Use open(), fstat() and fdopen() to prevent "time of check, time of use" problem

jelu · jelu · commit 63b480beb454 · 2017-05-22T14:15:11.000+02:00
diff --git a/src/server.cpp b/src/server.cpp
@@ -820,10 +820,14 @@ class Page
         while ( (d=readdir(dir))!=0 )
         {
             std::string subject=join_path(directory,d->d_name);
-            const char* file = subject.c_str();
+            int fd = open(subject.c_str(), O_RDONLY);
 
-            if (stat(file, &statbuf) ==-1)
+            if (fd < 0)
                 continue;
+            if (fstat(fd, &statbuf) ==-1) {
+                close(fd);
+                continue;
+            }
             if (S_ISDIR(statbuf.st_mode))
             {
                 if ( (strcmp(d->d_name,".")!=0) && (strcmp(d->d_name,"..")!=0 ) )
@@ -836,9 +840,7 @@ class Page
             else
             {
                 bool found = false;
-                std::string str = subject;
-                transform(str.begin(), str.end(),str.begin(), tolower );
-                FILE *fp = fopen(file, "rb");
+                FILE *fp = fdopen(fd, "rb");
                 if (fp)
                 {
                     Pcap_file pfile(fp);
@@ -866,10 +868,10 @@ class Page
                         printf("  %c{\n     \"data\" : \"%s\",\n     \"attr\" : { \"id\" : \"%s\", \"size\": %d, \"type\": \"json\" },\n    \"children\" : []  }\n",
                                 comma,d->d_name,join_path(m_url.get_path(),d->d_name).substr(5).c_str(), int(statbuf.st_size) );
                         comma=  ',';
-                        found = true;
                     }
                 }
             }
+            close(fd);
         }
 
         printf("]\n");

Original file line number	Diff line number	Diff line change
`@@ -820,10 +820,14 @@ class Page`
`820`	`820`	`while ( (d=readdir(dir))!=0 )`
`821`	`821`	`{`
`822`	`822`	`std::string subject=join_path(directory,d->d_name);`
`823`		`- const char* file = subject.c_str();`
	`823`	`+ int fd = open(subject.c_str(), O_RDONLY);`
`824`	`824`
`825`		`- if (stat(file, &statbuf) ==-1)`
	`825`	`+ if (fd < 0)`
`826`	`826`	`continue;`
	`827`	`+ if (fstat(fd, &statbuf) ==-1) {`
	`828`	`+ close(fd);`
	`829`	`+ continue;`
	`830`	`+ }`
`827`	`831`	`if (S_ISDIR(statbuf.st_mode))`
`828`	`832`	`{`
`829`	`833`	`if ( (strcmp(d->d_name,".")!=0) && (strcmp(d->d_name,"..")!=0 ) )`
`@@ -836,9 +840,7 @@ class Page`
`836`	`840`	`else`
`837`	`841`	`{`
`838`	`842`	`bool found = false;`
`839`		`- std::string str = subject;`
`840`		`- transform(str.begin(), str.end(),str.begin(), tolower );`
`841`		`- FILE *fp = fopen(file, "rb");`
	`843`	`+ FILE *fp = fdopen(fd, "rb");`
`842`	`844`	`if (fp)`
`843`	`845`	`{`
`844`	`846`	`Pcap_file pfile(fp);`
`@@ -866,10 +868,10 @@ class Page`
`866`	`868`	`printf(" %c{\n \"data\" : \"%s\",\n \"attr\" : { \"id\" : \"%s\", \"size\": %d, \"type\": \"json\" },\n \"children\" : [] }\n",`
`867`	`869`	`comma,d->d_name,join_path(m_url.get_path(),d->d_name).substr(5).c_str(), int(statbuf.st_size) );`
`868`	`870`	`comma= ',';`
`869`		`- found = true;`
`870`	`871`	`}`
`871`	`872`	`}`
`872`	`873`	`}`
	`874`	`+ close(fd);`
`873`	`875`	`}`
`874`	`876`
`875`	`877`	`printf("]\n");`