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Merge pull request #1582 from bjwtaylor/pkcs-free-stale-pointers

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Add fix for stale pointer after mbedtls_pkcs7_free
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Ronald Cron 2026-06-22 17:54:17 +02:00 committed by GitHub
commit 27fcc8e3a0
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4 changed files with 59 additions and 1 deletions
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6
ChangeLog.d/pkcs-free-stale-pointers.txt Normal file
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@ -0,0 +1,6 @@
Security
* Fix a use-after-free/double-free risk in mbedtls_pkcs7_free() when reusing
an mbedtls_pkcs7 context across parse -> free -> parse -> free cycles. The
function now resets the context after freeing it, ensuring stale
signed_data.signers.next pointers cannot be walked by a later free
operation. CVE-2026-50579

2
library/pkcs7.c
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@ -766,7 +766,7 @@ void mbedtls_pkcs7_free(mbedtls_pkcs7 *pkcs7)
mbedtls_free(signer_prev);
}
pkcs7->raw.p = NULL;
mbedtls_platform_zeroize(pkcs7, sizeof(*pkcs7));
}
#endif

8
tests/suites/test_suite_pkcs7.data
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@ -14,6 +14,14 @@ PKCS7 Signed Data Parse with zero signers
depends_on:PSA_WANT_ALG_SHA_256
pkcs7_parse:"../framework/data_files/pkcs7_data_no_signers.der":MBEDTLS_PKCS7_SIGNED_DATA
PKCS7 Signed Data Parse reused object after multiple signers
depends_on:PSA_WANT_ALG_SHA_256:PSA_WANT_KEY_TYPE_RSA_PUBLIC_KEY
pkcs7_parse_reuse:"../framework/data_files/pkcs7_data_multiple_signed.der":"../framework/data_files/pkcs7_data_no_signers.der":MBEDTLS_PKCS7_SIGNED_DATA
PKCS7 Signed Data Parse reused object from multiple signers to one signer
depends_on:PSA_WANT_ALG_SHA_256:PSA_WANT_KEY_TYPE_RSA_PUBLIC_KEY
pkcs7_parse_reuse:"../framework/data_files/pkcs7_data_multiple_signed.der":"../framework/data_files/pkcs7_data_cert_signed_sha256.der":MBEDTLS_PKCS7_SIGNED_DATA
PKCS7 Signed Data Parse Fail with multiple certs #4
depends_on:PSA_WANT_ALG_SHA_256:PSA_WANT_KEY_TYPE_RSA_PUBLIC_KEY
pkcs7_parse:"../framework/data_files/pkcs7_data_multiple_certs_signed.der":MBEDTLS_ERR_PKCS7_FEATURE_UNAVAILABLE

44
tests/suites/test_suite_pkcs7.function
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@ -25,8 +25,10 @@ static int pkcs7_parse_buffer(unsigned char *pkcs7_buf, int buflen)
mbedtls_pkcs7_init(&pkcs7);
res = mbedtls_pkcs7_parse_der(&pkcs7, pkcs7_buf, buflen);
mbedtls_pkcs7_free(&pkcs7);
return res;
}
/* END_SUITE_HELPERS */
/* BEGIN_CASE */
@ -71,6 +73,48 @@ exit:
}
/* END_CASE */
/* BEGIN_CASE depends_on:MBEDTLS_FS_IO */
void pkcs7_parse_reuse(char *first_pkcs7_file, char *second_pkcs7_file,
int res_expect)
{
unsigned char *first_pkcs7_buf = NULL;
unsigned char *second_pkcs7_buf = NULL;
mbedtls_pkcs7 pkcs7;
size_t first_buflen;
size_t second_buflen;
mbedtls_pkcs7_init(&pkcs7);
/* PKCS7 uses X509 which itself relies on PK under the hood and the latter
* can use PSA to store keys and perform operations so psa_crypto_init()
* must be called before. */
USE_PSA_INIT();
TEST_EQUAL(mbedtls_pk_load_file(first_pkcs7_file, &first_pkcs7_buf,
&first_buflen), 0);
TEST_EQUAL(mbedtls_pk_load_file(second_pkcs7_file, &second_pkcs7_buf,
&second_buflen), 0);
TEST_EQUAL(mbedtls_pkcs7_parse_der(&pkcs7, first_pkcs7_buf,
first_buflen),
MBEDTLS_PKCS7_SIGNED_DATA);
mbedtls_pkcs7_free(&pkcs7);
TEST_ASSERT(pkcs7.raw.p == NULL);
TEST_ASSERT(pkcs7.signed_data.signers.next == NULL);
TEST_EQUAL(mbedtls_pkcs7_parse_der(&pkcs7, second_pkcs7_buf,
second_buflen),
res_expect);
exit:
mbedtls_free(first_pkcs7_buf);
mbedtls_free(second_pkcs7_buf);
mbedtls_pkcs7_free(&pkcs7);
USE_PSA_DONE();
}
/* END_CASE */
/* BEGIN_CASE depends_on:MBEDTLS_FS_IO:MBEDTLS_X509_CRT_PARSE_C:PSA_HAVE_ALG_SOME_RSA_VERIFY */
void pkcs7_verify(char *pkcs7_file,
char *crt_files,