upstream commit

introduce hostkeys_foreach() to allow iteration over a
 known_hosts file or controlled subset thereof. This will allow us to pull out
 some ugly and duplicated code, and will be used to implement hostkey rotation
 later.

feedback and ok markus

1 files changed, 145 insertions, 2 deletions

diff --git a/hostfile.c b/hostfile.c
index 40dbbd478..5f0366310 100644
--- a/hostfile.c
+++ b/hostfile.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: hostfile.c,v 1.59 2015/01/15 09:40:00 djm Exp $ */
+/* $OpenBSD: hostfile.c,v 1.60 2015/01/18 21:40:23 djm Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -42,6 +42,7 @@
 
 #include <netinet/in.h>
 
+#include <errno.h>
 #include <resolv.h>
 #include <stdarg.h>
 #include <stdio.h>
@@ -64,6 +65,8 @@ struct hostkeys {
         u_int num_entries;
 };
 
+/* XXX hmac is too easy to dictionary attack; use bcrypt? */
+
 static int
 extract_salt(const char *s, u_int l, u_char *salt, size_t salt_len)
 {
@@ -496,7 +499,147 @@ add_host_to_hostfile(const char *filename, const char *host,
                     __func__, filename, ssh_err(r));
         } else
                 success = 1;
-        fputs("\n", f);
+        fputc('\n', f);
         fclose(f);
         return success;
 }
+
+static int
+match_maybe_hashed(const char *host, const char *names, int *was_hashed)
+{
+        int hashed = *names == HASH_DELIM;
+        const char *hashed_host;
+        size_t nlen = strlen(names);
+
+        if (was_hashed != NULL)
+                *was_hashed = hashed;
+        if (hashed) {
+                if ((hashed_host = host_hash(host, names, nlen)) == NULL)
+                        return -1;
+                return nlen == strlen(hashed_host) &&
+                    strncmp(hashed_host, names, nlen) == 0;
+        }
+        return match_hostname(host, names, nlen) == 1;
+}
+
+int
+hostkeys_foreach(const char *path, hostkeys_foreach_fn *callback, void *ctx,
+    const char *host, u_int options)
+{
+        FILE *f;
+        char line[8192], oline[8192];
+        u_long linenum = 0;
+        char *cp, *cp2;
+        u_int kbits;
+        int s, r = 0;
+        struct hostkey_foreach_line lineinfo;
+
+        memset(&lineinfo, 0, sizeof(lineinfo));
+        if (host == NULL && (options & HKF_WANT_MATCH_HOST) != 0)
+                return SSH_ERR_INVALID_ARGUMENT;
+        if ((f = fopen(path, "r")) == NULL)
+                return SSH_ERR_SYSTEM_ERROR;
+
+        debug3("%s: reading file \"%s\"", __func__, path);
+        while (read_keyfile_line(f, path, line, sizeof(line), &linenum) == 0) {
+                line[strcspn(line, "\n")] = '\0';
+                strlcpy(oline, line, sizeof(oline));
+
+                sshkey_free(lineinfo.key);
+                memset(&lineinfo, 0, sizeof(lineinfo));
+                lineinfo.path = path;
+                lineinfo.linenum = linenum;
+                lineinfo.line = oline;
+                lineinfo.status = HKF_STATUS_OK;
+
+                /* Skip any leading whitespace, comments and empty lines. */
+                for (cp = line; *cp == ' ' || *cp == '\t'; cp++)
+                        ;
+                if (!*cp || *cp == '#' || *cp == '\n') {
+                        if ((options & HKF_WANT_MATCH_HOST) == 0) {
+                                lineinfo.status = HKF_STATUS_COMMENT;
+                                if ((r = callback(&lineinfo, ctx)) != 0)
+                                        break;
+                        }
+                        continue;
+                }
+
+                if ((lineinfo.marker = check_markers(&cp)) == MRK_ERROR) {
+                        verbose("%s: invalid marker at %s:%lu",
+                            __func__, path, linenum);
+                        if ((options & HKF_WANT_MATCH_HOST) == 0)
+                                goto bad;
+                        continue;
+                }
+
+                /* Find the end of the host name portion. */
+                for (cp2 = cp; *cp2 && *cp2 != ' ' && *cp2 != '\t'; cp2++)
+                        ;
+                lineinfo.hosts = cp;
+                *cp2++ = '\0';
+
+                /* Check if the host name matches. */
+                if (host != NULL) {
+                        s = match_maybe_hashed(host, lineinfo.hosts,
+                            &lineinfo.was_hashed);
+                        if (s == 1)
+                                lineinfo.status = HKF_STATUS_HOST_MATCHED;
+                        else if ((options & HKF_WANT_MATCH_HOST) != 0)
+                                continue;
+                        else if (s == -1) {
+                                debug2("%s: %s:%ld: bad host hash \"%.32s\"",
+                                    __func__, path, linenum, lineinfo.hosts);
+                                goto bad;
+                        }
+                }
+
+                /* Got a match.  Skip host name and any following whitespace */
+                for (; *cp2 == ' ' || *cp2 == '\t'; cp2++)
+                        ;
+                if (*cp2 == '\0' || *cp2 == '#') {
+                        debug2("%s:%ld: truncated before key", path, linenum);
+                        goto bad;
+                }
+                lineinfo.rawkey = cp = cp2;
+
+                if ((options & HKF_WANT_PARSE_KEY) != 0) {
+                        /*
+                         * Extract the key from the line.  This will skip
+                         * any leading whitespace.  Ignore badly formatted
+                         * lines.
+                         */
+                        if ((lineinfo.key = sshkey_new(KEY_UNSPEC)) == NULL) {
+                                error("%s: sshkey_new failed", __func__);
+                                return SSH_ERR_ALLOC_FAIL;
+                        }
+                        if (!hostfile_read_key(&cp, &kbits, lineinfo.key)) {
+#ifdef WITH_SSH1
+                                sshkey_free(lineinfo.key);
+                                lineinfo.key = sshkey_new(KEY_RSA1);
+                                if (lineinfo.key  == NULL) {
+                                        error("%s: sshkey_new fail", __func__);
+                                        return SSH_ERR_ALLOC_FAIL;
+                                }
+                                if (!hostfile_read_key(&cp, &kbits,
+                                    lineinfo.key))
+                                        goto bad;
+#else
+                                goto bad;
+#endif
+                        }
+                        if (!hostfile_check_key(kbits, lineinfo.key, host,
+                            path, linenum)) {
+ bad:
+                                lineinfo.status = HKF_STATUS_INVALID;
+                                if ((r = callback(&lineinfo, ctx)) != 0)
+                                        break;
+                                continue;
+                        }
+                }
+                if ((r = callback(&lineinfo, ctx)) != 0)
+                        break;
+        }
+        sshkey_free(lineinfo.key);
+        fclose(f);
+        return r;
+}