From: Christopher Faulet <cfaulet@haproxy.com>
Date: Thu, 17 Sep 2026 06:44:23 +0000 (+0200)
Subject: MINOR: htx: Add macros for the header/trailer name and value max lengths
X-Git-Tag: v3.5-dev8~176
X-Git-Url: https://git.kaiwu.me/?a=commitdiff_plain;h=dee32a05d7ed2391801ea40a631b9dd468e8312b;p=haproxy.git

MINOR: htx: Add macros for the header/trailer name and value max lengths

The maximum length of the name and the value of a header or a trailer were
hardcoded in the different places where they are tested. Let's define
HTX_HDR_NAME_MAX_LEN and HTX_HDR_VALUE_MAX_LEN to avoid these magic values
and document why these limits exist.
---

diff --git a/include/haproxy/htx-t.h b/include/haproxy/htx-t.h
index 2e2b1b58d..42b10b0f5 100644
--- a/include/haproxy/htx-t.h
+++ b/include/haproxy/htx-t.h
@@ -220,6 +220,15 @@ struct htx_blk {
 	uint32_t info; /* information about the block (type, length) */
 };
 
+/* Maximum length of the name and the value of a header or a trailer. For these
+ * blocks, the <info> field above encodes the name length on 8 bits and the
+ * value length on 20 bits. Above these limits, the lengths would silently
+ * overflow on the other fields, corrupting the block. So these limits must
+ * always be checked when a header or a trailer is added or updated.
+ */
+#define HTX_HDR_NAME_MAX_LEN   255
+#define HTX_HDR_VALUE_MAX_LEN  1048575
+
 /* Composite return value used by some HTX functions */
 struct htx_ret {
 	int32_t ret;         /* A numerical value */
diff --git a/include/haproxy/htx.h b/include/haproxy/htx.h
index 55b41838f..1fe851cf7 100644
--- a/include/haproxy/htx.h
+++ b/include/haproxy/htx.h
@@ -360,7 +360,7 @@ static inline void htx_change_blk_value_len(struct htx *htx, struct htx_blk *blk
 	switch (type) {
 		case HTX_BLK_HDR:
 		case HTX_BLK_TLR:
-			BUG_ON(newlen > 1048575);
+			BUG_ON(newlen > HTX_HDR_VALUE_MAX_LEN);
 			oldlen = (blk->info >> 8) & 0xfffff;
 			blk->info = (type << 28) + (newlen << 8) + (blk->info & 0xff);
 			break;
@@ -393,7 +393,7 @@ static inline void htx_set_blk_value_len(struct htx_blk *blk, uint32_t vlen)
 	switch (type) {
 		case HTX_BLK_HDR:
 		case HTX_BLK_TLR:
-			BUG_ON(vlen > 1048575);
+			BUG_ON(vlen > HTX_HDR_VALUE_MAX_LEN);
 			blk->info = (type << 28) + (vlen << 8) + (blk->info & 0xff);
 			break;
 		case HTX_BLK_REQ_SL:
@@ -505,7 +505,7 @@ static inline struct htx_blk *htx_add_header(struct htx *htx, const struct ist n
 {
 	struct htx_blk *blk, *tailblk;
 
-	if (name.len > 255 || value.len > 1048575)
+	if (name.len > HTX_HDR_NAME_MAX_LEN || value.len > HTX_HDR_VALUE_MAX_LEN)
 		return NULL;
 
 	tailblk = htx_get_tail_blk(htx);
@@ -529,7 +529,7 @@ static inline struct htx_blk *htx_add_trailer(struct htx *htx, const struct ist
 {
 	struct htx_blk *blk, *tailblk;
 
-	if (name.len > 255 || value.len > 1048575)
+	if (name.len > HTX_HDR_NAME_MAX_LEN || value.len > HTX_HDR_VALUE_MAX_LEN)
 		return NULL;
 
 	tailblk = htx_get_tail_blk(htx);
diff --git a/src/htx.c b/src/htx.c
index 100abab32..bac133a7c 100644
--- a/src/htx.c
+++ b/src/htx.c
@@ -659,7 +659,7 @@ struct htx_blk *htx_replace_blk_value(struct htx *htx, struct htx_blk *blk,
 	 * must not overflow on the other fields of the block descriptor.
 	 */
 	if (unlikely((type == HTX_BLK_HDR || type == HTX_BLK_TLR) &&
-		     v.len + delta > 1048575))
+		     v.len + delta > HTX_HDR_VALUE_MAX_LEN))
 		return NULL;
 
 	if (unlikely(type < HTX_BLK_EOH && htx_hdrs_too_big(htx, delta)))
@@ -929,7 +929,7 @@ struct htx_blk *htx_replace_header(struct htx *htx, struct htx_blk *blk,
 	if (type != HTX_BLK_HDR)
 		return NULL;
 
-	if (name.len > 255 || value.len > 1048575)
+	if (name.len > HTX_HDR_NAME_MAX_LEN || value.len > HTX_HDR_VALUE_MAX_LEN)
 		return NULL;
 
 	delta = name.len + value.len - htx_get_blksz(blk);