177 lines
6.9 KiB
Diff
177 lines
6.9 KiB
Diff
From ed5095ed94281989e103c72e032200b83be37878 Mon Sep 17 00:00:00 2001
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From: Daniel Stenberg <daniel@haxx.se>
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Date: Thu, 6 Oct 2022 00:49:10 +0200
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Subject: [PATCH] strcase: add and use Curl_timestrcmp
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This is a strcmp() alternative function for comparing "secrets",
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designed to take the same time no matter the content to not leak
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match/non-match info to observers based on how fast it is.
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The time this function takes is only a function of the shortest input
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string.
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Reported-by: Trail of Bits
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Closes #9658
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---
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lib/netrc.c | 6 +++---
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lib/strcase.c | 22 ++++++++++++++++++++++
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lib/strcase.h | 1 +
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lib/url.c | 34 +++++++++++++---------------------
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lib/vauth/digest_sspi.c | 4 ++--
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lib/vtls/vtls.c | 4 ++--
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6 files changed, 43 insertions(+), 28 deletions(-)
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--- a/lib/netrc.c
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+++ b/lib/netrc.c
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@@ -140,9 +140,9 @@ static int parsenetrc(const char *host,
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/* we are now parsing sub-keywords concerning "our" host */
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if(state_login) {
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if(specific_login) {
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- state_our_login = strcasecompare(login, tok);
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+ state_our_login = !Curl_timestrcmp(login, tok);
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}
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- else if(!login || strcmp(login, tok)) {
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+ else if(!login || Curl_timestrcmp(login, tok)) {
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if(login_alloc) {
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free(login);
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login_alloc = FALSE;
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@@ -158,7 +158,7 @@ static int parsenetrc(const char *host,
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}
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else if(state_password) {
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if((state_our_login || !specific_login)
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- && (!password || strcmp(password, tok))) {
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+ && (!password || Curl_timestrcmp(password, tok))) {
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if(password_alloc) {
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free(password);
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password_alloc = FALSE;
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--- a/lib/strcase.c
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+++ b/lib/strcase.c
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@@ -261,6 +261,28 @@ bool Curl_safecmp(char *a, char *b)
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return !a && !b;
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}
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+/*
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+ * Curl_timestrcmp() returns 0 if the two strings are identical. The time this
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+ * function spends is a function of the shortest string, not of the contents.
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+ */
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+int Curl_timestrcmp(const char *a, const char *b)
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+{
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+ int match = 0;
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+ int i = 0;
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+
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+ if(a && b) {
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+ while(1) {
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+ match |= a[i]^b[i];
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+ if(!a[i] || !b[i])
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+ break;
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+ i++;
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+ }
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+ }
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+ else
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+ return a || b;
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+ return match;
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+}
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+
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/* --- public functions --- */
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int curl_strequal(const char *first, const char *second)
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--- a/lib/strcase.h
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+++ b/lib/strcase.h
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@@ -49,5 +49,6 @@ void Curl_strntoupper(char *dest, const
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void Curl_strntolower(char *dest, const char *src, size_t n);
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bool Curl_safecmp(char *a, char *b);
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+int Curl_timestrcmp(const char *first, const char *second);
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#endif /* HEADER_CURL_STRCASE_H */
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--- a/lib/url.c
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+++ b/lib/url.c
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@@ -946,19 +946,10 @@ socks_proxy_info_matches(const struct pr
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/* the user information is case-sensitive
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or at least it is not defined as case-insensitive
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see https://tools.ietf.org/html/rfc3986#section-3.2.1 */
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- if(!data->user != !needle->user)
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- return FALSE;
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- /* curl_strequal does a case insentive comparison, so do not use it here! */
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- if(data->user &&
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- needle->user &&
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- strcmp(data->user, needle->user) != 0)
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- return FALSE;
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- if(!data->passwd != !needle->passwd)
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- return FALSE;
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+
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/* curl_strequal does a case insentive comparison, so do not use it here! */
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- if(data->passwd &&
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- needle->passwd &&
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- strcmp(data->passwd, needle->passwd) != 0)
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+ if(Curl_timestrcmp(data->user, needle->user) ||
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+ Curl_timestrcmp(data->passwd, needle->passwd))
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return FALSE;
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return TRUE;
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}
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@@ -1357,10 +1348,10 @@ ConnectionExists(struct Curl_easy *data,
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if(!(needle->handler->flags & PROTOPT_CREDSPERREQUEST)) {
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/* This protocol requires credentials per connection,
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so verify that we're using the same name and password as well */
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- if(strcmp(needle->user, check->user) ||
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- strcmp(needle->passwd, check->passwd) ||
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- !Curl_safecmp(needle->sasl_authzid, check->sasl_authzid) ||
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- !Curl_safecmp(needle->oauth_bearer, check->oauth_bearer)) {
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+ if(Curl_timestrcmp(needle->user, check->user) ||
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+ Curl_timestrcmp(needle->passwd, check->passwd) ||
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+ Curl_timestrcmp(needle->sasl_authzid, check->sasl_authzid) ||
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+ Curl_timestrcmp(needle->oauth_bearer, check->oauth_bearer)) {
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/* one of them was different */
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continue;
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}
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@@ -1436,8 +1427,8 @@ ConnectionExists(struct Curl_easy *data,
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possible. (Especially we must not reuse the same connection if
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partway through a handshake!) */
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if(wantNTLMhttp) {
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- if(strcmp(needle->user, check->user) ||
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- strcmp(needle->passwd, check->passwd)) {
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+ if(Curl_timestrcmp(needle->user, check->user) ||
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+ Curl_timestrcmp(needle->passwd, check->passwd)) {
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/* we prefer a credential match, but this is at least a connection
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that can be reused and "upgraded" to NTLM */
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@@ -1459,8 +1450,10 @@ ConnectionExists(struct Curl_easy *data,
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if(!check->http_proxy.user || !check->http_proxy.passwd)
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continue;
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- if(strcmp(needle->http_proxy.user, check->http_proxy.user) ||
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- strcmp(needle->http_proxy.passwd, check->http_proxy.passwd))
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+ if(Curl_timestrcmp(needle->http_proxy.user,
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+ check->http_proxy.user) ||
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+ Curl_timestrcmp(needle->http_proxy.passwd,
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+ check->http_proxy.passwd))
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continue;
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}
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else if(check->proxy_ntlm_state != NTLMSTATE_NONE) {
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--- a/lib/vauth/digest_sspi.c
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+++ b/lib/vauth/digest_sspi.c
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@@ -429,8 +429,8 @@ CURLcode Curl_auth_create_digest_http_me
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has changed then delete that context. */
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if((userp && !digest->user) || (!userp && digest->user) ||
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(passwdp && !digest->passwd) || (!passwdp && digest->passwd) ||
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- (userp && digest->user && strcmp(userp, digest->user)) ||
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- (passwdp && digest->passwd && strcmp(passwdp, digest->passwd))) {
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+ (userp && digest->user && Curl_timestrcmp(userp, digest->user)) ||
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+ (passwdp && digest->passwd && Curl_timestrcmp(passwdp, digest->passwd))) {
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if(digest->http_context) {
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s_pSecFn->DeleteSecurityContext(digest->http_context);
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Curl_safefree(digest->http_context);
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--- a/lib/vtls/vtls.c
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+++ b/lib/vtls/vtls.c
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@@ -146,8 +146,8 @@ Curl_ssl_config_matches(struct ssl_prima
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Curl_safecmp(data->random_file, needle->random_file) &&
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Curl_safecmp(data->egdsocket, needle->egdsocket) &&
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#ifdef USE_TLS_SRP
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- Curl_safecmp(data->username, needle->username) &&
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- Curl_safecmp(data->password, needle->password) &&
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+ !Curl_timestrcmp(data->username, needle->username) &&
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+ !Curl_timestrcmp(data->password, needle->password) &&
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(data->authtype == needle->authtype) &&
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#endif
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Curl_safe_strcasecompare(data->cipher_list, needle->cipher_list) &&
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