hs: Fix bad use of sizeof() when encoding ESTABLISH_INTRO legacy cell

When encoding a legacy ESTABLISH_INTRO cell, we were using the sizeof() on a
pointer instead of using the real size of the destination buffer leading to an
overflow passing an enormous value to the signing digest function.
Fortunately, that value was only used to make sure the destination buffer
length was big enough for the key size and in this case it always was because
of the overflow.

Fixes #21553

Signed-off-by: David Goulet <dgoulet@torproject.org>

1 files changed, 7 insertions, 0 deletions

diff --git a/changes/bug21553 b/changes/bug21553
new file mode 100644
index 0000000000..6ffa3e29a2
--- /dev/null
+++ b/changes/bug21553
@@ -0,0 +1,7 @@
+  o Minor bugfixes (hidden service):
+    - When encoding a legacy ESTABLISH_INTRO cell, we were using the sizeof()
+      on a pointer instead of real size of the destination buffer leading to
+      an overflow passing an enormous value to the signing digest function.
+      Fortunately, that value was only used to make sure the destination
+      buffer length was big enough for the key size and in this case it was.
+      Fixes bug 21553; bugfix on tor-0.3.0.1-alpha.