X-Git-Url: https://git.distorted.org.uk/~mdw/sgt/putty/blobdiff_plain/02237972725a2ee327ff5684bd09742d8c1b15e9..a8cc197c711b4381e8050e0ecfc3458873f24468:/sshrsa.c diff --git a/sshrsa.c b/sshrsa.c index 53001277..7f1d790e 100644 --- a/sshrsa.c +++ b/sshrsa.c @@ -88,8 +88,8 @@ int rsastr_len(struct RSAKey *key) { md = key->modulus; ex = key->exponent; - mdlen = (ssh1_bignum_bitcount(md)+15) / 16; - exlen = (ssh1_bignum_bitcount(ex)+15) / 16; + mdlen = (bignum_bitcount(md)+15) / 16; + exlen = (bignum_bitcount(ex)+15) / 16; return 4 * (mdlen+exlen) + 20; } @@ -103,13 +103,13 @@ void rsastr_fmt(char *str, struct RSAKey *key) { len += sprintf(str+len, "0x"); - nibbles = (3 + ssh1_bignum_bitcount(ex))/4; if (nibbles<1) nibbles=1; + nibbles = (3 + bignum_bitcount(ex))/4; if (nibbles<1) nibbles=1; for (i=nibbles; i-- ;) str[len++] = hex[(bignum_byte(ex, i/2) >> (4*(i%2))) & 0xF]; len += sprintf(str+len, ",0x"); - nibbles = (3 + ssh1_bignum_bitcount(md))/4; if (nibbles<1) nibbles=1; + nibbles = (3 + bignum_bitcount(md))/4; if (nibbles<1) nibbles=1; for (i=nibbles; i-- ;) str[len++] = hex[(bignum_byte(md, i/2) >> (4*(i%2))) & 0xF]; @@ -139,7 +139,7 @@ void rsa_fingerprint(char *str, int len, struct RSAKey *key) { } MD5Final(digest, &md5c); - sprintf(buffer, "%d ", ssh1_bignum_bitcount(key->modulus)); + sprintf(buffer, "%d ", bignum_bitcount(key->modulus)); for (i = 0; i < 16; i++) sprintf(buffer+strlen(buffer), "%s%02x", i?":":"", digest[i]); strncpy(str, buffer, len); str[len-1] = '\0'; @@ -151,6 +151,57 @@ void rsa_fingerprint(char *str, int len, struct RSAKey *key) { } } +/* + * Verify that the public data in an RSA key matches the private + * data. We also check the private data itself: we ensure that p > + * q and that iqmp really is the inverse of q mod p. + */ +int rsa_verify(struct RSAKey *key) { + Bignum n, ed, pm1, qm1; + int cmp; + + /* n must equal pq. */ + n = bigmul(key->p, key->q); + cmp = bignum_cmp(n, key->modulus); + freebn(n); + if (cmp != 0) + return 0; + + /* e * d must be congruent to 1, modulo (p-1) and modulo (q-1). */ + pm1 = copybn(key->p); + decbn(pm1); + ed = modmul(key->exponent, key->private_exponent, pm1); + cmp = bignum_cmp(ed, One); + sfree(ed); + if (cmp != 0) + return 0; + + qm1 = copybn(key->q); + decbn(qm1); + ed = modmul(key->exponent, key->private_exponent, qm1); + cmp = bignum_cmp(ed, One); + sfree(ed); + if (cmp != 0) + return 0; + + /* + * Ensure p > q. + */ + if (bignum_cmp(key->p, key->q) <= 0) + return 0; + + /* + * Ensure iqmp * q is congruent to 1, modulo p. + */ + n = modmul(key->iqmp, key->q, key->p); + cmp = bignum_cmp(n, One); + sfree(n); + if (cmp != 0) + return 0; + + return 1; +} + void freersakey(struct RSAKey *key) { if (key->modulus) freebn(key->modulus); if (key->exponent) freebn(key->exponent); @@ -231,7 +282,7 @@ static char *rsa2_fmtkey(void *key) { len = rsastr_len(rsa); p = smalloc(len); - rsastr_fmt(p, rsa); + rsastr_fmt(p, rsa); return p; } @@ -241,8 +292,8 @@ static unsigned char *rsa2_public_blob(void *key, int *len) { int i; unsigned char *blob, *p; - elen = (ssh1_bignum_bitcount(rsa->exponent)+8)/8; - mlen = (ssh1_bignum_bitcount(rsa->modulus)+8)/8; + elen = (bignum_bitcount(rsa->exponent)+8)/8; + mlen = (bignum_bitcount(rsa->modulus)+8)/8; /* * string "ssh-rsa", mpint exp, mpint mod. Total 19+elen+mlen. @@ -268,10 +319,10 @@ static unsigned char *rsa2_private_blob(void *key, int *len) { int i; unsigned char *blob, *p; - dlen = (ssh1_bignum_bitcount(rsa->private_exponent)+8)/8; - plen = (ssh1_bignum_bitcount(rsa->p)+8)/8; - qlen = (ssh1_bignum_bitcount(rsa->q)+8)/8; - ulen = (ssh1_bignum_bitcount(rsa->iqmp)+8)/8; + dlen = (bignum_bitcount(rsa->private_exponent)+8)/8; + plen = (bignum_bitcount(rsa->p)+8)/8; + qlen = (bignum_bitcount(rsa->q)+8)/8; + ulen = (bignum_bitcount(rsa->iqmp)+8)/8; /* * mpint private_exp, mpint p, mpint q, mpint iqmp. Total 16 + @@ -304,14 +355,17 @@ static void *rsa2_createkey(unsigned char *pub_blob, int pub_len, rsa->q = getmp(&pb, &priv_len); rsa->iqmp = getmp(&pb, &priv_len); + if (!rsa_verify(rsa)) { + rsa2_freekey(rsa); + return NULL; + } + return rsa; } static void *rsa2_openssh_createkey(unsigned char **blob, int *len) { char **b = (char **)blob; struct RSAKey *rsa; - char *p; - int slen; rsa = smalloc(sizeof(struct RSAKey)); if (!rsa) return NULL; @@ -339,6 +393,35 @@ static void *rsa2_openssh_createkey(unsigned char **blob, int *len) { return rsa; } +static int *rsa2_openssh_fmtkey(void *key, unsigned char *blob, int len) { + struct RSAKey *rsa = (struct RSAKey *)key; + int bloblen, i; + + bloblen = + ssh2_bignum_length(rsa->modulus) + + ssh2_bignum_length(rsa->exponent) + + ssh2_bignum_length(rsa->private_exponent) + + ssh2_bignum_length(rsa->iqmp) + + ssh2_bignum_length(rsa->p) + + ssh2_bignum_length(rsa->q); + + if (bloblen > len) + return bloblen; + + bloblen = 0; +#define ENC(x) \ + PUT_32BIT(blob+bloblen, ssh2_bignum_length((x))-4); bloblen += 4; \ + for (i = ssh2_bignum_length((x))-4; i-- ;) blob[bloblen++]=bignum_byte((x),i); + ENC(rsa->modulus); + ENC(rsa->exponent); + ENC(rsa->private_exponent); + ENC(rsa->iqmp); + ENC(rsa->p); + ENC(rsa->q); + + return bloblen; +} + static char *rsa2_fingerprint(void *key) { struct RSAKey *rsa = (struct RSAKey *)key; struct MD5Context md5c; @@ -351,7 +434,7 @@ static char *rsa2_fingerprint(void *key) { MD5Update(&md5c, "\0\0\0\7ssh-rsa", 11); #define ADD_BIGNUM(bignum) \ - numlen = (ssh1_bignum_bitcount(bignum)+8)/8; \ + numlen = (bignum_bitcount(bignum)+8)/8; \ PUT_32BIT(lenbuf, numlen); MD5Update(&md5c, lenbuf, 4); \ for (i = numlen; i-- ;) { \ unsigned char c = bignum_byte(bignum, i); \ @@ -363,7 +446,7 @@ static char *rsa2_fingerprint(void *key) { MD5Final(digest, &md5c); - sprintf(buffer, "ssh-rsa %d ", ssh1_bignum_bitcount(rsa->modulus)); + sprintf(buffer, "ssh-rsa %d ", bignum_bitcount(rsa->modulus)); for (i = 0; i < 16; i++) sprintf(buffer+strlen(buffer), "%s%02x", i?":":"", digest[i]); ret = smalloc(strlen(buffer)+1); @@ -375,23 +458,34 @@ static char *rsa2_fingerprint(void *key) { /* * This is the magic ASN.1/DER prefix that goes in the decoded * signature, between the string of FFs and the actual SHA hash - * value. As closely as I can tell, the meaning of it is: + * value. The meaning of it is: * * 00 -- this marks the end of the FFs; not part of the ASN.1 bit itself * * 30 21 -- a constructed SEQUENCE of length 0x21 * 30 09 -- a constructed sub-SEQUENCE of length 9 * 06 05 -- an object identifier, length 5 - * 2B 0E 03 02 1A -- + * 2B 0E 03 02 1A -- object id { 1 3 14 3 2 26 } + * (the 1,3 comes from 0x2B = 43 = 40*1+3) * 05 00 -- NULL * 04 14 -- a primitive OCTET STRING of length 0x14 * [0x14 bytes of hash data follows] + * + * The object id in the middle there is listed as `id-sha1' in + * ftp://ftp.rsasecurity.com/pub/pkcs/pkcs-1/pkcs-1v2-1d2.asn (the + * ASN module for PKCS #1) and its expanded form is as follows: + * + * id-sha1 OBJECT IDENTIFIER ::= { + * iso(1) identified-organization(3) oiw(14) secsig(3) + * algorithms(2) 26 } */ static unsigned char asn1_weird_stuff[] = { 0x00,0x30,0x21,0x30,0x09,0x06,0x05,0x2B, 0x0E,0x03,0x02,0x1A,0x05,0x00,0x04,0x14, }; +#define ASN1_LEN ( (int) sizeof(asn1_weird_stuff) ) + static int rsa2_verifysig(void *key, char *sig, int siglen, char *data, int datalen) { struct RSAKey *rsa = (struct RSAKey *)key; @@ -411,7 +505,7 @@ static int rsa2_verifysig(void *key, char *sig, int siglen, ret = 1; - bytes = ssh1_bignum_bitcount(rsa->modulus) / 8; + bytes = bignum_bitcount(rsa->modulus) / 8; /* Top (partial) byte should be zero. */ if (bignum_byte(out, bytes-1) != 0) ret = 0; @@ -419,12 +513,12 @@ static int rsa2_verifysig(void *key, char *sig, int siglen, if (bignum_byte(out, bytes-2) != 1) ret = 0; /* Most of the rest should be FF. */ - for (i = bytes-3; i >= 20 + sizeof(asn1_weird_stuff); i--) { + for (i = bytes-3; i >= 20 + ASN1_LEN; i--) { if (bignum_byte(out, i) != 0xFF) ret = 0; } /* Then we expect to see the asn1_weird_stuff. */ - for (i = 20 + sizeof(asn1_weird_stuff) - 1, j=0; i >= 20; i--,j++) { + for (i = 20 + ASN1_LEN - 1, j=0; i >= 20; i--,j++) { if (bignum_byte(out, i) != asn1_weird_stuff[j]) ret = 0; } @@ -448,13 +542,13 @@ unsigned char *rsa2_sign(void *key, char *data, int datalen, int *siglen) { SHA_Simple(data, datalen, hash); - nbytes = (ssh1_bignum_bitcount(rsa->modulus)-1) / 8; + nbytes = (bignum_bitcount(rsa->modulus)-1) / 8; bytes = smalloc(nbytes); bytes[0] = 1; - for (i = 1; i < nbytes-20-sizeof(asn1_weird_stuff); i++) + for (i = 1; i < nbytes-20-ASN1_LEN; i++) bytes[i] = 0xFF; - for (i = nbytes-20-sizeof(asn1_weird_stuff), j=0; i < nbytes-20; i++,j++) + for (i = nbytes-20-ASN1_LEN, j=0; i < nbytes-20; i++,j++) bytes[i] = asn1_weird_stuff[j]; for (i = nbytes-20, j=0; i < nbytes; i++,j++) bytes[i] = hash[j]; @@ -465,7 +559,7 @@ unsigned char *rsa2_sign(void *key, char *data, int datalen, int *siglen) { out = modpow(in, rsa->private_exponent, rsa->modulus); freebn(in); - nbytes = (ssh1_bignum_bitcount(out)+7)/8; + nbytes = (bignum_bitcount(out)+7)/8; bytes = smalloc(4+7+4+nbytes); PUT_32BIT(bytes, 7); memcpy(bytes+4, "ssh-rsa", 7); @@ -486,6 +580,7 @@ const struct ssh_signkey ssh_rsa = { rsa2_private_blob, rsa2_createkey, rsa2_openssh_createkey, + rsa2_openssh_fmtkey, rsa2_fingerprint, rsa2_verifysig, rsa2_sign,