From 0b1a3eed393dce132fa2bb812fea12e26f306985 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?colin=20axn=C3=A9r?=
 <25233464+colin-axner@users.noreply.github.com>
Date: Fri, 13 Nov 2020 15:32:33 +0100
Subject: [PATCH] add docs and make prefix a const (#7926)

Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>
---
 x/ibc/applications/transfer/keeper/relay.go     | 4 +++-
 x/ibc/applications/transfer/spec/01_concepts.md | 6 ++++++
 x/ibc/applications/transfer/types/keys.go       | 3 +++
 x/ibc/applications/transfer/types/trace.go      | 6 +++---
 4 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/x/ibc/applications/transfer/keeper/relay.go b/x/ibc/applications/transfer/keeper/relay.go
index c9bc4470d3..d26e71e984 100644
--- a/x/ibc/applications/transfer/keeper/relay.go
+++ b/x/ibc/applications/transfer/keeper/relay.go
@@ -361,7 +361,9 @@ func (k Keeper) refundPacketToken(ctx sdk.Context, packet channeltypes.Packet, d
 // DenomPathFromHash returns the full denomination path prefix from an ibc denom with a hash
 // component.
 func (k Keeper) DenomPathFromHash(ctx sdk.Context, denom string) (string, error) {
-	hexHash := denom[4:]
+	// trim the denomination prefix, by default "ibc/"
+	hexHash := denom[len(types.DenomPrefix+"/"):]
+
 	hash, err := types.ParseHexHash(hexHash)
 	if err != nil {
 		return "", sdkerrors.Wrap(types.ErrInvalidDenomForTransfer, err.Error())
diff --git a/x/ibc/applications/transfer/spec/01_concepts.md b/x/ibc/applications/transfer/spec/01_concepts.md
index 55b8a6c0c6..96f05f12a7 100644
--- a/x/ibc/applications/transfer/spec/01_concepts.md
+++ b/x/ibc/applications/transfer/spec/01_concepts.md
@@ -109,3 +109,9 @@ Cosmos Hub for the `uatom`). Sending a token back to the same chain across a dif
 **not** move the token back across its timeline. If a channel in the chain history closes before the
 token can be sent back across that channel, then the token will not be returnable to its original
 form.
+
+
+## Security Considerations
+
+For safety, no other module must be capable of minting tokens with the `ibc/` prefix. The IBC
+transfer module needs a subset of the denomination space that only it can create tokens in.
diff --git a/x/ibc/applications/transfer/types/keys.go b/x/ibc/applications/transfer/types/keys.go
index b9d4b3085e..f1fbffd951 100644
--- a/x/ibc/applications/transfer/types/keys.go
+++ b/x/ibc/applications/transfer/types/keys.go
@@ -25,6 +25,9 @@ const (
 
 	// QuerierRoute is the querier route for IBC transfer
 	QuerierRoute = ModuleName
+
+	// DenomPrefix is the prefix used for internal SDK coin representation.
+	DenomPrefix = "ibc"
 )
 
 var (
diff --git a/x/ibc/applications/transfer/types/trace.go b/x/ibc/applications/transfer/types/trace.go
index d465dcbc29..b4527d668f 100644
--- a/x/ibc/applications/transfer/types/trace.go
+++ b/x/ibc/applications/transfer/types/trace.go
@@ -54,7 +54,7 @@ func (dt DenomTrace) GetPrefix() string {
 // 'ibc/{hash(tracePath + baseDenom)}'. If the trace is empty, it will return the base denomination.
 func (dt DenomTrace) IBCDenom() string {
 	if dt.Path != "" {
-		return fmt.Sprintf("ibc/%s", dt.Hash())
+		return fmt.Sprintf("%s/%s", DenomPrefix, dt.Hash())
 	}
 	return dt.BaseDenom
 }
@@ -172,8 +172,8 @@ func ValidateIBCDenom(denom string) error {
 
 	switch {
 	case strings.TrimSpace(denom) == "",
-		len(denomSplit) == 1 && denomSplit[0] == "ibc",
-		len(denomSplit) == 2 && (denomSplit[0] != "ibc" || strings.TrimSpace(denomSplit[1]) == ""):
+		len(denomSplit) == 1 && denomSplit[0] == DenomPrefix,
+		len(denomSplit) == 2 && (denomSplit[0] != DenomPrefix || strings.TrimSpace(denomSplit[1]) == ""):
 		return sdkerrors.Wrapf(ErrInvalidDenomForTransfer, "denomination should be prefixed with the format 'ibc/{hash(trace + \"/\" + %s)}'", denom)
 
 	case denomSplit[0] == denom && strings.TrimSpace(denom) != "":