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fix(sbtc-pool-v3): rescale get-share-price so it resolves fee accrual (ajv.3.4, F-11) #138

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fix(sbtc-pool-v3): rescale get-share-price so it resolves fee accrual (ajv.3.4, F-11) #138

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20 changes: 14 additions & 6 deletions contracts/flashstack-sbtc-pool-v3.clar
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Expand Up @@ -29,7 +29,7 @@
;; => each share worth more sBTC over time
;;
;; Collateral oracle:
;; get-share-price returns sats per share (scaled by SHARE-PRECISION)
;; get-share-price returns sats per share, scaled by PRICE-PRECISION (1e16)
;; Lending protocols can call this directly - no external oracle needed
;; Flash loan manipulation-resistant: reserve invariant guarantees
;; pool balance only ever grows by >= fee per loan
Expand Down Expand Up @@ -80,6 +80,13 @@
(define-data-var reentrancy-locked bool false)

(define-constant SHARE-PRECISION u100000000) ;; 1e8 - matches sBTC sat precision
;; ajv.3.4 (F-11 shape): deposit mints 1e8 shares per sat, so one share is
;; worth ~1e-8 sat. Scaling the oracle by SHARE-PRECISION alone made it read
;; 1 at launch and ignore any gain short of +100%. The oracle scales by
;; 1e16 instead, so launch reads 1e8 and it resolves a change of 1 part in
;; 1e8. Read-only output only; share mint/burn math is unchanged.
;; Overflow: (21e6 BTC = 2.1e15 sats) * 1e16 = 2.1e31, far below u128 max.
(define-constant PRICE-PRECISION u10000000000000000) ;; 1e16 = SHARE-PRECISION * 1e8

;; F-1 fix (v2): virtual shares + virtual assets (OpenZeppelin ERC-4626
;; inflation-attack mitigation). A permanent phantom position absorbs
Expand Down Expand Up @@ -272,9 +279,10 @@
;; Read-only - including collateral oracle
;; =============================================

;; Current value of one pool share in sats, scaled by SHARE-PRECISION (1e8).
;; Divide result by 1e8 to get sats per share.
;; At launch: 1e8 (= 1 sat per share)
;; Current value of one pool share in sats, scaled by PRICE-PRECISION (1e16).
;; Divide result by 1e16 to get sats per share (equivalently, by 1e8 to get
;; sats per 1e8 shares, the amount one sat mints at launch).
;; At launch: 1e8 (= 1e-8 sat per share, i.e. 1 sat per 1e8 shares)
;; Over time: increases as flash loan fees accumulate
;;
;; This is the primary function lending protocols should consume.
Expand All @@ -286,7 +294,7 @@
(current-shares (var-get total-shares))
)
;; Virtual-offset price is well-defined at zero shares (no special case).
(ok (/ (* (+ pool-balance VIRTUAL-ASSETS) SHARE-PRECISION) (+ current-shares VIRTUAL-SHARES)))
(ok (/ (* (+ pool-balance VIRTUAL-ASSETS) PRICE-PRECISION) (+ current-shares VIRTUAL-SHARES)))
)
)

Expand Down Expand Up @@ -336,7 +344,7 @@
(current-shares (var-get total-shares))
)
(ok {
share-price: (/ (* (+ pool-balance VIRTUAL-ASSETS) SHARE-PRECISION) (+ current-shares VIRTUAL-SHARES)),
share-price: (/ (* (+ pool-balance VIRTUAL-ASSETS) PRICE-PRECISION) (+ current-shares VIRTUAL-SHARES)),
total-shares: current-shares,
pool-balance: pool-balance,
yield-accrued: (var-get total-fees),
Expand Down
20 changes: 14 additions & 6 deletions contracts/test/flashstack-sbtc-pool-v3.clar
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Original file line number Diff line number Diff line change
Expand Up @@ -29,7 +29,7 @@
;; => each share worth more sBTC over time
;;
;; Collateral oracle:
;; get-share-price returns sats per share (scaled by SHARE-PRECISION)
;; get-share-price returns sats per share, scaled by PRICE-PRECISION (1e16)
;; Lending protocols can call this directly - no external oracle needed
;; Flash loan manipulation-resistant: reserve invariant guarantees
;; pool balance only ever grows by >= fee per loan
Expand Down Expand Up @@ -80,6 +80,13 @@
(define-data-var reentrancy-locked bool false)

(define-constant SHARE-PRECISION u100000000) ;; 1e8 - matches sBTC sat precision
;; ajv.3.4 (F-11 shape): deposit mints 1e8 shares per sat, so one share is
;; worth ~1e-8 sat. Scaling the oracle by SHARE-PRECISION alone made it read
;; 1 at launch and ignore any gain short of +100%. The oracle scales by
;; 1e16 instead, so launch reads 1e8 and it resolves a change of 1 part in
;; 1e8. Read-only output only; share mint/burn math is unchanged.
;; Overflow: (21e6 BTC = 2.1e15 sats) * 1e16 = 2.1e31, far below u128 max.
(define-constant PRICE-PRECISION u10000000000000000) ;; 1e16 = SHARE-PRECISION * 1e8

;; F-1 fix (v2): virtual shares + virtual assets (OpenZeppelin ERC-4626
;; inflation-attack mitigation). A permanent phantom position absorbs
Expand Down Expand Up @@ -272,9 +279,10 @@
;; Read-only - including collateral oracle
;; =============================================

;; Current value of one pool share in sats, scaled by SHARE-PRECISION (1e8).
;; Divide result by 1e8 to get sats per share.
;; At launch: 1e8 (= 1 sat per share)
;; Current value of one pool share in sats, scaled by PRICE-PRECISION (1e16).
;; Divide result by 1e16 to get sats per share (equivalently, by 1e8 to get
;; sats per 1e8 shares, the amount one sat mints at launch).
;; At launch: 1e8 (= 1e-8 sat per share, i.e. 1 sat per 1e8 shares)
;; Over time: increases as flash loan fees accumulate
;;
;; This is the primary function lending protocols should consume.
Expand All @@ -286,7 +294,7 @@
(current-shares (var-get total-shares))
)
;; Virtual-offset price is well-defined at zero shares (no special case).
(ok (/ (* (+ pool-balance VIRTUAL-ASSETS) SHARE-PRECISION) (+ current-shares VIRTUAL-SHARES)))
(ok (/ (* (+ pool-balance VIRTUAL-ASSETS) PRICE-PRECISION) (+ current-shares VIRTUAL-SHARES)))
)
)

Expand Down Expand Up @@ -336,7 +344,7 @@
(current-shares (var-get total-shares))
)
(ok {
share-price: (/ (* (+ pool-balance VIRTUAL-ASSETS) SHARE-PRECISION) (+ current-shares VIRTUAL-SHARES)),
share-price: (/ (* (+ pool-balance VIRTUAL-ASSETS) PRICE-PRECISION) (+ current-shares VIRTUAL-SHARES)),
total-shares: current-shares,
pool-balance: pool-balance,
yield-accrued: (var-get total-fees),
Expand Down
8 changes: 4 additions & 4 deletions docs/TESTNET_STAGING.md
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Expand Up @@ -770,10 +770,10 @@ mainnet:
- Never `clarinet deployments apply --mainnet` from this repo
(`deployments/README.md`, D6/ajv.6.6).
- The v2 → v3 LP migration path (`Flashstack-ajv.4.4`) has to be decided first.
- Two findings outside this plan apply before mainnet: sbtc-pool-v3's
`get-share-price` has the F-11 scaling gap (`Flashstack-ajv.3.4`, #123). Rescale it
before mainnet, or accept and document it. If it's rescaled, this plan runs against
the rescaled source.
- sbtc-pool-v3's `get-share-price` F-11 scaling gap (`Flashstack-ajv.3.4`, #123) is
fixed: it now scales by `PRICE-PRECISION` (1e16) and reads `1e8` at launch. This plan
runs against the rescaled source, so a staged instance deployed before the fix is
not the audited version.

---

Expand Down
3 changes: 2 additions & 1 deletion docs/security/CLARITY_AUDIT_V2_POOLS.md
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Expand Up @@ -123,7 +123,8 @@ on-chain caller would have to be a published contract that names it. No integrat
The same F-11 structure (`VIRTUAL-SHARES` equal to `SHARE-PRECISION`) appears in
`flashstack-sbtc-pool-v2`'s built-in `get-share-price` (1e8/1e8). Checked 2026-10-15
(`Flashstack-ajv.4.12`): it is affected the same way. It reads `1` live, and the detail is in
the FINDINGS_REGISTER F-11 row.
the FINDINGS_REGISTER F-11 row. The undeployed successor `flashstack-sbtc-pool-v3` is
rescaled to 1e16 (`Flashstack-ajv.3.4`).

## Notes

Expand Down
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