Informational 20 Bitcoin Committed Apr 2, 2026 · 00:06 UTC

decode: print htlc_minimum_msat / htlc_maximum_msat in blinded paths.

f4b85859 View source ↗

Public commit record

What the developer wrote

Authored by Rusty Russell

81/100 · Strong

decode: print htlc_minimum_msat / htlc_maximum_msat in blinded paths.

Weird we didn't print this before!

Reported-by: https://github.com/Lagrang3
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

✓ Specific, descriptive subject✓ Names a concrete action or component✓ Provides detailed explanatory context✓ Links an issue, advisory, or supporting reference

The short version

What changed, and why it matters

This commit adds two missing fields, htlc_minimum_msat and htlc_maximum_msat, to the output of the 'decode' command when it shows blinded payment paths. Previously these values were decoded internally but not printed in JSON or CLI output. It is a display/information fix, not a code-execution vulnerability.

Recommended action

No security action required; treat as a normal feature/bug-fix update. Users relying on decode output for blinded path analysis may want to update to obtain complete payinfo fields.

Security signals we found

Missing output field in decode command for blinded path payinfo

No change to parsing, validation, or cryptographic handling

No memory safety, authorization, or consensus code modified

Reported-by line credits an external contributor

Technical analysis

Evidence from the diff

The patch exposes htlc_minimum_msat and htlc_maximum_msat from struct blinded_payinfo in decode, bolt12-cli, gRPC conversion, schema docs, and tests. No parsing, validation, or payment logic is changed. The fields were already present in the underlying BOLT12 data structure; the commit only surfaces them to users.

Changed components

plugins/offers.c decode outputdevtools/bolt12-cli.ccontrib/pyln-testing/pyln/testing/grpc2py.pydoc/schemas/decode.jsoncontrib/msggen/msggen/schema.json.msggen.jsontests/test_pay.py

Inspect captured patch +51 / −1

diff --git a/.msggen.json b/.msggen.json
index 337d2c7e..e1b4c984 100644
--- a/.msggen.json
+++ b/.msggen.json
@@ -6293,6 +6293,14 @@
             "added": "v23.05",
             "deprecated": null
         },
+        "Decode.invoice_paths[].payinfo.htlc_maximum_msat": {
+            "added": "v26.04",
+            "deprecated": null
+        },
+        "Decode.invoice_paths[].payinfo.htlc_minimum_msat": {
+            "added": "v26.04",
+            "deprecated": null
+        },
         "Decode.invoice_payment_hash": {
             "added": "v23.05",
             "deprecated": null
diff --git a/contrib/msggen/msggen/schema.json b/contrib/msggen/msggen/schema.json
index 8af25ff5..9ed9be9c 100644
--- a/contrib/msggen/msggen/schema.json
+++ b/contrib/msggen/msggen/schema.json
@@ -9422,6 +9422,8 @@
                           "fee_base_msat",
                           "fee_proportional_millionths",
                           "cltv_expiry_delta",
+                          "htlc_minimum_msat",
+                          "htlc_maximum_msat",
                           "features"
                         ],
                         "additionalProperties": false,
@@ -9444,6 +9446,20 @@
                               "CLTV delta for path."
                             ]
                           },
+                          "htlc_minimum_msat": {
+                            "type": "msat",
+                            "added": "v26.04",
+                            "description": [
+                              "Minimum amount which can be sent via path."
+                            ]
+                          },
+                          "htlc_maximum_msat": {
+                            "type": "msat",
+                            "added": "v26.04",
+                            "description": [
+                              "Maximum amount which can be sent via path."
+                            ]
+                          },
                           "features": {
                             "type": "hex",
                             "description": [
diff --git a/contrib/pyln-testing/pyln/testing/grpc2py.py b/contrib/pyln-testing/pyln/testing/grpc2py.py
index 5243f326..d49c7c4f 100644
--- a/contrib/pyln-testing/pyln/testing/grpc2py.py
+++ b/contrib/pyln-testing/pyln/testing/grpc2py.py
@@ -1151,6 +1151,8 @@ def decode_invoice_paths_payinfo2py(m):
         "features": hexlify(m.features),  # PrimitiveField in generate_composite
         "fee_base_msat": amount2msat(m.fee_base_msat),  # PrimitiveField in generate_composite
         "fee_proportional_millionths": m.fee_proportional_millionths,  # PrimitiveField in generate_composite
+        "htlc_maximum_msat": amount2msat(m.htlc_maximum_msat),  # PrimitiveField in generate_composite
+        "htlc_minimum_msat": amount2msat(m.htlc_minimum_msat),  # PrimitiveField in generate_composite
     })
 
 
diff --git a/devtools/bolt12-cli.c b/devtools/bolt12-cli.c
index 9d8e0b6e..a72d57a1 100644
--- a/devtools/bolt12-cli.c
+++ b/devtools/bolt12-cli.c
@@ -276,10 +276,12 @@ static bool print_blindedpaths(const char *fieldname,
 			       tal_hex(tmpctx, p[j]->encrypted_recipient_data));
 		}
 		if (i < tal_count(blindedpay)) {
-			printf(" blindedpay: fee=%u/%u,cltv=%u,features=%s",
+			printf(" blindedpay: fee=%u/%u,cltv=%u,min/max=%s/%s,features=%s",
 			       blindedpay[i]->fee_base_msat,
 			       blindedpay[i]->fee_proportional_millionths,
 			       blindedpay[i]->cltv_expiry_delta,
+			       fmt_amount_msat(tmpctx, blindedpay[i]->htlc_minimum_msat),
+			       fmt_amount_msat(tmpctx, blindedpay[i]->htlc_maximum_msat),
 			       tal_hex(tmpctx, blindedpay[i]->features));
 		}
 		printf("\n");
diff --git a/doc/schemas/decode.json b/doc/schemas/decode.json
index e21bca5a..20bb6d5a 100644
--- a/doc/schemas/decode.json
+++ b/doc/schemas/decode.json
@@ -1624,6 +1624,8 @@
                       "fee_base_msat",
                       "fee_proportional_millionths",
                       "cltv_expiry_delta",
+                      "htlc_minimum_msat",
+                      "htlc_maximum_msat",
                       "features"
                     ],
                     "additionalProperties": false,
@@ -1646,6 +1648,20 @@
                           "CLTV delta for path."
                         ]
                       },
+                      "htlc_minimum_msat": {
+                        "type": "msat",
+                        "added": "v26.04",
+                        "description": [
+                          "Minimum amount which can be sent via path."
+                        ]
+                      },
+                      "htlc_maximum_msat": {
+                        "type": "msat",
+                        "added": "v26.04",
+                        "description": [
+                          "Maximum amount which can be sent via path."
+                        ]
+                      },
                       "features": {
                         "type": "hex",
                         "description": [
diff --git a/plugins/offers.c b/plugins/offers.c
index 0a9a82b2..841ebb17 100644
--- a/plugins/offers.c
+++ b/plugins/offers.c
@@ -754,6 +754,10 @@ static bool json_add_blinded_paths(struct command *cmd,
 				     blindedpay[i]->fee_proportional_millionths);
 			json_add_u32(js, "cltv_expiry_delta",
 				     blindedpay[i]->cltv_expiry_delta);
+			json_add_amount_msat(js, "htlc_minimum_msat",
+					     blindedpay[i]->htlc_minimum_msat);
+			json_add_amount_msat(js, "htlc_maximum_msat",
+					     blindedpay[i]->htlc_maximum_msat);
 			json_add_hex_talarr(js, "features", blindedpay[i]->features);
 			json_object_end(js);
 		}
diff --git a/tests/test_pay.py b/tests/test_pay.py
index 77456788..4b2cf800 100644
--- a/tests/test_pay.py
+++ b/tests/test_pay.py
@@ -6957,6 +6957,8 @@ def test_decode_expired_bolt12(node_factory):
                            'path': [{'blinded_node_id': '03f293aad04524af9d25e37e30975c9c48df7f46bb5707f5103c5f15477882ef0d',
                                      'encrypted_recipient_data': 'ae4ae7ed0b821d8bbb394f8cd3013ed6c56d0b29baeddb1ce21fb8c34ce33ff59e2250758574924b03a1b567606479c7c9b0'}],
                            'payinfo': {'cltv_expiry_delta': 18,
+                                       'htlc_maximum_msat': 2100000000000000000,
+                                       'htlc_minimum_msat': 0,
                                        'features': '',
                                        'fee_base_msat': 0,
                                        'fee_proportional_millionths': 0}}],

Risk score

Why this scored 20/100

Our methodology →

Potential impact 2/30

Exploitability 0/25

Stealth signal 0/15

Affected reach 5/15

Confidence 9/10

Evidence quality 4/5

Human-validated context

Community notes

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What the developer wrote

What changed, and why it matters

Security signals we found

Evidence from the diff

Changed components

Why this scored 20/100

Community notes

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