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Fix detection of point to insert signatures on a pending consensus.

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We were looking for the first instance of "directory-signature "
when instead the correct behavior is to look for the first instance
of "directory-signature " at the start of a line.

Unfortunately, this can be exploited as to crash authorities while
they're voting.

Fixes #40316; bugfix on 0.2.2.4-alpha.  This is TROVE-2021-002,
also tracked as CVE-2021-28090.
This commit is contained in:
Nick Mathewson
2021-03-03 15:14:31 -05:00
parent 296a557bfc
commit 890ae4fb1a
2 changed files with 6 additions and 1 deletions
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changes/bug40316
+5
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@@ -0,0 +1,5 @@
o Major bugfixes (security, denial of service):
- Fix a bug in appending detached signatures to a pending consensus
document that could be used to crash a directory authority.
Fixes bug 40316; bugfix on 0.2.2.6-alpha. Tracked as
TROVE-2021-002 and CVE-2021-28090.
src/feature/dirauth/dirvote.c
+1 -1
View File
@@ -3520,7 +3520,7 @@ dirvote_add_signatures_to_pending_consensus(
strlen(pc->body) + strlen(new_signatures) + 1;
pc->body = tor_realloc(pc->body, new_consensus_len);
dst_end = pc->body + new_consensus_len;
dst = strstr(pc->body, "directory-signature ");
dst = (char *) find_str_at_start_of_line(pc->body, "directory-signature ");
tor_assert(dst);
strlcpy(dst, new_signatures, dst_end-dst);