From 9b02d8b49ce7070362e6eb1f051af560c42e4cad Mon Sep 17 00:00:00 2001
From: Nicholas Connor <nicholas.k.connor@gmail.com>
Date: Tue, 17 May 2022 12:11:24 -0400
Subject: [PATCH 1/3] add optimized parsing rule for known bad ipv4

---
 library/std/src/net/parser.rs | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/library/std/src/net/parser.rs b/library/std/src/net/parser.rs
index 069b660998559..cc3bed535ad92 100644
--- a/library/std/src/net/parser.rs
+++ b/library/std/src/net/parser.rs
@@ -285,8 +285,8 @@ impl FromStr for IpAddr {
 impl FromStr for Ipv4Addr {
     type Err = AddrParseError;
     fn from_str(s: &str) -> Result<Ipv4Addr, AddrParseError> {
-        // don't try to parse if too long
-        if s.len() > 15 {
+        // don't try to parse if too long or too short
+        if s.len() < 7 || s.len() > 15 {
             Err(AddrParseError(AddrKind::Ipv4))
         } else {
             Parser::new(s).parse_with(|p| p.read_ipv4_addr(), AddrKind::Ipv4)

From 4783dc5ba18a71179cf4a01dcd080e3346277745 Mon Sep 17 00:00:00 2001
From: nkconnor <nicholas.k.connor@gmail.com>
Date: Tue, 9 Aug 2022 14:58:48 -0400
Subject: [PATCH 2/3] apply ipv4 parser length checks to more situations

---
 library/std/src/net/parser.rs | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/library/std/src/net/parser.rs b/library/std/src/net/parser.rs
index cc3bed535ad92..b1c684d5fc53e 100644
--- a/library/std/src/net/parser.rs
+++ b/library/std/src/net/parser.rs
@@ -140,6 +140,11 @@ impl<'a> Parser<'a> {
 
     /// Read an IPv4 address.
     fn read_ipv4_addr(&mut self) -> Option<Ipv4Addr> {
+        // don't try to parse if too short or long
+        if self.state.len() < 7 || self.state.len() > 15 {
+            return None;
+        }
+
         self.read_atomically(|p| {
             let mut groups = [0; 4];
 
@@ -285,12 +290,7 @@ impl FromStr for IpAddr {
 impl FromStr for Ipv4Addr {
     type Err = AddrParseError;
     fn from_str(s: &str) -> Result<Ipv4Addr, AddrParseError> {
-        // don't try to parse if too long or too short
-        if s.len() < 7 || s.len() > 15 {
-            Err(AddrParseError(AddrKind::Ipv4))
-        } else {
-            Parser::new(s).parse_with(|p| p.read_ipv4_addr(), AddrKind::Ipv4)
-        }
+        Parser::new(s).parse_with(|p| p.read_ipv4_addr(), AddrKind::Ipv4)
     }
 }
 

From 2aab9afd01ed71b6df3024c7f6a2c6d2343a4739 Mon Sep 17 00:00:00 2001
From: nkconnor <nicholas.k.connor@gmail.com>
Date: Tue, 9 Aug 2022 16:11:41 -0400
Subject: [PATCH 3/3] fix parser length checks to depend on the type of addr
 being parsed

---
 library/std/src/net/parser.rs | 32 +++++++++++++++++++++++++++-----
 1 file changed, 27 insertions(+), 5 deletions(-)

diff --git a/library/std/src/net/parser.rs b/library/std/src/net/parser.rs
index b1c684d5fc53e..5c5ff90fa518c 100644
--- a/library/std/src/net/parser.rs
+++ b/library/std/src/net/parser.rs
@@ -62,6 +62,13 @@ impl<'a> Parser<'a> {
     where
         F: FnOnce(&mut Parser<'_>) -> Option<T>,
     {
+        // don't try to parse if too short or too long
+        if self.state.len() > kind.max_string_length()
+            || self.state.len() < kind.min_string_length()
+        {
+            return Err(AddrParseError(kind));
+        }
+
         let result = inner(self);
         if self.state.is_empty() { result } else { None }.ok_or(AddrParseError(kind))
     }
@@ -140,11 +147,6 @@ impl<'a> Parser<'a> {
 
     /// Read an IPv4 address.
     fn read_ipv4_addr(&mut self) -> Option<Ipv4Addr> {
-        // don't try to parse if too short or long
-        if self.state.len() < 7 || self.state.len() > 15 {
-            return None;
-        }
-
         self.read_atomically(|p| {
             let mut groups = [0; 4];
 
@@ -336,6 +338,26 @@ enum AddrKind {
     SocketV6,
 }
 
+impl AddrKind {
+    // the minimum length of a parsable string with this `AddrKind`
+    const fn min_string_length(&self) -> usize {
+        match self {
+            Self::Ip | Self::Ipv4 => 7,
+            // FIXME
+            _ => 0,
+        }
+    }
+
+    // the maximum length of a parsable string with this `AddrKind`
+    const fn max_string_length(&self) -> usize {
+        match self {
+            Self::Ipv4 => 15,
+            // FIXME
+            _ => usize::MAX,
+        }
+    }
+}
+
 /// An error which can be returned when parsing an IP address or a socket address.
 ///
 /// This error is used as the error type for the [`FromStr`] implementation for