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,...) ({ \
332 load_err(l,(lc),0,0,__VA_ARGS__); \
336 static struct rsapub *rsa_loadpub_core(RSAPUB_BNS(RSAPUB_LOADCORE_DEFBN)
342 st->cl.description="rsapub";
343 st->cl.type=CL_SIGPUBKEY;
345 st->cl.interface=&st->ops;
347 st->ops.sethash=rsa_pub_sethash;
348 st->common.hashbuf=NULL;
349 st->ops.unpick=rsa_sig_unpick;
350 st->ops.check=rsa_sig_check;
352 st->ops.dispose=rsapub_dispose;
354 RSAPUB_BNS(RSAPUB_INIT_ST_BN)
356 #define RSAPUB_LOADCORE_GETBN(ix,en,what) \
357 if (mpz_init_set_str(&st->en,en##s,10)!=0) { \
358 LDPUBFATAL(&en##_loc, what " \"%s\" is not a " \
359 "decimal number string\n",en##s); \
361 if (mpz_sizeinbase(&st->en, 256) > RSA_MAX_MODBYTES) { \
362 LDPUBFATAL(&en##_loc, "implausibly large " what "\n"); \
365 RSAPUB_BNS(RSAPUB_LOADCORE_GETBN)
374 static list_t *rsapub_apply(closure_t *self, struct cloc loc, dict_t *context,
377 struct load_ctx l[1];
378 l->verror=verror_cfgfatal;
380 l->what="rsa-public";
383 #define RSAPUB_APPLY_GETBN(ix,en,what) \
386 en##i=list_elem(args,ix); \
388 cfgfatal(loc,"rsa-public", \
389 "you must provide an encryption key\n"); \
390 struct cloc en##_loc=en##i->loc; \
391 if (en##i->type!=t_string) \
392 cfgfatal(en##_loc,"rsa-public", \
393 "first argument must be a string\n"); \
394 en##s=en##i->data.string;
396 RSAPUB_BNS(RSAPUB_APPLY_GETBN)
398 struct rsapub *st=rsa_loadpub_core(RSAPUB_BNS(RSAPUB_LOADCORE_PASSBN)
401 return new_closure(&st->cl);
404 #define LDFATAL(...) ({ load_err(l,0,0,0,__VA_ARGS__); goto error_out; })
405 #define LDUNSUP(...) ({ load_err(l,0,0,1,__VA_ARGS__); goto error_out; })
406 #define LDFATAL_FILE(...) ({ load_err(l,0,f,0,__VA_ARGS__); goto error_out; })
407 #define LDUNSUP_FILE(...) ({ load_err(l,0,f,1,__VA_ARGS__); goto error_out; })
408 #define KEYFILE_GET(is) ({ \
409 uint##is##_t keyfile_get_tmp=keyfile_get_##is(l,f); \
410 if (!l->postreadcheck(l,f)) goto error_out; \
414 static uint32_t keyfile_get_32(struct load_ctx *l, FILE *f)
424 static uint16_t keyfile_get_16(struct load_ctx *l, FILE *f)
432 static void rsapriv_dispose(void *sst)
434 struct rsapriv *st=sst;
436 mpz_clear(&st->p); mpz_clear(&st->dp);
437 mpz_clear(&st->q); mpz_clear(&st->dq);
439 rsacommon_dispose(&st->common);
443 static struct rsapriv *rsa_loadpriv_core(struct load_ctx *l,
444 FILE *f, struct cloc loc,
445 bool_t do_validity_check)
447 struct rsapriv *st=0;
451 MP_INT e,d,iqmp,tmp,tmp2,tmp3;
462 st->cl.description="rsapriv";
463 st->cl.type=CL_SIGPRIVKEY;
465 st->cl.interface=&st->ops;
467 st->ops.sethash=rsa_priv_sethash;
468 st->common.hashbuf=NULL;
469 st->ops.sign=rsa_sign;
471 st->ops.dispose=rsapriv_dispose;
481 assert(just_check_config);
485 /* Check that the ID string is correct */
486 length=strlen(AUTHFILE_ID_STRING)+1;
487 b=safe_malloc(length,"rsapriv_apply");
488 if (fread(b,length,1,f)!=1 || memcmp(b,AUTHFILE_ID_STRING,length)!=0) {
489 LDUNSUP_FILE("failed to read magic ID"
490 " string from SSH1 private keyfile\n");
494 cipher_type=fgetc(f);
495 KEYFILE_GET(32); /* "Reserved data" */
496 if (cipher_type != 0) {
497 LDUNSUP("we don't support encrypted keyfiles\n");
500 /* Read the public key */
501 KEYFILE_GET(32); /* Not sure what this is */
502 length=(KEYFILE_GET(16)+7)/8;
503 if (length>RSA_MAX_MODBYTES) {
504 LDFATAL("implausible length %ld for modulus\n",
507 b=safe_malloc(length,"rsapriv_apply");
508 if (fread(b,length,1,f) != 1) {
509 LDFATAL_FILE("error reading modulus\n");
511 read_mpbin(&st->n,b,length);
513 length=(KEYFILE_GET(16)+7)/8;
514 if (length>RSA_MAX_MODBYTES) {
515 LDFATAL("implausible length %ld for e\n",length);
517 b=safe_malloc(length,"rsapriv_apply");
518 if (fread(b,length,1,f)!=1) {
519 LDFATAL_FILE("error reading e\n");
521 read_mpbin(&e,b,length);
524 length=KEYFILE_GET(32);
526 LDFATAL("implausibly long (%ld) key comment\n",
529 c=safe_malloc(length+1,"rsapriv_apply");
530 if (fread(c,length,1,f)!=1) {
531 LDFATAL_FILE("error reading key comment\n");
535 /* Check that the next two pairs of characters are identical - the
536 keyfile is not encrypted, so they should be */
538 if (KEYFILE_GET(16) != KEYFILE_GET(16)) {
539 LDFATAL("corrupt keyfile\n");
543 length=(KEYFILE_GET(16)+7)/8;
544 if (length>RSA_MAX_MODBYTES) {
545 LDFATAL("implausibly long (%ld) decryption key\n",
548 b=safe_malloc(length,"rsapriv_apply");
549 if (fread(b,length,1,f)!=1) {
550 LDFATAL_FILE("error reading decryption key\n");
552 read_mpbin(&d,b,length);
554 /* Read iqmp (inverse of q mod p) */
555 length=(KEYFILE_GET(16)+7)/8;
556 if (length>RSA_MAX_MODBYTES) {
557 LDFATAL("implausibly long (%ld)"
558 " iqmp auxiliary value\n", length);
560 b=safe_malloc(length,"rsapriv_apply");
561 if (fread(b,length,1,f)!=1) {
562 LDFATAL_FILE("error reading decryption key\n");
564 read_mpbin(&iqmp,b,length);
566 /* Read q (the smaller of the two primes) */
567 length=(KEYFILE_GET(16)+7)/8;
568 if (length>RSA_MAX_MODBYTES) {
569 LDFATAL("implausibly long (%ld) q value\n",
572 b=safe_malloc(length,"rsapriv_apply");
573 if (fread(b,length,1,f)!=1) {
574 LDFATAL_FILE("error reading q value\n");
576 read_mpbin(&st->q,b,length);
578 /* Read p (the larger of the two primes) */
579 length=(KEYFILE_GET(16)+7)/8;
580 if (length>RSA_MAX_MODBYTES) {
581 LDFATAL("implausibly long (%ld) p value\n",
584 b=safe_malloc(length,"rsapriv_apply");
585 if (fread(b,length,1,f)!=1) {
586 LDFATAL_FILE("error reading p value\n");
588 read_mpbin(&st->p,b,length);
592 fatal_perror("rsa-private (%s:%d): ferror",loc.file,loc.line);
596 * Now verify the validity of the key, and set up the auxiliary
597 * values for fast CRT signing.
600 if (do_validity_check) {
601 /* Verify that p*q is equal to n. */
602 mpz_mul(&tmp, &st->p, &st->q);
603 if (mpz_cmp(&tmp, &st->n) != 0)
607 * Verify that d*e is congruent to 1 mod (p-1), and mod
608 * (q-1). This is equivalent to it being congruent to 1 mod
609 * lambda(n) = lcm(p-1,q-1). The usual `textbook' condition,
610 * that d e == 1 (mod (p-1)(q-1)) is sufficient, but not
611 * actually necessary.
613 mpz_mul(&tmp, &d, &e);
614 mpz_sub_ui(&tmp2, &st->p, 1);
615 mpz_mod(&tmp3, &tmp, &tmp2);
616 if (mpz_cmp_si(&tmp3, 1) != 0)
618 mpz_sub_ui(&tmp2, &st->q, 1);
619 mpz_mod(&tmp3, &tmp, &tmp2);
620 if (mpz_cmp_si(&tmp3, 1) != 0)
623 /* Verify that q*iqmp is congruent to 1 mod p. */
624 mpz_mul(&tmp, &st->q, &iqmp);
625 mpz_mod(&tmp2, &tmp, &st->p);
626 if (mpz_cmp_si(&tmp2, 1) != 0)
629 /* Now we know the key is valid (or we don't care). */
633 * Now we compute auxiliary values dp, dq and w to allow us
634 * to use the CRT optimisation when signing.
636 * dp == d mod (p-1) so that a^dp == a^d mod p, for all a
637 * dq == d mod (q-1) similarly mod q
638 * w == iqmp * q so that w == 0 mod q, and w == 1 mod p
640 mpz_sub_ui(&tmp, &st->p, 1);
641 mpz_mod(&st->dp, &d, &tmp);
642 mpz_sub_ui(&tmp, &st->q, 1);
643 mpz_mod(&st->dq, &d, &tmp);
644 mpz_mul(&st->w, &iqmp, &st->q);
648 LDFATAL("file does not contain a "
667 if (st) rsapriv_dispose(st);
672 static bool_t postreadcheck_tryload(struct load_ctx *l, FILE *f)
675 if (feof(f)) { load_err(l,0,0,0,"eof mid-integer"); return False; }
679 bool_t rsa1_loadpriv(const struct sigscheme_info *algo,
680 struct buffer_if *privkeydata,
681 struct sigprivkey_if **sigpriv_r,
682 struct log_if *log, struct cloc loc)
685 struct rsapriv *st=0;
687 f=fmemopen(privkeydata->start,privkeydata->size,"r");
689 slilog(log,M_ERR,"failed to fmemopen private key file\n");
693 struct load_ctx l[1];
694 l->what="rsa1priv load";
695 l->verror=verror_tryload;
696 l->postreadcheck=postreadcheck_tryload;
698 l->u.tryload.log=log;
700 st=rsa_loadpriv_core(l,f,loc,False);
701 if (!st) goto error_out;
708 if (!st) return False;
713 static bool_t postreadcheck_apply(struct load_ctx *l, FILE *f)
715 cfgfile_postreadcheck(l->loc,f);
719 static list_t *rsapriv_apply(closure_t *self, struct cloc loc, dict_t *context,
726 struct load_ctx l[1];
728 l->what="rsa-private";
729 l->verror=verror_cfgfatal;
730 l->postreadcheck=postreadcheck_apply;
733 /* Argument is filename pointing to SSH1 private key file */
736 if (i->type!=t_string) {
737 cfgfatal(i->loc,"rsa-private","first argument must be a string\n");
739 filename=i->data.string;
741 filename=NULL; /* Make compiler happy */
742 cfgfatal(i->loc,"rsa-private","you must provide a filename\n");
745 f=fopen(filename,"rb");
747 if (just_check_config) {
748 Message(M_WARNING,"rsa-private (%s:%d): cannot open keyfile "
749 "\"%s\"; assuming it's valid while we check the "
750 "rest of the configuration\n",loc.file,loc.line,filename);
752 fatal_perror("rsa-private (%s:%d): cannot open file \"%s\"",
753 loc.file,loc.line,filename);
757 bool_t do_validity_check=True;
759 if (i && i->type==t_bool && i->data.bool==False) {
760 Message(M_INFO,"rsa-private (%s:%d): skipping RSA key validity "
761 "check\n",loc.file,loc.line);
762 do_validity_check=False;
765 st=rsa_loadpriv_core(l,f,loc,do_validity_check);
767 return new_closure(&st->cl);
770 void rsa_module(dict_t *dict)
772 add_closure(dict,"rsa-private",rsapriv_apply);
773 add_closure(dict,"rsa-public",rsapub_apply);