From: HenrikHolst <henrik.holst@millistream.com>
Date: Tue, 8 Feb 2022 23:57:00 +0000 (+0100)
Subject: misc: remove strlen for Curl_checkheaders + Curl_checkProxyheaders
X-Git-Tag: curl-7_82_0~98
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=9bc3cebc9271c79f4ab229fecced1f54dec6bc3d;p=thirdparty%2Fcurl.git

misc: remove strlen for Curl_checkheaders + Curl_checkProxyheaders

Closes #8409
---

diff --git a/lib/c-hyper.c b/lib/c-hyper.c
index 352ba9785b..8015de25bc 100644
--- a/lib/c-hyper.c
+++ b/lib/c-hyper.c
@@ -1022,7 +1022,8 @@ CURLcode Curl_http(struct Curl_easy *data, bool *done)
       goto error;
   }
 
-  p_accept = Curl_checkheaders(data, "Accept")?NULL:"Accept: */*\r\n";
+  p_accept = Curl_checkheaders(data,
+                               STRCONST("Accept"))?NULL:"Accept: */*\r\n";
   if(p_accept) {
     result = Curl_hyper_header(data, headers, p_accept);
     if(result)
@@ -1036,8 +1037,8 @@ CURLcode Curl_http(struct Curl_easy *data, bool *done)
 
 #ifndef CURL_DISABLE_PROXY
   if(conn->bits.httpproxy && !conn->bits.tunnel_proxy &&
-     !Curl_checkheaders(data, "Proxy-Connection") &&
-     !Curl_checkProxyheaders(data, conn, "Proxy-Connection")) {
+     !Curl_checkheaders(data, STRCONST("Proxy-Connection")) &&
+     !Curl_checkProxyheaders(data, conn, STRCONST("Proxy-Connection"))) {
     result = Curl_hyper_header(data, headers, "Proxy-Connection: Keep-Alive");
     if(result)
       goto error;
@@ -1045,7 +1046,7 @@ CURLcode Curl_http(struct Curl_easy *data, bool *done)
 #endif
 
   Curl_safefree(data->state.aptr.ref);
-  if(data->state.referer && !Curl_checkheaders(data, "Referer")) {
+  if(data->state.referer && !Curl_checkheaders(data, STRCONST("Referer"))) {
     data->state.aptr.ref = aprintf("Referer: %s\r\n", data->state.referer);
     if(!data->state.aptr.ref)
       result = CURLE_OUT_OF_MEMORY;
@@ -1055,7 +1056,7 @@ CURLcode Curl_http(struct Curl_easy *data, bool *done)
       goto error;
   }
 
-  if(!Curl_checkheaders(data, "Accept-Encoding") &&
+  if(!Curl_checkheaders(data, STRCONST("Accept-Encoding")) &&
      data->set.str[STRING_ENCODING]) {
     Curl_safefree(data->state.aptr.accept_encoding);
     data->state.aptr.accept_encoding =
diff --git a/lib/h2h3.c b/lib/h2h3.c
index bd1334a59b..f6695d355d 100644
--- a/lib/h2h3.c
+++ b/lib/h2h3.c
@@ -186,7 +186,7 @@ CURLcode Curl_pseudo_headers(struct Curl_easy *data,
 
   nva[2].name = H2H3_PSEUDO_SCHEME;
   nva[2].namelen = sizeof(H2H3_PSEUDO_SCHEME) - 1;
-  vptr = Curl_checkheaders(data, H2H3_PSEUDO_SCHEME);
+  vptr = Curl_checkheaders(data, STRCONST(H2H3_PSEUDO_SCHEME));
   if(vptr) {
     vptr += sizeof(H2H3_PSEUDO_SCHEME);
     while(*vptr && ISSPACE(*vptr))
diff --git a/lib/http.c b/lib/http.c
index 81bc846ded..9f37dedafd 100644
--- a/lib/http.c
+++ b/lib/http.c
@@ -215,10 +215,10 @@ static CURLcode http_setup_conn(struct Curl_easy *data,
  */
 char *Curl_checkProxyheaders(struct Curl_easy *data,
                              const struct connectdata *conn,
-                             const char *thisheader)
+                             const char *thisheader,
+                             const size_t thislen)
 {
   struct curl_slist *head;
-  size_t thislen = strlen(thisheader);
 
   for(head = (conn->bits.proxy && data->set.sep_headers) ?
         data->set.proxyheaders : data->set.headers;
@@ -232,7 +232,7 @@ char *Curl_checkProxyheaders(struct Curl_easy *data,
 }
 #else
 /* disabled */
-#define Curl_checkProxyheaders(x,y,z) NULL
+#define Curl_checkProxyheaders(x,y,z,a) NULL
 #endif
 
 /*
@@ -724,10 +724,10 @@ output_auth_headers(struct Curl_easy *data,
     if(
 #ifndef CURL_DISABLE_PROXY
       (proxy && conn->bits.proxy_user_passwd &&
-       !Curl_checkProxyheaders(data, conn, "Proxy-authorization")) ||
+       !Curl_checkProxyheaders(data, conn, STRCONST("Proxy-authorization"))) ||
 #endif
       (!proxy && conn->bits.user_passwd &&
-       !Curl_checkheaders(data, "Authorization"))) {
+       !Curl_checkheaders(data, STRCONST("Authorization")))) {
       auth = "Basic";
       result = http_output_basic(data, proxy);
       if(result)
@@ -741,7 +741,7 @@ output_auth_headers(struct Curl_easy *data,
   if(authstatus->picked == CURLAUTH_BEARER) {
     /* Bearer */
     if((!proxy && data->set.str[STRING_BEARER] &&
-        !Curl_checkheaders(data, "Authorization"))) {
+        !Curl_checkheaders(data, STRCONST("Authorization")))) {
       auth = "Bearer";
       result = http_output_bearer(data);
       if(result)
@@ -1707,7 +1707,7 @@ static CURLcode expect100(struct Curl_easy *data,
     /* if not doing HTTP 1.0 or version 2, or disabled explicitly, we add an
        Expect: 100-continue to the headers which actually speeds up post
        operations (as there is one packet coming back from the web server) */
-    const char *ptr = Curl_checkheaders(data, "Expect");
+    const char *ptr = Curl_checkheaders(data, STRCONST("Expect"));
     if(ptr) {
       data->state.expect100header =
         Curl_compareheader(ptr, STRCONST("Expect:"), STRCONST("100-continue"));
@@ -1943,6 +1943,7 @@ CURLcode Curl_add_timecondition(struct Curl_easy *data,
   CURLcode result;
   char datestr[80];
   const char *condp;
+  size_t len;
 
   if(data->set.timecondition == CURL_TIMECOND_NONE)
     /* no condition was asked for */
@@ -1961,16 +1962,19 @@ CURLcode Curl_add_timecondition(struct Curl_easy *data,
 
   case CURL_TIMECOND_IFMODSINCE:
     condp = "If-Modified-Since";
+    len = 17;
     break;
   case CURL_TIMECOND_IFUNMODSINCE:
     condp = "If-Unmodified-Since";
+    len = 19;
     break;
   case CURL_TIMECOND_LASTMOD:
     condp = "Last-Modified";
+    len = 13;
     break;
   }
 
-  if(Curl_checkheaders(data, condp)) {
+  if(Curl_checkheaders(data, condp, len)) {
     /* A custom header was specified; it will be sent instead. */
     return CURLE_OK;
   }
@@ -2059,7 +2063,7 @@ CURLcode Curl_http_useragent(struct Curl_easy *data)
      it might have been used in the proxy connect, but if we have got a header
      with the user-agent string specified, we erase the previously made string
      here. */
-  if(Curl_checkheaders(data, "User-Agent")) {
+  if(Curl_checkheaders(data, STRCONST("User-Agent"))) {
     free(data->state.aptr.uagent);
     data->state.aptr.uagent = NULL;
   }
@@ -2082,7 +2086,7 @@ CURLcode Curl_http_host(struct Curl_easy *data, struct connectdata *conn)
   }
   Curl_safefree(data->state.aptr.host);
 
-  ptr = Curl_checkheaders(data, "Host");
+  ptr = Curl_checkheaders(data, STRCONST("Host"));
   if(ptr && (!data->state.this_is_a_follow ||
              strcasecompare(data->state.first_host, conn->host.name))) {
 #if !defined(CURL_DISABLE_COOKIES)
@@ -2299,7 +2303,7 @@ CURLcode Curl_http_body(struct Curl_easy *data, struct connectdata *conn,
 
 #ifndef CURL_DISABLE_MIME
   if(http->sendit) {
-    const char *cthdr = Curl_checkheaders(data, "Content-Type");
+    const char *cthdr = Curl_checkheaders(data, STRCONST("Content-Type"));
 
     /* Read and seek body only. */
     http->sendit->flags |= MIME_BODY_ONLY;
@@ -2324,7 +2328,7 @@ CURLcode Curl_http_body(struct Curl_easy *data, struct connectdata *conn,
   }
 #endif
 
-  ptr = Curl_checkheaders(data, "Transfer-Encoding");
+  ptr = Curl_checkheaders(data, STRCONST("Transfer-Encoding"));
   if(ptr) {
     /* Some kind of TE is requested, check if 'chunked' is chosen */
     data->req.upload_chunky =
@@ -2389,7 +2393,8 @@ CURLcode Curl_http_bodysend(struct Curl_easy *data, struct connectdata *conn,
       http->postsize = data->state.infilesize;
 
     if((http->postsize != -1) && !data->req.upload_chunky &&
-       (conn->bits.authneg || !Curl_checkheaders(data, "Content-Length"))) {
+       (conn->bits.authneg ||
+        !Curl_checkheaders(data, STRCONST("Content-Length")))) {
       /* only add Content-Length if not uploading chunked */
       result = Curl_dyn_addf(r, "Content-Length: %" CURL_FORMAT_CURL_OFF_T
                              "\r\n", http->postsize);
@@ -2449,7 +2454,8 @@ CURLcode Curl_http_bodysend(struct Curl_easy *data, struct connectdata *conn,
        we don't upload data chunked, as RFC2616 forbids us to set both
        kinds of headers (Transfer-Encoding: chunked and Content-Length) */
     if(http->postsize != -1 && !data->req.upload_chunky &&
-       (conn->bits.authneg || !Curl_checkheaders(data, "Content-Length"))) {
+       (conn->bits.authneg ||
+        !Curl_checkheaders(data, STRCONST("Content-Length")))) {
       /* we allow replacing this header if not during auth negotiation,
          although it isn't very wise to actually set your own */
       result = Curl_dyn_addf(r,
@@ -2476,7 +2482,7 @@ CURLcode Curl_http_bodysend(struct Curl_easy *data, struct connectdata *conn,
        the somewhat bigger ones we allow the app to disable it. Just make
        sure that the expect100header is always set to the preferred value
        here. */
-    ptr = Curl_checkheaders(data, "Expect");
+    ptr = Curl_checkheaders(data, STRCONST("Expect"));
     if(ptr) {
       data->state.expect100header =
         Curl_compareheader(ptr, STRCONST("Expect:"), STRCONST("100-continue"));
@@ -2529,7 +2535,8 @@ CURLcode Curl_http_bodysend(struct Curl_easy *data, struct connectdata *conn,
        we don't upload data chunked, as RFC2616 forbids us to set both
        kinds of headers (Transfer-Encoding: chunked and Content-Length) */
     if((http->postsize != -1) && !data->req.upload_chunky &&
-       (conn->bits.authneg || !Curl_checkheaders(data, "Content-Length"))) {
+       (conn->bits.authneg ||
+        !Curl_checkheaders(data, STRCONST("Content-Length")))) {
       /* we allow replacing this header if not during auth negotiation,
          although it isn't very wise to actually set your own */
       result = Curl_dyn_addf(r, "Content-Length: %" CURL_FORMAT_CURL_OFF_T
@@ -2538,9 +2545,9 @@ CURLcode Curl_http_bodysend(struct Curl_easy *data, struct connectdata *conn,
         return result;
     }
 
-    if(!Curl_checkheaders(data, "Content-Type")) {
+    if(!Curl_checkheaders(data, STRCONST("Content-Type"))) {
       result = Curl_dyn_addn(r, STRCONST("Content-Type: application/"
-                            "x-www-form-urlencoded\r\n"));
+                                         "x-www-form-urlencoded\r\n"));
       if(result)
         return result;
     }
@@ -2549,7 +2556,7 @@ CURLcode Curl_http_bodysend(struct Curl_easy *data, struct connectdata *conn,
        the somewhat bigger ones we allow the app to disable it. Just make
        sure that the expect100header is always set to the preferred value
        here. */
-    ptr = Curl_checkheaders(data, "Expect");
+    ptr = Curl_checkheaders(data, STRCONST("Expect"));
     if(ptr) {
       data->state.expect100header =
         Curl_compareheader(ptr, STRCONST("Expect:"), STRCONST("100-continue"));
@@ -2697,7 +2704,8 @@ CURLcode Curl_http_cookies(struct Curl_easy *data,
 {
   CURLcode result = CURLE_OK;
   char *addcookies = NULL;
-  if(data->set.str[STRING_COOKIE] && !Curl_checkheaders(data, "Cookie"))
+  if(data->set.str[STRING_COOKIE] &&
+     !Curl_checkheaders(data, STRCONST("Cookie")))
     addcookies = data->set.str[STRING_COOKIE];
 
   if(data->cookies || addcookies) {
@@ -2765,14 +2773,14 @@ CURLcode Curl_http_range(struct Curl_easy *data,
      * ones if any such are specified.
      */
     if(((httpreq == HTTPREQ_GET) || (httpreq == HTTPREQ_HEAD)) &&
-       !Curl_checkheaders(data, "Range")) {
+       !Curl_checkheaders(data, STRCONST("Range"))) {
       /* if a line like this was already allocated, free the previous one */
       free(data->state.aptr.rangeline);
       data->state.aptr.rangeline = aprintf("Range: bytes=%s\r\n",
                                            data->state.range);
     }
     else if((httpreq == HTTPREQ_POST || httpreq == HTTPREQ_PUT) &&
-            !Curl_checkheaders(data, "Content-Range")) {
+            !Curl_checkheaders(data, STRCONST("Content-Range"))) {
 
       /* if a line like this was already allocated, free the previous one */
       free(data->state.aptr.rangeline);
@@ -2957,14 +2965,14 @@ CURLcode Curl_http_firstwrite(struct Curl_easy *data,
 #ifdef HAVE_LIBZ
 CURLcode Curl_transferencode(struct Curl_easy *data)
 {
-  if(!Curl_checkheaders(data, "TE") &&
+  if(!Curl_checkheaders(data, STRCONST("TE")) &&
      data->set.http_transfer_encoding) {
     /* When we are to insert a TE: header in the request, we must also insert
        TE in a Connection: header, so we need to merge the custom provided
        Connection: header and prevent the original to get sent. Note that if
        the user has inserted his/her own TE: header we don't do this magic
        but then assume that the user will handle it all! */
-    char *cptr = Curl_checkheaders(data, "Connection");
+    char *cptr = Curl_checkheaders(data, STRCONST("Connection"));
 #define TE_HEADER "TE: gzip\r\n"
 
     Curl_safefree(data->state.aptr.te);
@@ -3084,13 +3092,13 @@ CURLcode Curl_http(struct Curl_easy *data, bool *done)
   }
 
   Curl_safefree(data->state.aptr.ref);
-  if(data->state.referer && !Curl_checkheaders(data, "Referer")) {
+  if(data->state.referer && !Curl_checkheaders(data, STRCONST("Referer"))) {
     data->state.aptr.ref = aprintf("Referer: %s\r\n", data->state.referer);
     if(!data->state.aptr.ref)
       return CURLE_OUT_OF_MEMORY;
   }
 
-  if(!Curl_checkheaders(data, "Accept-Encoding") &&
+  if(!Curl_checkheaders(data, STRCONST("Accept-Encoding")) &&
      data->set.str[STRING_ENCODING]) {
     Curl_safefree(data->state.aptr.accept_encoding);
     data->state.aptr.accept_encoding =
@@ -3112,7 +3120,8 @@ CURLcode Curl_http(struct Curl_easy *data, bool *done)
   if(result)
     return result;
 
-  p_accept = Curl_checkheaders(data, "Accept")?NULL:"Accept: */*\r\n";
+  p_accept = Curl_checkheaders(data,
+                               STRCONST("Accept"))?NULL:"Accept: */*\r\n";
 
   result = Curl_http_resume(data, conn, httpreq);
   if(result)
@@ -3142,7 +3151,7 @@ CURLcode Curl_http(struct Curl_easy *data, bool *done)
   }
 
 #ifndef CURL_DISABLE_ALTSVC
-  if(conn->bits.altused && !Curl_checkheaders(data, "Alt-Used")) {
+  if(conn->bits.altused && !Curl_checkheaders(data, STRCONST("Alt-Used"))) {
     altused = aprintf("Alt-Used: %s:%d\r\n",
                       conn->conn_to_host.name, conn->conn_to_port);
     if(!altused) {
@@ -3189,8 +3198,10 @@ CURLcode Curl_http(struct Curl_easy *data, bool *done)
 #ifndef CURL_DISABLE_PROXY
                   (conn->bits.httpproxy &&
                    !conn->bits.tunnel_proxy &&
-                   !Curl_checkheaders(data, "Proxy-Connection") &&
-                   !Curl_checkProxyheaders(data, conn, "Proxy-Connection"))?
+                   !Curl_checkheaders(data, STRCONST("Proxy-Connection")) &&
+                   !Curl_checkProxyheaders(data,
+                                           conn,
+                                           STRCONST("Proxy-Connection")))?
                   "Proxy-Connection: Keep-Alive\r\n":"",
 #else
                   "",
diff --git a/lib/http.h b/lib/http.h
index 0fa016cfef..07e963dc48 100644
--- a/lib/http.h
+++ b/lib/http.h
@@ -55,7 +55,8 @@ char *Curl_copy_header_value(const char *header);
 
 char *Curl_checkProxyheaders(struct Curl_easy *data,
                              const struct connectdata *conn,
-                             const char *thisheader);
+                             const char *thisheader,
+                             const size_t thislen);
 CURLcode Curl_buffer_send(struct dynbuf *in,
                           struct Curl_easy *data,
                           curl_off_t *bytes_written,
diff --git a/lib/http_aws_sigv4.c b/lib/http_aws_sigv4.c
index 751e5af5f9..210c3dbe56 100644
--- a/lib/http_aws_sigv4.c
+++ b/lib/http_aws_sigv4.c
@@ -5,7 +5,7 @@
  *                            | (__| |_| |  _ <| |___
  *                             \___|\___/|_| \_\_____|
  *
- * Copyright (C) 1998 - 2021, Daniel Stenberg, <daniel@haxx.se>, et al.
+ * Copyright (C) 1998 - 2022, Daniel Stenberg, <daniel@haxx.se>, et al.
  *
  * This software is licensed as described in the file COPYING, which
  * you should have received as part of this distribution. The terms
@@ -87,7 +87,7 @@ CURLcode Curl_output_aws_sigv4(struct Curl_easy *data, bool proxy)
   struct tm tm;
   char timestamp[17];
   char date[9];
-  const char *content_type = Curl_checkheaders(data, "Content-Type");
+  const char *content_type = Curl_checkheaders(data, STRCONST("Content-Type"));
   char *canonical_headers = NULL;
   char *signed_headers = NULL;
   Curl_HttpReq httpreq;
@@ -110,7 +110,7 @@ CURLcode Curl_output_aws_sigv4(struct Curl_easy *data, bool proxy)
   DEBUGASSERT(!proxy);
   (void)proxy;
 
-  if(Curl_checkheaders(data, "Authorization")) {
+  if(Curl_checkheaders(data, STRCONST("Authorization"))) {
     /* Authorization already present, Bailing out */
     return CURLE_OK;
   }
diff --git a/lib/http_proxy.c b/lib/http_proxy.c
index 3ffb026a10..5d5ffc0e1c 100644
--- a/lib/http_proxy.c
+++ b/lib/http_proxy.c
@@ -244,7 +244,7 @@ static CURLcode CONNECT_host(struct Curl_easy *data,
   if(!hostheader)
     return CURLE_OUT_OF_MEMORY;
 
-  if(!Curl_checkProxyheaders(data, conn, "Host")) {
+  if(!Curl_checkProxyheaders(data, conn, STRCONST("Host"))) {
     host = aprintf("Host: %s\r\n", hostheader);
     if(!host) {
       free(hostheader);
@@ -323,12 +323,14 @@ static CURLcode CONNECT(struct Curl_easy *data,
                         data->state.aptr.proxyuserpwd?
                         data->state.aptr.proxyuserpwd:"");
 
-        if(!result && !Curl_checkProxyheaders(data, conn, "User-Agent") &&
+        if(!result && !Curl_checkProxyheaders(data,
+                                              conn, STRCONST("User-Agent")) &&
            data->set.str[STRING_USERAGENT])
           result = Curl_dyn_addf(req, "User-Agent: %s\r\n",
                                  data->set.str[STRING_USERAGENT]);
 
-        if(!result && !Curl_checkProxyheaders(data, conn, "Proxy-Connection"))
+        if(!result && !Curl_checkProxyheaders(data, conn,
+                                              STRCONST("Proxy-Connection")))
           result = Curl_dyn_addn(req,
                                  STRCONST("Proxy-Connection: Keep-Alive\r\n"));
 
@@ -875,7 +877,7 @@ static CURLcode CONNECT(struct Curl_easy *data,
           goto error;
       }
 
-      if(!Curl_checkProxyheaders(data, conn, "User-Agent") &&
+      if(!Curl_checkProxyheaders(data, conn, STRCONST("User-Agent")) &&
          data->set.str[STRING_USERAGENT]) {
         struct dynbuf ua;
         Curl_dyn_init(&ua, DYN_HTTP_REQUEST);
@@ -889,7 +891,7 @@ static CURLcode CONNECT(struct Curl_easy *data,
         Curl_dyn_free(&ua);
       }
 
-      if(!Curl_checkProxyheaders(data, conn, "Proxy-Connection")) {
+      if(!Curl_checkProxyheaders(data, conn, STRCONST("Proxy-Connection"))) {
         result = Curl_hyper_header(data, headers,
                                    "Proxy-Connection: Keep-Alive");
         if(result)
diff --git a/lib/imap.c b/lib/imap.c
index 70e4b8306e..c043bfa3b5 100644
--- a/lib/imap.c
+++ b/lib/imap.c
@@ -777,7 +777,7 @@ static CURLcode imap_perform_append(struct Curl_easy *data)
                                        NULL, MIMESTRATEGY_MAIL);
 
     if(!result)
-      if(!Curl_checkheaders(data, "Mime-Version"))
+      if(!Curl_checkheaders(data, STRCONST("Mime-Version")))
         result = Curl_mime_add_header(&data->set.mimepost.curlheaders,
                                       "Mime-Version: 1.0");
 
diff --git a/lib/rtsp.c b/lib/rtsp.c
index cf1933abe7..f16e87c12d 100644
--- a/lib/rtsp.c
+++ b/lib/rtsp.c
@@ -340,7 +340,7 @@ static CURLcode rtsp_do(struct Curl_easy *data, bool *done)
   }
 
   /* Transport Header for SETUP requests */
-  p_transport = Curl_checkheaders(data, "Transport");
+  p_transport = Curl_checkheaders(data, STRCONST("Transport"));
   if(rtspreq == RTSPREQ_SETUP && !p_transport) {
     /* New Transport: setting? */
     if(data->set.str[STRING_RTSP_TRANSPORT]) {
@@ -364,11 +364,11 @@ static CURLcode rtsp_do(struct Curl_easy *data, bool *done)
   /* Accept Headers for DESCRIBE requests */
   if(rtspreq == RTSPREQ_DESCRIBE) {
     /* Accept Header */
-    p_accept = Curl_checkheaders(data, "Accept")?
+    p_accept = Curl_checkheaders(data, STRCONST("Accept"))?
       NULL:"Accept: application/sdp\r\n";
 
     /* Accept-Encoding header */
-    if(!Curl_checkheaders(data, "Accept-Encoding") &&
+    if(!Curl_checkheaders(data, STRCONST("Accept-Encoding")) &&
        data->set.str[STRING_ENCODING]) {
       Curl_safefree(data->state.aptr.accept_encoding);
       data->state.aptr.accept_encoding =
@@ -385,11 +385,12 @@ static CURLcode rtsp_do(struct Curl_easy *data, bool *done)
      it might have been used in the proxy connect, but if we have got a header
      with the user-agent string specified, we erase the previously made string
      here. */
-  if(Curl_checkheaders(data, "User-Agent") && data->state.aptr.uagent) {
+  if(Curl_checkheaders(data, STRCONST("User-Agent")) &&
+     data->state.aptr.uagent) {
     Curl_safefree(data->state.aptr.uagent);
     data->state.aptr.uagent = NULL;
   }
-  else if(!Curl_checkheaders(data, "User-Agent") &&
+  else if(!Curl_checkheaders(data, STRCONST("User-Agent")) &&
           data->set.str[STRING_USERAGENT]) {
     p_uagent = data->state.aptr.uagent;
   }
@@ -405,7 +406,7 @@ static CURLcode rtsp_do(struct Curl_easy *data, bool *done)
 
   /* Referrer */
   Curl_safefree(data->state.aptr.ref);
-  if(data->state.referer && !Curl_checkheaders(data, "Referer"))
+  if(data->state.referer && !Curl_checkheaders(data, STRCONST("Referer")))
     data->state.aptr.ref = aprintf("Referer: %s\r\n", data->state.referer);
   else
     data->state.aptr.ref = NULL;
@@ -422,7 +423,7 @@ static CURLcode rtsp_do(struct Curl_easy *data, bool *done)
      (rtspreq  & (RTSPREQ_PLAY | RTSPREQ_PAUSE | RTSPREQ_RECORD))) {
 
     /* Check to see if there is a range set in the custom headers */
-    if(!Curl_checkheaders(data, "Range") && data->state.range) {
+    if(!Curl_checkheaders(data, STRCONST("Range")) && data->state.range) {
       Curl_safefree(data->state.aptr.rangeline);
       data->state.aptr.rangeline = aprintf("Range: %s\r\n", data->state.range);
       p_range = data->state.aptr.rangeline;
@@ -432,11 +433,11 @@ static CURLcode rtsp_do(struct Curl_easy *data, bool *done)
   /*
    * Sanity check the custom headers
    */
-  if(Curl_checkheaders(data, "CSeq")) {
+  if(Curl_checkheaders(data, STRCONST("CSeq"))) {
     failf(data, "CSeq cannot be set as a custom header.");
     return CURLE_RTSP_CSEQ_ERROR;
   }
-  if(Curl_checkheaders(data, "Session")) {
+  if(Curl_checkheaders(data, STRCONST("Session"))) {
     failf(data, "Session ID cannot be set as a custom header.");
     return CURLE_BAD_FUNCTION_ARGUMENT;
   }
@@ -523,7 +524,7 @@ static CURLcode rtsp_do(struct Curl_easy *data, bool *done)
     if(putsize > 0 || postsize > 0) {
       /* As stated in the http comments, it is probably not wise to
        * actually set a custom Content-Length in the headers */
-      if(!Curl_checkheaders(data, "Content-Length")) {
+      if(!Curl_checkheaders(data, STRCONST("Content-Length"))) {
         result =
           Curl_dyn_addf(&req_buffer,
                         "Content-Length: %" CURL_FORMAT_CURL_OFF_T"\r\n",
@@ -534,7 +535,7 @@ static CURLcode rtsp_do(struct Curl_easy *data, bool *done)
 
       if(rtspreq == RTSPREQ_SET_PARAMETER ||
          rtspreq == RTSPREQ_GET_PARAMETER) {
-        if(!Curl_checkheaders(data, "Content-Type")) {
+        if(!Curl_checkheaders(data, STRCONST("Content-Type"))) {
           result = Curl_dyn_addn(&req_buffer,
                                  STRCONST("Content-Type: "
                                           "text/parameters\r\n"));
@@ -544,7 +545,7 @@ static CURLcode rtsp_do(struct Curl_easy *data, bool *done)
       }
 
       if(rtspreq == RTSPREQ_ANNOUNCE) {
-        if(!Curl_checkheaders(data, "Content-Type")) {
+        if(!Curl_checkheaders(data, STRCONST("Content-Type"))) {
           result = Curl_dyn_addn(&req_buffer,
                                  STRCONST("Content-Type: "
                                           "application/sdp\r\n"));
diff --git a/lib/smtp.c b/lib/smtp.c
index dbae801b1e..d589153240 100644
--- a/lib/smtp.c
+++ b/lib/smtp.c
@@ -698,7 +698,7 @@ static CURLcode smtp_perform_mail(struct Curl_easy *data)
                                        NULL, MIMESTRATEGY_MAIL);
 
     if(!result)
-      if(!Curl_checkheaders(data, "Mime-Version"))
+      if(!Curl_checkheaders(data, STRCONST("Mime-Version")))
         result = Curl_mime_add_header(&data->set.mimepost.curlheaders,
                                       "Mime-Version: 1.0");
 
diff --git a/lib/transfer.c b/lib/transfer.c
index 8477bdeaab..1f8019b3d0 100644
--- a/lib/transfer.c
+++ b/lib/transfer.c
@@ -94,10 +94,10 @@
  * Returns a pointer to the first matching header or NULL if none matched.
  */
 char *Curl_checkheaders(const struct Curl_easy *data,
-                        const char *thisheader)
+                        const char *thisheader,
+                        const size_t thislen)
 {
   struct curl_slist *head;
-  size_t thislen = strlen(thisheader);
   DEBUGASSERT(thislen);
   DEBUGASSERT(thisheader[thislen-1] != ':');
 
diff --git a/lib/transfer.h b/lib/transfer.h
index 0fa3d55e82..56d2fd1ee3 100644
--- a/lib/transfer.h
+++ b/lib/transfer.h
@@ -7,7 +7,7 @@
  *                            | (__| |_| |  _ <| |___
  *                             \___|\___/|_| \_\_____|
  *
- * Copyright (C) 1998 - 2021, Daniel Stenberg, <daniel@haxx.se>, et al.
+ * Copyright (C) 1998 - 2022, Daniel Stenberg, <daniel@haxx.se>, et al.
  *
  * This software is licensed as described in the file COPYING, which
  * you should have received as part of this distribution. The terms
@@ -24,7 +24,8 @@
 
 #define Curl_headersep(x) ((((x)==':') || ((x)==';')))
 char *Curl_checkheaders(const struct Curl_easy *data,
-                        const char *thisheader);
+                        const char *thisheader,
+                        const size_t thislen);
 
 void Curl_init_CONNECT(struct Curl_easy *data);