hostfile.c - security/openssh-library - Rivoreo Source Code Repositories

 /*
  *
  * hostfile.c
  *
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  *
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
  *                    All rights reserved
  *
  * Created: Thu Jun 29 07:10:56 1995 ylo
  *
  * Functions for manipulating the known hosts files.
  *
  */

 #include "includes.h"
 RCSID("$Id: hostfile.c,v 1.6 1999/11/25 00:54:59 damien Exp $");

 #include "packet.h"
 #include "ssh.h"

 /*
  * Reads a multiple-precision integer in hex from the buffer, and advances
  * the pointer.  The integer must already be initialized.  This function is
  * permitted to modify the buffer.  This leaves *cpp to point just beyond the
  * last processed (and maybe modified) character.  Note that this may modify
  * the buffer containing the number.
  */

 int
 auth_rsa_read_bignum(char **cpp, BIGNUM * value)
 {
 	char *cp = *cpp;
 	int len, old;

 	/* Skip any leading whitespace. */
 	for (; *cp == ' ' || *cp == '\t'; cp++)
 		;

 	/* Check that it begins with a hex digit. */
 	if (*cp < '0' || *cp > '9')
 		return 0;

 	/* Save starting position. */
 	*cpp = cp;

 	/* Move forward until all hex digits skipped. */
 	for (; *cp >= '0' && *cp <= '9'; cp++)
 		;

 	/* Compute the length of the hex number. */
 	len = cp - *cpp;

 	/* Save the old terminating character, and replace it by \0. */
 	old = *cp;
 	*cp = 0;

 	/* Parse the number. */
 	if (BN_dec2bn(&value, *cpp) == 0)
 		return 0;

 	/* Restore old terminating character. */
 	*cp = old;

 	/* Move beyond the number and return success. */
 	*cpp = cp;
 	return 1;
 }

 /*
  * Parses an RSA key (number of bits, e, n) from a string.  Moves the pointer
  * over the key.  Skips any whitespace at the beginning and at end.
  */

 int
 auth_rsa_read_key(char **cpp, unsigned int *bitsp, BIGNUM * e, BIGNUM * n)
 {
 	unsigned int bits;
 	char *cp;

 	/* Skip leading whitespace. */
 	for (cp = *cpp; *cp == ' ' || *cp == '\t'; cp++)
 		;

 	/* Get number of bits. */
 	if (*cp < '0' || *cp > '9')
 		return 0;	/* Bad bit count... */
 	for (bits = 0; *cp >= '0' && *cp <= '9'; cp++)
 		bits = 10 * bits + *cp - '0';

 	/* Get public exponent. */
 	if (!auth_rsa_read_bignum(&cp, e))
 		return 0;

 	/* Get public modulus. */
 	if (!auth_rsa_read_bignum(&cp, n))
 		return 0;

 	/* Skip trailing whitespace. */
 	for (; *cp == ' ' || *cp == '\t'; cp++)
 		;

 	/* Return results. */
 	*cpp = cp;
 	*bitsp = bits;
 	return 1;
 }

 /*
  * Tries to match the host name (which must be in all lowercase) against the
  * comma-separated sequence of subpatterns (each possibly preceded by ! to
  * indicate negation).  Returns true if there is a positive match; zero
  * otherwise.
  */

 int
 match_hostname(const char *host, const char *pattern, unsigned int len)
 {
 	char sub[1024];
 	int negated;
 	int got_positive;
 	unsigned int i, subi;

 	got_positive = 0;
 	for (i = 0; i < len;) {
 		/* Check if the subpattern is negated. */
 		if (pattern[i] == '!') {
 			negated = 1;
 			i++;
 		} else
 			negated = 0;

 		/*
 		 * Extract the subpattern up to a comma or end.  Convert the
 		 * subpattern to lowercase.
 		 */
 		for (subi = 0;
 		     i < len && subi < sizeof(sub) - 1 && pattern[i] != ',';
 		     subi++, i++)
 			sub[subi] = isupper(pattern[i]) ? tolower(pattern[i]) : pattern[i];
 		/* If subpattern too long, return failure (no match). */
 		if (subi >= sizeof(sub) - 1)
 			return 0;

 		/* If the subpattern was terminated by a comma, skip the comma. */
 		if (i < len && pattern[i] == ',')
 			i++;

 		/* Null-terminate the subpattern. */
 		sub[subi] = '\0';

 		/* Try to match the subpattern against the host name. */
 		if (match_pattern(host, sub)) {
 			if (negated)
 				return 0;	/* Fail */
 			else
 				got_positive = 1;
 		}
 	}

 	/*
 	 * Return success if got a positive match.  If there was a negative
 	 * match, we have already returned zero and never get here.
 	 */
 	return got_positive;
 }

 /*
  * Checks whether the given host (which must be in all lowercase) is already
  * in the list of our known hosts. Returns HOST_OK if the host is known and
  * has the specified key, HOST_NEW if the host is not known, and HOST_CHANGED
  * if the host is known but used to have a different host key.
  */

 HostStatus
 check_host_in_hostfile(const char *filename, const char *host,
 		       BIGNUM * e, BIGNUM * n, BIGNUM * ke, BIGNUM * kn)
 {
 	FILE *f;
 	char line[8192];
 	int linenum = 0;
 	unsigned int bits, kbits, hostlen;
 	char *cp, *cp2;
 	HostStatus end_return;

 	/* Open the file containing the list of known hosts. */
 	f = fopen(filename, "r");
 	if (!f)
 		return HOST_NEW;

 	/* Cache the length of the host name. */
 	hostlen = strlen(host);

 	/*
 	 * Return value when the loop terminates.  This is set to
 	 * HOST_CHANGED if we have seen a different key for the host and have
 	 * not found the proper one.
 	 */
 	end_return = HOST_NEW;

 	/* size of modulus 'n' */
 	bits = BN_num_bits(n);

 	/* Go trough the file. */
 	while (fgets(line, sizeof(line), f)) {
 		cp = line;
 		linenum++;

 		/* Skip any leading whitespace, comments and empty lines. */
 		for (; *cp == ' ' || *cp == '\t'; cp++)
 			;
 		if (!*cp || *cp == '#' || *cp == '\n')
 			continue;

 		/* Find the end of the host name portion. */
 		for (cp2 = cp; *cp2 && *cp2 != ' ' && *cp2 != '\t'; cp2++)
 			;

 		/* Check if the host name matches. */
 		if (!match_hostname(host, cp, (unsigned int) (cp2 - cp)))
 			continue;

 		/* Got a match.  Skip host name. */
 		cp = cp2;

 		/*
 		 * Extract the key from the line.  This will skip any leading
 		 * whitespace.  Ignore badly formatted lines.
 		 */
 		if (!auth_rsa_read_key(&cp, &kbits, ke, kn))
 			continue;

 		if (kbits != BN_num_bits(kn)) {
 			error("Warning: error in %s, line %d: keysize mismatch for host %s: "
 			      "actual size %d vs. announced %d.",
 			filename, linenum, host, BN_num_bits(kn), kbits);
 			error("Warning: replace %d with %d in %s, line %d.",
 			      kbits, BN_num_bits(kn), filename, linenum);
 		}
 		/* Check if the current key is the same as the given key. */
 		if (BN_cmp(ke, e) == 0 && BN_cmp(kn, n) == 0) {
 			/* Ok, they match. */
 			fclose(f);
 			return HOST_OK;
 		}
 		/*
 		 * They do not match.  We will continue to go through the
 		 * file; however, we note that we will not return that it is
 		 * new.
 		 */
 		end_return = HOST_CHANGED;
 	}
 	/* Clear variables and close the file. */
 	fclose(f);

 	/*
 	 * Return either HOST_NEW or HOST_CHANGED, depending on whether we
 	 * saw a different key for the host.
 	 */
 	return end_return;
 }

 /*
  * Appends an entry to the host file.  Returns false if the entry could not
  * be appended.
  */

 int
 add_host_to_hostfile(const char *filename, const char *host,
 		     BIGNUM * e, BIGNUM * n)
 {
 	FILE *f;
 	char *buf;
 	unsigned int bits;

 	/* Open the file for appending. */
 	f = fopen(filename, "a");
 	if (!f)
 		return 0;

 	/* size of modulus 'n' */
 	bits = BN_num_bits(n);

 	/* Print the host name and key to the file. */
 	fprintf(f, "%s %u ", host, bits);
 	buf = BN_bn2dec(e);
 	if (buf == NULL) {
 		error("add_host_to_hostfile: BN_bn2dec(e) failed");
 		fclose(f);
 		return 0;
 	}
 	fprintf(f, "%s ", buf);
 	free(buf);
 	buf = BN_bn2dec(n);
 	if (buf == NULL) {
 		error("add_host_to_hostfile: BN_bn2dec(n) failed");
 		fclose(f);
 		return 0;
 	}
 	fprintf(f, "%s\n", buf);
 	free(buf);

 	/* Close the file. */
 	fclose(f);
 	return 1;
 }
	/*
	*
	* hostfile.c
	*
	* Author: Tatu Ylonen <ylo@cs.hut.fi>
	*
	* Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
	* All rights reserved
	*
	* Created: Thu Jun 29 07:10:56 1995 ylo
	*
	* Functions for manipulating the known hosts files.
	*
	*/

	#include "includes.h"
	RCSID("$Id: hostfile.c,v 1.6 1999/11/25 00:54:59 damien Exp $");

	#include "packet.h"
	#include "ssh.h"

	/*
	* Reads a multiple-precision integer in hex from the buffer, and advances
	* the pointer. The integer must already be initialized. This function is
	* permitted to modify the buffer. This leaves *cpp to point just beyond the
	* last processed (and maybe modified) character. Note that this may modify
	* the buffer containing the number.
	*/

	int
	auth_rsa_read_bignum(char *cpp, BIGNUM value)
	{
	char cp = cpp;
	int len, old;

	/* Skip any leading whitespace. */
	for (; cp == ' ' \|\| cp == '\t'; cp++)
	;

	/* Check that it begins with a hex digit. */
	if (cp < '0' \|\| cp > '9')
	return 0;

	/* Save starting position. */
	*cpp = cp;

	/* Move forward until all hex digits skipped. */
	for (; cp >= '0' && cp <= '9'; cp++)
	;

	/* Compute the length of the hex number. */
	len = cp - *cpp;

	/* Save the old terminating character, and replace it by \0. */
	old = *cp;
	*cp = 0;

	/* Parse the number. */
	if (BN_dec2bn(&value, *cpp) == 0)
	return 0;

	/* Restore old terminating character. */
	*cp = old;

	/* Move beyond the number and return success. */
	*cpp = cp;
	return 1;
	}

	/*
	* Parses an RSA key (number of bits, e, n) from a string. Moves the pointer
	* over the key. Skips any whitespace at the beginning and at end.
	*/

	int
	auth_rsa_read_key(char *cpp, unsigned int bitsp, BIGNUM * e, BIGNUM * n)
	{
	unsigned int bits;
	char *cp;

	/* Skip leading whitespace. */
	for (cp = cpp; cp == ' ' \|\| *cp == '\t'; cp++)
	;

	/* Get number of bits. */
	if (cp < '0' \|\| cp > '9')
	return 0; /* Bad bit count... */
	for (bits = 0; cp >= '0' && cp <= '9'; cp++)
	bits = 10 * bits + *cp - '0';

	/* Get public exponent. */
	if (!auth_rsa_read_bignum(&cp, e))
	return 0;

	/* Get public modulus. */
	if (!auth_rsa_read_bignum(&cp, n))
	return 0;

	/* Skip trailing whitespace. */
	for (; cp == ' ' \|\| cp == '\t'; cp++)
	;

	/* Return results. */
	*cpp = cp;
	*bitsp = bits;
	return 1;
	}

	/*
	* Tries to match the host name (which must be in all lowercase) against the
	* comma-separated sequence of subpatterns (each possibly preceded by ! to
	* indicate negation). Returns true if there is a positive match; zero
	* otherwise.
	*/

	int
	match_hostname(const char host, const char pattern, unsigned int len)
	{
	char sub[1024];
	int negated;
	int got_positive;
	unsigned int i, subi;

	got_positive = 0;
	for (i = 0; i < len;) {
	/* Check if the subpattern is negated. */
	if (pattern[i] == '!') {
	negated = 1;
	i++;
	} else
	negated = 0;

	/*
	* Extract the subpattern up to a comma or end. Convert the
	* subpattern to lowercase.
	*/
	for (subi = 0;
	i < len && subi < sizeof(sub) - 1 && pattern[i] != ',';
	subi++, i++)
	sub[subi] = isupper(pattern[i]) ? tolower(pattern[i]) : pattern[i];
	/* If subpattern too long, return failure (no match). */
	if (subi >= sizeof(sub) - 1)
	return 0;

	/* If the subpattern was terminated by a comma, skip the comma. */
	if (i < len && pattern[i] == ',')
	i++;

	/* Null-terminate the subpattern. */
	sub[subi] = '\0';

	/* Try to match the subpattern against the host name. */
	if (match_pattern(host, sub)) {
	if (negated)
	return 0; /* Fail */
	else
	got_positive = 1;
	}
	}

	/*
	* Return success if got a positive match. If there was a negative
	* match, we have already returned zero and never get here.
	*/
	return got_positive;
	}

	/*
	* Checks whether the given host (which must be in all lowercase) is already
	* in the list of our known hosts. Returns HOST_OK if the host is known and
	* has the specified key, HOST_NEW if the host is not known, and HOST_CHANGED
	* if the host is known but used to have a different host key.
	*/

	HostStatus
	check_host_in_hostfile(const char filename, const char host,
	BIGNUM * e, BIGNUM * n, BIGNUM * ke, BIGNUM * kn)
	{
	FILE *f;
	char line[8192];
	int linenum = 0;
	unsigned int bits, kbits, hostlen;
	char cp, cp2;
	HostStatus end_return;

	/* Open the file containing the list of known hosts. */
	f = fopen(filename, "r");
	if (!f)
	return HOST_NEW;

	/* Cache the length of the host name. */
	hostlen = strlen(host);

	/*
	* Return value when the loop terminates. This is set to
	* HOST_CHANGED if we have seen a different key for the host and have
	* not found the proper one.
	*/
	end_return = HOST_NEW;

	/* size of modulus 'n' */
	bits = BN_num_bits(n);

	/* Go trough the file. */
	while (fgets(line, sizeof(line), f)) {
	cp = line;
	linenum++;

	/* Skip any leading whitespace, comments and empty lines. */
	for (; cp == ' ' \|\| cp == '\t'; cp++)
	;
	if (!cp \|\| cp == '#' \|\| *cp == '\n')
	continue;

	/* Find the end of the host name portion. */
	for (cp2 = cp; cp2 && cp2 != ' ' && *cp2 != '\t'; cp2++)
	;

	/* Check if the host name matches. */
	if (!match_hostname(host, cp, (unsigned int) (cp2 - cp)))
	continue;

	/* Got a match. Skip host name. */
	cp = cp2;

	/*
	* Extract the key from the line. This will skip any leading
	* whitespace. Ignore badly formatted lines.
	*/
	if (!auth_rsa_read_key(&cp, &kbits, ke, kn))
	continue;

	if (kbits != BN_num_bits(kn)) {
	error("Warning: error in %s, line %d: keysize mismatch for host %s: "
	"actual size %d vs. announced %d.",
	filename, linenum, host, BN_num_bits(kn), kbits);
	error("Warning: replace %d with %d in %s, line %d.",
	kbits, BN_num_bits(kn), filename, linenum);
	}
	/* Check if the current key is the same as the given key. */
	if (BN_cmp(ke, e) == 0 && BN_cmp(kn, n) == 0) {
	/* Ok, they match. */
	fclose(f);
	return HOST_OK;
	}
	/*
	* They do not match. We will continue to go through the
	* file; however, we note that we will not return that it is
	* new.
	*/
	end_return = HOST_CHANGED;
	}
	/* Clear variables and close the file. */
	fclose(f);

	/*
	* Return either HOST_NEW or HOST_CHANGED, depending on whether we
	* saw a different key for the host.
	*/
	return end_return;
	}

	/*
	* Appends an entry to the host file. Returns false if the entry could not
	* be appended.
	*/

	int
	add_host_to_hostfile(const char filename, const char host,
	BIGNUM * e, BIGNUM * n)
	{
	FILE *f;
	char *buf;
	unsigned int bits;

	/* Open the file for appending. */
	f = fopen(filename, "a");
	if (!f)
	return 0;

	/* size of modulus 'n' */
	bits = BN_num_bits(n);

	/* Print the host name and key to the file. */
	fprintf(f, "%s %u ", host, bits);
	buf = BN_bn2dec(e);
	if (buf == NULL) {
	error("add_host_to_hostfile: BN_bn2dec(e) failed");
	fclose(f);
	return 0;
	}
	fprintf(f, "%s ", buf);
	free(buf);
	buf = BN_bn2dec(n);
	if (buf == NULL) {
	error("add_host_to_hostfile: BN_bn2dec(n) failed");
	fclose(f);
	return 0;
	}
	fprintf(f, "%s\n", buf);
	free(buf);

	/* Close the file. */
	fclose(f);
	return 1;
	}