bugfix: we now avoid generating a Content-Type header when getting/se…

…tting other response headers.

Signed-off-by: Thibault Charbonnier <thibaultcha@me.com>

README.markdown

@@ -4147,6 +4147,25 @@ to be returned when reading `ngx.header.Foo`.
 
 Note that `ngx.header` is not a normal Lua table and as such, it is not possible to iterate through it using the Lua `ipairs` function.
 
+Note: if the current response does not have a Content-Type header, but you use
+`ngx.header` to attempt retrieving it, a side effect will be that a
+Content-Type header will be created and returned according to your nginx
+configuration.
+
+For example:
+
+```nginx
+
+ location = /t {
+     default_type text/html;
+     content_by_lua_block {
+         -- even if the response had no Content-Type header,
+         -- it will now have: Content-Type: text/html
+         ngx.say(ngx.header['Content-Type'])
+     }
+ }
+```
+
 For reading *request* headers, use the [ngx.req.get_headers](#ngxreqget_headers) function instead.
 
 [Back to TOC](#nginx-api-for-lua)
@@ -4172,6 +4191,24 @@ Returns a Lua table holding all the current response headers for the current req
  end
 ```
 
+Note: if the current response does not have a Content-Type header, but you use
+`ngx.resp.get_headers` to attempt retrieving it, a side effect will
+be that a Content-Type header will be created and returned according to your
+nginx configuration.
+
+For example:
+
+```nginx
+
+ location = /t {
+     default_type text/html;
+     content_by_lua_block {
+         -- the Content-Type header will be text/html
+         ngx.say(ngx.resp.get_headers()['Content-Type'])
+     }
+ }
+```
+
 This function has the same signature as [ngx.req.get_headers](#ngxreqget_headers) except getting response headers instead of request headers.
 
 Note that a maximum of 100 response headers are parsed by default (including those with the same name) and that additional response headers are silently discarded to guard against potential denial of service attacks. Since `v0.10.13`, when the limit is exceeded, it will return a second value which is the string `"truncated"`.

doc/HttpLuaModule.wiki

@@ -3433,6 +3433,24 @@ to be returned when reading <code>ngx.header.Foo</code>.
 
 Note that <code>ngx.header</code> is not a normal Lua table and as such, it is not possible to iterate through it using the Lua <code>ipairs</code> function.
 
+Note: if the current response does not have a Content-Type header, but you use
+<code>ngx.header</code> to attempt retrieving it, a side effect will be that a
+Content-Type header will be created and returned according to your nginx
+configuration.
+
+For example:
+
+<geshi lang="nginx">
+    location = /t {
+        default_type text/html;
+        content_by_lua_block {
+            -- even if the response had no Content-Type header,
+            -- it will now have: Content-Type: text/html
+            ngx.say(ngx.header['Content-Type'])
+        }
+    }
+</geshi>
+
 For reading ''request'' headers, use the [[#ngx.req.get_headers|ngx.req.get_headers]] function instead.
 
 == ngx.resp.get_headers ==
@@ -3454,6 +3472,23 @@ for k, v in pairs(h) do
 end
 </geshi>
 
+Note: if the current response does not have a Content-Type header, but you use
+<code>ngx.resp.get_headers</code>, a side effect will be that a Content-Type
+header will be created and returned according to your nginx configuration.
+
+For example:
+
+<geshi lang="nginx">
+    location = /t {
+        default_type text/html;
+        content_by_lua_block {
+            -- even if the response had no Content-Type header,
+            -- it will now have: Content-Type: text/html
+            ngx.say(ngx.resp.get_headers()['Content-Type'])
+        }
+    }
+</geshi>
+
 This function has the same signature as [[#ngx.req.get_headers|ngx.req.get_headers]] except getting response headers instead of request headers.
 
 Note that a maximum of 100 response headers are parsed by default (including those with the same name) and that additional response headers are silently discarded to guard against potential denial of service attacks. Since <code>v0.10.13</code>, when the limit is exceeded, it will return a second value which is the string `"truncated"`.

src/ngx_http_lua_headers.c

@@ -544,17 +544,6 @@ ngx_http_lua_ngx_resp_get_headers(lua_State *L)
         return luaL_error(L, "no ctx found");
     }
 
-    if (!ctx->headers_set) {
-        rc = ngx_http_lua_set_content_type(r);
-        if (rc != NGX_OK) {
-            return luaL_error(L,
-                              "failed to set default content type: %d",
-                              (int) rc);
-        }
-
-        ctx->headers_set = 1;
-    }
-
     ngx_http_lua_check_fake_request(L, r);
 
     part = &r->headers_out.headers.part;
@@ -573,6 +562,17 @@ ngx_http_lua_ngx_resp_get_headers(lua_State *L)
         lua_setmetatable(L, -2);
     }
 
+    if (!r->headers_out.content_type.len) {
+        rc = ngx_http_lua_set_content_type(r);
+        if (rc != NGX_OK) {
+            return luaL_error(L,
+                              "failed to set default content type: %d",
+                              (int) rc);
+        }
+
+        ctx->headers_set = 1;
+    }
+
 #if 1
     if (r->headers_out.content_type.len) {
         extra++;
@@ -696,7 +696,6 @@ ngx_http_lua_ngx_header_get(lua_State *L)
     size_t                       len;
     ngx_http_lua_loc_conf_t     *llcf;
     ngx_http_lua_ctx_t          *ctx;
-    ngx_int_t                    rc;
 
     r = ngx_http_lua_get_req(L);
     if (r == NULL) {
@@ -739,18 +738,7 @@ ngx_http_lua_ngx_header_get(lua_State *L)
 
     key.len = len;
 
-    if (!ctx->headers_set) {
-        rc = ngx_http_lua_set_content_type(r);
-        if (rc != NGX_OK) {
-            return luaL_error(L,
-                              "failed to set default content type: %d",
-                              (int) rc);
-        }
-
-        ctx->headers_set = 1;
-    }
-
-    return ngx_http_lua_get_output_header(L, r, &key);
+    return ngx_http_lua_get_output_header(L, r, ctx, &key);
 }
 
 
@@ -813,16 +801,7 @@ ngx_http_lua_ngx_header_set(lua_State *L)
         }
     }
 
-    if (!ctx->headers_set) {
-        rc = ngx_http_lua_set_content_type(r);
-        if (rc != NGX_OK) {
-            return luaL_error(L,
-                              "failed to set default content type: %d",
-                              (int) rc);
-        }
-
-        ctx->headers_set = 1;
-    }
+    ctx->headers_set = 1;
 
     if (lua_type(L, 3) == LUA_TNIL) {
         ngx_str_null(&value);
@@ -1244,15 +1223,7 @@ ngx_http_lua_ffi_set_resp_header(ngx_http_request_t *r, const u_char *key_data,
         }
     }
 
-    if (!ctx->headers_set) {
-        rc = ngx_http_lua_set_content_type(r);
-        if (rc != NGX_OK) {
-            *errmsg = "failed to set default content type";
-            return NGX_ERROR;
-        }
-
-        ctx->headers_set = 1;
-    }
+    ctx->headers_set = 1;
 
     if (is_nil) {
         value.data = NULL;
@@ -1373,7 +1344,8 @@ ngx_http_lua_ffi_req_header_set_single_value(ngx_http_request_t *r,
 int
 ngx_http_lua_ffi_get_resp_header(ngx_http_request_t *r,
     const u_char *key, size_t key_len,
-    u_char *key_buf, ngx_http_lua_ffi_str_t *values, int max_nvalues)
+    u_char *key_buf, ngx_http_lua_ffi_str_t *values, int max_nvalues,
+    char **errmsg)
 {
     int                  found;
     u_char               c, *p;
@@ -1390,19 +1362,10 @@ ngx_http_lua_ffi_get_resp_header(ngx_http_request_t *r,
 
     ctx = ngx_http_get_module_ctx(r, ngx_http_lua_module);
     if (ctx == NULL) {
-        /* *errmsg = "no ctx found"; */
+        *errmsg = "no ctx found";
         return NGX_ERROR;
     }
 
-    if (!ctx->headers_set) {
-        if (ngx_http_lua_set_content_type(r) != NGX_OK) {
-            /* *errmsg = "failed to set default content type"; */
-            return NGX_ERROR;
-        }
-
-        ctx->headers_set = 1;
-    }
-
     llcf = ngx_http_get_module_loc_conf(r, ngx_http_lua_module);
     if (llcf->transform_underscores_in_resp_headers
         && memchr(key, '_', key_len) != NULL)
@@ -1428,6 +1391,7 @@ ngx_http_lua_ffi_get_resp_header(ngx_http_request_t *r,
         {
             p = ngx_palloc(r->pool, NGX_OFF_T_LEN);
             if (p == NULL) {
+                *errmsg = "no memory";
                 return NGX_ERROR;
             }
 
@@ -1441,12 +1405,21 @@ ngx_http_lua_ffi_get_resp_header(ngx_http_request_t *r,
         break;
 
     case 12:
-        if (r->headers_out.content_type.len
-            && ngx_strncasecmp(key_buf, (u_char *) "Content-Type", 12) == 0)
-        {
-            values[0].data = r->headers_out.content_type.data;
-            values[0].len = r->headers_out.content_type.len;
-            return 1;
+        if (ngx_strncasecmp(key_buf, (u_char *) "Content-Type", 12) == 0) {
+            if (!r->headers_out.content_type.len) {
+                if (ngx_http_lua_set_content_type(r) != NGX_OK) {
+                    *errmsg = "failed to set default content type";
+                    return NGX_ERROR;
+                }
+
+                ctx->headers_set = 1;
+            }
+
+            if (r->headers_out.content_type.len) {
+                values[0].data = r->headers_out.content_type.data;
+                values[0].len = r->headers_out.content_type.len;
+                return 1;
+            }
         }
 
         break;

src/ngx_http_lua_headers_out.c

@@ -528,10 +528,11 @@ ngx_http_lua_set_output_header(ngx_http_request_t *r, ngx_str_t key,
 
 int
 ngx_http_lua_get_output_header(lua_State *L, ngx_http_request_t *r,
-    ngx_str_t *key)
+    ngx_http_lua_ctx_t *ctx, ngx_str_t *key)
 {
     ngx_table_elt_t            *h;
     ngx_list_part_t            *part;
+    ngx_int_t                   rc;
     ngx_uint_t                  i;
     unsigned                    found;
 
@@ -550,12 +551,23 @@ ngx_http_lua_get_output_header(lua_State *L, ngx_http_request_t *r,
         break;
 
     case 12:
-        if (r->headers_out.content_type.len
-            && ngx_strncasecmp(key->data, (u_char *) "Content-Type", 12) == 0)
-        {
-            lua_pushlstring(L, (char *) r->headers_out.content_type.data,
-                            r->headers_out.content_type.len);
-            return 1;
+        if (ngx_strncasecmp(key->data, (u_char *) "Content-Type", 12) == 0) {
+            if (!r->headers_out.content_type.len) {
+                rc = ngx_http_lua_set_content_type(r);
+                if (rc != NGX_OK) {
+                    return luaL_error(L,
+                                      "failed to set default content type: %d",
+                                      (int) rc);
+                }
+
+                ctx->headers_set = 1;
+            }
+
+            if (r->headers_out.content_type.len) {
+                lua_pushlstring(L, (char *) r->headers_out.content_type.data,
+                                r->headers_out.content_type.len);
+                return 1;
+            }
         }
 
         break;

src/ngx_http_lua_headers_out.h

@@ -15,7 +15,7 @@
 ngx_int_t ngx_http_lua_set_output_header(ngx_http_request_t *r, ngx_str_t key,
     ngx_str_t value, unsigned override);
 int ngx_http_lua_get_output_header(lua_State *L, ngx_http_request_t *r,
-    ngx_str_t *key);
+    ngx_http_lua_ctx_t *ctx, ngx_str_t *key);
 
 
 #endif /* _NGX_HTTP_LUA_HEADERS_OUT_H_INCLUDED_ */

src/ngx_http_lua_subrequest.c

@@ -1031,6 +1031,14 @@ ngx_http_lua_post_subrequest(ngx_http_request_t *r, void *data, ngx_int_t rc)
     dd("pr_coctx status: %d", (int) pr_coctx->sr_statuses[ctx->index]);
 
     /* copy subrequest response headers */
+    if (ctx->headers_set) {
+        rc = ngx_http_lua_set_content_type(r);
+        if (rc != NGX_OK) {
+            ngx_log_error(NGX_LOG_ERR, r->connection->log, 0,
+                          "failed to set default content type: %i", rc);
+            return NGX_ERROR;
+        }
+    }
 
     pr_coctx->sr_headers[ctx->index] = &r->headers_out;