X509: clean up doc and implementation of X509{,_REQ}_check_private_key()

Also constify X509_REQ_get0_pubkey() and X509_REQ_check_private_key().

Reviewed-by: Tomas Mraz <tomas@openssl.org>
Reviewed-by: Dmitry Belyavskiy <beldmit@gmail.com>
Reviewed-by: David von Oheimb <david.von.oheimb@siemens.com>
(Merged from https://github.com/openssl/openssl/pull/18930)

2 files changed, 21 insertions, 32 deletions

diff --git a/crypto/x509/x509_cmp.c b/crypto/x509/x509_cmp.c
index 9f5b9403f2..18f9fba764 100644
--- a/crypto/x509/x509_cmp.c
+++ b/crypto/x509/x509_cmp.c
@@ -389,30 +389,38 @@ EVP_PKEY *X509_get_pubkey(X509 *x)
     return X509_PUBKEY_get(x->cert_info.key);
 }
 
-int X509_check_private_key(const X509 *x, const EVP_PKEY *k)
+int X509_check_private_key(const X509 *cert, const EVP_PKEY *pkey)
 {
-    const EVP_PKEY *xk;
-    int ret;
+    const EVP_PKEY *xk = X509_get0_pubkey(cert);
 
-    xk = X509_get0_pubkey(x);
     if (xk == NULL) {
         ERR_raise(ERR_LIB_X509, X509_R_UNABLE_TO_GET_CERTS_PUBLIC_KEY);
         return 0;
     }
+    return ossl_x509_check_private_key(xk, pkey);
+}
 
-    switch (ret = EVP_PKEY_eq(xk, k)) {
+int ossl_x509_check_private_key(const EVP_PKEY *x, const EVP_PKEY *pkey)
+{
+    if (x == NULL) {
+        ERR_raise(ERR_LIB_X509, ERR_R_PASSED_NULL_PARAMETER);
+        return 0;
+    }
+    switch (EVP_PKEY_eq(x, pkey)) {
+    case 1:
+        return 1;
     case 0:
         ERR_raise(ERR_LIB_X509, X509_R_KEY_VALUES_MISMATCH);
-        break;
+        return 0;
     case -1:
         ERR_raise(ERR_LIB_X509, X509_R_KEY_TYPE_MISMATCH);
-        break;
+        return 0;
     case -2:
         ERR_raise(ERR_LIB_X509, X509_R_UNKNOWN_KEY_TYPE);
-        break;
+        /* fall thru */
+    default:
+        return 0;
     }
-
-    return ret > 0;
 }
 
 /*
diff --git a/crypto/x509/x509_req.c b/crypto/x509/x509_req.c
index 858c6c566c..af12714472 100644
--- a/crypto/x509/x509_req.c
+++ b/crypto/x509/x509_req.c
@@ -67,7 +67,7 @@ EVP_PKEY *X509_REQ_get_pubkey(X509_REQ *req)
     return X509_PUBKEY_get(req->req_info.pubkey);
 }
 
-EVP_PKEY *X509_REQ_get0_pubkey(X509_REQ *req)
+EVP_PKEY *X509_REQ_get0_pubkey(const X509_REQ *req)
 {
     if (req == NULL)
         return NULL;
@@ -79,28 +79,9 @@ X509_PUBKEY *X509_REQ_get_X509_PUBKEY(X509_REQ *req)
     return req->req_info.pubkey;
 }
 
-int X509_REQ_check_private_key(X509_REQ *x, EVP_PKEY *k)
+int X509_REQ_check_private_key(const X509_REQ *req, EVP_PKEY *pkey)
 {
-    EVP_PKEY *xk = NULL;
-    int ok = 0;
-
-    xk = X509_REQ_get_pubkey(x);
-    switch (EVP_PKEY_eq(xk, k)) {
-    case 1:
-        ok = 1;
-        break;
-    case 0:
-        ERR_raise(ERR_LIB_X509, X509_R_KEY_VALUES_MISMATCH);
-        break;
-    case -1:
-        ERR_raise(ERR_LIB_X509, X509_R_KEY_TYPE_MISMATCH);
-        break;
-    case -2:
-        ERR_raise(ERR_LIB_X509, X509_R_UNKNOWN_KEY_TYPE);
-    }
-
-    EVP_PKEY_free(xk);
-    return ok;
+    return ossl_x509_check_private_key(X509_REQ_get0_pubkey(req), pkey);
 }
 
 /*