From 538b1e79a6e7b0bb829ab4cecc828d32105d0684 Mon Sep 17 00:00:00 2001 From: Daniel Stenberg 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 --- 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