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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: parse telnet options without sscanf & only accept option arguments in ascii
To avoid embedded telnet negotiation commands etc.
Reported-by: Harry Sintonen
Closes #10728
CVE: CVE-2023-27533
Upstream-Status: Backport [https://github.com/curl/curl/commit/0c28ba2faae2d7da780a66d2446045a560192cdc && https://github.com/curl/curl/commit/538b1e79a6e7b0bb829ab4cecc828d32105d0684]
Signed-off-by: Hitendra Prajapati <hprajapati@mvista.com>
---
lib/telnet.c | 149 +++++++++++++++++++++++++++++++--------------------
1 file changed, 91 insertions(+), 58 deletions(-)
diff --git a/lib/telnet.c b/lib/telnet.c
index e709973..3ecd680 100644
--- a/lib/telnet.c
+++ b/lib/telnet.c
@@ -768,22 +768,32 @@ static void printsub(struct Curl_easy *data,
}
}
+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 Curl_easy *data)
{
struct curl_slist *head;
struct curl_slist *beg;
- char option_keyword[128] = "";
- char option_arg[256] = "";
struct TELNET *tn = data->req.p.telnet;
- struct connectdata *conn = data->conn;
CURLcode result = CURLE_OK;
- int binary_option;
/* Add the user name as an environment variable if it
was given on the command line */
if(data->state.aptr.user) {
- msnprintf(option_arg, sizeof(option_arg), "USER,%s", conn->user);
- beg = curl_slist_append(tn->telnet_vars, option_arg);
+ char buffer[256];
+ if(str_is_nonascii(data->conn->user))
+ return CURLE_BAD_FUNCTION_ARGUMENT;
+ msnprintf(buffer, sizeof(buffer), "USER,%s", data->conn->user);
+ beg = curl_slist_append(tn->telnet_vars, buffer);
if(!beg) {
curl_slist_free_all(tn->telnet_vars);
tn->telnet_vars = NULL;
@@ -793,68 +803,91 @@ static CURLcode check_telnet_options(struct Curl_easy *data)
tn->us_preferred[CURL_TELOPT_NEW_ENVIRON] = CURL_YES;
}
- for(head = data->set.telnet_options; head; head = head->next) {
- if(sscanf(head->data, "%127[^= ]%*[ =]%255s",
- option_keyword, option_arg) == 2) {
-
- /* Terminal type */
- if(strcasecompare(option_keyword, "TTYPE")) {
- strncpy(tn->subopt_ttype, option_arg, 31);
- tn->subopt_ttype[31] = 0; /* String termination */
- tn->us_preferred[CURL_TELOPT_TTYPE] = CURL_YES;
+ for(head = data->set.telnet_options; head && !result; head = head->next) {
+ size_t olen;
+ char *option = head->data;
+ char *arg;
+ char *sep = strchr(option, '=');
+ if(sep) {
+ olen = sep - option;
+ arg = ++sep;
+ if(str_is_nonascii(arg))
continue;
- }
+ switch(olen) {
+ case 5:
+ /* Terminal type */
+ if(strncasecompare(option, "TTYPE", 5)) {
+ strncpy(tn->subopt_ttype, arg, 31);
+ tn->subopt_ttype[31] = 0; /* String termination */
+ tn->us_preferred[CURL_TELOPT_TTYPE] = CURL_YES;
+ }
+ else
+ result = CURLE_UNKNOWN_OPTION;
+ break;
- /* Display variable */
- if(strcasecompare(option_keyword, "XDISPLOC")) {
- strncpy(tn->subopt_xdisploc, option_arg, 127);
- tn->subopt_xdisploc[127] = 0; /* String termination */
- tn->us_preferred[CURL_TELOPT_XDISPLOC] = CURL_YES;
- continue;
- }
+ case 8:
+ /* Display variable */
+ if(strncasecompare(option, "XDISPLOC", 8)) {
+ strncpy(tn->subopt_xdisploc, arg, 127);
+ tn->subopt_xdisploc[127] = 0; /* String termination */
+ tn->us_preferred[CURL_TELOPT_XDISPLOC] = CURL_YES;
+ }
+ else
+ result = CURLE_UNKNOWN_OPTION;
+ break;
- /* Environment variable */
- if(strcasecompare(option_keyword, "NEW_ENV")) {
- beg = curl_slist_append(tn->telnet_vars, option_arg);
- if(!beg) {
- result = CURLE_OUT_OF_MEMORY;
- break;
+ case 7:
+ /* Environment variable */
+ if(strncasecompare(option, "NEW_ENV", 7)) {
+ beg = curl_slist_append(tn->telnet_vars, arg);
+ if(!beg) {
+ result = CURLE_OUT_OF_MEMORY;
+ break;
+ }
+ tn->telnet_vars = beg;
+ tn->us_preferred[CURL_TELOPT_NEW_ENVIRON] = CURL_YES;
}
- tn->telnet_vars = beg;
- tn->us_preferred[CURL_TELOPT_NEW_ENVIRON] = CURL_YES;
- continue;
- }
+ else
+ result = CURLE_UNKNOWN_OPTION;
+ break;
- /* Window Size */
- if(strcasecompare(option_keyword, "WS")) {
- if(sscanf(option_arg, "%hu%*[xX]%hu",
- &tn->subopt_wsx, &tn->subopt_wsy) == 2)
- tn->us_preferred[CURL_TELOPT_NAWS] = CURL_YES;
- else {
- failf(data, "Syntax error in telnet option: %s", head->data);
- result = CURLE_SETOPT_OPTION_SYNTAX;
- break;
+ case 2:
+ /* Window Size */
+ if(strncasecompare(option, "WS", 2)) {
+ if(sscanf(arg, "%hu%*[xX]%hu",
+ &tn->subopt_wsx, &tn->subopt_wsy) == 2)
+ tn->us_preferred[CURL_TELOPT_NAWS] = CURL_YES;
+ else {
+ failf(data, "Syntax error in telnet option: %s", head->data);
+ result = CURLE_SETOPT_OPTION_SYNTAX;
+ }
}
- continue;
- }
+ else
+ result = CURLE_UNKNOWN_OPTION;
+ break;
- /* To take care or not of the 8th bit in data exchange */
- if(strcasecompare(option_keyword, "BINARY")) {
- binary_option = atoi(option_arg);
- if(binary_option != 1) {
- tn->us_preferred[CURL_TELOPT_BINARY] = CURL_NO;
- tn->him_preferred[CURL_TELOPT_BINARY] = CURL_NO;
+ case 6:
+ /* To take care or not of the 8th bit in data exchange */
+ if(strncasecompare(option, "BINARY", 6)) {
+ int binary_option = atoi(arg);
+ if(binary_option != 1) {
+ tn->us_preferred[CURL_TELOPT_BINARY] = CURL_NO;
+ tn->him_preferred[CURL_TELOPT_BINARY] = CURL_NO;
+ }
}
- continue;
+ else
+ result = CURLE_UNKNOWN_OPTION;
+ break;
+ default:
+ failf(data, "Unknown telnet option %s", head->data);
+ result = CURLE_UNKNOWN_OPTION;
+ break;
}
-
- failf(data, "Unknown telnet option %s", head->data);
- result = CURLE_UNKNOWN_OPTION;
- break;
}
- failf(data, "Syntax error in telnet option: %s", head->data);
- result = CURLE_SETOPT_OPTION_SYNTAX;
- break;
+ else {
+ failf(data, "Syntax error in telnet option: %s", head->data);
+ result = CURLE_SETOPT_OPTION_SYNTAX;
+ }
}
if(result) {
--
2.25.1
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