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authorDamien Miller <djm@mindrot.org>1999-10-27 13:42:43 +1000
committerDamien Miller <djm@mindrot.org>1999-10-27 13:42:43 +1000
commitd4a8b7e34dd619a4debf9a206c81db26d1402ea6 (patch)
treea47d770a2f790f40d18b0982d4e55fa7cfb1fa3b /hostfile.c
Initial revision
Diffstat (limited to 'hostfile.c')
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+/*
+
+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 1.1 1999/10/27 03:42:44 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 if host matches any negated subpattern. */
+ 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, unsigned int bits,
+ BIGNUM *e, BIGNUM *n,
+ BIGNUM *ke, BIGNUM *kn)
+{
+ FILE *f;
+ char line[8192];
+ unsigned int kbits, hostlen;
+ char *cp, *cp2;
+ HostStatus end_return;
+ struct stat st;
+
+ /* Open the file containing the list of known hosts. */
+ f = fopen(filename, "r");
+ if (!f)
+ {
+ if (stat(filename, &st) >= 0)
+ {
+ packet_send_debug("Could not open %.900s for reading.", filename);
+ packet_send_debug("If your home directory is on an NFS volume, it may need to be world-readable.");
+ }
+ 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;
+
+ /* Go trough the file. */
+ while (fgets(line, sizeof(line), f))
+ {
+ cp = line;
+
+ /* Skip any leading whitespace. */
+ for (; *cp == ' ' || *cp == '\t'; cp++)
+ ;
+
+ /* Ignore comment lines and empty lines. */
+ 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;
+
+ /* Check if the current key is the same as the previous one. */
+ if (kbits == bits && 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,
+ unsigned int bits, BIGNUM *e, BIGNUM *n)
+{
+ FILE *f;
+ char *buf;
+
+ /* Open the file for appending. */
+ f = fopen(filename, "a");
+ if (!f)
+ return 0;
+
+ /* Print the host name and key to the file. */
+ fprintf(f, "%s %u ", host, bits);
+ buf = BN_bn2dec(e);
+ assert(buf != NULL);
+ fprintf(f, "%s ", buf);
+ free (buf);
+ buf = BN_bn2dec(n);
+ assert(buf != NULL);
+ fprintf(f, "%s\n", buf);
+ free (buf);
+
+ /* Close the file. */
+ fclose(f);
+ return 1;
+}