Merge bitcoin/bitcoin#22087: Validate port-options

04526787b5f6613d1f1ad78434e1dd24ab88dd76 Validate `port` options (amadeuszpawlik)
f8387c42343867779170a0f96ef64e6acff5c481 Validate port value in `SplitHostPort` (amadeuszpawlik)

Pull request description:

  Validate `port`-options, so that invalid values are rejected early in the startup.
  Ports are `uint16_t`s, which effectively limits a port's value to <=65535. As discussed in https://github.com/bitcoin/bitcoin/pull/24116 and https://github.com/bitcoin/bitcoin/pull/24344, port "0" is considered invalid too.
  Proposed in https://github.com/bitcoin/bitcoin/issues/21893#issuecomment-835784223

  The `SplitHostPort(std::string in, uint16_t& portOut, std::string& hostOut)` now returns a bool that indicates whether the port value was set and within the allowed range. This is an improvement that can be used not only for port validation of options at startup, but also in rpc calls, etc,

ACKs for top commit:
  luke-jr:
    utACK 04526787b5f6613d1f1ad78434e1dd24ab88dd76
  ryanofsky:
    Code review ACK 04526787b5f6613d1f1ad78434e1dd24ab88dd76. Just suggested changes since last review: reverting some SplitHostPort changes, adding release notes, avoiding 'GetArgs[0]` problem.

Tree-SHA512: f1ac80bf98520b287a6413ceadb41bc3a93c491955de9b9319ee1298ac0ab982751905762a287e748997ead6198a8bb7a3bc8817ac9e3d2468e11ab4a0f8496d

4 files changed, 24 insertions, 2 deletions

diff --git a/src/util/error.cpp b/src/util/error.cpp
index 33a35a6d59..390cb6c11b 100644
--- a/src/util/error.cpp
+++ b/src/util/error.cpp
@@ -49,6 +49,11 @@ bilingual_str ResolveErrMsg(const std::string& optname, const std::string& strBi
     return strprintf(_("Cannot resolve -%s address: '%s'"), optname, strBind);
 }
 
+bilingual_str InvalidPortErrMsg(const std::string& optname, const std::string& invalid_value)
+{
+    return strprintf(_("Invalid port specified in %s: '%s'"), optname, invalid_value);
+}
+
 bilingual_str AmountHighWarn(const std::string& optname)
 {
     return strprintf(_("%s is set very high!"), optname);
diff --git a/src/util/error.h b/src/util/error.h
index 0429de651a..27916501f0 100644
--- a/src/util/error.h
+++ b/src/util/error.h
@@ -39,6 +39,8 @@ bilingual_str TransactionErrorString(const TransactionError error);
 
 bilingual_str ResolveErrMsg(const std::string& optname, const std::string& strBind);
 
+bilingual_str InvalidPortErrMsg(const std::string& optname, const std::string& strPort);
+
 bilingual_str AmountHighWarn(const std::string& optname);
 
 bilingual_str AmountErrMsg(const std::string& optname, const std::string& strValue);
diff --git a/src/util/strencodings.cpp b/src/util/strencodings.cpp
index b5ac151374..e28ca8e73a 100644
--- a/src/util/strencodings.cpp
+++ b/src/util/strencodings.cpp
@@ -97,8 +97,9 @@ std::vector<Byte> ParseHex(std::string_view str)
 template std::vector<std::byte> ParseHex(std::string_view);
 template std::vector<uint8_t> ParseHex(std::string_view);
 
-void SplitHostPort(std::string_view in, uint16_t& portOut, std::string& hostOut)
+bool SplitHostPort(std::string_view in, uint16_t& portOut, std::string& hostOut)
 {
+    bool valid = false;
     size_t colon = in.find_last_of(':');
     // if a : is found, and it either follows a [...], or no other : is in the string, treat it as port separator
     bool fHaveColon = colon != in.npos;
@@ -109,13 +110,18 @@ void SplitHostPort(std::string_view in, uint16_t& portOut, std::string& hostOut)
         if (ParseUInt16(in.substr(colon + 1), &n)) {
             in = in.substr(0, colon);
             portOut = n;
+            valid = (portOut != 0);
         }
+    } else {
+        valid = true;
     }
     if (in.size() > 0 && in[0] == '[' && in[in.size() - 1] == ']') {
         hostOut = in.substr(1, in.size() - 2);
     } else {
         hostOut = in;
     }
+
+    return valid;
 }
 
 std::string EncodeBase64(Span<const unsigned char> input)
diff --git a/src/util/strencodings.h b/src/util/strencodings.h
index 14867b21b2..94bc6cc2f3 100644
--- a/src/util/strencodings.h
+++ b/src/util/strencodings.h
@@ -88,7 +88,16 @@ std::string EncodeBase32(Span<const unsigned char> input, bool pad = true);
  */
 std::string EncodeBase32(std::string_view str, bool pad = true);
 
-void SplitHostPort(std::string_view in, uint16_t& portOut, std::string& hostOut);
+/**
+ * Splits socket address string into host string and port value.
+ * Validates port value.
+ *
+ * @param[in] in        The socket address string to split.
+ * @param[out] portOut  Port-portion of the input, if found and parsable.
+ * @param[out] hostOut  Host-portion of the input, if found.
+ * @return              true if port-portion is absent or within its allowed range, otherwise false
+ */
+bool SplitHostPort(std::string_view in, uint16_t& portOut, std::string& hostOut);
 
 // LocaleIndependentAtoi is provided for backwards compatibility reasons.
 //