EVP_SealInit(): minor cleanup.

Explicitly compare pointers against NULL, turn the function into single
exit, add hint at why npubk <= 0 or pubk == NULL are a success path:

The documentation briefly explains that EVP_OpenInit() and EVP_SealInit()
is able to initialize the EVP_CIPHER_CTX in two steps exactly like the
EVP_CipherInit_ex() API they wrap: the first call with non-NULL cipher
(aka type) only sets the cipher on the ctx, then it returns to allow
callers to customize the EVP_CIPHER_CTX, and a second call with
cipher == NULL skips the initialization and finishes the ctx setup
by setting key and iv.

Prompted by a report by Niels Dossche.

ok jsing kenjiro

1 files changed, 25 insertions, 11 deletions

diff --git a/src/lib/libcrypto/evp/p_legacy.c b/src/lib/libcrypto/evp/p_legacy.c
index 521bddaa02..02153be20b 100644
--- a/src/lib/libcrypto/evp/p_legacy.c
+++ b/src/lib/libcrypto/evp/p_legacy.c
@@ -1,4 +1,4 @@
-/*      $OpenBSD: p_legacy.c,v 1.9 2026/01/30 13:47:22 tb Exp $ */
+/*      $OpenBSD: p_legacy.c,v 1.10 2026/01/30 13:51:44 tb Exp $ */
 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
  * All rights reserved.
  *
@@ -164,33 +164,47 @@ EVP_SealInit(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type, unsigned char **ek,
 {
         unsigned char key[EVP_MAX_KEY_LENGTH];
         int i, iv_len;
+        int ret = 0;
 
-        if (type) {
+        if (type != NULL) {
                 if (!EVP_CIPHER_CTX_reset(ctx))
-                        return 0;
+                        goto err;
                 if (!EVP_EncryptInit_ex(ctx, type, NULL, NULL, NULL))
-                        return 0;
+                        goto err;
         }
-        if ((npubk <= 0) || !pubk)
-                return 1;
+
+        /*
+         * Per manpage: "it is possible to call EVP_SealInit() twice in the
+         * same way as EVP_EncryptInit(3)." The return 1 indicates success.
+         */
+        if (npubk <= 0 || pubk == NULL) {
+                npubk = 1;
+                goto done;
+        }
+
         if (EVP_CIPHER_CTX_rand_key(ctx, key) <= 0)
-                return 0;
+                goto err;
         /* XXX - upper bound? */
         if ((iv_len = EVP_CIPHER_CTX_iv_length(ctx)) < 0)
-                return 0;
+                goto err;
         if (iv_len > 0)
                 arc4random_buf(iv, iv_len);
 
         if (!EVP_EncryptInit_ex(ctx, NULL, NULL, key, iv))
-                return 0;
+                goto err;
 
         for (i = 0; i < npubk; i++) {
                 ekl[i] = EVP_PKEY_encrypt_old(ek[i], key,
                     EVP_CIPHER_CTX_key_length(ctx), pubk[i]);
                 if (ekl[i] <= 0)
-                        return 0;
+                        goto err;
         }
-        return (npubk);
+
+ done:
+        ret = npubk;
+
+ err:
+        return ret;
 }
 LCRYPTO_ALIAS(EVP_SealInit);