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Backport of:
From 538b1e79a6e7b0bb829ab4cecc828d32105d0684 Mon Sep 17 00:00:00 2001
From: Daniel Stenberg <daniel@haxx.se>
Date: Mon, 6 Mar 2023 12:07:33 +0100
Subject: [PATCH] telnet: only accept option arguments in ascii
To avoid embedded telnet negotiation commands etc.
Reported-by: Harry Sintonen
Closes #10728
Upstream-Status: Backport [import from ubuntu https://git.launchpad.net/ubuntu/+source/curl/tree/debian/patches/CVE-2023-27533.patch?h=ubuntu/focal-security
Upstream commit https://github.com/curl/curl/commit/538b1e79a6e7b0bb829ab4cecc828d32105d0684]
CVE: CVE-2023-27533
Signed-off-by: Vijay Anusuri <vanusuri@mvista.com>
---
lib/telnet.c | 15 +++++++++++++++
1 file changed, 15 insertions(+)
--- a/lib/telnet.c
+++ b/lib/telnet.c
@@ -815,6 +815,17 @@ static void printsub(struct Curl_easy *d
}
}
+static bool str_is_nonascii(const char *str)
+{
+ size_t len = strlen(str);
+ while(len--) {
+ if(*str & 0x80)
+ return TRUE;
+ str++;
+ }
+ return FALSE;
+}
+
static CURLcode check_telnet_options(struct connectdata *conn)
{
struct curl_slist *head;
@@ -829,6 +840,8 @@ static CURLcode check_telnet_options(str
/* Add the user name as an environment variable if it
was given on the command line */
if(conn->bits.user_passwd) {
+ if(str_is_nonascii(data->conn->user))
+ return CURLE_BAD_FUNCTION_ARGUMENT;
msnprintf(option_arg, sizeof(option_arg), "USER,%s", conn->user);
beg = curl_slist_append(tn->telnet_vars, option_arg);
if(!beg) {
@@ -844,6 +857,9 @@ static CURLcode check_telnet_options(str
if(sscanf(head->data, "%127[^= ]%*[ =]%255s",
option_keyword, option_arg) == 2) {
+ if(str_is_nonascii(option_arg))
+ continue;
+
/* Terminal type */
if(strcasecompare(option_keyword, "TTYPE")) {
strncpy(tn->subopt_ttype, option_arg, 31);
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