зеркало из https://github.com/github/putty.git
464 строки
12 KiB
C
464 строки
12 KiB
C
/*
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* RSA implementation just sufficient for ssh client-side
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* initialisation step
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*
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* Rewritten for more speed by Joris van Rantwijk, Jun 1999.
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <assert.h>
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#include <windows.h> // FIXME
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#include "putty.h" // FIXME
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#include "ssh.h"
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int makekey(unsigned char *data, struct RSAKey *result,
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unsigned char **keystr, int order) {
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unsigned char *p = data;
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int i;
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if (result) {
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result->bits = 0;
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for (i=0; i<4; i++)
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result->bits = (result->bits << 8) + *p++;
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} else
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p += 4;
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/*
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* order=0 means exponent then modulus (the keys sent by the
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* server). order=1 means modulus then exponent (the keys
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* stored in a keyfile).
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*/
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if (order == 0)
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p += ssh1_read_bignum(p, result ? &result->exponent : NULL);
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if (result)
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result->bytes = (((p[0] << 8) + p[1]) + 7) / 8;
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if (keystr) *keystr = p+2;
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p += ssh1_read_bignum(p, result ? &result->modulus : NULL);
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if (order == 1)
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p += ssh1_read_bignum(p, result ? &result->exponent : NULL);
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return p - data;
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}
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int makeprivate(unsigned char *data, struct RSAKey *result) {
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return ssh1_read_bignum(data, &result->private_exponent);
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}
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void rsaencrypt(unsigned char *data, int length, struct RSAKey *key) {
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Bignum b1, b2;
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int i;
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unsigned char *p;
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memmove(data+key->bytes-length, data, length);
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data[0] = 0;
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data[1] = 2;
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for (i = 2; i < key->bytes-length-1; i++) {
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do {
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data[i] = random_byte();
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} while (data[i] == 0);
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}
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data[key->bytes-length-1] = 0;
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b1 = bignum_from_bytes(data, key->bytes);
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b2 = modpow(b1, key->exponent, key->modulus);
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p = data;
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for (i=key->bytes; i-- ;) {
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*p++ = bignum_byte(b2, i);
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}
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freebn(b1);
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freebn(b2);
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}
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Bignum rsadecrypt(Bignum input, struct RSAKey *key) {
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Bignum ret;
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ret = modpow(input, key->private_exponent, key->modulus);
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return ret;
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}
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int rsastr_len(struct RSAKey *key) {
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Bignum md, ex;
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int mdlen, exlen;
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md = key->modulus;
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ex = key->exponent;
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mdlen = (ssh1_bignum_bitcount(md)+15) / 16;
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exlen = (ssh1_bignum_bitcount(ex)+15) / 16;
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return 4 * (mdlen+exlen) + 20;
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}
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void rsastr_fmt(char *str, struct RSAKey *key) {
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Bignum md, ex;
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int len = 0, i, nibbles;
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static const char hex[] = "0123456789abcdef";
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md = key->modulus;
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ex = key->exponent;
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len += sprintf(str+len, "0x");
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nibbles = (3 + ssh1_bignum_bitcount(ex))/4; if (nibbles<1) nibbles=1;
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for (i=nibbles; i-- ;)
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str[len++] = hex[(bignum_byte(ex, i/2) >> (4*(i%2))) & 0xF];
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len += sprintf(str+len, ",0x");
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nibbles = (3 + ssh1_bignum_bitcount(md))/4; if (nibbles<1) nibbles=1;
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for (i=nibbles; i-- ;)
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str[len++] = hex[(bignum_byte(md, i/2) >> (4*(i%2))) & 0xF];
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str[len] = '\0';
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}
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/*
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* Generate a fingerprint string for the key. Compatible with the
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* OpenSSH fingerprint code.
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*/
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void rsa_fingerprint(char *str, int len, struct RSAKey *key) {
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struct MD5Context md5c;
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unsigned char digest[16];
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char buffer[16*3+40];
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int numlen, slen, i;
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MD5Init(&md5c);
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numlen = ssh1_bignum_length(key->modulus) - 2;
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for (i = numlen; i-- ;) {
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unsigned char c = bignum_byte(key->modulus, i);
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MD5Update(&md5c, &c, 1);
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}
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numlen = ssh1_bignum_length(key->exponent) - 2;
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for (i = numlen; i-- ;) {
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unsigned char c = bignum_byte(key->exponent, i);
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MD5Update(&md5c, &c, 1);
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}
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MD5Final(digest, &md5c);
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sprintf(buffer, "%d ", ssh1_bignum_bitcount(key->modulus));
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for (i = 0; i < 16; i++)
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sprintf(buffer+strlen(buffer), "%s%02x", i?":":"", digest[i]);
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strncpy(str, buffer, len); str[len-1] = '\0';
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slen = strlen(str);
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if (key->comment && slen < len-1) {
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str[slen] = ' ';
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strncpy(str+slen+1, key->comment, len-slen-1);
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str[len-1] = '\0';
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}
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}
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void freersakey(struct RSAKey *key) {
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if (key->modulus) freebn(key->modulus);
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if (key->exponent) freebn(key->exponent);
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if (key->private_exponent) freebn(key->private_exponent);
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if (key->comment) sfree(key->comment);
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}
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/* ----------------------------------------------------------------------
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* Implementation of the ssh-rsa signing key type.
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*/
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#define GET_32BIT(cp) \
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(((unsigned long)(unsigned char)(cp)[0] << 24) | \
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((unsigned long)(unsigned char)(cp)[1] << 16) | \
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((unsigned long)(unsigned char)(cp)[2] << 8) | \
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((unsigned long)(unsigned char)(cp)[3]))
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#define PUT_32BIT(cp, value) { \
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(cp)[0] = (unsigned char)((value) >> 24); \
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(cp)[1] = (unsigned char)((value) >> 16); \
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(cp)[2] = (unsigned char)((value) >> 8); \
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(cp)[3] = (unsigned char)(value); }
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static void getstring(char **data, int *datalen, char **p, int *length) {
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*p = NULL;
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if (*datalen < 4)
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return;
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*length = GET_32BIT(*data);
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*datalen -= 4; *data += 4;
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if (*datalen < *length)
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return;
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*p = *data;
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*data += *length; *datalen -= *length;
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}
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static Bignum getmp(char **data, int *datalen) {
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char *p;
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int length;
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Bignum b;
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getstring(data, datalen, &p, &length);
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if (!p)
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return NULL;
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b = bignum_from_bytes(p, length);
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return b;
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}
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static void *rsa2_newkey(char *data, int len) {
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char *p;
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int slen;
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struct RSAKey *rsa;
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rsa = smalloc(sizeof(struct RSAKey));
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if (!rsa) return NULL;
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getstring(&data, &len, &p, &slen);
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if (!p || memcmp(p, "ssh-rsa", 7)) {
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sfree(rsa);
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return NULL;
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}
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rsa->exponent = getmp(&data, &len);
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rsa->modulus = getmp(&data, &len);
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rsa->private_exponent = NULL;
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rsa->comment = NULL;
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return rsa;
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}
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static void rsa2_freekey(void *key) {
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struct RSAKey *rsa = (struct RSAKey *)key;
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freersakey(rsa);
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sfree(rsa);
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}
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static char *rsa2_fmtkey(void *key) {
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struct RSAKey *rsa = (struct RSAKey *)key;
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char *p;
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int len;
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len = rsastr_len(rsa);
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p = smalloc(len);
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rsastr_fmt(p, rsa);
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return p;
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}
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static unsigned char *rsa2_public_blob(void *key, int *len) {
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struct RSAKey *rsa = (struct RSAKey *)key;
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int elen, mlen, bloblen;
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int i;
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unsigned char *blob, *p;
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elen = (ssh1_bignum_bitcount(rsa->exponent)+8)/8;
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mlen = (ssh1_bignum_bitcount(rsa->modulus)+8)/8;
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/*
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* string "ssh-rsa", mpint exp, mpint mod. Total 19+elen+mlen.
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* (three length fields, 12+7=19).
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*/
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bloblen = 19+elen+mlen;
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blob = smalloc(bloblen);
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p = blob;
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PUT_32BIT(p, 7); p += 4;
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memcpy(p, "ssh-rsa", 7); p += 7;
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PUT_32BIT(p, elen); p += 4;
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for (i = elen; i-- ;) *p++ = bignum_byte(rsa->exponent, i);
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PUT_32BIT(p, mlen); p += 4;
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for (i = mlen; i-- ;) *p++ = bignum_byte(rsa->modulus, i);
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assert(p == blob + bloblen);
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*len = bloblen;
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return blob;
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}
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static unsigned char *rsa2_private_blob(void *key, int *len) {
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struct RSAKey *rsa = (struct RSAKey *)key;
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int dlen, plen, qlen, ulen, bloblen;
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int i;
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unsigned char *blob, *p;
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dlen = (ssh1_bignum_bitcount(rsa->private_exponent)+8)/8;
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plen = (ssh1_bignum_bitcount(rsa->p)+8)/8;
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qlen = (ssh1_bignum_bitcount(rsa->q)+8)/8;
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ulen = (ssh1_bignum_bitcount(rsa->iqmp)+8)/8;
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/*
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* mpint private_exp, mpint p, mpint q, mpint iqmp. Total 16 +
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* sum of lengths.
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*/
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bloblen = 16+dlen+plen+qlen+ulen;
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blob = smalloc(bloblen);
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p = blob;
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PUT_32BIT(p, dlen); p += 4;
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for (i = dlen; i-- ;) *p++ = bignum_byte(rsa->private_exponent, i);
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PUT_32BIT(p, plen); p += 4;
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for (i = plen; i-- ;) *p++ = bignum_byte(rsa->p, i);
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PUT_32BIT(p, qlen); p += 4;
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for (i = qlen; i-- ;) *p++ = bignum_byte(rsa->q, i);
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PUT_32BIT(p, ulen); p += 4;
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for (i = ulen; i-- ;) *p++ = bignum_byte(rsa->iqmp, i);
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assert(p == blob + bloblen);
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*len = bloblen;
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return blob;
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}
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static void *rsa2_createkey(unsigned char *pub_blob, int pub_len,
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unsigned char *priv_blob, int priv_len) {
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struct RSAKey *rsa;
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char *pb = (char *)priv_blob;
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rsa = rsa2_newkey((char *)pub_blob, pub_len);
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rsa->private_exponent = getmp(&pb, &priv_len);
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rsa->p = getmp(&pb, &priv_len);
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rsa->q = getmp(&pb, &priv_len);
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rsa->iqmp = getmp(&pb, &priv_len);
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return rsa;
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}
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static char *rsa2_fingerprint(void *key) {
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struct RSAKey *rsa = (struct RSAKey *)key;
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struct MD5Context md5c;
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unsigned char digest[16], lenbuf[4];
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char buffer[16*3+40];
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char *ret;
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int numlen, i;
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MD5Init(&md5c);
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MD5Update(&md5c, "\0\0\0\7ssh-rsa", 11);
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#define ADD_BIGNUM(bignum) \
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numlen = (ssh1_bignum_bitcount(bignum)+8)/8; \
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PUT_32BIT(lenbuf, numlen); MD5Update(&md5c, lenbuf, 4); \
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for (i = numlen; i-- ;) { \
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unsigned char c = bignum_byte(bignum, i); \
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MD5Update(&md5c, &c, 1); \
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}
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ADD_BIGNUM(rsa->exponent);
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ADD_BIGNUM(rsa->modulus);
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#undef ADD_BIGNUM
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MD5Final(digest, &md5c);
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sprintf(buffer, "ssh-rsa %d ", ssh1_bignum_bitcount(rsa->modulus));
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for (i = 0; i < 16; i++)
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sprintf(buffer+strlen(buffer), "%s%02x", i?":":"", digest[i]);
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ret = smalloc(strlen(buffer)+1);
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if (ret)
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strcpy(ret, buffer);
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return ret;
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}
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/*
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* This is the magic ASN.1/DER prefix that goes in the decoded
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* signature, between the string of FFs and the actual SHA hash
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* value. As closely as I can tell, the meaning of it is:
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*
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* 00 -- this marks the end of the FFs; not part of the ASN.1 bit itself
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*
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* 30 21 -- a constructed SEQUENCE of length 0x21
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* 30 09 -- a constructed sub-SEQUENCE of length 9
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* 06 05 -- an object identifier, length 5
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* 2B 0E 03 02 1A --
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* 05 00 -- NULL
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* 04 14 -- a primitive OCTET STRING of length 0x14
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* [0x14 bytes of hash data follows]
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*/
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static unsigned char asn1_weird_stuff[] = {
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0x00,0x30,0x21,0x30,0x09,0x06,0x05,0x2B,
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0x0E,0x03,0x02,0x1A,0x05,0x00,0x04,0x14,
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};
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static int rsa2_verifysig(void *key, char *sig, int siglen,
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char *data, int datalen) {
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struct RSAKey *rsa = (struct RSAKey *)key;
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Bignum in, out;
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char *p;
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int slen;
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int bytes, i, j, ret;
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unsigned char hash[20];
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getstring(&sig, &siglen, &p, &slen);
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if (!p || slen != 7 || memcmp(p, "ssh-rsa", 7)) {
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return 0;
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}
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in = getmp(&sig, &siglen);
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out = modpow(in, rsa->exponent, rsa->modulus);
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freebn(in);
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ret = 1;
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bytes = ssh1_bignum_bitcount(rsa->modulus) / 8;
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/* Top (partial) byte should be zero. */
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if (bignum_byte(out, bytes-1) != 0)
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ret = 0;
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/* First whole byte should be 1. */
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if (bignum_byte(out, bytes-2) != 1)
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ret = 0;
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/* Most of the rest should be FF. */
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for (i = bytes-3; i >= 20 + sizeof(asn1_weird_stuff); i--) {
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if (bignum_byte(out, i) != 0xFF)
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ret = 0;
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}
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/* Then we expect to see the asn1_weird_stuff. */
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for (i = 20 + sizeof(asn1_weird_stuff) - 1, j=0; i >= 20; i--,j++) {
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if (bignum_byte(out, i) != asn1_weird_stuff[j])
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ret = 0;
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}
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/* Finally, we expect to see the SHA-1 hash of the signed data. */
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SHA_Simple(data, datalen, hash);
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for (i = 19, j=0; i >= 0; i--,j++) {
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if (bignum_byte(out, i) != hash[j])
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ret = 0;
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}
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return ret;
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}
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unsigned char *rsa2_sign(void *key, char *data, int datalen, int *siglen) {
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struct RSAKey *rsa = (struct RSAKey *)key;
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unsigned char *bytes;
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int nbytes;
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unsigned char hash[20];
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Bignum in, out;
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int i, j;
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SHA_Simple(data, datalen, hash);
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nbytes = (ssh1_bignum_bitcount(rsa->modulus)-1) / 8;
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bytes = smalloc(nbytes);
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bytes[0] = 1;
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for (i = 1; i < nbytes-20-sizeof(asn1_weird_stuff); i++)
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bytes[i] = 0xFF;
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for (i = nbytes-20-sizeof(asn1_weird_stuff), j=0; i < nbytes-20; i++,j++)
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bytes[i] = asn1_weird_stuff[j];
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for (i = nbytes-20, j=0; i < nbytes; i++,j++)
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bytes[i] = hash[j];
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in = bignum_from_bytes(bytes, nbytes);
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sfree(bytes);
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out = modpow(in, rsa->private_exponent, rsa->modulus);
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freebn(in);
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nbytes = (ssh1_bignum_bitcount(out)+7)/8;
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bytes = smalloc(4+7+4+nbytes);
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PUT_32BIT(bytes, 7);
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memcpy(bytes+4, "ssh-rsa", 7);
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PUT_32BIT(bytes+4+7, nbytes);
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for (i = 0; i < nbytes; i++)
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bytes[4+7+4+i] = bignum_byte(out, nbytes-1-i);
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freebn(out);
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*siglen = 4+7+4+nbytes;
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return bytes;
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}
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const struct ssh_signkey ssh_rsa = {
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rsa2_newkey,
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rsa2_freekey,
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rsa2_fmtkey,
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rsa2_public_blob,
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rsa2_private_blob,
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rsa2_createkey,
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rsa2_fingerprint,
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rsa2_verifysig,
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rsa2_sign,
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"ssh-rsa",
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"rsa2"
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};
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