ssh-keygen.c - third_party/openssh-portable - Git at Google

 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1994 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
  *                    All rights reserved
  * Created: Mon Mar 27 02:26:40 1995 ylo
  * Identity and host key generation and maintenance.
  */

 #include "includes.h"
 RCSID("$Id: ssh-keygen.c,v 1.10 1999/11/25 00:54:59 damien Exp $");

 #include "rsa.h"
 #include "ssh.h"
 #include "xmalloc.h"
 #include "fingerprint.h"

 /* Generated private key. */
 RSA *private_key;

 /* Generated public key. */
 RSA *public_key;

 /* Number of bits in the RSA key.  This value can be changed on the command line. */
 int bits = 1024;

 /*
  * Flag indicating that we just want to change the passphrase.  This can be
  * set on the command line.
  */
 int change_passphrase = 0;

 /*
  * Flag indicating that we just want to change the comment.  This can be set
  * on the command line.
  */
 int change_comment = 0;

 int quiet = 0;

 /* Flag indicating that we just want to see the key fingerprint */
 int print_fingerprint = 0;

 /* The identity file name, given on the command line or entered by the user. */
 char identity_file[1024];
 int have_identity = 0;

 /* This is set to the passphrase if given on the command line. */
 char *identity_passphrase = NULL;

 /* This is set to the new passphrase if given on the command line. */
 char *identity_new_passphrase = NULL;

 /* This is set to the new comment if given on the command line. */
 char *identity_comment = NULL;

 /* argv0 */
 #ifdef HAVE___PROGNAME
 extern char *__progname;
 #else /* HAVE___PROGNAME */
 const char *__progname = "ssh-keygen";
 #endif /* HAVE___PROGNAME */

 void
 ask_filename(struct passwd *pw, const char *prompt)
 {
 	char buf[1024];
 	snprintf(identity_file, sizeof(identity_file), "%s/%s",
 		 pw->pw_dir, SSH_CLIENT_IDENTITY);
 	printf("%s (%s): ", prompt, identity_file);
 	fflush(stdout);
 	if (fgets(buf, sizeof(buf), stdin) == NULL)
 		exit(1);
 	if (strchr(buf, '\n'))
 		*strchr(buf, '\n') = 0;
 	if (strcmp(buf, "") != 0)
 		strlcpy(identity_file, buf, sizeof(identity_file));
 	have_identity = 1;
 }

 void
 do_fingerprint(struct passwd *pw)
 {
 	char *comment;
 	RSA *public_key;
 	struct stat st;

 	if (!have_identity)
 		ask_filename(pw, "Enter file in which the key is");
 	if (stat(identity_file, &st) < 0) {
 		perror(identity_file);
 		exit(1);
 	}
 	public_key = RSA_new();
 	if (!load_public_key(identity_file, public_key, &comment)) {
 		char *cp, line[1024];
 		BIGNUM *e, *n;
 		int dummy, invalid = 0;
 		FILE *f = fopen(identity_file, "r");
 		n = BN_new();
 		e = BN_new();
 		if (f && fgets(line, sizeof(line), f)) {
 			cp = line;
 			line[strlen(line) - 1] = '\0';
 			if (auth_rsa_read_key(&cp, &dummy, e, n)) {
 				public_key->e = e;
 				public_key->n = n;
 				comment = xstrdup(cp ? cp : "no comment");
 			} else {
 				invalid = 1;
 			}
 		} else {
 			invalid = 1;
 		}
 		if (invalid) {
 			printf("%s is not a valid key file.\n", identity_file);
 			BN_free(e);
 			BN_free(n);
 			exit(1);
 		}
 	}
 	printf("%d %s %s\n", BN_num_bits(public_key->n),
 	       fingerprint(public_key->e, public_key->n),
 	       comment);
 	RSA_free(public_key);
 	exit(0);
 }

 /*
  * Perform changing a passphrase.  The argument is the passwd structure
  * for the current user.
  */
 void
 do_change_passphrase(struct passwd *pw)
 {
 	char *comment;
 	char *old_passphrase, *passphrase1, *passphrase2;
 	struct stat st;
 	RSA *private_key;

 	if (!have_identity)
 		ask_filename(pw, "Enter file in which the key is");
 	if (stat(identity_file, &st) < 0) {
 		perror(identity_file);
 		exit(1);
 	}
 	public_key = RSA_new();
 	if (!load_public_key(identity_file, public_key, NULL)) {
 		printf("%s is not a valid key file.\n", identity_file);
 		exit(1);
 	}
 	/* Clear the public key since we are just about to load the whole file. */
 	RSA_free(public_key);

 	/* Try to load the file with empty passphrase. */
 	private_key = RSA_new();
 	if (!load_private_key(identity_file, "", private_key, &comment)) {
 		if (identity_passphrase)
 			old_passphrase = xstrdup(identity_passphrase);
 		else
 			old_passphrase = read_passphrase("Enter old passphrase: ", 1);
 		if (!load_private_key(identity_file, old_passphrase, private_key, &comment)) {
 			memset(old_passphrase, 0, strlen(old_passphrase));
 			xfree(old_passphrase);
 			printf("Bad passphrase.\n");
 			exit(1);
 		}
 		memset(old_passphrase, 0, strlen(old_passphrase));
 		xfree(old_passphrase);
 	}
 	printf("Key has comment '%s'\n", comment);

 	/* Ask the new passphrase (twice). */
 	if (identity_new_passphrase) {
 		passphrase1 = xstrdup(identity_new_passphrase);
 		passphrase2 = NULL;
 	} else {
 		passphrase1 =
 			read_passphrase("Enter new passphrase (empty for no passphrase): ", 1);
 		passphrase2 = read_passphrase("Enter same passphrase again: ", 1);

 		/* Verify that they are the same. */
 		if (strcmp(passphrase1, passphrase2) != 0) {
 			memset(passphrase1, 0, strlen(passphrase1));
 			memset(passphrase2, 0, strlen(passphrase2));
 			xfree(passphrase1);
 			xfree(passphrase2);
 			printf("Pass phrases do not match.  Try again.\n");
 			exit(1);
 		}
 		/* Destroy the other copy. */
 		memset(passphrase2, 0, strlen(passphrase2));
 		xfree(passphrase2);
 	}

 	/* Save the file using the new passphrase. */
 	if (!save_private_key(identity_file, passphrase1, private_key, comment)) {
 		printf("Saving the key failed: %s: %s.\n",
 		       identity_file, strerror(errno));
 		memset(passphrase1, 0, strlen(passphrase1));
 		xfree(passphrase1);
 		RSA_free(private_key);
 		xfree(comment);
 		exit(1);
 	}
 	/* Destroy the passphrase and the copy of the key in memory. */
 	memset(passphrase1, 0, strlen(passphrase1));
 	xfree(passphrase1);
 	RSA_free(private_key);	/* Destroys contents */
 	xfree(comment);

 	printf("Your identification has been saved with the new passphrase.\n");
 	exit(0);
 }

 /*
  * Change the comment of a private key file.
  */
 void
 do_change_comment(struct passwd *pw)
 {
 	char new_comment[1024], *comment;
 	RSA *private_key;
 	char *passphrase;
 	struct stat st;
 	FILE *f;
 	char *tmpbuf;

 	if (!have_identity)
 		ask_filename(pw, "Enter file in which the key is");
 	if (stat(identity_file, &st) < 0) {
 		perror(identity_file);
 		exit(1);
 	}
 	/*
 	 * Try to load the public key from the file the verify that it is
 	 * readable and of the proper format.
 	 */
 	public_key = RSA_new();
 	if (!load_public_key(identity_file, public_key, NULL)) {
 		printf("%s is not a valid key file.\n", identity_file);
 		exit(1);
 	}
 	private_key = RSA_new();

 	if (load_private_key(identity_file, "", private_key, &comment))
 		passphrase = xstrdup("");
 	else {
 		if (identity_passphrase)
 			passphrase = xstrdup(identity_passphrase);
 		else if (identity_new_passphrase)
 			passphrase = xstrdup(identity_new_passphrase);
 		else
 			passphrase = read_passphrase("Enter passphrase: ", 1);
 		/* Try to load using the passphrase. */
 		if (!load_private_key(identity_file, passphrase, private_key, &comment)) {
 			memset(passphrase, 0, strlen(passphrase));
 			xfree(passphrase);
 			printf("Bad passphrase.\n");
 			exit(1);
 		}
 	}
 	printf("Key now has comment '%s'\n", comment);

 	if (identity_comment) {
 		strlcpy(new_comment, identity_comment, sizeof(new_comment));
 	} else {
 		printf("Enter new comment: ");
 		fflush(stdout);
 		if (!fgets(new_comment, sizeof(new_comment), stdin)) {
 			memset(passphrase, 0, strlen(passphrase));
 			RSA_free(private_key);
 			exit(1);
 		}
 		if (strchr(new_comment, '\n'))
 			*strchr(new_comment, '\n') = 0;
 	}

 	/* Save the file using the new passphrase. */
 	if (!save_private_key(identity_file, passphrase, private_key, new_comment)) {
 		printf("Saving the key failed: %s: %s.\n",
 		       identity_file, strerror(errno));
 		memset(passphrase, 0, strlen(passphrase));
 		xfree(passphrase);
 		RSA_free(private_key);
 		xfree(comment);
 		exit(1);
 	}
 	memset(passphrase, 0, strlen(passphrase));
 	xfree(passphrase);
 	RSA_free(private_key);

 	strlcat(identity_file, ".pub", sizeof(identity_file));
 	f = fopen(identity_file, "w");
 	if (!f) {
 		printf("Could not save your public key in %s\n", identity_file);
 		exit(1);
 	}
 	fprintf(f, "%d ", BN_num_bits(public_key->n));
 	tmpbuf = BN_bn2dec(public_key->e);
 	fprintf(f, "%s ", tmpbuf);
 	free(tmpbuf);
 	tmpbuf = BN_bn2dec(public_key->n);
 	fprintf(f, "%s %s\n", tmpbuf, new_comment);
 	free(tmpbuf);
 	fclose(f);

 	xfree(comment);

 	printf("The comment in your key file has been changed.\n");
 	exit(0);
 }

 void
 usage(void)
 {
 	printf("ssh-keygen version %s\n", SSH_VERSION);
 	printf("Usage: %s [-b bits] [-p] [-c] [-f file] [-P pass] [-N new-pass] [-C comment]\n", __progname);
 	exit(1);
 }

 /*
  * Main program for key management.
  */
 int
 main(int ac, char **av)
 {
 	char dotsshdir[16 * 1024], comment[1024], *passphrase1, *passphrase2;
 	struct passwd *pw;
 	char *tmpbuf;
 	int opt;
 	struct stat st;
 	FILE *f;
 	char hostname[MAXHOSTNAMELEN];
 	extern int optind;
 	extern char *optarg;

 	/* check if RSA support exists */
 	if (rsa_alive() == 0) {
 		fprintf(stderr,
 			"%s: no RSA support in libssl and libcrypto.  See ssl(8).\n",
 			__progname);
 		exit(1);
 	}
 	/* we need this for the home * directory.  */
 	pw = getpwuid(getuid());
 	if (!pw) {
 		printf("You don't exist, go away!\n");
 		exit(1);
 	}

 	while ((opt = getopt(ac, av, "qpclb:f:P:N:C:")) != EOF) {
 		switch (opt) {
 		case 'b':
 			bits = atoi(optarg);
 			if (bits < 512 || bits > 32768) {
 				printf("Bits has bad value.\n");
 				exit(1);
 			}
 			break;

 		case 'l':
 			print_fingerprint = 1;
 			break;

 		case 'p':
 			change_passphrase = 1;
 			break;

 		case 'c':
 			change_comment = 1;
 			break;

 		case 'f':
 			strlcpy(identity_file, optarg, sizeof(identity_file));
 			have_identity = 1;
 			break;

 		case 'P':
 			identity_passphrase = optarg;
 			break;

 		case 'N':
 			identity_new_passphrase = optarg;
 			break;

 		case 'C':
 			identity_comment = optarg;
 			break;

 		case 'q':
 			quiet = 1;
 			break;

 		case '?':
 		default:
 			usage();
 		}
 	}
 	if (optind < ac) {
 		printf("Too many arguments.\n");
 		usage();
 	}
 	if (change_passphrase && change_comment) {
 		printf("Can only have one of -p and -c.\n");
 		usage();
 	}
 	if (print_fingerprint)
 		do_fingerprint(pw);
 	if (change_passphrase)
 		do_change_passphrase(pw);
 	if (change_comment)
 		do_change_comment(pw);

 	arc4random_stir();

 	if (quiet)
 		rsa_set_verbose(0);

 	/* Generate the rsa key pair. */
 	private_key = RSA_new();
 	public_key = RSA_new();
 	rsa_generate_key(private_key, public_key, bits);

 	if (!have_identity)
 		ask_filename(pw, "Enter file in which to save the key");

 	/* Create ~/.ssh directory if it doesn\'t already exist. */
 	snprintf(dotsshdir, sizeof dotsshdir, "%s/%s", pw->pw_dir, SSH_USER_DIR);
 	if (strstr(identity_file, dotsshdir) != NULL &&
 	    stat(dotsshdir, &st) < 0) {
 		if (mkdir(dotsshdir, 0755) < 0)
 			error("Could not create directory '%s'.", dotsshdir);
 		else if (!quiet)
 			printf("Created directory '%s'.\n", dotsshdir);
 	}
 	/* If the file already exists, ask the user to confirm. */
 	if (stat(identity_file, &st) >= 0) {
 		char yesno[3];
 		printf("%s already exists.\n", identity_file);
 		printf("Overwrite (y/n)? ");
 		fflush(stdout);
 		if (fgets(yesno, sizeof(yesno), stdin) == NULL)
 			exit(1);
 		if (yesno[0] != 'y' && yesno[0] != 'Y')
 			exit(1);
 	}
 	/* Ask for a passphrase (twice). */
 	if (identity_passphrase)
 		passphrase1 = xstrdup(identity_passphrase);
 	else if (identity_new_passphrase)
 		passphrase1 = xstrdup(identity_new_passphrase);
 	else {
 passphrase_again:
 		passphrase1 =
 			read_passphrase("Enter passphrase (empty for no passphrase): ", 1);
 		passphrase2 = read_passphrase("Enter same passphrase again: ", 1);
 		if (strcmp(passphrase1, passphrase2) != 0) {
 			/* The passphrases do not match.  Clear them and retry. */
 			memset(passphrase1, 0, strlen(passphrase1));
 			memset(passphrase2, 0, strlen(passphrase2));
 			xfree(passphrase1);
 			xfree(passphrase2);
 			printf("Passphrases do not match.  Try again.\n");
 			goto passphrase_again;
 		}
 		/* Clear the other copy of the passphrase. */
 		memset(passphrase2, 0, strlen(passphrase2));
 		xfree(passphrase2);
 	}

 	if (identity_comment) {
 		strlcpy(comment, identity_comment, sizeof(comment));
 	} else {
 	  	/* Create default commend field for the passphrase. */
 		if (gethostname(hostname, sizeof(hostname)) < 0) {
 			perror("gethostname");
 			exit(1);
 		}
 		snprintf(comment, sizeof comment, "%s@%s", pw->pw_name, hostname);
 	}

 	/* Save the key with the given passphrase and comment. */
 	if (!save_private_key(identity_file, passphrase1, private_key, comment)) {
 		printf("Saving the key failed: %s: %s.\n",
 		       identity_file, strerror(errno));
 		memset(passphrase1, 0, strlen(passphrase1));
 		xfree(passphrase1);
 		exit(1);
 	}
 	/* Clear the passphrase. */
 	memset(passphrase1, 0, strlen(passphrase1));
 	xfree(passphrase1);

 	/* Clear the private key and the random number generator. */
 	RSA_free(private_key);
 	arc4random_stir();

 	if (!quiet)
 		printf("Your identification has been saved in %s.\n", identity_file);

 	strlcat(identity_file, ".pub", sizeof(identity_file));
 	f = fopen(identity_file, "w");
 	if (!f) {
 		printf("Could not save your public key in %s\n", identity_file);
 		exit(1);
 	}
 	fprintf(f, "%d ", BN_num_bits(public_key->n));
 	tmpbuf = BN_bn2dec(public_key->e);
 	fprintf(f, "%s ", tmpbuf);
 	free(tmpbuf);
 	tmpbuf = BN_bn2dec(public_key->n);
 	fprintf(f, "%s %s\n", tmpbuf, comment);
 	free(tmpbuf);
 	fclose(f);

 	if (!quiet) {
 		printf("Your public key has been saved in %s.\n", identity_file);
 		printf("The key fingerprint is:\n");
 		printf("%d %s %s\n", BN_num_bits(public_key->n),
 		       fingerprint(public_key->e, public_key->n),
 		       comment);
 	}
 	exit(0);
 }
	/*
	* Author: Tatu Ylonen <ylo@cs.hut.fi>
	* Copyright (c) 1994 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
	* All rights reserved
	* Created: Mon Mar 27 02:26:40 1995 ylo
	* Identity and host key generation and maintenance.
	*/

	#include "includes.h"
	RCSID("$Id: ssh-keygen.c,v 1.10 1999/11/25 00:54:59 damien Exp $");

	#include "rsa.h"
	#include "ssh.h"
	#include "xmalloc.h"
	#include "fingerprint.h"

	/* Generated private key. */
	RSA *private_key;

	/* Generated public key. */
	RSA *public_key;

	/* Number of bits in the RSA key. This value can be changed on the command line. */
	int bits = 1024;

	/*
	* Flag indicating that we just want to change the passphrase. This can be
	* set on the command line.
	*/
	int change_passphrase = 0;

	/*
	* Flag indicating that we just want to change the comment. This can be set
	* on the command line.
	*/
	int change_comment = 0;

	int quiet = 0;

	/* Flag indicating that we just want to see the key fingerprint */
	int print_fingerprint = 0;

	/* The identity file name, given on the command line or entered by the user. */
	char identity_file[1024];
	int have_identity = 0;

	/* This is set to the passphrase if given on the command line. */
	char *identity_passphrase = NULL;

	/* This is set to the new passphrase if given on the command line. */
	char *identity_new_passphrase = NULL;

	/* This is set to the new comment if given on the command line. */
	char *identity_comment = NULL;

	/* argv0 */
	#ifdef HAVE___PROGNAME
	extern char *__progname;
	#else /* HAVE___PROGNAME */
	const char *__progname = "ssh-keygen";
	#endif /* HAVE___PROGNAME */

	void
	ask_filename(struct passwd pw, const char prompt)
	{
	char buf[1024];
	snprintf(identity_file, sizeof(identity_file), "%s/%s",
	pw->pw_dir, SSH_CLIENT_IDENTITY);
	printf("%s (%s): ", prompt, identity_file);
	fflush(stdout);
	if (fgets(buf, sizeof(buf), stdin) == NULL)
	exit(1);
	if (strchr(buf, '\n'))
	*strchr(buf, '\n') = 0;
	if (strcmp(buf, "") != 0)
	strlcpy(identity_file, buf, sizeof(identity_file));
	have_identity = 1;
	}

	void
	do_fingerprint(struct passwd *pw)
	{
	char *comment;
	RSA *public_key;
	struct stat st;

	if (!have_identity)
	ask_filename(pw, "Enter file in which the key is");
	if (stat(identity_file, &st) < 0) {
	perror(identity_file);
	exit(1);
	}
	public_key = RSA_new();
	if (!load_public_key(identity_file, public_key, &comment)) {
	char *cp, line[1024];
	BIGNUM e, n;
	int dummy, invalid = 0;
	FILE *f = fopen(identity_file, "r");
	n = BN_new();
	e = BN_new();
	if (f && fgets(line, sizeof(line), f)) {
	cp = line;
	line[strlen(line) - 1] = '\0';
	if (auth_rsa_read_key(&cp, &dummy, e, n)) {
	public_key->e = e;
	public_key->n = n;
	comment = xstrdup(cp ? cp : "no comment");
	} else {
	invalid = 1;
	}
	} else {
	invalid = 1;
	}
	if (invalid) {
	printf("%s is not a valid key file.\n", identity_file);
	BN_free(e);
	BN_free(n);
	exit(1);
	}
	}
	printf("%d %s %s\n", BN_num_bits(public_key->n),
	fingerprint(public_key->e, public_key->n),
	comment);
	RSA_free(public_key);
	exit(0);
	}

	/*
	* Perform changing a passphrase. The argument is the passwd structure
	* for the current user.
	*/
	void
	do_change_passphrase(struct passwd *pw)
	{
	char *comment;
	char old_passphrase, passphrase1, *passphrase2;
	struct stat st;
	RSA *private_key;

	if (!have_identity)
	ask_filename(pw, "Enter file in which the key is");
	if (stat(identity_file, &st) < 0) {
	perror(identity_file);
	exit(1);
	}
	public_key = RSA_new();
	if (!load_public_key(identity_file, public_key, NULL)) {
	printf("%s is not a valid key file.\n", identity_file);
	exit(1);
	}
	/* Clear the public key since we are just about to load the whole file. */
	RSA_free(public_key);

	/* Try to load the file with empty passphrase. */
	private_key = RSA_new();
	if (!load_private_key(identity_file, "", private_key, &comment)) {
	if (identity_passphrase)
	old_passphrase = xstrdup(identity_passphrase);
	else
	old_passphrase = read_passphrase("Enter old passphrase: ", 1);
	if (!load_private_key(identity_file, old_passphrase, private_key, &comment)) {
	memset(old_passphrase, 0, strlen(old_passphrase));
	xfree(old_passphrase);
	printf("Bad passphrase.\n");
	exit(1);
	}
	memset(old_passphrase, 0, strlen(old_passphrase));
	xfree(old_passphrase);
	}
	printf("Key has comment '%s'\n", comment);

	/* Ask the new passphrase (twice). */
	if (identity_new_passphrase) {
	passphrase1 = xstrdup(identity_new_passphrase);
	passphrase2 = NULL;
	} else {
	passphrase1 =
	read_passphrase("Enter new passphrase (empty for no passphrase): ", 1);
	passphrase2 = read_passphrase("Enter same passphrase again: ", 1);

	/* Verify that they are the same. */
	if (strcmp(passphrase1, passphrase2) != 0) {
	memset(passphrase1, 0, strlen(passphrase1));
	memset(passphrase2, 0, strlen(passphrase2));
	xfree(passphrase1);
	xfree(passphrase2);
	printf("Pass phrases do not match. Try again.\n");
	exit(1);
	}
	/* Destroy the other copy. */
	memset(passphrase2, 0, strlen(passphrase2));
	xfree(passphrase2);
	}

	/* Save the file using the new passphrase. */
	if (!save_private_key(identity_file, passphrase1, private_key, comment)) {
	printf("Saving the key failed: %s: %s.\n",
	identity_file, strerror(errno));
	memset(passphrase1, 0, strlen(passphrase1));
	xfree(passphrase1);
	RSA_free(private_key);
	xfree(comment);
	exit(1);
	}
	/* Destroy the passphrase and the copy of the key in memory. */
	memset(passphrase1, 0, strlen(passphrase1));
	xfree(passphrase1);
	RSA_free(private_key); /* Destroys contents */
	xfree(comment);

	printf("Your identification has been saved with the new passphrase.\n");
	exit(0);
	}

	/*
	* Change the comment of a private key file.
	*/
	void
	do_change_comment(struct passwd *pw)
	{
	char new_comment[1024], *comment;
	RSA *private_key;
	char *passphrase;
	struct stat st;
	FILE *f;
	char *tmpbuf;

	if (!have_identity)
	ask_filename(pw, "Enter file in which the key is");
	if (stat(identity_file, &st) < 0) {
	perror(identity_file);
	exit(1);
	}
	/*
	* Try to load the public key from the file the verify that it is
	* readable and of the proper format.
	*/
	public_key = RSA_new();
	if (!load_public_key(identity_file, public_key, NULL)) {
	printf("%s is not a valid key file.\n", identity_file);
	exit(1);
	}
	private_key = RSA_new();

	if (load_private_key(identity_file, "", private_key, &comment))
	passphrase = xstrdup("");
	else {
	if (identity_passphrase)
	passphrase = xstrdup(identity_passphrase);
	else if (identity_new_passphrase)
	passphrase = xstrdup(identity_new_passphrase);
	else
	passphrase = read_passphrase("Enter passphrase: ", 1);
	/* Try to load using the passphrase. */
	if (!load_private_key(identity_file, passphrase, private_key, &comment)) {
	memset(passphrase, 0, strlen(passphrase));
	xfree(passphrase);
	printf("Bad passphrase.\n");
	exit(1);
	}
	}
	printf("Key now has comment '%s'\n", comment);

	if (identity_comment) {
	strlcpy(new_comment, identity_comment, sizeof(new_comment));
	} else {
	printf("Enter new comment: ");
	fflush(stdout);
	if (!fgets(new_comment, sizeof(new_comment), stdin)) {
	memset(passphrase, 0, strlen(passphrase));
	RSA_free(private_key);
	exit(1);
	}
	if (strchr(new_comment, '\n'))
	*strchr(new_comment, '\n') = 0;
	}

	/* Save the file using the new passphrase. */
	if (!save_private_key(identity_file, passphrase, private_key, new_comment)) {
	printf("Saving the key failed: %s: %s.\n",
	identity_file, strerror(errno));
	memset(passphrase, 0, strlen(passphrase));
	xfree(passphrase);
	RSA_free(private_key);
	xfree(comment);
	exit(1);
	}
	memset(passphrase, 0, strlen(passphrase));
	xfree(passphrase);
	RSA_free(private_key);

	strlcat(identity_file, ".pub", sizeof(identity_file));
	f = fopen(identity_file, "w");
	if (!f) {
	printf("Could not save your public key in %s\n", identity_file);
	exit(1);
	}
	fprintf(f, "%d ", BN_num_bits(public_key->n));
	tmpbuf = BN_bn2dec(public_key->e);
	fprintf(f, "%s ", tmpbuf);
	free(tmpbuf);
	tmpbuf = BN_bn2dec(public_key->n);
	fprintf(f, "%s %s\n", tmpbuf, new_comment);
	free(tmpbuf);
	fclose(f);

	xfree(comment);

	printf("The comment in your key file has been changed.\n");
	exit(0);
	}

	void
	usage(void)
	{
	printf("ssh-keygen version %s\n", SSH_VERSION);
	printf("Usage: %s [-b bits] [-p] [-c] [-f file] [-P pass] [-N new-pass] [-C comment]\n", __progname);
	exit(1);
	}

	/*
	* Main program for key management.
	*/
	int
	main(int ac, char **av)
	{
	char dotsshdir[16 * 1024], comment[1024], passphrase1, passphrase2;
	struct passwd *pw;
	char *tmpbuf;
	int opt;
	struct stat st;
	FILE *f;
	char hostname[MAXHOSTNAMELEN];
	extern int optind;
	extern char *optarg;

	/* check if RSA support exists */
	if (rsa_alive() == 0) {
	fprintf(stderr,
	"%s: no RSA support in libssl and libcrypto. See ssl(8).\n",
	__progname);
	exit(1);
	}
	/* we need this for the home * directory. */
	pw = getpwuid(getuid());
	if (!pw) {
	printf("You don't exist, go away!\n");
	exit(1);
	}

	while ((opt = getopt(ac, av, "qpclb:f:P:N:C:")) != EOF) {
	switch (opt) {
	case 'b':
	bits = atoi(optarg);
	if (bits < 512 \|\| bits > 32768) {
	printf("Bits has bad value.\n");
	exit(1);
	}
	break;

	case 'l':
	print_fingerprint = 1;
	break;

	case 'p':
	change_passphrase = 1;
	break;

	case 'c':
	change_comment = 1;
	break;

	case 'f':
	strlcpy(identity_file, optarg, sizeof(identity_file));
	have_identity = 1;
	break;

	case 'P':
	identity_passphrase = optarg;
	break;

	case 'N':
	identity_new_passphrase = optarg;
	break;

	case 'C':
	identity_comment = optarg;
	break;

	case 'q':
	quiet = 1;
	break;

	case '?':
	default:
	usage();
	}
	}
	if (optind < ac) {
	printf("Too many arguments.\n");
	usage();
	}
	if (change_passphrase && change_comment) {
	printf("Can only have one of -p and -c.\n");
	usage();
	}
	if (print_fingerprint)
	do_fingerprint(pw);
	if (change_passphrase)
	do_change_passphrase(pw);
	if (change_comment)
	do_change_comment(pw);

	arc4random_stir();

	if (quiet)
	rsa_set_verbose(0);

	/* Generate the rsa key pair. */
	private_key = RSA_new();
	public_key = RSA_new();
	rsa_generate_key(private_key, public_key, bits);

	if (!have_identity)
	ask_filename(pw, "Enter file in which to save the key");

	/* Create ~/.ssh directory if it doesn\'t already exist. */
	snprintf(dotsshdir, sizeof dotsshdir, "%s/%s", pw->pw_dir, SSH_USER_DIR);
	if (strstr(identity_file, dotsshdir) != NULL &&
	stat(dotsshdir, &st) < 0) {
	if (mkdir(dotsshdir, 0755) < 0)
	error("Could not create directory '%s'.", dotsshdir);
	else if (!quiet)
	printf("Created directory '%s'.\n", dotsshdir);
	}
	/* If the file already exists, ask the user to confirm. */
	if (stat(identity_file, &st) >= 0) {
	char yesno[3];
	printf("%s already exists.\n", identity_file);
	printf("Overwrite (y/n)? ");
	fflush(stdout);
	if (fgets(yesno, sizeof(yesno), stdin) == NULL)
	exit(1);
	if (yesno[0] != 'y' && yesno[0] != 'Y')
	exit(1);
	}
	/* Ask for a passphrase (twice). */
	if (identity_passphrase)
	passphrase1 = xstrdup(identity_passphrase);
	else if (identity_new_passphrase)
	passphrase1 = xstrdup(identity_new_passphrase);
	else {
	passphrase_again:
	passphrase1 =
	read_passphrase("Enter passphrase (empty for no passphrase): ", 1);
	passphrase2 = read_passphrase("Enter same passphrase again: ", 1);
	if (strcmp(passphrase1, passphrase2) != 0) {
	/* The passphrases do not match. Clear them and retry. */
	memset(passphrase1, 0, strlen(passphrase1));
	memset(passphrase2, 0, strlen(passphrase2));
	xfree(passphrase1);
	xfree(passphrase2);
	printf("Passphrases do not match. Try again.\n");
	goto passphrase_again;
	}
	/* Clear the other copy of the passphrase. */
	memset(passphrase2, 0, strlen(passphrase2));
	xfree(passphrase2);
	}

	if (identity_comment) {
	strlcpy(comment, identity_comment, sizeof(comment));
	} else {
	/* Create default commend field for the passphrase. */
	if (gethostname(hostname, sizeof(hostname)) < 0) {
	perror("gethostname");
	exit(1);
	}
	snprintf(comment, sizeof comment, "%s@%s", pw->pw_name, hostname);
	}

	/* Save the key with the given passphrase and comment. */
	if (!save_private_key(identity_file, passphrase1, private_key, comment)) {
	printf("Saving the key failed: %s: %s.\n",
	identity_file, strerror(errno));
	memset(passphrase1, 0, strlen(passphrase1));
	xfree(passphrase1);
	exit(1);
	}
	/* Clear the passphrase. */
	memset(passphrase1, 0, strlen(passphrase1));
	xfree(passphrase1);

	/* Clear the private key and the random number generator. */
	RSA_free(private_key);
	arc4random_stir();

	if (!quiet)
	printf("Your identification has been saved in %s.\n", identity_file);

	strlcat(identity_file, ".pub", sizeof(identity_file));
	f = fopen(identity_file, "w");
	if (!f) {
	printf("Could not save your public key in %s\n", identity_file);
	exit(1);
	}
	fprintf(f, "%d ", BN_num_bits(public_key->n));
	tmpbuf = BN_bn2dec(public_key->e);
	fprintf(f, "%s ", tmpbuf);
	free(tmpbuf);
	tmpbuf = BN_bn2dec(public_key->n);
	fprintf(f, "%s %s\n", tmpbuf, comment);
	free(tmpbuf);
	fclose(f);

	if (!quiet) {
	printf("Your public key has been saved in %s.\n", identity_file);
	printf("The key fingerprint is:\n");
	printf("%d %s %s\n", BN_num_bits(public_key->n),
	fingerprint(public_key->e, public_key->n),
	comment);
	}
	exit(0);
	}