http-client: fix heap overflow caused by large URLs. #7778
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The function flb_http_client allocates a buffer for the method, URL and headers and uses snprintf to expand the first line of the http request. When it does so it uses the ret value from snprintf as the header_len for the length of the used buffer, but snprintf returns the size it wants to create the entire string not how long the string it writes is. This can lead to a heap overflow when adding headers. This PR fixes that by running snprintf initially without a buffer to calculate how large a buffer we actually need. Signed-off-by: Phillip Whelan <[email protected]>
pwhelan
requested review from
edsiper,
leonardo-albertovich,
fujimotos and
koleini
as code owners
edsiper
requested changes
Sep 13, 2023
| struct flb_http_client *c; | ||
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| header_size = str_gen_header(method, uri, host, port, proxy, flags, NULL, 0); |
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would you please move the composition of this string to use a flb_sds_printf() family functions ?, that will help us to get rid of size calculation
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If we do that we loose all control over the maximum size of the URL.
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ping on comments. |
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This PR is stale because it has been open 45 days with no activity. Remove stale label or comment or this will be closed in 10 days. |
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The function flb_http_client allocates a buffer for the method, URL and headers and uses snprintf to expand the first line of the http request. When it does so it uses the ret value from snprintf as the header_len for the length of the used buffer, but snprintf returns the size it wants to create the entire string not how long the string it writes is. This can lead to a heap overflow when adding headers.
This PR fixes that by running snprintf initially without a buffer to calculate how large a buffer we actually need.
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