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,
52 FILE *maybe_f, bool_t unsup,
53 const char *message, va_list args);
54 bool_t (*postreadcheck)(struct load_ctx *l, FILE *f);
64 static void load_err(struct load_ctx *l,
65 const struct cloc *maybe_loc, FILE *maybe_f,
66 bool_t unsup, const char *fmt, ...)
70 l->verror(l, maybe_loc ? *maybe_loc : l->loc, maybe_f,unsup,fmt,al);
75 static void verror_tryload(struct load_ctx *l, struct cloc loc,
76 FILE *maybe_f, bool_t unsup,
77 const char *message, va_list args)
79 int class=unsup ? M_DEBUG : M_ERR;
80 slilog_part(l->u.tryload.log,class,"%s: ",l->what);
81 vslilog(l->u.tryload.log,class,message,args);
84 static void verror_cfgfatal(struct load_ctx *l, struct cloc loc,
85 FILE *maybe_f, bool_t unsup,
86 const char *message, va_list args)
88 vcfgfatal_maybefile(maybe_f,l->loc,l->what,message,args);
93 struct sigprivkey_if ops;
95 struct rsacommon common;
102 #define RSAPUB_BNS(each) \
103 each(0,e,"public exponent") \
106 #define RSAPUB_LOADCORE_PASSBN(ix,en,what) \
109 #define RSAPUB_INIT_ST_BN( ix,en,what) mpz_init (&st->en);
110 #define RSAPUB_CLEAR_ST_BN(ix,en,what) mpz_clear(&st->en);
114 struct sigpubkey_if ops;
116 struct rsacommon common;
120 /* Sign data. NB data must be smaller than modulus */
122 #define RSA_MAX_MODBYTES 2048
123 /* The largest modulus I've seen is 15360 bits, which works out at 1920
124 * bytes. Using keys this big is quite implausible, but it doesn't cost us
125 * much to support them.
128 static const char *hexchars="0123456789abcdef";
130 static void rsa_sethash(struct rsacommon *c, struct hash_if *hash,
131 const struct hash_if **in_ops)
134 c->hashbuf=safe_malloc(hash->hlen, "generate_msg");
137 static void rsa_pub_sethash(void *sst, struct hash_if *hash)
139 struct rsapub *st=sst;
140 rsa_sethash(&st->common, hash, &st->ops.hash);
142 static void rsa_priv_sethash(void *sst, struct hash_if *hash)
144 struct rsapriv *st=sst;
145 rsa_sethash(&st->common, hash, &st->ops.hash);
147 static void rsacommon_dispose(struct rsacommon *c)
152 static void emsa_pkcs1(MP_INT *n, MP_INT *m,
153 const uint8_t *data, int32_t datalen)
155 char buff[2*RSA_MAX_MODBYTES + 1];
158 /* RSA PKCS#1 v1.5 signature padding:
160 * <------------ msize hex digits ---------->
162 * 00 01 ff ff .... ff ff 00 vv vv vv .... vv
166 * = datalen*2 hex digits
168 * NB that according to PKCS#1 v1.5 we're supposed to include a
169 * hash function OID in the data. We don't do that (because we
170 * don't have the hash function OID to hand here), thus violating
171 * the spec in a way that affects interop but not security.
176 msize=mpz_sizeinbase(n, 16);
178 if (datalen*2+6>=msize) {
179 fatal("rsa: message too big");
184 for (i=0; i<datalen; i++) {
185 buff[msize+(-datalen+i)*2]=hexchars[(data[i]&0xf0)>>4];
186 buff[msize+(-datalen+i)*2+1]=hexchars[data[i]&0xf];
189 buff[msize-datalen*2-2]= '0';
190 buff[msize-datalen*2-1]= '0';
192 for (i=4; i<msize-datalen*2-2; i++)
197 mpz_set_str(m, buff, 16);
200 static bool_t rsa_sign(void *sst, uint8_t *data, int32_t datalen,
201 struct buffer_if *msg)
203 struct rsapriv *st=sst;
204 MP_INT a, b, u, v, tmp, tmp2;
205 string_t signature = 0;
211 hash_hash(st->ops.hash,data,datalen,st->common.hashbuf);
212 /* Construct the message representative. */
213 emsa_pkcs1(&st->n, &a, st->common.hashbuf, st->ops.hash->hlen);
216 * Produce an RSA signature (a^d mod n) using the Chinese
217 * Remainder Theorem. We compute:
219 * u = a^dp mod p (== a^d mod p, since dp == d mod (p-1))
220 * v = a^dq mod q (== a^d mod q, similarly)
222 * We also know w == iqmp * q, which has the property that w ==
223 * 0 mod q and w == 1 mod p. So (1-w) has the reverse property
224 * (congruent to 0 mod p and to 1 mod q). Hence we now compute
226 * b = w * u + (1-w) * v
229 * so that b is congruent to a^d both mod p and mod q. Hence b,
230 * reduced mod n, is the required signature.
237 mpz_powm_sec(&u, &a, &st->dp, &st->p);
238 mpz_powm_sec(&v, &a, &st->dq, &st->q);
239 mpz_sub(&tmp, &u, &v);
240 mpz_mul(&tmp2, &tmp, &st->w);
241 mpz_add(&tmp, &tmp2, &v);
242 mpz_mod(&b, &tmp, &st->n);
249 signature=write_mpstring(&b);
251 uint8_t *op = buf_append(msg,2);
252 if (!op) { ok=False; goto out; }
253 size_t l = strlen(signature);
256 op = buf_append(msg,l);
257 if (!op) { ok=False; goto out; }
258 memcpy(op, signature, l);
269 static bool_t rsa_sig_unpick(void *sst, struct buffer_if *msg,
270 struct alg_msg_data *sig)
272 uint8_t *lp = buf_unprepend(msg, 2);
273 if (!lp) return False;
274 sig->len = get_uint16(lp);
275 sig->start = buf_unprepend(msg, sig->len);
276 if (!sig->start) return False;
278 /* In `rsa_sig_check' below, we assume that we can write a nul
279 * terminator following the signature. Make sure there's enough space.
281 if (msg->start >= msg->base + msg->alloclen)
287 static sig_checksig_fn rsa_sig_check;
288 static bool_t rsa_sig_check(void *sst, uint8_t *data, int32_t datalen,
289 const struct alg_msg_data *sig)
291 struct rsapub *st=sst;
299 hash_hash(st->ops.hash,data,datalen,st->common.hashbuf);
300 emsa_pkcs1(&st->n, &a, st->common.hashbuf, st->ops.hash->hlen);
302 /* Terminate signature with a '0' - already checked that this will fit */
303 int save = sig->start[sig->len];
304 sig->start[sig->len] = 0;
305 mpz_set_str(&b, sig->start, 16);
306 sig->start[sig->len] = save;
308 mpz_powm(&c, &b, &st->e, &st->n);
310 ok=(mpz_cmp(&a, &c)==0);
319 static void rsapub_dispose(void *sst) {
320 struct rsapub *st=sst;
323 RSAPUB_BNS(RSAPUB_CLEAR_ST_BN)
324 rsacommon_dispose(&st->common);
328 #define RSAPUB_LOADCORE_DEFBN(ix,en,what) \
329 const char *en##s, struct cloc en##_loc,
331 #define LDPUBFATAL(lc,...) ({load_err(l,&lc,0,0,__VA_ARGS__); goto error_out;})
333 static struct rsapub *rsa_loadpub_core(RSAPUB_BNS(RSAPUB_LOADCORE_DEFBN)
339 st->cl.description="rsapub";
340 st->cl.type=CL_SIGPUBKEY;
342 st->cl.interface=&st->ops;
344 st->ops.sethash=rsa_pub_sethash;
345 st->common.hashbuf=NULL;
346 st->ops.unpick=rsa_sig_unpick;
347 st->ops.check=rsa_sig_check;
349 st->ops.dispose=rsapub_dispose;
351 RSAPUB_BNS(RSAPUB_INIT_ST_BN)
353 #define RSAPUB_LOADCORE_GETBN(ix,en,what) \
354 if (mpz_init_set_str(&st->en,en##s,10)!=0) { \
355 LDPUBFATAL(en##_loc, what " \"%s\" is not a " \
356 "decimal number string\n",en##s); \
358 if (mpz_sizeinbase(&st->en, 256) > RSA_MAX_MODBYTES) { \
359 LDPUBFATAL(en##_loc, "implausibly large " what "\n"); \
362 RSAPUB_BNS(RSAPUB_LOADCORE_GETBN)
371 static list_t *rsapub_apply(closure_t *self, struct cloc loc, dict_t *context,
374 struct load_ctx l[1];
375 l->verror=verror_cfgfatal;
377 l->what="rsa-public";
380 #define RSAPUB_APPLY_GETBN(ix,en,what) \
383 en##i=list_elem(args,ix); \
385 cfgfatal(loc,"rsa-public", \
386 "you must provide an encryption key\n"); \
387 struct cloc en##_loc=en##i->loc; \
388 if (en##i->type!=t_string) \
389 cfgfatal(en##_loc,"rsa-public", \
390 "first argument must be a string\n"); \
391 en##s=en##i->data.string;
393 RSAPUB_BNS(RSAPUB_APPLY_GETBN)
395 struct rsapub *st=rsa_loadpub_core(RSAPUB_BNS(RSAPUB_LOADCORE_PASSBN)
398 return new_closure(&st->cl);
401 #define LDFATAL(...) ({ load_err(l,0,0,0,__VA_ARGS__); goto error_out; })
402 #define LDUNSUP(...) ({ load_err(l,0,0,1,__VA_ARGS__); goto error_out; })
403 #define LDFATAL_FILE(...) ({ load_err(l,0,f,0,__VA_ARGS__); goto error_out; })
404 #define LDUNSUP_FILE(...) ({ load_err(l,0,f,1,__VA_ARGS__); goto error_out; })
405 #define KEYFILE_GET(is) ({ \
406 uint##is##_t keyfile_get_tmp=keyfile_get_##is(l,f); \
407 if (!l->postreadcheck(l,f)) goto error_out; \
411 static uint32_t keyfile_get_32(struct load_ctx *l, FILE *f)
421 static uint16_t keyfile_get_16(struct load_ctx *l, FILE *f)
429 static void rsapriv_dispose(void *sst)
431 struct rsapriv *st=sst;
433 mpz_clear(&st->p); mpz_clear(&st->dp);
434 mpz_clear(&st->q); mpz_clear(&st->dq);
436 rsacommon_dispose(&st->common);
440 static struct rsapriv *rsa_loadpriv_core(struct load_ctx *l,
441 FILE *f, struct cloc loc,
442 bool_t do_validity_check)
444 struct rsapriv *st=0;
448 MP_INT e,d,iqmp,tmp,tmp2,tmp3;
459 st->cl.description="rsapriv";
460 st->cl.type=CL_SIGPRIVKEY;
462 st->cl.interface=&st->ops;
464 st->ops.sethash=rsa_priv_sethash;
465 st->common.hashbuf=NULL;
466 st->ops.sign=rsa_sign;
468 st->ops.dispose=rsapriv_dispose;
478 assert(just_check_config);
482 /* Check that the ID string is correct */
483 length=strlen(AUTHFILE_ID_STRING)+1;
484 b=safe_malloc(length,"rsapriv_apply");
485 if (fread(b,length,1,f)!=1 || memcmp(b,AUTHFILE_ID_STRING,length)!=0) {
486 LDUNSUP_FILE("failed to read magic ID"
487 " string from SSH1 private keyfile\n");
491 cipher_type=fgetc(f);
492 KEYFILE_GET(32); /* "Reserved data" */
493 if (cipher_type != 0) {
494 LDUNSUP("we don't support encrypted keyfiles\n");
497 /* Read the public key */
498 KEYFILE_GET(32); /* Not sure what this is */
499 length=(KEYFILE_GET(16)+7)/8;
500 if (length>RSA_MAX_MODBYTES) {
501 LDFATAL("implausible length %ld for modulus\n",
504 b=safe_malloc(length,"rsapriv_apply");
505 if (fread(b,length,1,f) != 1) {
506 LDFATAL_FILE("error reading modulus\n");
508 read_mpbin(&st->n,b,length);
510 length=(KEYFILE_GET(16)+7)/8;
511 if (length>RSA_MAX_MODBYTES) {
512 LDFATAL("implausible length %ld for e\n",length);
514 b=safe_malloc(length,"rsapriv_apply");
515 if (fread(b,length,1,f)!=1) {
516 LDFATAL_FILE("error reading e\n");
518 read_mpbin(&e,b,length);
521 length=KEYFILE_GET(32);
523 LDFATAL("implausibly long (%ld) key comment\n",
526 c=safe_malloc(length+1,"rsapriv_apply");
527 if (fread(c,length,1,f)!=1) {
528 LDFATAL_FILE("error reading key comment\n");
532 /* Check that the next two pairs of characters are identical - the
533 keyfile is not encrypted, so they should be */
535 if (KEYFILE_GET(16) != KEYFILE_GET(16)) {
536 LDFATAL("corrupt keyfile\n");
540 length=(KEYFILE_GET(16)+7)/8;
541 if (length>RSA_MAX_MODBYTES) {
542 LDFATAL("implausibly long (%ld) decryption key\n",
545 b=safe_malloc(length,"rsapriv_apply");
546 if (fread(b,length,1,f)!=1) {
547 LDFATAL_FILE("error reading decryption key\n");
549 read_mpbin(&d,b,length);
551 /* Read iqmp (inverse of q mod p) */
552 length=(KEYFILE_GET(16)+7)/8;
553 if (length>RSA_MAX_MODBYTES) {
554 LDFATAL("implausibly long (%ld)"
555 " iqmp auxiliary value\n", length);
557 b=safe_malloc(length,"rsapriv_apply");
558 if (fread(b,length,1,f)!=1) {
559 LDFATAL_FILE("error reading decryption key\n");
561 read_mpbin(&iqmp,b,length);
563 /* Read q (the smaller of the two primes) */
564 length=(KEYFILE_GET(16)+7)/8;
565 if (length>RSA_MAX_MODBYTES) {
566 LDFATAL("implausibly long (%ld) q value\n",
569 b=safe_malloc(length,"rsapriv_apply");
570 if (fread(b,length,1,f)!=1) {
571 LDFATAL_FILE("error reading q value\n");
573 read_mpbin(&st->q,b,length);
575 /* Read p (the larger of the two primes) */
576 length=(KEYFILE_GET(16)+7)/8;
577 if (length>RSA_MAX_MODBYTES) {
578 LDFATAL("implausibly long (%ld) p value\n",
581 b=safe_malloc(length,"rsapriv_apply");
582 if (fread(b,length,1,f)!=1) {
583 LDFATAL_FILE("error reading p value\n");
585 read_mpbin(&st->p,b,length);
589 fatal_perror("rsa-private (%s:%d): ferror",loc.file,loc.line);
593 * Now verify the validity of the key, and set up the auxiliary
594 * values for fast CRT signing.
597 if (do_validity_check) {
598 /* Verify that p*q is equal to n. */
599 mpz_mul(&tmp, &st->p, &st->q);
600 if (mpz_cmp(&tmp, &st->n) != 0)
604 * Verify that d*e is congruent to 1 mod (p-1), and mod
605 * (q-1). This is equivalent to it being congruent to 1 mod
606 * lambda(n) = lcm(p-1,q-1). The usual `textbook' condition,
607 * that d e == 1 (mod (p-1)(q-1)) is sufficient, but not
608 * actually necessary.
610 mpz_mul(&tmp, &d, &e);
611 mpz_sub_ui(&tmp2, &st->p, 1);
612 mpz_mod(&tmp3, &tmp, &tmp2);
613 if (mpz_cmp_si(&tmp3, 1) != 0)
615 mpz_sub_ui(&tmp2, &st->q, 1);
616 mpz_mod(&tmp3, &tmp, &tmp2);
617 if (mpz_cmp_si(&tmp3, 1) != 0)
620 /* Verify that q*iqmp is congruent to 1 mod p. */
621 mpz_mul(&tmp, &st->q, &iqmp);
622 mpz_mod(&tmp2, &tmp, &st->p);
623 if (mpz_cmp_si(&tmp2, 1) != 0)
626 /* Now we know the key is valid (or we don't care). */
630 * Now we compute auxiliary values dp, dq and w to allow us
631 * to use the CRT optimisation when signing.
633 * dp == d mod (p-1) so that a^dp == a^d mod p, for all a
634 * dq == d mod (q-1) similarly mod q
635 * w == iqmp * q so that w == 0 mod q, and w == 1 mod p
637 mpz_sub_ui(&tmp, &st->p, 1);
638 mpz_mod(&st->dp, &d, &tmp);
639 mpz_sub_ui(&tmp, &st->q, 1);
640 mpz_mod(&st->dq, &d, &tmp);
641 mpz_mul(&st->w, &iqmp, &st->q);
645 LDFATAL("file does not contain a "
664 if (st) rsapriv_dispose(st);
669 static bool_t postreadcheck_tryload(struct load_ctx *l, FILE *f)
672 if (feof(f)) { load_err(l,0,0,0,"eof mid-integer"); return False; }
676 bool_t rsa1_loadpriv(const struct sigscheme_info *algo,
677 struct buffer_if *privkeydata,
678 struct sigprivkey_if **sigpriv_r,
679 struct log_if *log, struct cloc loc)
682 struct rsapriv *st=0;
684 f=fmemopen(privkeydata->start,privkeydata->size,"r");
686 slilog(log,M_ERR,"failed to fmemopen private key file\n");
690 struct load_ctx l[1];
691 l->what="rsa1priv load";
692 l->verror=verror_tryload;
693 l->postreadcheck=postreadcheck_tryload;
695 l->u.tryload.log=log;
697 st=rsa_loadpriv_core(l,f,loc,False);
698 if (!st) goto error_out;
702 if (st) { free(st); st=0; }
705 if (!st) return False;
710 static bool_t postreadcheck_apply(struct load_ctx *l, FILE *f)
712 cfgfile_postreadcheck(l->loc,f);
716 static list_t *rsapriv_apply(closure_t *self, struct cloc loc, dict_t *context,
723 struct load_ctx l[1];
725 l->what="rsa-private";
726 l->verror=verror_cfgfatal;
727 l->postreadcheck=postreadcheck_apply;
730 /* Argument is filename pointing to SSH1 private key file */
733 if (i->type!=t_string) {
734 cfgfatal(i->loc,"rsa-private","first argument must be a string\n");
736 filename=i->data.string;
738 filename=NULL; /* Make compiler happy */
739 cfgfatal(i->loc,"rsa-private","you must provide a filename\n");
742 f=fopen(filename,"rb");
744 if (just_check_config) {
745 Message(M_WARNING,"rsa-private (%s:%d): cannot open keyfile "
746 "\"%s\"; assuming it's valid while we check the "
747 "rest of the configuration\n",loc.file,loc.line,filename);
749 fatal_perror("rsa-private (%s:%d): cannot open file \"%s\"",
750 loc.file,loc.line,filename);
754 bool_t do_validity_check=True;
756 if (i && i->type==t_bool && i->data.bool==False) {
757 Message(M_INFO,"rsa-private (%s:%d): skipping RSA key validity "
758 "check\n",loc.file,loc.line);
759 do_validity_check=False;
762 st=rsa_loadpriv_core(l,f,loc,do_validity_check);
764 return new_closure(&st->cl);
767 void rsa_module(dict_t *dict)
769 add_closure(dict,"rsa-private",rsapriv_apply);
770 add_closure(dict,"rsa-public",rsapub_apply);