280 lines
6.9 KiB
C
280 lines
6.9 KiB
C
/*
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hostfile.c
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Author: Tatu Ylonen <ylo@cs.hut.fi>
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Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
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All rights reserved
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Created: Thu Jun 29 07:10:56 1995 ylo
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Functions for manipulating the known hosts files.
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*/
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#include "includes.h"
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RCSID("$Id: hostfile.c,v 1.1 1999/10/27 03:42:44 damien Exp $");
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#include "packet.h"
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#include "ssh.h"
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/* Reads a multiple-precision integer in hex from the buffer, and advances the
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pointer. The integer must already be initialized. This function is
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permitted to modify the buffer. This leaves *cpp to point just beyond
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the last processed (and maybe modified) character. Note that this may
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modify the buffer containing the number. */
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int
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auth_rsa_read_bignum(char **cpp, BIGNUM *value)
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{
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char *cp = *cpp;
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int len, old;
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/* Skip any leading whitespace. */
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for (; *cp == ' ' || *cp == '\t'; cp++)
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;
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/* Check that it begins with a hex digit. */
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if (*cp < '0' || *cp > '9')
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return 0;
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/* Save starting position. */
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*cpp = cp;
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/* Move forward until all hex digits skipped. */
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for (; *cp >= '0' && *cp <= '9'; cp++)
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;
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/* Compute the length of the hex number. */
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len = cp - *cpp;
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/* Save the old terminating character, and replace it by \0. */
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old = *cp;
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*cp = 0;
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/* Parse the number. */
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if (BN_dec2bn(&value, *cpp) == 0)
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return 0;
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/* Restore old terminating character. */
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*cp = old;
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/* Move beyond the number and return success. */
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*cpp = cp;
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return 1;
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}
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/* Parses an RSA key (number of bits, e, n) from a string. Moves the pointer
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over the key. Skips any whitespace at the beginning and at end. */
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int
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auth_rsa_read_key(char **cpp, unsigned int *bitsp, BIGNUM *e, BIGNUM *n)
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{
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unsigned int bits;
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char *cp;
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/* Skip leading whitespace. */
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for (cp = *cpp; *cp == ' ' || *cp == '\t'; cp++)
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;
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/* Get number of bits. */
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if (*cp < '0' || *cp > '9')
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return 0; /* Bad bit count... */
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for (bits = 0; *cp >= '0' && *cp <= '9'; cp++)
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bits = 10 * bits + *cp - '0';
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/* Get public exponent. */
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if (!auth_rsa_read_bignum(&cp, e))
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return 0;
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/* Get public modulus. */
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if (!auth_rsa_read_bignum(&cp, n))
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return 0;
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/* Skip trailing whitespace. */
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for (; *cp == ' ' || *cp == '\t'; cp++)
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;
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/* Return results. */
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*cpp = cp;
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*bitsp = bits;
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return 1;
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}
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/* Tries to match the host name (which must be in all lowercase) against the
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comma-separated sequence of subpatterns (each possibly preceded by ! to
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indicate negation). Returns true if there is a positive match; zero
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otherwise. */
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int
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match_hostname(const char *host, const char *pattern, unsigned int len)
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{
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char sub[1024];
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int negated;
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int got_positive;
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unsigned int i, subi;
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got_positive = 0;
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for (i = 0; i < len;)
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{
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/* Check if the subpattern is negated. */
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if (pattern[i] == '!')
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{
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negated = 1;
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i++;
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}
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else
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negated = 0;
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/* Extract the subpattern up to a comma or end. Convert the subpattern
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to lowercase. */
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for (subi = 0;
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i < len && subi < sizeof(sub) - 1 && pattern[i] != ',';
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subi++, i++)
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sub[subi] = isupper(pattern[i]) ? tolower(pattern[i]) : pattern[i];
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/* If subpattern too long, return failure (no match). */
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if (subi >= sizeof(sub) - 1)
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return 0;
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/* If the subpattern was terminated by a comma, skip the comma. */
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if (i < len && pattern[i] == ',')
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i++;
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/* Null-terminate the subpattern. */
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sub[subi] = '\0';
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/* Try to match the subpattern against the host name. */
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if (match_pattern(host, sub)) {
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if (negated)
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return 0; /* Fail if host matches any negated subpattern. */
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else
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got_positive = 1;
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}
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}
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/* Return success if got a positive match. If there was a negative match,
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we have already returned zero and never get here. */
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return got_positive;
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}
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/* Checks whether the given host (which must be in all lowercase) is
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already in the list of our known hosts.
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Returns HOST_OK if the host is known and has the specified key,
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HOST_NEW if the host is not known, and HOST_CHANGED if the host is known
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but used to have a different host key. */
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HostStatus
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check_host_in_hostfile(const char *filename,
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const char *host, unsigned int bits,
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BIGNUM *e, BIGNUM *n,
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BIGNUM *ke, BIGNUM *kn)
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{
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FILE *f;
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char line[8192];
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unsigned int kbits, hostlen;
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char *cp, *cp2;
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HostStatus end_return;
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struct stat st;
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/* Open the file containing the list of known hosts. */
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f = fopen(filename, "r");
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if (!f)
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{
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if (stat(filename, &st) >= 0)
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{
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packet_send_debug("Could not open %.900s for reading.", filename);
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packet_send_debug("If your home directory is on an NFS volume, it may need to be world-readable.");
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}
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return HOST_NEW;
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}
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/* Cache the length of the host name. */
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hostlen = strlen(host);
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/* Return value when the loop terminates. This is set to HOST_CHANGED if
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we have seen a different key for the host and have not found the proper
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one. */
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end_return = HOST_NEW;
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/* Go trough the file. */
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while (fgets(line, sizeof(line), f))
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{
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cp = line;
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/* Skip any leading whitespace. */
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for (; *cp == ' ' || *cp == '\t'; cp++)
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;
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/* Ignore comment lines and empty lines. */
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if (!*cp || *cp == '#' || *cp == '\n')
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continue;
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/* Find the end of the host name portion. */
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for (cp2 = cp; *cp2 && *cp2 != ' ' && *cp2 != '\t'; cp2++)
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;
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/* Check if the host name matches. */
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if (!match_hostname(host, cp, (unsigned int)(cp2 - cp)))
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continue;
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/* Got a match. Skip host name. */
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cp = cp2;
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/* Extract the key from the line. This will skip any leading
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whitespace. Ignore badly formatted lines. */
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if (!auth_rsa_read_key(&cp, &kbits, ke, kn))
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continue;
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/* Check if the current key is the same as the previous one. */
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if (kbits == bits && BN_cmp(ke, e) == 0 && BN_cmp(kn, n) == 0)
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{
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/* Ok, they match. */
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fclose(f);
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return HOST_OK;
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}
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/* They do not match. We will continue to go through the file; however,
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we note that we will not return that it is new. */
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end_return = HOST_CHANGED;
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}
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/* Clear variables and close the file. */
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fclose(f);
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/* Return either HOST_NEW or HOST_CHANGED, depending on whether we saw a
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different key for the host. */
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return end_return;
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}
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/* Appends an entry to the host file. Returns false if the entry
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could not be appended. */
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int
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add_host_to_hostfile(const char *filename, const char *host,
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unsigned int bits, BIGNUM *e, BIGNUM *n)
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{
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FILE *f;
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char *buf;
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/* Open the file for appending. */
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f = fopen(filename, "a");
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if (!f)
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return 0;
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/* Print the host name and key to the file. */
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fprintf(f, "%s %u ", host, bits);
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buf = BN_bn2dec(e);
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assert(buf != NULL);
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fprintf(f, "%s ", buf);
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free (buf);
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buf = BN_bn2dec(n);
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assert(buf != NULL);
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fprintf(f, "%s\n", buf);
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free (buf);
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/* Close the file. */
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fclose(f);
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return 1;
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}
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