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,
52 FILE *maybe_f, bool_t unsup,
53 const char *message, va_list args);
54 bool_t (*postreadcheck)(struct load_ctx *l, FILE *f);
65 static void verror_tryload(struct load_ctx *l,
66 FILE *maybe_f, bool_t unsup,
67 const char *message, va_list args)
69 int class=unsup ? M_DEBUG : M_ERR;
70 slilog_part(l->u.tryload.log,class,"%s: ",l->what);
71 vslilog(l->u.tryload.log,class,message,args);
74 static void verror_cfgfatal(struct load_ctx *l,
75 FILE *maybe_f, bool_t unsup,
76 const char *message, va_list args)
78 vcfgfatal_maybefile(maybe_f,*l->loc,l->what,message,args);
83 struct sigprivkey_if ops;
85 struct rsacommon common;
92 #define RSAPUB_BNS(each) \
93 each(0,e,"public exponent") \
96 #define RSAPUB_LOADCORE_PASSBN(ix,en,what) \
99 #define RSAPUB_INIT_ST_BN( ix,en,what) mpz_init (&st->en);
100 #define RSAPUB_CLEAR_ST_BN(ix,en,what) mpz_clear(&st->en);
104 struct sigpubkey_if ops;
106 struct rsacommon common;
110 /* Sign data. NB data must be smaller than modulus */
112 #define RSA_MAX_MODBYTES 2048
113 /* The largest modulus I've seen is 15360 bits, which works out at 1920
114 * bytes. Using keys this big is quite implausible, but it doesn't cost us
115 * much to support them.
118 static const char *hexchars="0123456789abcdef";
120 static void rsa_sethash(struct rsacommon *c, struct hash_if *hash,
121 const struct hash_if **in_ops)
124 c->hashbuf=safe_malloc(hash->hlen, "generate_msg");
127 static void rsa_pub_sethash(void *sst, struct hash_if *hash)
129 struct rsapub *st=sst;
130 rsa_sethash(&st->common, hash, &st->ops.hash);
132 static void rsa_priv_sethash(void *sst, struct hash_if *hash)
134 struct rsapriv *st=sst;
135 rsa_sethash(&st->common, hash, &st->ops.hash);
137 static void rsacommon_dispose(struct rsacommon *c)
142 static void emsa_pkcs1(MP_INT *n, MP_INT *m,
143 const uint8_t *data, int32_t datalen)
145 char buff[2*RSA_MAX_MODBYTES + 1];
148 /* RSA PKCS#1 v1.5 signature padding:
150 * <------------ msize hex digits ---------->
152 * 00 01 ff ff .... ff ff 00 vv vv vv .... vv
156 * = datalen*2 hex digits
158 * NB that according to PKCS#1 v1.5 we're supposed to include a
159 * hash function OID in the data. We don't do that (because we
160 * don't have the hash function OID to hand here), thus violating
161 * the spec in a way that affects interop but not security.
166 msize=mpz_sizeinbase(n, 16);
168 if (datalen*2+6>=msize) {
169 fatal("rsa: message too big");
174 for (i=0; i<datalen; i++) {
175 buff[msize+(-datalen+i)*2]=hexchars[(data[i]&0xf0)>>4];
176 buff[msize+(-datalen+i)*2+1]=hexchars[data[i]&0xf];
179 buff[msize-datalen*2-2]= '0';
180 buff[msize-datalen*2-1]= '0';
182 for (i=4; i<msize-datalen*2-2; i++)
187 mpz_set_str(m, buff, 16);
190 static bool_t rsa_sign(void *sst, uint8_t *data, int32_t datalen,
191 struct buffer_if *msg)
193 struct rsapriv *st=sst;
194 MP_INT a, b, u, v, tmp, tmp2;
195 string_t signature = 0;
201 hash_hash(st->ops.hash,data,datalen,st->common.hashbuf);
202 /* Construct the message representative. */
203 emsa_pkcs1(&st->n, &a, st->common.hashbuf, st->ops.hash->hlen);
206 * Produce an RSA signature (a^d mod n) using the Chinese
207 * Remainder Theorem. We compute:
209 * u = a^dp mod p (== a^d mod p, since dp == d mod (p-1))
210 * v = a^dq mod q (== a^d mod q, similarly)
212 * We also know w == iqmp * q, which has the property that w ==
213 * 0 mod q and w == 1 mod p. So (1-w) has the reverse property
214 * (congruent to 0 mod p and to 1 mod q). Hence we now compute
216 * b = w * u + (1-w) * v
219 * so that b is congruent to a^d both mod p and mod q. Hence b,
220 * reduced mod n, is the required signature.
227 mpz_powm_sec(&u, &a, &st->dp, &st->p);
228 mpz_powm_sec(&v, &a, &st->dq, &st->q);
229 mpz_sub(&tmp, &u, &v);
230 mpz_mul(&tmp2, &tmp, &st->w);
231 mpz_add(&tmp, &tmp2, &v);
232 mpz_mod(&b, &tmp, &st->n);
239 signature=write_mpstring(&b);
241 uint8_t *op = buf_append(msg,2);
242 if (!op) { ok=False; goto out; }
243 size_t l = strlen(signature);
246 op = buf_append(msg,l);
247 if (!op) { ok=False; goto out; }
248 memcpy(op, signature, l);
259 static bool_t rsa_sig_unpick(void *sst, struct buffer_if *msg,
260 struct alg_msg_data *sig)
262 uint8_t *lp = buf_unprepend(msg, 2);
263 if (!lp) return False;
264 sig->len = get_uint16(lp);
265 sig->start = buf_unprepend(msg, sig->len);
266 if (!sig->start) return False;
268 /* In `rsa_sig_check' below, we assume that we can write a nul
269 * terminator following the signature. Make sure there's enough space.
271 if (msg->start >= msg->base + msg->alloclen)
277 static sig_checksig_fn rsa_sig_check;
278 static bool_t rsa_sig_check(void *sst, uint8_t *data, int32_t datalen,
279 const struct alg_msg_data *sig)
281 struct rsapub *st=sst;
289 hash_hash(st->ops.hash,data,datalen,st->common.hashbuf);
290 emsa_pkcs1(&st->n, &a, st->common.hashbuf, st->ops.hash->hlen);
292 /* Terminate signature with a '0' - already checked that this will fit */
293 int save = sig->start[sig->len];
294 sig->start[sig->len] = 0;
295 mpz_set_str(&b, sig->start, 16);
296 sig->start[sig->len] = save;
298 mpz_powm(&c, &b, &st->e, &st->n);
300 ok=(mpz_cmp(&a, &c)==0);
309 static void rsapub_dispose(void *sst) {
310 struct rsapub *st=sst;
314 rsacommon_dispose(&st->common);
318 #define RSAPUB_LOADCORE_DEFBN(ix,en,what) \
319 const char *en##s, struct cloc en##_loc,
321 #define LDPUBFATAL(enloc,...) \
322 cfgfatal(enloc, "rsa-public", __VA_ARGS__)
324 static struct rsapub *rsa_loadpub_core(RSAPUB_BNS(RSAPUB_LOADCORE_DEFBN)
325 struct cloc overall_loc)
330 st->cl.description="rsapub";
331 st->cl.type=CL_SIGPUBKEY;
333 st->cl.interface=&st->ops;
335 st->ops.sethash=rsa_pub_sethash;
336 st->common.hashbuf=NULL;
337 st->ops.unpick=rsa_sig_unpick;
338 st->ops.check=rsa_sig_check;
340 st->ops.dispose=rsapub_dispose;
343 #define RSAPUB_LOADCORE_GETBN(ix,en,what) \
344 if (mpz_init_set_str(&st->en,en##s,10)!=0) { \
345 LDPUBFATAL(en##_loc, what " \"%s\" is not a " \
346 "decimal number string\n",en##s); \
348 if (mpz_sizeinbase(&st->en, 256) > RSA_MAX_MODBYTES) { \
349 LDPUBFATAL(en##_loc, "implausibly large " what "\n"); \
352 RSAPUB_BNS(RSAPUB_LOADCORE_GETBN)
357 static list_t *rsapub_apply(closure_t *self, struct cloc loc, dict_t *context,
361 #define RSAPUB_APPLY_GETBN(ix,en,what) \
364 en##i=list_elem(args,ix); \
366 cfgfatal(loc,"rsa-public", \
367 "you must provide an encryption key\n"); \
368 struct cloc en##_loc=en##i->loc; \
369 if (en##i->type!=t_string) \
370 cfgfatal(en##_loc,"rsa-public", \
371 "first argument must be a string\n"); \
372 en##s=en##i->data.string;
374 RSAPUB_BNS(RSAPUB_APPLY_GETBN)
376 struct rsapub *st=rsa_loadpub_core(RSAPUB_BNS(RSAPUB_LOADCORE_PASSBN)
379 return new_closure(&st->cl);
382 static void load_error(struct load_ctx *l, FILE *maybe_f,
383 bool_t unsup, const char *fmt, ...)
387 l->verror(l,maybe_f,unsup,fmt,al);
391 #define LDFATAL(...) ({ load_error(l,0,0,__VA_ARGS__); goto error_out; })
392 #define LDUNSUP(...) ({ load_error(l,0,1,__VA_ARGS__); goto error_out; })
393 #define LDFATAL_FILE(...) ({ load_error(l,f,0,__VA_ARGS__); goto error_out; })
394 #define LDUNSUP_FILE(...) ({ load_error(l,f,1,__VA_ARGS__); goto error_out; })
395 #define KEYFILE_GET(is) ({ \
396 uint##is##_t keyfile_get_tmp=keyfile_get_##is(l,f); \
397 if (!l->postreadcheck(l,f)) goto error_out; \
401 static uint32_t keyfile_get_32(struct load_ctx *l, FILE *f)
411 static uint16_t keyfile_get_16(struct load_ctx *l, FILE *f)
419 static void rsapriv_dispose(void *sst)
421 struct rsapriv *st=sst;
423 mpz_clear(&st->p); mpz_clear(&st->dp);
424 mpz_clear(&st->q); mpz_clear(&st->dq);
426 rsacommon_dispose(&st->common);
430 static struct rsapriv *rsa_loadpriv_core(struct load_ctx *l,
431 FILE *f, struct cloc loc,
432 bool_t do_validity_check)
434 struct rsapriv *st=0;
438 MP_INT e,d,iqmp,tmp,tmp2,tmp3;
449 st->cl.description="rsapriv";
450 st->cl.type=CL_SIGPRIVKEY;
452 st->cl.interface=&st->ops;
454 st->ops.sethash=rsa_priv_sethash;
455 st->common.hashbuf=NULL;
456 st->ops.sign=rsa_sign;
458 st->ops.dispose=rsapriv_dispose;
468 assert(just_check_config);
472 /* Check that the ID string is correct */
473 length=strlen(AUTHFILE_ID_STRING)+1;
474 b=safe_malloc(length,"rsapriv_apply");
475 if (fread(b,length,1,f)!=1 || memcmp(b,AUTHFILE_ID_STRING,length)!=0) {
476 LDUNSUP_FILE("failed to read magic ID"
477 " string from SSH1 private keyfile\n");
481 cipher_type=fgetc(f);
482 KEYFILE_GET(32); /* "Reserved data" */
483 if (cipher_type != 0) {
484 LDUNSUP("we don't support encrypted keyfiles\n");
487 /* Read the public key */
488 KEYFILE_GET(32); /* Not sure what this is */
489 length=(KEYFILE_GET(16)+7)/8;
490 if (length>RSA_MAX_MODBYTES) {
491 LDFATAL("implausible length %ld for modulus\n",
494 b=safe_malloc(length,"rsapriv_apply");
495 if (fread(b,length,1,f) != 1) {
496 LDFATAL_FILE("error reading modulus\n");
498 read_mpbin(&st->n,b,length);
500 length=(KEYFILE_GET(16)+7)/8;
501 if (length>RSA_MAX_MODBYTES) {
502 LDFATAL("implausible length %ld for e\n",length);
504 b=safe_malloc(length,"rsapriv_apply");
505 if (fread(b,length,1,f)!=1) {
506 LDFATAL_FILE("error reading e\n");
508 read_mpbin(&e,b,length);
511 length=KEYFILE_GET(32);
513 LDFATAL("implausibly long (%ld) key comment\n",
516 c=safe_malloc(length+1,"rsapriv_apply");
517 if (fread(c,length,1,f)!=1) {
518 LDFATAL_FILE("error reading key comment\n");
522 /* Check that the next two pairs of characters are identical - the
523 keyfile is not encrypted, so they should be */
525 if (KEYFILE_GET(16) != KEYFILE_GET(16)) {
526 LDFATAL("corrupt keyfile\n");
530 length=(KEYFILE_GET(16)+7)/8;
531 if (length>RSA_MAX_MODBYTES) {
532 LDFATAL("implausibly long (%ld) decryption key\n",
535 b=safe_malloc(length,"rsapriv_apply");
536 if (fread(b,length,1,f)!=1) {
537 LDFATAL_FILE("error reading decryption key\n");
539 read_mpbin(&d,b,length);
541 /* Read iqmp (inverse of q mod p) */
542 length=(KEYFILE_GET(16)+7)/8;
543 if (length>RSA_MAX_MODBYTES) {
544 LDFATAL("implausibly long (%ld)"
545 " iqmp auxiliary value\n", length);
547 b=safe_malloc(length,"rsapriv_apply");
548 if (fread(b,length,1,f)!=1) {
549 LDFATAL_FILE("error reading decryption key\n");
551 read_mpbin(&iqmp,b,length);
553 /* Read q (the smaller of the two primes) */
554 length=(KEYFILE_GET(16)+7)/8;
555 if (length>RSA_MAX_MODBYTES) {
556 LDFATAL("implausibly long (%ld) q value\n",
559 b=safe_malloc(length,"rsapriv_apply");
560 if (fread(b,length,1,f)!=1) {
561 LDFATAL_FILE("error reading q value\n");
563 read_mpbin(&st->q,b,length);
565 /* Read p (the larger of the two primes) */
566 length=(KEYFILE_GET(16)+7)/8;
567 if (length>RSA_MAX_MODBYTES) {
568 LDFATAL("implausibly long (%ld) p value\n",
571 b=safe_malloc(length,"rsapriv_apply");
572 if (fread(b,length,1,f)!=1) {
573 LDFATAL_FILE("error reading p value\n");
575 read_mpbin(&st->p,b,length);
579 fatal_perror("rsa-private (%s:%d): ferror",loc.file,loc.line);
583 * Now verify the validity of the key, and set up the auxiliary
584 * values for fast CRT signing.
587 if (do_validity_check) {
588 /* Verify that p*q is equal to n. */
589 mpz_mul(&tmp, &st->p, &st->q);
590 if (mpz_cmp(&tmp, &st->n) != 0)
594 * Verify that d*e is congruent to 1 mod (p-1), and mod
595 * (q-1). This is equivalent to it being congruent to 1 mod
596 * lambda(n) = lcm(p-1,q-1). The usual `textbook' condition,
597 * that d e == 1 (mod (p-1)(q-1)) is sufficient, but not
598 * actually necessary.
600 mpz_mul(&tmp, &d, &e);
601 mpz_sub_ui(&tmp2, &st->p, 1);
602 mpz_mod(&tmp3, &tmp, &tmp2);
603 if (mpz_cmp_si(&tmp3, 1) != 0)
605 mpz_sub_ui(&tmp2, &st->q, 1);
606 mpz_mod(&tmp3, &tmp, &tmp2);
607 if (mpz_cmp_si(&tmp3, 1) != 0)
610 /* Verify that q*iqmp is congruent to 1 mod p. */
611 mpz_mul(&tmp, &st->q, &iqmp);
612 mpz_mod(&tmp2, &tmp, &st->p);
613 if (mpz_cmp_si(&tmp2, 1) != 0)
616 /* Now we know the key is valid (or we don't care). */
620 * Now we compute auxiliary values dp, dq and w to allow us
621 * to use the CRT optimisation when signing.
623 * dp == d mod (p-1) so that a^dp == a^d mod p, for all a
624 * dq == d mod (q-1) similarly mod q
625 * w == iqmp * q so that w == 0 mod q, and w == 1 mod p
627 mpz_sub_ui(&tmp, &st->p, 1);
628 mpz_mod(&st->dp, &d, &tmp);
629 mpz_sub_ui(&tmp, &st->q, 1);
630 mpz_mod(&st->dq, &d, &tmp);
631 mpz_mul(&st->w, &iqmp, &st->q);
635 LDFATAL("file does not contain a "
654 if (st) rsapriv_dispose(st);
659 static bool_t postreadcheck_tryload(struct load_ctx *l, FILE *f)
662 if (feof(f)) { load_error(l,0,0,"eof mid-integer"); return False; }
666 bool_t rsa1_loadpriv(const struct sigscheme_info *algo,
667 struct buffer_if *privkeydata,
668 struct sigprivkey_if **sigpriv_r,
669 struct log_if *log, struct cloc loc)
672 struct rsapriv *st=0;
674 f=fmemopen(privkeydata->start,privkeydata->size,"r");
676 slilog(log,M_ERR,"failed to fmemopen private key file\n");
680 struct load_ctx l[1];
681 l->what="rsa1priv load";
682 l->verror=verror_tryload;
683 l->postreadcheck=postreadcheck_tryload;
685 l->u.tryload.log=log;
687 st=rsa_loadpriv_core(l,f,loc,False);
688 if (!st) goto error_out;
692 if (st) { free(st); st=0; }
695 if (!st) return False;
700 static bool_t postreadcheck_apply(struct load_ctx *l, FILE *f)
702 cfgfile_postreadcheck(*l->loc,f);
706 static list_t *rsapriv_apply(closure_t *self, struct cloc loc, dict_t *context,
713 struct load_ctx l[1];
715 l->what="rsa-private";
716 l->verror=verror_cfgfatal;
717 l->postreadcheck=postreadcheck_apply;
720 /* Argument is filename pointing to SSH1 private key file */
723 if (i->type!=t_string) {
724 cfgfatal(i->loc,"rsa-private","first argument must be a string\n");
726 filename=i->data.string;
728 filename=NULL; /* Make compiler happy */
729 cfgfatal(i->loc,"rsa-private","you must provide a filename\n");
732 f=fopen(filename,"rb");
734 if (just_check_config) {
735 Message(M_WARNING,"rsa-private (%s:%d): cannot open keyfile "
736 "\"%s\"; assuming it's valid while we check the "
737 "rest of the configuration\n",loc.file,loc.line,filename);
739 fatal_perror("rsa-private (%s:%d): cannot open file \"%s\"",
740 loc.file,loc.line,filename);
744 bool_t do_validity_check=True;
746 if (i && i->type==t_bool && i->data.bool==False) {
747 Message(M_INFO,"rsa-private (%s:%d): skipping RSA key validity "
748 "check\n",loc.file,loc.line);
749 do_validity_check=False;
752 st=rsa_loadpriv_core(l,f,loc,do_validity_check);
754 return new_closure(&st->cl);
757 void rsa_module(dict_t *dict)
759 add_closure(dict,"rsa-private",rsapriv_apply);
760 add_closure(dict,"rsa-public",rsapub_apply);