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.

Author: sipa

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(':'));

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]);
     }
 

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]);
     }
 

src/util/strencodings.cpp

@@ -167,17 +167,15 @@ 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;
 }
 
 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);
@@ -245,17 +243,15 @@ 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;
 }
 
 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);

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.