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<base href="https://bugzilla.netfilter.org/" />
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<body><table border="1" cellspacing="0" cellpadding="8">
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - incorrect handling of json_unpack return value in json_verify_metainfo"
href="https://bugzilla.netfilter.org/show_bug.cgi?id=1490">1490</a>
</td>
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<th>Summary</th>
<td>incorrect handling of json_unpack return value in json_verify_metainfo
</td>
</tr>
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<th>Product</th>
<td>nftables
</td>
</tr>
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<th>Version</th>
<td>unspecified
</td>
</tr>
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<th>Hardware</th>
<td>x86_64
</td>
</tr>
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<th>OS</th>
<td>All
</td>
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<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>minor
</td>
</tr>
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<th>Priority</th>
<td>P5
</td>
</tr>
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<th>Component</th>
<td>nft
</td>
</tr>
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<th>Assignee</th>
<td>pablo@netfilter.org
</td>
</tr>
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<th>Reporter</th>
<td>niels@qacafe.com
</td>
</tr></table>
<p>
<div>
<pre>According to the libjansson documenatation, json_unpack returns 0 on success
and -1 on failure:
<a href="https://jansson.readthedocs.io/en/latest/apiref.html#c.json_unpack">https://jansson.readthedocs.io/en/latest/apiref.html#c.json_unpack</a>
However, json_verify_metainfo in src/parser_json.c calls json_unpack but treats
a non-zero return value as a failure:
<a href="https://git.netfilter.org/nftables/tree/src/parser_json.c#n3748">https://git.netfilter.org/nftables/tree/src/parser_json.c#n3748</a>
The documentation indicates that the metainfo object can provided as input in
order to verify that nft supports a given JSON schema version:
<a href="https://git.netfilter.org/nftables/tree/doc/libnftables-json.adoc#n66">https://git.netfilter.org/nftables/tree/doc/libnftables-json.adoc#n66</a>
However, the bug makes it appear that nft supports *any* schema version. The
only way to make nft reject the schema version is to encode the
"json_schema_version" field as something other than an integer, which causes
json_verify_metainfo to compare the uninitialized local variable schema_version
against JSON_SCHEMA_VERSION, leading to a confusing error message:
# nft -jae '{"nftables": [{"metainfo": {"json_schema_version": 999}}]}'
{"nftables": [{"metainfo": {"json_schema_version": 999}}]}
# echo $?
0
# nft -jae '{"nftables": [{"metainfo": {"json_schema_version": "1"}}]}'
internal:0:0-0: Error: Schema version 31509440 not supported, maximum supported
version is 1
internal:0:0-0: Error: Metainfo verification failed.
# echo $?
1
Please let me know if I can provide any other information. I'm using nft
v0.9.6, but it looks to me like the bug still exists in master.</pre>
</div>
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