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content_encoding: fix inflate_stream for no bytes available

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- Don't call zlib's inflate() when avail_in stream bytes is 0.

This is a follow up to the parent commit 19e66e5. Prior to that change
libcurl's inflate_stream could call zlib's inflate even when no bytes
were available, causing inflate to return Z_BUF_ERROR, and then
inflate_stream would treat that as a hard error and return
CURLE_BAD_CONTENT_ENCODING.

According to the zlib FAQ, Z_BUF_ERROR is not fatal.

This bug would happen randomly since packet sizes are arbitrary. A test
of 10,000 transfers had 55 fail (ie 0.55%).

Ref: https://zlib.net/zlib_faq.html#faq05

Closes https://github.com/curl/curl/pull/2060
This commit is contained in:
Jay Satiro 2017-11-07 00:46:59 -05:00
parent 19e66e5362
commit fa64b0fc4b
1 changed files with 6 additions and 4 deletions
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10
lib/content_encoding.c
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@ -139,6 +139,11 @@ inflate_stream(struct connectdata *conn, contenc_writer *writer)
/* because the buffer size is fixed, iteratively decompress and transfer to /* because the buffer size is fixed, iteratively decompress and transfer to
the client via client_write. */ the client via client_write. */
for(;;) { for(;;) {
if(z->avail_in == 0) {
free(decomp);
return result;
}
/* (re)set buffer for decompressed output for every iteration */ /* (re)set buffer for decompressed output for every iteration */
z->next_out = (Bytef *) decomp; z->next_out = (Bytef *) decomp;
z->avail_out = DSIZ; z->avail_out = DSIZ;
@ -163,10 +168,7 @@ inflate_stream(struct connectdata *conn, contenc_writer *writer)
/* Done with these bytes, exit */ /* Done with these bytes, exit */
/* status is always Z_OK at this point! */ /* status is always Z_OK at this point! */
if(z->avail_in == 0) { continue;
free(decomp);
return result;
}
} }
else if(allow_restart && status == Z_DATA_ERROR) { else if(allow_restart && status == Z_DATA_ERROR) {
/* some servers seem to not generate zlib headers, so this is an attempt /* some servers seem to not generate zlib headers, so this is an attempt