From bbcf509bd046b34cca19c766bbddc31683d0858b Mon Sep 17 00:00:00 2001
From: Matt Caswell <matt@openssl.org>
Date: Tue, 13 Dec 2022 14:54:55 +0000
Subject: [PATCH 2/6] Avoid dangling ptrs in header and data params for
 PEM_read_bio_ex

In the event of a failure in PEM_read_bio_ex() we free the buffers we
allocated for the header and data buffers. However we were not clearing
the ptrs stored in *header and *data. Since, on success, the caller is
responsible for freeing these ptrs this can potentially lead to a double
free if the caller frees them even on failure.

Thanks to Dawei Wang for reporting this issue.

Based on a proposed patch by Kurt Roeckx.

CVE-2022-4450

Reviewed-by: Paul Dale <pauli@openssl.org>
Reviewed-by: Hugo Landau <hlandau@openssl.org>
---
 crypto/pem/pem_lib.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/crypto/pem/pem_lib.c b/crypto/pem/pem_lib.c
index d416d939ea..328c30cdbb 100644
--- a/crypto/pem/pem_lib.c
+++ b/crypto/pem/pem_lib.c
@@ -957,7 +957,9 @@ int PEM_read_bio_ex(BIO *bp, char **name_out, char **header,
     *data = pem_malloc(len, flags);
     if (*header == NULL || *data == NULL) {
         pem_free(*header, flags, 0);
+        *header = NULL;
         pem_free(*data, flags, 0);
+        *data = NULL;
         goto end;
     }
     BIO_read(headerB, *header, headerlen);
-- 
2.39.1

From 2bd611267868a008afa576846ba71566bd0d4d15 Mon Sep 17 00:00:00 2001
From: Matt Caswell <matt@openssl.org>
Date: Tue, 13 Dec 2022 15:02:26 +0000
Subject: [PATCH 3/6] Add a test for CVE-2022-4450

Call PEM_read_bio_ex() and expect a failure. There should be no dangling
ptrs and therefore there should be no double free if we free the ptrs on
error.

Reviewed-by: Paul Dale <pauli@openssl.org>
Reviewed-by: Hugo Landau <hlandau@openssl.org>
---
 test/pemtest.c | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/test/pemtest.c b/test/pemtest.c
index 3203d976be..edeb0a1205 100644
--- a/test/pemtest.c
+++ b/test/pemtest.c
@@ -83,9 +83,39 @@ static int test_invalid(void)
     return 1;
 }
 
+static int test_empty_payload(void)
+{
+    BIO *b;
+    static char *emptypay =
+        "-----BEGIN CERTIFICATE-----\n"
+        "-\n" /* Base64 EOF character */
+        "-----END CERTIFICATE-----";
+    char *name = NULL, *header = NULL;
+    unsigned char *data = NULL;
+    long len;
+    int ret = 0;
+
+    b = BIO_new_mem_buf(emptypay, strlen(emptypay));
+    if (!TEST_ptr(b))
+        return 0;
+
+    /* Expected to fail because the payload is empty */
+    if (!TEST_false(PEM_read_bio_ex(b, &name, &header, &data, &len, 0)))
+        goto err;
+
+    ret = 1;
+ err:
+    OPENSSL_free(name);
+    OPENSSL_free(header);
+    OPENSSL_free(data);
+    BIO_free(b);
+    return ret;
+}
+
 int setup_tests(void)
 {
     ADD_ALL_TESTS(test_b64, OSSL_NELEM(b64_pem_data));
     ADD_TEST(test_invalid);
+    ADD_TEST(test_empty_payload);
     return 1;
 }
-- 
2.39.1