From 3e566818f747baa135e1b693ab2ab67fe4f942e2 Mon Sep 17 00:00:00 2001
From: Michael Brown <mcb30@ipxe.org>
Date: Tue, 2 Dec 2025 13:13:01 +0000
Subject: [PATCH] [crypto] Remove obsolete maximum output length method

Now that public-key algorithms use ASN.1 builders to dynamically
allocate the output data, there is no further need for callers to be
able to determine the maximum output length.

Signed-off-by: Michael Brown <mcb30@ipxe.org>
---
 src/crypto/crypto_null.c  |  5 -----
 src/crypto/rsa.c          | 22 ----------------------
 src/include/ipxe/crypto.h | 13 -------------
 3 files changed, 40 deletions(-)

diff --git a/src/crypto/crypto_null.c b/src/crypto/crypto_null.c
index e8f8cbde8..e80f2707f 100644
--- a/src/crypto/crypto_null.c
+++ b/src/crypto/crypto_null.c
@@ -93,10 +93,6 @@ struct cipher_algorithm cipher_null = {
 	.auth = cipher_null_auth,
 };
 
-size_t pubkey_null_max_len ( const struct asn1_cursor *key __unused ) {
-	return 0;
-}
-
 int pubkey_null_encrypt ( const struct asn1_cursor *key __unused,
 			  const struct asn1_cursor *plaintext __unused,
 			  struct asn1_builder *ciphertext __unused ) {
@@ -125,7 +121,6 @@ int pubkey_null_verify ( const struct asn1_cursor *key __unused,
 
 struct pubkey_algorithm pubkey_null = {
 	.name = "null",
-	.max_len = pubkey_null_max_len,
 	.encrypt = pubkey_null_encrypt,
 	.decrypt = pubkey_null_decrypt,
 	.sign = pubkey_null_sign,
diff --git a/src/crypto/rsa.c b/src/crypto/rsa.c
index 18b2b1c14..051bbfa08 100644
--- a/src/crypto/rsa.c
+++ b/src/crypto/rsa.c
@@ -287,27 +287,6 @@ static int rsa_init ( struct rsa_context *context,
 	return rc;
 }
 
-/**
- * Calculate RSA maximum output length
- *
- * @v key		Key
- * @ret max_len		Maximum output length
- */
-static size_t rsa_max_len ( const struct asn1_cursor *key ) {
-	struct asn1_cursor modulus;
-	struct asn1_cursor exponent;
-	int rc;
-
-	/* Parse moduli and exponents */
-	if ( ( rc = rsa_parse_mod_exp ( &modulus, &exponent, key ) ) != 0 ) {
-		/* Return a zero maximum length on error */
-		return 0;
-	}
-
-	/* Output length can never exceed modulus length */
-	return modulus.len;
-}
-
 /**
  * Perform RSA cipher operation
  *
@@ -706,7 +685,6 @@ static int rsa_match ( const struct asn1_cursor *private_key,
 /** RSA public-key algorithm */
 struct pubkey_algorithm rsa_algorithm = {
 	.name		= "rsa",
-	.max_len	= rsa_max_len,
 	.encrypt	= rsa_encrypt,
 	.decrypt	= rsa_decrypt,
 	.sign		= rsa_sign,
diff --git a/src/include/ipxe/crypto.h b/src/include/ipxe/crypto.h
index 68bd23048..ee63423c9 100644
--- a/src/include/ipxe/crypto.h
+++ b/src/include/ipxe/crypto.h
@@ -121,12 +121,6 @@ struct cipher_algorithm {
 struct pubkey_algorithm {
 	/** Algorithm name */
 	const char *name;
-	/** Calculate maximum output length
-	 *
-	 * @v key		Key
-	 * @ret max_len		Maximum output length
-	 */
-	size_t ( * max_len ) ( const struct asn1_cursor *key );
 	/** Encrypt
 	 *
 	 * @v key		Key
@@ -266,12 +260,6 @@ is_auth_cipher ( struct cipher_algorithm *cipher ) {
 	return cipher->authsize;
 }
 
-static inline __attribute__ (( always_inline )) size_t
-pubkey_max_len ( struct pubkey_algorithm *pubkey,
-		 const struct asn1_cursor *key ) {
-	return pubkey->max_len ( key );
-}
-
 static inline __attribute__ (( always_inline )) int
 pubkey_encrypt ( struct pubkey_algorithm *pubkey, const struct asn1_cursor *key,
 		 const struct asn1_cursor *plaintext,
@@ -325,7 +313,6 @@ extern void cipher_null_decrypt ( void *ctx, const void *src, void *dst,
 				  size_t len );
 extern void cipher_null_auth ( void *ctx, void *auth );
 
-extern size_t pubkey_null_max_len ( const struct asn1_cursor *key );
 extern int pubkey_null_encrypt ( const struct asn1_cursor *key,
 				 const struct asn1_cursor *plaintext,
 				 struct asn1_builder *ciphertext );