From 894f085f402e023a98cbb6f5a3d117bd88d93b09 Mon Sep 17 00:00:00 2001 From: Michal Sekletar Date: Mon, 23 Oct 2023 13:38:35 +0200 Subject: [PATCH] core: extract host name using avahi_unescape_label() Previously we could create invalid escape sequence when we split the string on dot. For example, from valid host name "foo\\.bar" we have created invalid name "foo\\" and tried to set that as the host name which crashed the daemon. Fixes #453 CVE-2023-38471 Upstream-Status: Backport [import from ubuntu https://git.launchpad.net/ubuntu/+source/avahi/tree/debian/patches/CVE-2023-38471-1.patch?h=ubuntu/focal-security Upstream commit https://github.com/lathiat/avahi/commit/894f085f402e023a98cbb6f5a3d117bd88d93b09] CVE: CVE-2023-38471 Signed-off-by: Vijay Anusuri --- avahi-core/server.c | 27 +++++++++++++++++++++------ 1 file changed, 21 insertions(+), 6 deletions(-) Index: avahi-0.7/avahi-core/server.c =================================================================== --- avahi-0.7.orig/avahi-core/server.c +++ avahi-0.7/avahi-core/server.c @@ -1253,7 +1253,11 @@ static void update_fqdn(AvahiServer *s) } int avahi_server_set_host_name(AvahiServer *s, const char *host_name) { - char *hn = NULL; + char label_escaped[AVAHI_LABEL_MAX*4+1]; + char label[AVAHI_LABEL_MAX]; + char *hn = NULL, *h; + size_t len; + assert(s); AVAHI_CHECK_VALIDITY(s, !host_name || avahi_is_valid_host_name(host_name), AVAHI_ERR_INVALID_HOST_NAME); @@ -1263,17 +1267,28 @@ int avahi_server_set_host_name(AvahiServ else hn = avahi_normalize_name_strdup(host_name); - hn[strcspn(hn, ".")] = 0; + h = hn; + if (!avahi_unescape_label((const char **)&hn, label, sizeof(label))) { + avahi_free(h); + return AVAHI_ERR_INVALID_HOST_NAME; + } + + avahi_free(h); - if (avahi_domain_equal(s->host_name, hn) && s->state != AVAHI_SERVER_COLLISION) { - avahi_free(hn); + h = label_escaped; + len = sizeof(label_escaped); + if (!avahi_escape_label(label, strlen(label), &h, &len)) + return AVAHI_ERR_INVALID_HOST_NAME; + + if (avahi_domain_equal(s->host_name, label_escaped) && s->state != AVAHI_SERVER_COLLISION) return avahi_server_set_errno(s, AVAHI_ERR_NO_CHANGE); - } withdraw_host_rrs(s); avahi_free(s->host_name); - s->host_name = hn; + s->host_name = avahi_strdup(label_escaped); + if (!s->host_name) + return AVAHI_ERR_NO_MEMORY; update_fqdn(s);