diff options
| -rw-r--r-- | sshconnect.c | 219 |
1 files changed, 191 insertions, 28 deletions
diff --git a/sshconnect.c b/sshconnect.c index 70b2dee04..02f569c1a 100644 --- a/sshconnect.c +++ b/sshconnect.c @@ -1,4 +1,4 @@ -/* $OpenBSD: sshconnect.c,v 1.341 2020/10/18 11:32:02 djm Exp $ */ +/* $OpenBSD: sshconnect.c,v 1.342 2020/11/12 22:56:00 djm Exp $ */ /* * Author: Tatu Ylonen <ylo@cs.hut.fi> * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland @@ -700,6 +700,166 @@ path_in_hostfiles(const char *path, char **hostfiles, u_int num_hostfiles) return 0; } +struct find_by_key_ctx { + const char *host, *ip; + const struct sshkey *key; + char **names; + u_int nnames; +}; + +/* Try to replace home directory prefix (per $HOME) with a ~/ sequence */ +static char * +try_tilde_unexpand(const char *path) +{ + char *home, *ret = NULL; + size_t l; + + if (*path != '/') + return xstrdup(path); + if ((home = getenv("HOME")) == NULL || (l = strlen(home)) == 0) + return xstrdup(path); + if (strncmp(path, home, l) != 0) + return xstrdup(path); + /* + * ensure we have matched on a path boundary: either the $HOME that + * we just compared ends with a '/' or the next character of the path + * must be a '/'. + */ + if (home[l - 1] != '/' && path[l] != '/') + return xstrdup(path); + if (path[l] == '/') + l++; + xasprintf(&ret, "~/%s", path + l); + return ret; +} + +static int +hostkeys_find_by_key_cb(struct hostkey_foreach_line *l, void *_ctx) +{ + struct find_by_key_ctx *ctx = (struct find_by_key_ctx *)_ctx; + char *path; + + /* we are looking for keys with names that *do not* match */ + if ((l->match & HKF_MATCH_HOST) != 0) + return 0; + /* not interested in marker lines */ + if (l->marker != MRK_NONE) + return 0; + /* we are only interested in exact key matches */ + if (l->key == NULL || !sshkey_equal(ctx->key, l->key)) + return 0; + path = try_tilde_unexpand(l->path); + debug_f("found matching key in %s:%lu", path, l->linenum); + ctx->names = xrecallocarray(ctx->names, + ctx->nnames, ctx->nnames + 1, sizeof(*ctx->names)); + xasprintf(&ctx->names[ctx->nnames], "%s:%lu: %s", path, l->linenum, + strncmp(l->hosts, HASH_MAGIC, strlen(HASH_MAGIC)) == 0 ? + "[hashed name]" : l->hosts); + ctx->nnames++; + free(path); + return 0; +} + +static int +hostkeys_find_by_key_hostfile(const char *file, const char *which, + struct find_by_key_ctx *ctx) +{ + int r; + + debug3_f("trying %s hostfile \"%s\"", which, file); + if ((r = hostkeys_foreach(file, hostkeys_find_by_key_cb, ctx, + ctx->host, ctx->ip, HKF_WANT_PARSE_KEY)) != 0) { + if (r == SSH_ERR_SYSTEM_ERROR && errno == ENOENT) { + debug_f("hostkeys file %s does not exist", file); + return 0; + } + error_fr(r, "hostkeys_foreach failed for %s", file); + return r; + } + return 0; +} + +/* + * Find 'key' in known hosts file(s) that do not match host/ip. + * Used to display also-known-as information for previously-unseen hostkeys. + */ +static void +hostkeys_find_by_key(const char *host, const char *ip, const struct sshkey *key, + char **user_hostfiles, u_int num_user_hostfiles, + char **system_hostfiles, u_int num_system_hostfiles, + char ***names, u_int *nnames) +{ + struct find_by_key_ctx ctx = {0}; + u_int i; + + *names = NULL; + *nnames = 0; + + if (key == NULL || sshkey_is_cert(key)) + return; + + ctx.host = host; + ctx.ip = ip; + ctx.key = key; + + for (i = 0; i < num_user_hostfiles; i++) { + if (hostkeys_find_by_key_hostfile(user_hostfiles[i], + "user", &ctx) != 0) + goto fail; + } + for (i = 0; i < num_system_hostfiles; i++) { + if (hostkeys_find_by_key_hostfile(system_hostfiles[i], + "system", &ctx) != 0) + goto fail; + } + /* success */ + *names = ctx.names; + *nnames = ctx.nnames; + ctx.names = NULL; + ctx.nnames = 0; + return; + fail: + for (i = 0; i < ctx.nnames; i++) + free(ctx.names[i]); + free(ctx.names); +} + +#define MAX_OTHER_NAMES 8 /* Maximum number of names to list */ +static char * +other_hostkeys_message(const char *host, const char *ip, + const struct sshkey *key, + char **user_hostfiles, u_int num_user_hostfiles, + char **system_hostfiles, u_int num_system_hostfiles) +{ + char *ret = NULL, **othernames = NULL; + u_int i, n, num_othernames = 0; + + hostkeys_find_by_key(host, ip, key, + user_hostfiles, num_user_hostfiles, + system_hostfiles, num_system_hostfiles, + &othernames, &num_othernames); + if (num_othernames == 0) + return xstrdup("This key is not known by any other names"); + + xasprintf(&ret, "This host key is known by the following other " + "names/addresses:"); + + n = num_othernames; + if (n > MAX_OTHER_NAMES) + n = MAX_OTHER_NAMES; + for (i = 0; i < n; i++) { + xextendf(&ret, "\n", " %s", othernames[i]); + } + if (n < num_othernames) { + xextendf(&ret, "\n", " (%d additional names ommitted)", + num_othernames - n); + } + for (i = 0; i < num_othernames; i++) + free(othernames[i]); + free(othernames); + return ret; +} + /* * check whether the supplied host key is valid, return -1 if the key * is not valid. user_hostfile[0] will not be updated if 'readonly' is true. @@ -876,45 +1036,48 @@ check_host_key(char *hostname, struct sockaddr *hostaddr, u_short port, goto fail; } else if (options.strict_host_key_checking == SSH_STRICT_HOSTKEY_ASK) { - char msg1[1024], msg2[1024]; + char *msg1 = NULL, *msg2 = NULL; + + xasprintf(&msg1, "The authenticity of host " + "'%.200s (%s)' can't be established", host, ip); + + if (show_other_keys(host_hostkeys, host_key)) { + xextendf(&msg1, "\n", "but keys of different " + "type are already known for this host."); + } else + xextendf(&msg1, "", "."); - if (show_other_keys(host_hostkeys, host_key)) - snprintf(msg1, sizeof(msg1), - "\nbut keys of different type are already" - " known for this host."); - else - snprintf(msg1, sizeof(msg1), "."); - /* The default */ fp = sshkey_fingerprint(host_key, options.fingerprint_hash, SSH_FP_DEFAULT); ra = sshkey_fingerprint(host_key, options.fingerprint_hash, SSH_FP_RANDOMART); if (fp == NULL || ra == NULL) fatal_f("sshkey_fingerprint failed"); - msg2[0] = '\0'; + xextendf(&msg1, "\n", "%s key fingerprint is %s.", + type, fp); + if (options.visual_host_key) + xextendf(&msg1, "\n", "%s", ra); if (options.verify_host_key_dns) { - if (matching_host_key_dns) - snprintf(msg2, sizeof(msg2), - "Matching host key fingerprint" - " found in DNS.\n"); - else - snprintf(msg2, sizeof(msg2), - "No matching host key fingerprint" - " found in DNS.\n"); + xextendf(&msg1, "\n", + "%s host key fingerprint found in DNS.", + matching_host_key_dns ? + "Matching" : "No matching"); } - snprintf(msg, sizeof(msg), - "The authenticity of host '%.200s (%s)' can't be " - "established%s\n" - "%s key fingerprint is %s.%s%s\n%s" + /* msg2 informs for other names matching this key */ + if ((msg2 = other_hostkeys_message(host, ip, host_key, + user_hostfiles, num_user_hostfiles, + system_hostfiles, num_system_hostfiles)) != NULL) + xextendf(&msg1, "\n", "%s", msg2); + + xextendf(&msg1, "\n", "Are you sure you want to continue connecting " - "(yes/no/[fingerprint])? ", - host, ip, msg1, type, fp, - options.visual_host_key ? "\n" : "", - options.visual_host_key ? ra : "", - msg2); + "(yes/no/[fingerprint])? "); + + confirmed = confirm(msg1, fp); free(ra); - confirmed = confirm(msg, fp); free(fp); + free(msg1); + free(msg2); if (!confirmed) goto fail; hostkey_trusted = 1; /* user explicitly confirmed */ |