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easy: resize receive buffer on easy handle reset

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- In curl_easy_reset attempt to resize the receive buffer to its default
  size. If realloc fails then continue using the previous size.

Prior to this change curl_easy_reset did not properly handle resetting
the receive buffer (data->state.buffer). It reset the variable holding
its size (data->set.buffer_size) to the default size (READBUFFER_SIZE)
but then did not actually resize the buffer. If a user resized the
buffer by using CURLOPT_BUFFERSIZE to set the size smaller than the
default, later called curl_easy_reset and attempted to reuse the handle
then a heap overflow would very likely occur during that handle's next
transfer.

Reported-by: Felix Hädicke

Fixes https://github.com/curl/curl/issues/4143
Closes https://github.com/curl/curl/pull/4145
This commit is contained in:
Jay Satiro 2019-07-23 17:59:18 -04:00
parent fd5ab4358f
commit 78ed3abe11
1 changed files with 14 additions and 0 deletions
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14
lib/easy.c
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@ -942,6 +942,8 @@ struct Curl_easy *curl_easy_duphandle(struct Curl_easy *data)
*/
void curl_easy_reset(struct Curl_easy *data)
{
long old_buffer_size = data->set.buffer_size;
Curl_free_request_state(data);
/* zero out UserDefined data: */
@ -965,6 +967,18 @@ void curl_easy_reset(struct Curl_easy *data)
#if !defined(CURL_DISABLE_HTTP) && !defined(CURL_DISABLE_CRYPTO_AUTH)
Curl_http_auth_cleanup_digest(data);
#endif
/* resize receive buffer */
if(old_buffer_size != data->set.buffer_size) {
char *newbuff = realloc(data->state.buffer, data->set.buffer_size + 1);
if(!newbuff) {
DEBUGF(fprintf(stderr, "Error: realloc of buffer failed\n"));
/* nothing we can do here except use the old size */
data->set.buffer_size = old_buffer_size;
}
else
data->state.buffer = newbuff;
}
}
/*