test: only match Ledger "To" screen on the title row
What the developer wrote
Authored by Sjors Provoost
test: only match Ledger "To" screen on the title row
The Speculos automation file advances through screens by matching
text fragments. The rule for the "To" screen matched any fragment
starting with "To", including parts of the destination address
shown below that title.
This is what failed in CI run 28680592019 (job 85066632783). The
address mzmauywUy3WF1TX3YxzQMA5PR4zXqJVLTo was split on the device
screen into "mzmauywUy3WF1TX", "3YxzQMA5PR4zXqJVL" and "To". The
latter confused the automation rule for "To", which pressed an
extra right button:
automation: getting actions for "To" (57, 3)
automation: getting actions for "mzmauywUy3WF1TX" (9, 19)
automation: getting actions for "3YxzQMA5PR4zXqJVL" (8, 33)
automation: getting actions for "To" (57, 47)
seproxyhal: applying automation ['button', 2, True]
seproxyhal: applying automation ['button', 2, False]
From there every press landed one screen late; the approval hit
"Reject transaction" and the app returned 0x6985, so signtx
reported a canceled error. "T" and "o" are both valid base58
characters, and bitcoind generates fresh addresses on every run,
which makes this a rare and random failure. Bech32 addresses
cannot trigger it ("o" is not in the bech32 character set).
Limit the "To" rule to the title row (y=3), where address text
never appears. The rule file format does not allow comments, so a
warning about short words in automation rules goes in the README.
Co-authored-by: Claude (Fable 5) <noreply@anthropic.com>
What changed, and why it matters
This commit fixes a flaky automated test for Ledger hardware wallets. The test script was pressing an extra button because a randomly generated Bitcoin address happened to end in the letters 'To', which matched a screen-title rule. The fix narrows the rule so it only matches the word 'To' at the top of the screen, not inside wrapped address text. There is no security issue in the actual wallet software.
No security action needed. This is a test-only reliability fix. Reviewers may want to verify that other short-word rules in the automation file are similarly pinned to the title row or made multi-word to avoid future flaky failures.
Security signals we found
No strong security signals were identified.
Evidence from the diff
The change is in HWI’s Speculos automation JSON used for Ledger emulator tests. A single regexp rule previously matched many screen titles including ‘To’ against any on-screen text fragment. Because base58 addresses can contain ‘T’ and ‘o’, an address ending in ‘To’ (e.g., mzmauywUy3WF1TX3YxzQMA5PR4zXqJVLTo) wrapped onto a new line triggered the rule, causing an extra right-button press and a subsequent 0x6985 ‘transaction canceled’ test failure. The patch splits the ‘To’ match into its own rule constrained to y=3 (the title row) and adds a README warning about short-word rules matching wrapped addresses.
Changed components
test/data/speculos-automation.jsontest/README.mdInspect captured patch +21 / −1
diff --git a/test/README.md b/test/README.md
index 1e1264e..099f9d0 100644
--- a/test/README.md
+++ b/test/README.md
@@ -311,6 +311,18 @@ $ cmake -Bbuild -H.
$ make -C build/
```
+### Automation rules
+
+The Ledger tests drive the emulator's buttons with
+`data/speculos-automation.json`. Speculos matches each rule against every
+text fragment drawn on the screen, so beware of this pitfall when editing
+it: screens can contain randomly generated base58 addresses, wrapped over
+several lines, and a rule matching a short word can accidentally match a
+wrapped address line. The resulting extra button press derails the rest of
+the flow. This happened with a rule for the "To" screen title when an
+address ended in "To". Keep rules multi-word where possible, or pin them to
+the title row with `"y": 3` like the "To" rule.
+
## Coldcard emulator
Clone the repository:
diff --git a/test/data/speculos-automation.json b/test/data/speculos-automation.json
index f17a9c6..31f69f7 100644
--- a/test/data/speculos-automation.json
+++ b/test/data/speculos-automation.json
@@ -28,7 +28,15 @@
]
},
{
- "regexp": "^(Address|Review|Amount|Fee|Confirm|The derivation|Derivation path|Reject if|The change path|Change path|Register wallet|Policy map|Key|Path|Public key|Spend from|Wallet name|Wallet policy|Descriptor template|Verify Bitcoin|To|Output|Warning).*",
+ "regexp": "^(Address|Review|Amount|Fee|Confirm|The derivation|Derivation path|Reject if|The change path|Change path|Register wallet|Policy map|Key|Path|Public key|Spend from|Wallet name|Wallet policy|Descriptor template|Verify Bitcoin|Output|Warning).*",
+ "actions": [
+ [ "button", 2, true ],
+ [ "button", 2, false ]
+ ]
+ },
+ {
+ "regexp": "^To.*",
+ "y": 3,
"actions": [
[ "button", 2, true ],
[ "button", 2, false ]
Why this scored 15/100
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