_FILE(...) ({ load_err(l,0,f,__VA_ARGS__); goto error_out; })
451 #define KEYFILE_GET(is) ({ \
452 uint##is##_t keyfile_get_tmp=keyfile_get_##is(l,f); \
453 if (!l->postreadcheck(l,f)) goto error_out; \
457 static uint32_t keyfile_get_32(struct load_ctx *l, FILE *f)
467 static uint16_t keyfile_get_16(struct load_ctx *l, FILE *f)
475 static void rsapriv_dispose(void *sst)
477 struct rsapriv *st=sst;
479 mpz_clear(&st->p); mpz_clear(&st->dp);
480 mpz_clear(&st->q); mpz_clear(&st->dq);
482 rsacommon_dispose(&st->common);
486 static struct rsapriv *rsa_loadpriv_core(struct load_ctx *l,
487 FILE *f, struct cloc loc,
488 bool_t do_validity_check)
490 struct rsapriv *st=0;
494 MP_INT e,d,iqmp,tmp,tmp2,tmp3;
505 st->cl.description="rsapriv";
506 st->cl.type=CL_SIGPRIVKEY;
508 st->cl.interface=&st->ops;
510 st->ops.sethash=rsa_priv_sethash;
511 st->common.hashbuf=NULL;
512 st->ops.sign=rsa_sign;
514 st->ops.dispose=rsapriv_dispose;
524 assert(just_check_config);
528 /* Check that the ID string is correct */
529 length=strlen(AUTHFILE_ID_STRING)+1;
530 b=safe_malloc(length,"rsapriv_apply");
531 if (fread(b,length,1,f)!=1 || memcmp(b,AUTHFILE_ID_STRING,length)!=0) {
532 LDFATAL_FILE("failed to read magic ID"
533 " string from SSH1 private keyfile\n");
537 cipher_type=fgetc(f);
538 KEYFILE_GET(32); /* "Reserved data" */
539 if (cipher_type != 0) {
540 LDFATAL("we don't support encrypted keyfiles\n");
543 /* Read the public key */
544 KEYFILE_GET(32); /* Not sure what this is */
545 length=(KEYFILE_GET(16)+7)/8;
546 if (length>RSA_MAX_MODBYTES) {
547 LDFATAL("implausible length %ld for modulus\n",
550 b=safe_malloc(length,"rsapriv_apply");
551 if (fread(b,length,1,f) != 1) {
552 LDFATAL_FILE("error reading modulus\n");
554 read_mpbin(&st->n,b,length);
556 length=(KEYFILE_GET(16)+7)/8;
557 if (length>RSA_MAX_MODBYTES) {
558 LDFATAL("implausible length %ld for e\n",length);
560 b=safe_malloc(length,"rsapriv_apply");
561 if (fread(b,length,1,f)!=1) {
562 LDFATAL_FILE("error reading e\n");
564 read_mpbin(&e,b,length);
567 length=KEYFILE_GET(32);
569 LDFATAL("implausibly long (%ld) key comment\n",
572 c=safe_malloc(length+1,"rsapriv_apply");
573 if (fread(c,length,1,f)!=1) {
574 LDFATAL_FILE("error reading key comment\n");
578 /* Check that the next two pairs of characters are identical - the
579 keyfile is not encrypted, so they should be */
581 if (KEYFILE_GET(16) != KEYFILE_GET(16)) {
582 LDFATAL("corrupt keyfile\n");
586 length=(KEYFILE_GET(16)+7)/8;
587 if (length>RSA_MAX_MODBYTES) {
588 LDFATAL("implausibly long (%ld) decryption key\n",
591 b=safe_malloc(length,"rsapriv_apply");
592 if (fread(b,length,1,f)!=1) {
593 LDFATAL_FILE("error reading decryption key\n");
595 read_mpbin(&d,b,length);
597 /* Read iqmp (inverse of q mod p) */
598 length=(KEYFILE_GET(16)+7)/8;
599 if (length>RSA_MAX_MODBYTES) {
600 LDFATAL("implausibly long (%ld)"
601 " iqmp auxiliary value\n", length);
603 b=safe_malloc(length,"rsapriv_apply");
604 if (fread(b,length,1,f)!=1) {
605 LDFATAL_FILE("error reading decryption key\n");
607 read_mpbin(&iqmp,b,length);
609 /* Read q (the smaller of the two primes) */
610 length=(KEYFILE_GET(16)+7)/8;
611 if (length>RSA_MAX_MODBYTES) {
612 LDFATAL("implausibly long (%ld) q value\n",
615 b=safe_malloc(length,"rsapriv_apply");
616 if (fread(b,length,1,f)!=1) {
617 LDFATAL_FILE("error reading q value\n");
619 read_mpbin(&st->q,b,length);
621 /* Read p (the larger of the two primes) */
622 length=(KEYFILE_GET(16)+7)/8;
623 if (length>RSA_MAX_MODBYTES) {
624 LDFATAL("implausibly long (%ld) p value\n",
627 b=safe_malloc(length,"rsapriv_apply");
628 if (fread(b,length,1,f)!=1) {
629 LDFATAL_FILE("error reading p value\n");
631 read_mpbin(&st->p,b,length);
635 fatal_perror("rsa-private (%s:%d): ferror",loc.file,loc.line);
639 * Now verify the validity of the key, and set up the auxiliary
640 * values for fast CRT signing.
643 if (do_validity_check) {
644 /* Verify that p*q is equal to n. */
645 mpz_mul(&tmp, &st->p, &st->q);
646 if (mpz_cmp(&tmp, &st->n) != 0)
650 * Verify that d*e is congruent to 1 mod (p-1), and mod
651 * (q-1). This is equivalent to it being congruent to 1 mod
652 * lambda(n) = lcm(p-1,q-1). The usual `textbook' condition,
653 * that d e == 1 (mod (p-1)(q-1)) is sufficient, but not
654 * actually necessary.
656 mpz_mul(&tmp, &d, &e);
657 mpz_sub_ui(&tmp2, &st->p, 1);
658 mpz_mod(&tmp3, &tmp, &tmp2);
659 if (mpz_cmp_si(&tmp3, 1) != 0)
661 mpz_sub_ui(&tmp2, &st->q, 1);
662 mpz_mod(&tmp3, &tmp, &tmp2);
663 if (mpz_cmp_si(&tmp3, 1) != 0)
666 /* Verify that q*iqmp is congruent to 1 mod p. */
667 mpz_mul(&tmp, &st->q, &iqmp);
668 mpz_mod(&tmp2, &tmp, &st->p);
669 if (mpz_cmp_si(&tmp2, 1) != 0)
672 /* Now we know the key is valid (or we don't care). */
676 * Now we compute auxiliary values dp, dq and w to allow us
677 * to use the CRT optimisation when signing.
679 * dp == d mod (p-1) so that a^dp == a^d mod p, for all a
680 * dq == d mod (q-1) similarly mod q
681 * w == iqmp * q so that w == 0 mod q, and w == 1 mod p
683 mpz_sub_ui(&tmp, &st->p, 1);
684 mpz_mod(&st->dp, &d, &tmp);
685 mpz_sub_ui(&tmp, &st->q, 1);
686 mpz_mod(&st->dq, &d, &tmp);
687 mpz_mul(&st->w, &iqmp, &st->q);
691 LDFATAL("file does not contain a "
710 if (st) rsapriv_dispose(st);
715 static bool_t postreadcheck_tryload(struct load_ctx *l, FILE *f)
718 if (feof(f)) { load_err(l,0,0,"eof mid-integer"); return False; }
722 bool_t rsa1_loadpriv(const struct sigscheme_info *algo,
723 struct buffer_if *privkeydata,
724 struct sigprivkey_if **sigpriv_r,
725 closure_t **closure_r,
726 struct log_if *log, struct cloc loc)
729 struct rsapriv *st=0;
731 f=fmemopen(privkeydata->start,privkeydata->size,"r");
733 slilog(log,M_ERR,"failed to fmemopen private key file\n");
737 struct load_ctx l[1];
738 l->what="rsa1priv load";
739 l->verror=verror_tryload;
740 l->postreadcheck=postreadcheck_tryload;
743 l->u.tryload.log=log;
745 st=rsa_loadpriv_core(l,f,loc,False);
746 if (!st) goto error_out;
753 if (!st) return False;
759 static bool_t postreadcheck_apply(struct load_ctx *l, FILE *f)
761 cfgfile_postreadcheck(l->loc,f);
765 static list_t *rsapriv_apply(closure_t *self, struct cloc loc, dict_t *context,
772 struct load_ctx l[1];
774 l->what="rsa-private";
775 l->verror=verror_cfgfatal;
776 l->postreadcheck=postreadcheck_apply;
780 /* Argument is filename pointing to SSH1 private key file */
783 if (i->type!=t_string) {
784 cfgfatal(i->loc,"rsa-private","first argument must be a string\n");
786 filename=i->data.string;
788 filename=NULL; /* Make compiler happy */
789 cfgfatal(i->loc,"rsa-private","you must provide a filename\n");
792 f=fopen(filename,"rb");
794 if (just_check_config) {
795 Message(M_WARNING,"rsa-private (%s:%d): cannot open keyfile "
796 "\"%s\"; assuming it's valid while we check the "
797 "rest of the configuration\n",loc.file,loc.line,filename);
799 fatal_perror("rsa-private (%s:%d): cannot open file \"%s\"",
800 loc.file,loc.line,filename);
804 bool_t do_validity_check=True;
806 if (i && i->type==t_bool && i->data.bool==False) {
807 Message(M_INFO,"rsa-private (%s:%d): skipping RSA key validity "
808 "check\n",loc.file,loc.line);
809 do_validity_check=False;
812 st=rsa_loadpriv_core(l,f,loc,do_validity_check);
814 return new_closure(&st->cl);
817 void rsa_module(dict_t *dict)
819 add_closure(dict,"rsa-private",rsapriv_apply);
820 add_closure(dict,"rsa-public",rsapub_apply);