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