X-Git-Url: https://git.distorted.org.uk/u/mdw/putty/blobdiff_plain/1c2a93c4834e2cc84f29c997b16a28e2c9c4fb4d..260f3dec11d702a907fdaf5aaee143abb01d0eb2:/sshrsa.c diff --git a/sshrsa.c b/sshrsa.c index 5ea4cc72..930d151c 100644 --- a/sshrsa.c +++ b/sshrsa.c @@ -8,6 +8,7 @@ #include #include #include +#include #include "ssh.h" @@ -48,7 +49,7 @@ int makeprivate(unsigned char *data, struct RSAKey *result) { void rsaencrypt(unsigned char *data, int length, struct RSAKey *key) { Bignum b1, b2; - int w, i; + int i; unsigned char *p; memmove(data+key->bytes-length, data, length); @@ -62,32 +63,13 @@ void rsaencrypt(unsigned char *data, int length, struct RSAKey *key) { } data[key->bytes-length-1] = 0; - w = (key->bytes+1)/2; - - b1 = newbn(w); - b2 = newbn(w); - - p = data; - for (i=1; i<=w; i++) - b1[i] = 0; - for (i=key->bytes; i-- ;) { - unsigned char byte = *p++; - if (i & 1) - b1[1+i/2] |= byte<<8; - else - b1[1+i/2] |= byte; - } + b1 = bignum_from_bytes(data, key->bytes); - modpow(b1, key->exponent, key->modulus, b2); + b2 = modpow(b1, key->exponent, key->modulus); p = data; for (i=key->bytes; i-- ;) { - unsigned char b; - if (i & 1) - b = b2[1+i/2] >> 8; - else - b = b2[1+i/2] & 0xFF; - *p++ = b; + *p++ = bignum_byte(b2, i); } freebn(b1); @@ -96,35 +78,41 @@ void rsaencrypt(unsigned char *data, int length, struct RSAKey *key) { Bignum rsadecrypt(Bignum input, struct RSAKey *key) { Bignum ret; - ret = newbn(key->modulus[0]); - modpow(input, key->private_exponent, key->modulus, ret); + ret = modpow(input, key->private_exponent, key->modulus); return ret; } int rsastr_len(struct RSAKey *key) { Bignum md, ex; + int mdlen, exlen; md = key->modulus; ex = key->exponent; - return 4 * (ex[0]+md[0]) + 10; + mdlen = (bignum_bitcount(md)+15) / 16; + exlen = (bignum_bitcount(ex)+15) / 16; + return 4 * (mdlen+exlen) + 20; } void rsastr_fmt(char *str, struct RSAKey *key) { Bignum md, ex; - int len = 0, i; + int len = 0, i, nibbles; + static const char hex[] = "0123456789abcdef"; md = key->modulus; ex = key->exponent; - for (i=1; i<=ex[0]; i++) { - sprintf(str+len, "%04x", ex[i]); - len += strlen(str+len); - } - str[len++] = '/'; - for (i=1; i<=md[0]; i++) { - sprintf(str+len, "%04x", md[i]); - len += strlen(str+len); - } + len += sprintf(str+len, "0x"); + + 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 + 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]; + str[len] = '\0'; } @@ -151,7 +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'; @@ -163,9 +151,439 @@ 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); if (key->private_exponent) freebn(key->private_exponent); - if (key->comment) free(key->comment); + if (key->comment) sfree(key->comment); +} + +/* ---------------------------------------------------------------------- + * Implementation of the ssh-rsa signing key type. + */ + +#define GET_32BIT(cp) \ + (((unsigned long)(unsigned char)(cp)[0] << 24) | \ + ((unsigned long)(unsigned char)(cp)[1] << 16) | \ + ((unsigned long)(unsigned char)(cp)[2] << 8) | \ + ((unsigned long)(unsigned char)(cp)[3])) + +#define PUT_32BIT(cp, value) { \ + (cp)[0] = (unsigned char)((value) >> 24); \ + (cp)[1] = (unsigned char)((value) >> 16); \ + (cp)[2] = (unsigned char)((value) >> 8); \ + (cp)[3] = (unsigned char)(value); } + +static void getstring(char **data, int *datalen, char **p, int *length) { + *p = NULL; + if (*datalen < 4) + return; + *length = GET_32BIT(*data); + *datalen -= 4; *data += 4; + if (*datalen < *length) + return; + *p = *data; + *data += *length; *datalen -= *length; +} +static Bignum getmp(char **data, int *datalen) { + char *p; + int length; + Bignum b; + + getstring(data, datalen, &p, &length); + if (!p) + return NULL; + b = bignum_from_bytes(p, length); + return b; +} + +static void *rsa2_newkey(char *data, int len) { + char *p; + int slen; + struct RSAKey *rsa; + + rsa = smalloc(sizeof(struct RSAKey)); + if (!rsa) return NULL; + getstring(&data, &len, &p, &slen); + + if (!p || slen != 7 || memcmp(p, "ssh-rsa", 7)) { + sfree(rsa); + return NULL; + } + rsa->exponent = getmp(&data, &len); + rsa->modulus = getmp(&data, &len); + rsa->private_exponent = NULL; + rsa->comment = NULL; + + return rsa; +} + +static void rsa2_freekey(void *key) { + struct RSAKey *rsa = (struct RSAKey *)key; + freersakey(rsa); + sfree(rsa); +} + +static char *rsa2_fmtkey(void *key) { + struct RSAKey *rsa = (struct RSAKey *)key; + char *p; + int len; + + len = rsastr_len(rsa); + p = smalloc(len); + rsastr_fmt(p, rsa); + return p; +} + +static unsigned char *rsa2_public_blob(void *key, int *len) { + struct RSAKey *rsa = (struct RSAKey *)key; + int elen, mlen, bloblen; + int i; + unsigned char *blob, *p; + + 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. + * (three length fields, 12+7=19). + */ + bloblen = 19+elen+mlen; + blob = smalloc(bloblen); + p = blob; + PUT_32BIT(p, 7); p += 4; + memcpy(p, "ssh-rsa", 7); p += 7; + PUT_32BIT(p, elen); p += 4; + for (i = elen; i-- ;) *p++ = bignum_byte(rsa->exponent, i); + PUT_32BIT(p, mlen); p += 4; + for (i = mlen; i-- ;) *p++ = bignum_byte(rsa->modulus, i); + assert(p == blob + bloblen); + *len = bloblen; + return blob; +} + +static unsigned char *rsa2_private_blob(void *key, int *len) { + struct RSAKey *rsa = (struct RSAKey *)key; + int dlen, plen, qlen, ulen, bloblen; + int i; + unsigned char *blob, *p; + + 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 + + * sum of lengths. + */ + bloblen = 16+dlen+plen+qlen+ulen; + blob = smalloc(bloblen); + p = blob; + PUT_32BIT(p, dlen); p += 4; + for (i = dlen; i-- ;) *p++ = bignum_byte(rsa->private_exponent, i); + PUT_32BIT(p, plen); p += 4; + for (i = plen; i-- ;) *p++ = bignum_byte(rsa->p, i); + PUT_32BIT(p, qlen); p += 4; + for (i = qlen; i-- ;) *p++ = bignum_byte(rsa->q, i); + PUT_32BIT(p, ulen); p += 4; + for (i = ulen; i-- ;) *p++ = bignum_byte(rsa->iqmp, i); + assert(p == blob + bloblen); + *len = bloblen; + return blob; } + +static void *rsa2_createkey(unsigned char *pub_blob, int pub_len, + unsigned char *priv_blob, int priv_len) { + struct RSAKey *rsa; + char *pb = (char *)priv_blob; + + rsa = rsa2_newkey((char *)pub_blob, pub_len); + rsa->private_exponent = getmp(&pb, &priv_len); + rsa->p = getmp(&pb, &priv_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; + + rsa = smalloc(sizeof(struct RSAKey)); + if (!rsa) return NULL; + rsa->comment = NULL; + + rsa->modulus = getmp(b, len); + rsa->exponent = getmp(b, len); + rsa->private_exponent = getmp(b, len); + rsa->iqmp = getmp(b, len); + rsa->p = getmp(b, len); + rsa->q = getmp(b, len); + + if (!rsa->modulus || !rsa->exponent || !rsa->private_exponent || + !rsa->iqmp || !rsa->p || !rsa->q) { + sfree(rsa->modulus); + sfree(rsa->exponent); + sfree(rsa->private_exponent); + sfree(rsa->iqmp); + sfree(rsa->p); + sfree(rsa->q); + sfree(rsa); + return NULL; + } + + 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; + unsigned char digest[16], lenbuf[4]; + char buffer[16*3+40]; + char *ret; + int numlen, i; + + MD5Init(&md5c); + MD5Update(&md5c, "\0\0\0\7ssh-rsa", 11); + +#define ADD_BIGNUM(bignum) \ + 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); \ + MD5Update(&md5c, &c, 1); \ + } + ADD_BIGNUM(rsa->exponent); + ADD_BIGNUM(rsa->modulus); +#undef ADD_BIGNUM + + MD5Final(digest, &md5c); + + 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); + if (ret) + strcpy(ret, buffer); + return ret; +} + +/* + * 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. 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 -- 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; + Bignum in, out; + char *p; + int slen; + int bytes, i, j, ret; + unsigned char hash[20]; + + getstring(&sig, &siglen, &p, &slen); + if (!p || slen != 7 || memcmp(p, "ssh-rsa", 7)) { + return 0; + } + in = getmp(&sig, &siglen); + out = modpow(in, rsa->exponent, rsa->modulus); + freebn(in); + + ret = 1; + + bytes = bignum_bitcount(rsa->modulus) / 8; + /* Top (partial) byte should be zero. */ + if (bignum_byte(out, bytes-1) != 0) + ret = 0; + /* First whole byte should be 1. */ + if (bignum_byte(out, bytes-2) != 1) + ret = 0; + /* Most of the rest should be FF. */ + 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 + ASN1_LEN - 1, j=0; i >= 20; i--,j++) { + if (bignum_byte(out, i) != asn1_weird_stuff[j]) + ret = 0; + } + /* Finally, we expect to see the SHA-1 hash of the signed data. */ + SHA_Simple(data, datalen, hash); + for (i = 19, j=0; i >= 0; i--,j++) { + if (bignum_byte(out, i) != hash[j]) + ret = 0; + } + + return ret; +} + +unsigned char *rsa2_sign(void *key, char *data, int datalen, int *siglen) { + struct RSAKey *rsa = (struct RSAKey *)key; + unsigned char *bytes; + int nbytes; + unsigned char hash[20]; + Bignum in, out; + int i, j; + + SHA_Simple(data, datalen, hash); + + nbytes = (bignum_bitcount(rsa->modulus)-1) / 8; + bytes = smalloc(nbytes); + + bytes[0] = 1; + for (i = 1; i < nbytes-20-ASN1_LEN; i++) + bytes[i] = 0xFF; + 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]; + + in = bignum_from_bytes(bytes, nbytes); + sfree(bytes); + + out = modpow(in, rsa->private_exponent, rsa->modulus); + freebn(in); + + nbytes = (bignum_bitcount(out)+7)/8; + bytes = smalloc(4+7+4+nbytes); + PUT_32BIT(bytes, 7); + memcpy(bytes+4, "ssh-rsa", 7); + PUT_32BIT(bytes+4+7, nbytes); + for (i = 0; i < nbytes; i++) + bytes[4+7+4+i] = bignum_byte(out, nbytes-1-i); + freebn(out); + + *siglen = 4+7+4+nbytes; + return bytes; +} + +const struct ssh_signkey ssh_rsa = { + rsa2_newkey, + rsa2_freekey, + rsa2_fmtkey, + rsa2_public_blob, + rsa2_private_blob, + rsa2_createkey, + rsa2_openssh_createkey, + rsa2_openssh_fmtkey, + rsa2_fingerprint, + rsa2_verifysig, + rsa2_sign, + "ssh-rsa", + "rsa2" +};