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From: Michal Sekletar <msekleta@redhat.com>
Date: Wed, 11 Oct 2023 17:45:44 +0200
Subject: common: derive alternative host name from its unescaped version
Normalization of input makes sure we don't have to deal with special
cases like unescaped dot at the end of label.
Fixes #451 #487
CVE-2023-38473
(cherry picked from commit b448c9f771bada14ae8de175695a9729f8646797)
Origin: https://github.com/avahi/avahi/commit/b448c9f771bada14ae8de175695a9729f8646797
---
avahi-common/alternative-test.c | 3 +++
avahi-common/alternative.c | 27 +++++++++++++++++++--------
2 files changed, 22 insertions(+), 8 deletions(-)
diff --git a/avahi-common/alternative-test.c b/avahi-common/alternative-test.c
index 9255435..681fc15 100644
--- a/avahi-common/alternative-test.c
+++ b/avahi-common/alternative-test.c
@@ -31,6 +31,9 @@ int main(AVAHI_GCC_UNUSED int argc, AVAHI_GCC_UNUSED char *argv[]) {
const char* const test_strings[] = {
"XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX",
"XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXüüüüüüü",
+ ").",
+ "\\.",
+ "AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA\\\\",
"gurke",
"-",
" #",
diff --git a/avahi-common/alternative.c b/avahi-common/alternative.c
index b3d39f0..a094e6d 100644
--- a/avahi-common/alternative.c
+++ b/avahi-common/alternative.c
@@ -49,15 +49,20 @@ static void drop_incomplete_utf8(char *c) {
}
char *avahi_alternative_host_name(const char *s) {
+ char label[AVAHI_LABEL_MAX], alternative[AVAHI_LABEL_MAX*4+1];
+ char *alt, *r, *ret;
const char *e;
- char *r;
+ size_t len;
assert(s);
if (!avahi_is_valid_host_name(s))
return NULL;
- if ((e = strrchr(s, '-'))) {
+ if (!avahi_unescape_label(&s, label, sizeof(label)))
+ return NULL;
+
+ if ((e = strrchr(label, '-'))) {
const char *p;
e++;
@@ -74,19 +79,18 @@ char *avahi_alternative_host_name(const char *s) {
if (e) {
char *c, *m;
- size_t l;
int n;
n = atoi(e)+1;
if (!(m = avahi_strdup_printf("%i", n)))
return NULL;
- l = e-s-1;
+ len = e-label-1;
- if (l >= AVAHI_LABEL_MAX-1-strlen(m)-1)
- l = AVAHI_LABEL_MAX-1-strlen(m)-1;
+ if (len >= AVAHI_LABEL_MAX-1-strlen(m)-1)
+ len = AVAHI_LABEL_MAX-1-strlen(m)-1;
- if (!(c = avahi_strndup(s, l))) {
+ if (!(c = avahi_strndup(label, len))) {
avahi_free(m);
return NULL;
}
@@ -100,7 +104,7 @@ char *avahi_alternative_host_name(const char *s) {
} else {
char *c;
- if (!(c = avahi_strndup(s, AVAHI_LABEL_MAX-1-2)))
+ if (!(c = avahi_strndup(label, AVAHI_LABEL_MAX-1-2)))
return NULL;
drop_incomplete_utf8(c);
@@ -109,6 +113,13 @@ char *avahi_alternative_host_name(const char *s) {
avahi_free(c);
}
+ alt = alternative;
+ len = sizeof(alternative);
+ ret = avahi_escape_label(r, strlen(r), &alt, &len);
+
+ avahi_free(r);
+ r = avahi_strdup(ret);
+
assert(avahi_is_valid_host_name(r));
return r;
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