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cookies: make saving atomic with a rename

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Saves the file as "[filename].[8 random hex digits].tmp" and renames
away the extension when done.

Co-authored-by: Jay Satiro
Reported-by: Mike Frysinger
Fixes #4914
Closes #4926
This commit is contained in:
Daniel Stenberg 2020-02-14 14:36:50 +01:00
parent 3ea15be3f3
commit b834890a3f
No known key found for this signature in database
GPG Key ID: 5CC908FDB71E12C2
1 changed files with 64 additions and 17 deletions
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81
lib/cookie.c
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@ -97,6 +97,7 @@ Example set of cookies:
#include "curl_memrchr.h"
#include "inet_pton.h"
#include "parsedate.h"
#include "rand.h"
/* The last 3 #include files should be in this order */
#include "curl_printf.h"
@ -1493,6 +1494,31 @@ static char *get_netscape_format(const struct Cookie *co)
co->value?co->value:"");
}
/* return 0 on success, 1 on error */
static int xrename(const char *oldpath, const char *newpath)
{
#ifdef WIN32
/* rename() on Windows doesn't overwrite, so we can't use it here.
MoveFileExA() will overwrite and is usually atomic, however it fails
when there are open handles to the file. */
const int max_wait_ms = 1000;
struct curltime start = Curl_now();
for(;;) {
timediff_t diff;
if(MoveFileExA(oldpath, newpath, MOVEFILE_REPLACE_EXISTING))
break;
diff = Curl_timediff(Curl_now(), start);
if(diff < 0 || diff > max_wait_ms)
return 1;
Sleep(1);
}
#else
if(rename(oldpath, newpath))
return 1;
#endif
return 0;
}
/*
* cookie_output()
*
@ -1501,11 +1527,14 @@ static char *get_netscape_format(const struct Cookie *co)
*
* The function returns non-zero on write failure.
*/
static int cookie_output(struct CookieInfo *c, const char *dumphere)
static int cookie_output(struct Curl_easy *data,
struct CookieInfo *c, const char *filename)
{
struct Cookie *co;
FILE *out;
FILE *out = NULL;
bool use_stdout = FALSE;
char *tempstore = NULL;
bool error = false;
if(!c)
/* no cookie engine alive */
@ -1514,16 +1543,24 @@ static int cookie_output(struct CookieInfo *c, const char *dumphere)
/* at first, remove expired cookies */
remove_expired(c);
if(!strcmp("-", dumphere)) {
if(!strcmp("-", filename)) {
/* use stdout */
out = stdout;
use_stdout = TRUE;
}
else {
out = fopen(dumphere, FOPEN_WRITETEXT);
if(!out) {
return 1; /* failure */
}
unsigned char randsuffix[9];
if(Curl_rand_hex(data, randsuffix, sizeof(randsuffix)))
return 2;
tempstore = aprintf("%s.%s.tmp", filename, randsuffix);
if(!tempstore)
return 1;
out = fopen(tempstore, FOPEN_WRITETEXT);
if(!out)
goto error;
}
fputs("# Netscape HTTP Cookie File\n"
@ -1538,9 +1575,7 @@ static int cookie_output(struct CookieInfo *c, const char *dumphere)
array = calloc(1, sizeof(struct Cookie *) * c->numcookies);
if(!array) {
if(!use_stdout)
fclose(out);
return 1;
goto error;
}
/* only sort the cookies with a domain property */
@ -1559,9 +1594,7 @@ static int cookie_output(struct CookieInfo *c, const char *dumphere)
if(format_ptr == NULL) {
fprintf(out, "#\n# Fatal libcurl error\n");
free(array);
if(!use_stdout)
fclose(out);
return 1;
goto error;
}
fprintf(out, "%s\n", format_ptr);
free(format_ptr);
@ -1569,10 +1602,24 @@ static int cookie_output(struct CookieInfo *c, const char *dumphere)
free(array);
}
if(!use_stdout)
fclose(out);
return 0;
if(out && !use_stdout) {
fclose(out);
out = NULL;
if(xrename(tempstore, filename)) {
unlink(tempstore);
goto error;
}
}
goto cleanup;
error:
error = true;
cleanup:
if(out && !use_stdout)
fclose(out);
free(tempstore);
return error ? 1 : 0;
}
static struct curl_slist *cookie_list(struct Curl_easy *data)
@ -1631,7 +1678,7 @@ void Curl_flush_cookies(struct Curl_easy *data, bool cleanup)
Curl_share_lock(data, CURL_LOCK_DATA_COOKIE, CURL_LOCK_ACCESS_SINGLE);
/* if we have a destination file for all the cookies to get dumped to */
if(cookie_output(data->cookies, data->set.str[STRING_COOKIEJAR]))
if(cookie_output(data, data->cookies, data->set.str[STRING_COOKIEJAR]))
infof(data, "WARNING: failed to save cookies in %s\n",
data->set.str[STRING_COOKIEJAR]);
}