Commit message: Fix a read buffer overrun in X509_aux_print().

The ASN1_STRING_get0_data(3) manual explitely cautions the reader
that the data is not necessarily NUL-terminated, and the function
X509_alias_set1(3) does not sanitize the data passed into it in any
way either, so we must assume the return value from X509_alias_get0(3)
is merely a byte array and not necessarily a string in the sense
of the C language.

I found this bug while writing manual pages for X509_print_ex(3)
and related functions.  Theo Buehler <tb@openbsd.org> checked my
patch to fix the same bug in LibreSSL, see

http://cvsweb.openbsd.org/src/lib/libcrypto/asn1/t_x509a.c#rev1.9

As an aside, note that the function still produces incomplete and
misleading results when the data contains a NUL byte in the middle
and that error handling is consistently absent throughout, even
though the function provides an "int" return value obviously intended
to be 1 for success and 0 for failure, and even though this function
is called by another function that also wants to return 1 for success
and 0 for failure and even does so in many of its code paths, though
not in others.  But let's stay focussed.  Many things would be nice
to have in the wide wild world, but a buffer overflow must not be
allowed to remain in our backyard.

CLA: trivial

Reviewed-by: Tim Hudson <tjh@openssl.org>
Reviewed-by: Paul Dale <pauli@openssl.org>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/16108)

(cherry picked from commit c5dc9ab965f2a69bca964c709e648158f3e4cd67)
CVE: CVE-2021-3712
CWE: CWE-125
Vulnerability description: ASN.1 strings are represented internally within OpenSSL as an ASN1_STRING structure which contains a buffer holding the string data and a field holding the buffer length. This contrasts with normal C strings which are repesented as a buffer for the string data which is terminated with a NUL (0) byte. Although not a strict requirement, ASN.1 strings that are parsed using OpenSSL's own "d2i" functions (and other similar parsing functions) as well as any string whose value has been set with the ASN1_STRING_set() function will additionally NUL terminate the byte array in the ASN1_STRING structure. However, it is possible for applications to directly construct valid ASN1_STRING structures which do not NUL terminate the byte array by directly setting the "data" and "length" fields in the ASN1_STRING array. This can also happen by using the ASN1_STRING_set0() function. Numerous OpenSSL functions that print ASN.1 data have been found to assume that the ASN1_STRING byte array will be NUL terminated, even though this is not guaranteed for strings that have been directly constructed. Where an application requests an ASN.1 structure to be printed, and where that ASN.1 structure contains ASN1_STRINGs that have been directly constructed by the application without NUL terminating the "data" field, then a read buffer overrun can occur. The same thing can also occur during name constraints processing of certificates (for example if a certificate has been directly constructed by the application instead of loading it via the OpenSSL parsing functions, and the certificate contains non NUL terminated ASN1_STRING structures). It can also occur in the X509_get1_email(), X509_REQ_get1_email() and X509_get1_ocsp() functions. If a malicious actor can cause an application to directly construct an ASN1_STRING and then process it through one of the affected OpenSSL functions then this issue could be hit. This might result in a crash (causing a Denial of Service attack). It could also result in the disclosure of private memory contents (such as private keys, or sensitive plaintext). Fixed in OpenSSL 1.1.1l (Affected 1.1.1-1.1.1k). Fixed in OpenSSL 1.0.2za (Affected 1.0.2-1.0.2y).

Project: openssl

int X509_aux_print(BIO *out, X509 *x, int indent)
{
    char oidstr[80], first;
    STACK_OF(ASN1_OBJECT) *trust, *reject;
    const unsigned char *alias, *keyid;
    int keyidlen;
    int i;
    if (X509_trusted(x) == 0)
        return 1;
    trust = X509_get0_trust_objects(x);
    reject = X509_get0_reject_objects(x);
    if (trust) {
        first = 1;
        BIO_printf(out, "%*sTrusted Uses:\n%*s", indent, "", indent + 2, "");
        for (i = 0; i < sk_ASN1_OBJECT_num(trust); i++) {
            if (!first)
                BIO_puts(out, ", ");
            else
                first = 0;
            OBJ_obj2txt(oidstr, sizeof(oidstr),
                        sk_ASN1_OBJECT_value(trust, i), 0);
            BIO_puts(out, oidstr);
        }
        BIO_puts(out, "\n");
    } else
        BIO_printf(out, "%*sNo Trusted Uses.\n", indent, "");
    if (reject) {
        first = 1;
        BIO_printf(out, "%*sRejected Uses:\n%*s", indent, "", indent + 2, "");
        for (i = 0; i < sk_ASN1_OBJECT_num(reject); i++) {
            if (!first)
                BIO_puts(out, ", ");
            else
                first = 0;
            OBJ_obj2txt(oidstr, sizeof(oidstr),
                        sk_ASN1_OBJECT_value(reject, i), 0);
            BIO_puts(out, oidstr);
        }
        BIO_puts(out, "\n");
    } else
        BIO_printf(out, "%*sNo Rejected Uses.\n", indent, "");
    alias = X509_alias_get0(x, NULL);
    if (alias)
        BIO_printf(out, "%*sAlias: %s\n", indent, "", alias);
    keyid = X509_keyid_get0(x, &keyidlen);
    if (keyid) {
        BIO_printf(out, "%*sKey Id: ", indent, "");
        for (i = 0; i < keyidlen; i++)
            BIO_printf(out, "%s%02X", i ? ":" : "", keyid[i]);
        BIO_write(out, "\n", 1);
    }
    return 1;
}