From 7f0bdbda112cd8021e3af67ef8cc341783b4c47f Mon Sep 17 00:00:00 2001
From: fanquake <fanquake@gmail.com>
Date: Thu, 10 Feb 2022 07:14:11 +0000
Subject: [PATCH] Merge bitcoin/bitcoin#24298: fuzz: Avoid unsigned integer
 overflow in FormatParagraph

fa2f7d005932bff9b7d27744ae517b9e7910df8d fuzz: Avoid unsigned integer overflow in FormatParagraph (MarcoFalke)

Pull request description:

  `FormatParagraph` is only ever called with compile time constant arguments, so I don't see the need for fuzzing it.

  Though, keep it for now, but avoid the unsigned integer overflow with this patch.

ACKs for top commit:
  laanwj:
    Code review ACK fa2f7d005932bff9b7d27744ae517b9e7910df8d

Tree-SHA512: 01fc64a9ef73c183921ca1b0cd8db9514c0a242e3acf215a3393f383ae129e01625ebb16eaf9cb86370eda62d0145c3dcf8f62e40edf5958abc1f777c5687280
---
 src/test/fuzz/string.cpp  | 3 ++-
 src/util/strencodings.cpp | 1 +
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/test/fuzz/string.cpp b/src/test/fuzz/string.cpp
index 2c7b19e39a..e7c046373e 100644
--- a/src/test/fuzz/string.cpp
+++ b/src/test/fuzz/string.cpp
@@ -45,7 +45,8 @@ void test_one_input(const std::vector<uint8_t>& buffer)
     (void)CopyrightHolders(random_string_1, fuzzed_data_provider.ConsumeIntegral<unsigned int>(), fuzzed_data_provider.ConsumeIntegral<unsigned int>());
     FeeEstimateMode fee_estimate_mode;
     (void)FeeModeFromString(random_string_1, fee_estimate_mode);
-    (void)FormatParagraph(random_string_1, fuzzed_data_provider.ConsumeIntegralInRange<size_t>(0, 1000), fuzzed_data_provider.ConsumeIntegralInRange<size_t>(0, 1000));
+    const auto width{fuzzed_data_provider.ConsumeIntegralInRange<size_t>(1, 1000)};
+    (void)FormatParagraph(random_string_1, width, fuzzed_data_provider.ConsumeIntegralInRange<size_t>(0, width));
     (void)FormatSubVersion(random_string_1, fuzzed_data_provider.ConsumeIntegral<int>(), random_string_vector);
     (void)GetDescriptorChecksum(random_string_1);
     (void)HelpExampleCli(random_string_1, random_string_2);
diff --git a/src/util/strencodings.cpp b/src/util/strencodings.cpp
index bcbaac3291..0bfdb083a1 100644
--- a/src/util/strencodings.cpp
+++ b/src/util/strencodings.cpp
@@ -384,6 +384,7 @@ bool ParseDouble(const std::string& str, double *out)
 
 std::string FormatParagraph(const std::string& in, size_t width, size_t indent)
 {
+    assert(width >= indent);
     std::stringstream out;
     size_t ptr = 0;
     size_t indented = 0;