source: libabac/abac_verifier.c @ 342e28f

#include <assert.h>

#include <library.h>
#include <credentials/certificates/certificate.h>
#include <credentials/certificates/x509.h>
#include <credentials/certificates/ac.h>

#include "abac_verifier.h"

#include "abac_list.h"
#include "abac_util.h"

typedef struct _abac_id_cert_t {
    char *keyid;
    certificate_t *cert;

    UT_hash_handle hh;
} abac_id_cert_t;

struct _abac_credential_t {
    abac_role_t *head;
    abac_role_t *tail;
    abac_list_t *prereqs; // an intersecton has prereqs, not a tail
    certificate_t *cert;
    certificate_t *issuer;

    int refcount;
};

abac_id_cert_t *id_certs = NULL;

// convert a chunk to a lowercase binary string
// malloc's the string
static char *_chunk_to_string(chunk_t chunk) {
    int i;

    char *ret = abac_xmalloc(chunk.len * 2 + 1);

    for (i = 0; i < chunk.len; ++i)
        sprintf(ret + 2 * i, "%02x", chunk.ptr[i]);

    return ret;
}

// verify that cert was issued by issuer
// cert and issuer can be the same, in which case the self-sig is validated
static int _verify_signature(certificate_t *issuer, certificate_t *cert) {
    if (cert->issued_by(cert, issuer))
        if (cert->get_validity(cert, NULL, NULL, NULL))
            return 1;
    return 0;
}

/**
 * Init the verifier subsystem.
 */
void abac_verifier_init(void) {
    atexit(library_deinit);

    // silence all debugging
    dbg_default_set_level(-1);

    if (!library_init(NULL))
        exit(SS_RC_LIBSTRONGSWAN_INTEGRITY);

    if (!lib->plugins->load(lib->plugins, NULL,
            lib->settings->get_str(lib->settings, "pki.load", PLUGINS)))
        exit(SS_RC_INITIALIZATION_FAILED);
}

/**
 * Uninitialize the system, free up any allocated memory.
 */
void abac_verifier_deinit(void) {
    abac_id_cert_t *id;

    while ((id = id_certs) != NULL) {
        HASH_DEL(id_certs, id);

        free(id->keyid);
        id->cert->destroy(id->cert);
        free(id);
    }
}

/**
 * Load an ID certificate.
 */
static int _load_id(certificate_t *cert) {
    abac_id_cert_t *id_cert = NULL;
    char *keyid = NULL;
    chunk_t id;
    int ret;
    x509_t *x509 = (x509_t *)cert;

    assert(cert != NULL);

    // get the key ID
    id = x509->get_subjectKeyIdentifier(x509);
    keyid = _chunk_to_string(id);

    // if we already have this cert 'error' with success
    HASH_FIND_STR(id_certs, keyid, id_cert);
    if (id_cert != NULL) {
        ret = ABAC_CERT_SUCCESS;
        goto error;
    }

    // validate sig
    ret = _verify_signature(cert, cert);
    if (!ret) {
        ret = ABAC_CERT_BAD_SIG;
        goto error;
    }

    // success, add the key to the map of certificates
    id_cert = abac_xmalloc(sizeof(abac_id_cert_t));
    id_cert->keyid = keyid;
    id_cert->cert = cert;
    HASH_ADD_KEYPTR(hh, id_certs, id_cert->keyid, strlen(id_cert->keyid), id_cert);

    return ABAC_CERT_SUCCESS;

error:
    if (keyid != NULL) free(keyid);

    return ret;
}

/**
 * Load an ID cert from a file.
 */
int abac_verifier_load_id_file(char *filename) {
    if (lib == NULL)
        errx(1, "looks like you didn't call libabac_init() (lib is NULL)");

    // load the cert
    certificate_t *cert = lib->creds->create(
        lib->creds, CRED_CERTIFICATE, CERT_X509,
        BUILD_FROM_FILE, filename,
        BUILD_X509_FLAG, X509_AA, // attribute authority, dumb
        BUILD_END
    );
    if (cert == NULL)
        return ABAC_CERT_INVALID;
    return _load_id(cert);
}

/**
 * Load an ID cert from a chunk.
 */
int abac_verifier_load_id_chunk(chunk_t chunk) {
    // load the cert
    certificate_t *cert = lib->creds->create(
        lib->creds, CRED_CERTIFICATE, CERT_X509,
        BUILD_BLOB_ASN1_DER, chunk,
        BUILD_X509_FLAG, X509_AA, // attribute authority, dumb
        BUILD_END
    );
    if (cert == NULL)
        return ABAC_CERT_INVALID;
    return _load_id(cert);
}

/**
 * Split a string based on the given delimiter.
 */
static void _split(char *string, char *delim, char **ret, int *num) {
    int len = strlen(delim);
    char *start = string;
    int count = 0;

    // split the string by the delim
    while ((start = strstr(string, delim)) != NULL) {
        *start = 0;
        ret[count++] = string;
        string = start + len;
    }
    ret[count++] = string;

    *num = count;
}

/**
 * Load an attribute cert.
 * Returns true only if the certificate is valid and is issued by the proper
 * authority.
 */
static int _load_attribute_cert(certificate_t *cert, abac_credential_t **cred_ret) {
    ietf_attributes_t *attr_cert = NULL;
    abac_role_t *head_role = NULL;
    abac_role_t *tail_role = NULL;
    abac_id_cert_t *issuer;
    abac_list_t *prereqs = NULL;
    int ret, i;

    // get the attr
    ac_t *ac = (ac_t *)cert;
    attr_cert = ac->get_groups(ac);
    if (attr_cert == NULL) {
        ret = ABAC_CERT_INVALID;
        goto error;
    }

    char *attr_string = attr_cert->get_string(attr_cert);
    if (attr_string == NULL) {
        ret = ABAC_CERT_INVALID;
        goto error;
    }

    // split into head/tail parts
    char *head_tail[2];
    _split(attr_string, " <- ", head_tail, &ret);
    if (ret != 2) {
        ret = ABAC_CERT_INVALID;
        goto error;
    }

    // must be a role
    head_role = abac_role_from_string(head_tail[0]);
    if (head_role == NULL) goto error;
    if (!abac_role_is_role(head_role)) {
        ret = ABAC_CERT_INVALID;
        goto error;
    }

    // split the tail (in case of an intersection num_tails > 1)
    char *tails[256];
    int num_tails;
    _split(head_tail[1], " & ", tails, &num_tails);

    if (num_tails > 1)
        prereqs = abac_list_new();

    for (i = 0; i < num_tails; ++i) {
        // make sure the tail role is valid
        tail_role = abac_role_from_string(tails[i]);
        if (tail_role == NULL) {
            ret = ABAC_CERT_INVALID;
            goto error;
        }

        // add to the list if intersection
        if (num_tails > 1)
            abac_list_add(prereqs, tail_role);
    }

    if (num_tails > 1)
        tail_role = NULL;

    // get the issuer based on keyid
    char *principal = abac_role_principal(head_role);
    HASH_FIND_STR(id_certs, principal, issuer);
    if (issuer == NULL) {
        ret = ABAC_CERT_MISSING_ISSUER;
        goto error;
    }

    // make sure the issuer's signed it
    ret = _verify_signature(issuer->cert, cert);
    if (!ret) {
        ret = ABAC_CERT_BAD_SIG;
        goto error;
    }

    // at this point we know we have a good attribute cert
    abac_credential_t *cred = abac_xmalloc(sizeof(abac_credential_t));
    cred->head = head_role;
    cred->tail = tail_role;
    cred->prereqs = prereqs;
    cred->cert = cert;
    cred->issuer = issuer->cert->get_ref(issuer->cert);
    cred->refcount = 1;
    *cred_ret = cred;

    // free up some crap
    attr_cert->destroy(attr_cert);

    return ABAC_CERT_SUCCESS;

error:
    if (cert != NULL) cert->destroy(cert);
    if (attr_cert != NULL) attr_cert->destroy(attr_cert);
    if (head_role != NULL) abac_role_free(head_role);
    if (tail_role != NULL) abac_role_free(tail_role);

    // free all the tail roles
    if (prereqs != NULL) {
        abac_list_foreach(prereqs, tail_role,
            abac_role_free(tail_role);
        );
        abac_list_free(prereqs);
    }

    return ret;
}

/**
 * Load an attribute cert from a file.
 */
int abac_verifier_load_attribute_cert_file(char *filename, abac_credential_t **cred) {
    // load the cert
    certificate_t *cert = lib->creds->create(
        lib->creds, CRED_CERTIFICATE, CERT_X509_AC,
        BUILD_FROM_FILE, filename,
        BUILD_END
    );
    if (cert == NULL)
        return ABAC_CERT_INVALID;
    return _load_attribute_cert(cert, cred);
}

/**
 * Load an attribute cert from a chunk.
 */
int abac_verifier_load_attribute_cert_chunk(chunk_t chunk, abac_credential_t **cred) {
    // load the cert
    certificate_t *cert = lib->creds->create(
        lib->creds, CRED_CERTIFICATE, CERT_X509_AC,
        BUILD_BLOB_ASN1_DER, chunk,
        BUILD_END
    );
    if (cert == NULL)
        return ABAC_CERT_INVALID;
    return _load_attribute_cert(cert, cred);
}

/**
 * Return the head role.
 */
abac_role_t *abac_credential_head(abac_credential_t *cred) {
    return cred->head;
}

/**
 * Return the tail role.
 */
abac_role_t *abac_credential_tail(abac_credential_t *cred) {
    return cred->tail;
}

/**
 * Return the prereqs. Non-NULL iff intersection.
 */
abac_list_t *abac_credential_prereqs(abac_credential_t *cred) {
    return cred->prereqs;
}

/**
 * Return the encoding of the attribute cert.
 */
abac_chunk_t abac_credential_attribute_cert(abac_credential_t *cred) {
    chunk_t encoding = cred->cert->get_encoding(cred->cert);
    abac_chunk_t ret = { encoding.ptr, encoding.len };
    return ret;
}

/**
 * Return the encoding of the issuer cert.
 */
abac_chunk_t abac_credential_issuer_cert(abac_credential_t *cred) {
    chunk_t encoding = cred->issuer->get_encoding(cred->issuer);
    abac_chunk_t ret = { encoding.ptr, encoding.len };
    return ret;
}

/**
 * Increase the ref count of a credential.
 */
abac_credential_t *abac_credential_dup(abac_credential_t *cred) {
    assert(cred != NULL);

    ++cred->refcount;
    return cred;
}

/**
 * Decrease the reference count of a credential, freeing it when it reaches 0.
 */
void abac_credential_free(abac_credential_t *cred) {
    if (cred == NULL)
        return;

    --cred->refcount;
    if (cred->refcount > 0)
        return;

    abac_role_free(cred->head);
    abac_role_free(cred->tail);
    cred->cert->destroy(cred->cert);
    cred->issuer->destroy(cred->issuer); // reference counted

    if (cred->prereqs != NULL) {
        abac_role_t *tail;
        abac_list_foreach(cred->prereqs, tail,
            abac_role_free(tail);
        );
        abac_list_free(cred->prereqs);
    }

    free(cred);
}