From a4377a0843636eae0aaf698510fc6518582545db Mon Sep 17 00:00:00 2001
From: Pieter Wuille <pieter@wuille.net>
Date: Fri, 8 Apr 2022 23:17:01 -0400
Subject: Reject incorrect base64 in HTTP auth

In addition, to make sure that no call site ignores the invalid
decoding status, make the pf_invalid argument mandatory.
---
 src/httprpc.cpp           |  4 +++-
 src/test/base32_tests.cpp |  4 +++-
 src/test/base64_tests.cpp |  4 +++-
 src/util/strencodings.cpp | 12 ++++--------
 src/util/strencodings.h   |  8 ++++----
 5 files changed, 17 insertions(+), 15 deletions(-)

diff --git a/src/httprpc.cpp b/src/httprpc.cpp
index 5d0b59f7cb..5d62568343 100644
--- a/src/httprpc.cpp
+++ b/src/httprpc.cpp
@@ -132,7 +132,9 @@ static bool RPCAuthorized(const std::string& strAuth, std::string& strAuthUserna
     if (strAuth.substr(0, 6) != "Basic ")
         return false;
     std::string strUserPass64 = TrimString(strAuth.substr(6));
-    std::string strUserPass = DecodeBase64(strUserPass64);
+    bool invalid;
+    std::string strUserPass = DecodeBase64(strUserPass64, &invalid);
+    if (invalid) return false;
 
     if (strUserPass.find(':') != std::string::npos)
         strAuthUsernameOut = strUserPass.substr(0, strUserPass.find(':'));
diff --git a/src/test/base32_tests.cpp b/src/test/base32_tests.cpp
index 5fab7f0d1e..8a44e65165 100644
--- a/src/test/base32_tests.cpp
+++ b/src/test/base32_tests.cpp
@@ -22,7 +22,9 @@ BOOST_AUTO_TEST_CASE(base32_testvectors)
         BOOST_CHECK_EQUAL(strEnc, vstrOut[i]);
         strEnc = EncodeBase32(vstrIn[i], false);
         BOOST_CHECK_EQUAL(strEnc, vstrOutNoPadding[i]);
-        std::string strDec = DecodeBase32(vstrOut[i]);
+        bool invalid;
+        std::string strDec = DecodeBase32(vstrOut[i], &invalid);
+        BOOST_CHECK(!invalid);
         BOOST_CHECK_EQUAL(strDec, vstrIn[i]);
     }
 
diff --git a/src/test/base64_tests.cpp b/src/test/base64_tests.cpp
index 6ee1b83691..04b5185653 100644
--- a/src/test/base64_tests.cpp
+++ b/src/test/base64_tests.cpp
@@ -19,7 +19,9 @@ BOOST_AUTO_TEST_CASE(base64_testvectors)
     {
         std::string strEnc = EncodeBase64(vstrIn[i]);
         BOOST_CHECK_EQUAL(strEnc, vstrOut[i]);
-        std::string strDec = DecodeBase64(strEnc);
+        bool invalid;
+        std::string strDec = DecodeBase64(strEnc, &invalid);
+        BOOST_CHECK(!invalid);
         BOOST_CHECK_EQUAL(strDec, vstrIn[i]);
     }
 
diff --git a/src/util/strencodings.cpp b/src/util/strencodings.cpp
index 6346bc0811..6b6644aa9f 100644
--- a/src/util/strencodings.cpp
+++ b/src/util/strencodings.cpp
@@ -167,7 +167,7 @@ std::vector<unsigned char> DecodeBase64(const char* p, bool* pf_invalid)
         ++p;
     }
     valid = valid && (p - e) % 4 == 0 && p - q < 4;
-    if (pf_invalid) *pf_invalid = !valid;
+    *pf_invalid = !valid;
 
     return ret;
 }
@@ -175,9 +175,7 @@ std::vector<unsigned char> DecodeBase64(const char* p, bool* pf_invalid)
 std::string DecodeBase64(const std::string& str, bool* pf_invalid)
 {
     if (!ValidAsCString(str)) {
-        if (pf_invalid) {
-            *pf_invalid = true;
-        }
+        *pf_invalid = true;
         return {};
     }
     std::vector<unsigned char> vchRet = DecodeBase64(str.c_str(), pf_invalid);
@@ -245,7 +243,7 @@ std::vector<unsigned char> DecodeBase32(const char* p, bool* pf_invalid)
         ++p;
     }
     valid = valid && (p - e) % 8 == 0 && p - q < 8;
-    if (pf_invalid) *pf_invalid = !valid;
+    *pf_invalid = !valid;
 
     return ret;
 }
@@ -253,9 +251,7 @@ std::vector<unsigned char> DecodeBase32(const char* p, bool* pf_invalid)
 std::string DecodeBase32(const std::string& str, bool* pf_invalid)
 {
     if (!ValidAsCString(str)) {
-        if (pf_invalid) {
-            *pf_invalid = true;
-        }
+        *pf_invalid = true;
         return {};
     }
     std::vector<unsigned char> vchRet = DecodeBase32(str.c_str(), pf_invalid);
diff --git a/src/util/strencodings.h b/src/util/strencodings.h
index 82645c6bf0..c87b2d2415 100644
--- a/src/util/strencodings.h
+++ b/src/util/strencodings.h
@@ -64,13 +64,13 @@ bool IsHex(std::string_view str);
 * Return true if the string is a hex number, optionally prefixed with "0x"
 */
 bool IsHexNumber(std::string_view str);
-std::vector<unsigned char> DecodeBase64(const char* p, bool* pf_invalid = nullptr);
-std::string DecodeBase64(const std::string& str, bool* pf_invalid = nullptr);
+std::vector<unsigned char> DecodeBase64(const char* p, bool* pf_invalid);
+std::string DecodeBase64(const std::string& str, bool* pf_invalid);
 std::string EncodeBase64(Span<const unsigned char> input);
 inline std::string EncodeBase64(Span<const std::byte> input) { return EncodeBase64(MakeUCharSpan(input)); }
 inline std::string EncodeBase64(const std::string& str) { return EncodeBase64(MakeUCharSpan(str)); }
-std::vector<unsigned char> DecodeBase32(const char* p, bool* pf_invalid = nullptr);
-std::string DecodeBase32(const std::string& str, bool* pf_invalid = nullptr);
+std::vector<unsigned char> DecodeBase32(const char* p, bool* pf_invalid);
+std::string DecodeBase32(const std::string& str, bool* pf_invalid);
 
 /**
  * Base32 encode.
-- 
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