Adding upstream version 247.3.upstream/247.3upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 932 insertions, 0 deletions

diff --git a/src/shared/pkcs11-util.c b/src/shared/pkcs11-util.c
new file mode 100644
index 0000000..e74f0be
--- /dev/null
+++ b/src/shared/pkcs11-util.c
@@ -0,0 +1,932 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <fcntl.h>
+
+#include "ask-password-api.h"
+#include "escape.h"
+#include "fd-util.h"
+#include "io-util.h"
+#include "memory-util.h"
+#if HAVE_OPENSSL
+#include "openssl-util.h"
+#endif
+#include "pkcs11-util.h"
+#include "random-util.h"
+#include "string-util.h"
+#include "strv.h"
+
+bool pkcs11_uri_valid(const char *uri) {
+        const char *p;
+
+        /* A very superficial checker for RFC7512 PKCS#11 URI syntax */
+
+        if (isempty(uri))
+                return false;
+
+        p = startswith(uri, "pkcs11:");
+        if (!p)
+                return false;
+
+        if (isempty(p))
+                return false;
+
+        if (!in_charset(p, ALPHANUMERICAL "-_?;&%="))
+                return false;
+
+        return true;
+}
+
+#if HAVE_P11KIT
+
+int uri_from_string(const char *p, P11KitUri **ret) {
+        _cleanup_(p11_kit_uri_freep) P11KitUri *uri = NULL;
+
+        assert(p);
+        assert(ret);
+
+        uri = p11_kit_uri_new();
+        if (!uri)
+                return -ENOMEM;
+
+        if (p11_kit_uri_parse(p, P11_KIT_URI_FOR_ANY, uri) != P11_KIT_URI_OK)
+                return -EINVAL;
+
+        *ret = TAKE_PTR(uri);
+        return 0;
+}
+
+P11KitUri *uri_from_module_info(const CK_INFO *info) {
+        P11KitUri *uri;
+
+        assert(info);
+
+        uri = p11_kit_uri_new();
+        if (!uri)
+                return NULL;
+
+        *p11_kit_uri_get_module_info(uri) = *info;
+        return uri;
+}
+
+P11KitUri *uri_from_slot_info(const CK_SLOT_INFO *slot_info) {
+        P11KitUri *uri;
+
+        assert(slot_info);
+
+        uri = p11_kit_uri_new();
+        if (!uri)
+                return NULL;
+
+        *p11_kit_uri_get_slot_info(uri) = *slot_info;
+        return uri;
+}
+
+P11KitUri *uri_from_token_info(const CK_TOKEN_INFO *token_info) {
+        P11KitUri *uri;
+
+        assert(token_info);
+
+        uri = p11_kit_uri_new();
+        if (!uri)
+                return NULL;
+
+        *p11_kit_uri_get_token_info(uri) = *token_info;
+        return uri;
+}
+
+CK_RV pkcs11_get_slot_list_malloc(
+                CK_FUNCTION_LIST *m,
+                CK_SLOT_ID **ret_slotids,
+                CK_ULONG *ret_n_slotids) {
+
+        CK_RV rv;
+
+        assert(m);
+        assert(ret_slotids);
+        assert(ret_n_slotids);
+
+        for (unsigned tries = 0; tries < 16; tries++) {
+                _cleanup_free_ CK_SLOT_ID *slotids = NULL;
+                CK_ULONG n_slotids = 0;
+
+                rv = m->C_GetSlotList(0, NULL, &n_slotids);
+                if (rv != CKR_OK)
+                        return rv;
+                if (n_slotids == 0) {
+                        *ret_slotids = NULL;
+                        *ret_n_slotids = 0;
+                        return CKR_OK;
+                }
+
+                slotids = new(CK_SLOT_ID, n_slotids);
+                if (!slotids)
+                        return CKR_HOST_MEMORY;
+
+                rv = m->C_GetSlotList(0, slotids, &n_slotids);
+                if (rv == CKR_OK) {
+                        *ret_slotids = TAKE_PTR(slotids);
+                        *ret_n_slotids = n_slotids;
+                        return CKR_OK;
+                }
+
+                if (rv != CKR_BUFFER_TOO_SMALL)
+                        return rv;
+
+                /* Hu? Maybe somebody plugged something in and things changed? Let's try again */
+        }
+
+        return CKR_BUFFER_TOO_SMALL;
+}
+
+char *pkcs11_token_label(const CK_TOKEN_INFO *token_info) {
+        char *t;
+
+        /* The label is not NUL terminated and likely padded with spaces, let's make a copy here, so that we
+         * can strip that. */
+        t = strndup((char*) token_info->label, sizeof(token_info->label));
+        if (!t)
+                return NULL;
+
+        strstrip(t);
+        return t;
+}
+
+char *pkcs11_token_manufacturer_id(const CK_TOKEN_INFO *token_info) {
+        char *t;
+
+        t = strndup((char*) token_info->manufacturerID, sizeof(token_info->manufacturerID));
+        if (!t)
+                return NULL;
+
+        strstrip(t);
+        return t;
+}
+
+char *pkcs11_token_model(const CK_TOKEN_INFO *token_info) {
+        char *t;
+
+        t = strndup((char*) token_info->model, sizeof(token_info->model));
+        if (!t)
+                return NULL;
+
+        strstrip(t);
+        return t;
+}
+
+int pkcs11_token_login(
+                CK_FUNCTION_LIST *m,
+                CK_SESSION_HANDLE session,
+                CK_SLOT_ID slotid,
+                const CK_TOKEN_INFO *token_info,
+                const char *friendly_name,
+                const char *icon_name,
+                const char *keyname,
+                usec_t until,
+                char **ret_used_pin) {
+
+        _cleanup_free_ char *token_uri_string = NULL, *token_uri_escaped = NULL, *id = NULL, *token_label = NULL;
+        _cleanup_(p11_kit_uri_freep) P11KitUri *token_uri = NULL;
+        CK_TOKEN_INFO updated_token_info;
+        int uri_result, r;
+        CK_RV rv;
+
+        assert(m);
+        assert(token_info);
+
+        token_label = pkcs11_token_label(token_info);
+        if (!token_label)
+                return log_oom();
+
+        token_uri = uri_from_token_info(token_info);
+        if (!token_uri)
+                return log_oom();
+
+        uri_result = p11_kit_uri_format(token_uri, P11_KIT_URI_FOR_ANY, &token_uri_string);
+        if (uri_result != P11_KIT_URI_OK)
+                return log_warning_errno(SYNTHETIC_ERRNO(EAGAIN), "Failed to format slot URI: %s", p11_kit_uri_message(uri_result));
+
+        if (FLAGS_SET(token_info->flags, CKF_PROTECTED_AUTHENTICATION_PATH)) {
+                rv = m->C_Login(session, CKU_USER, NULL, 0);
+                if (rv != CKR_OK)
+                        return log_error_errno(SYNTHETIC_ERRNO(EIO),
+                                               "Failed to log into security token '%s': %s", token_label, p11_kit_strerror(rv));
+
+                log_info("Successfully logged into security token '%s' via protected authentication path.", token_label);
+                if (ret_used_pin)
+                        *ret_used_pin = NULL;
+                return 0;
+        }
+
+        if (!FLAGS_SET(token_info->flags, CKF_LOGIN_REQUIRED)) {
+                log_info("No login into security token '%s' required.", token_label);
+                if (ret_used_pin)
+                        *ret_used_pin = NULL;
+                return 0;
+        }
+
+        token_uri_escaped = cescape(token_uri_string);
+        if (!token_uri_escaped)
+                return log_oom();
+
+        id = strjoin("pkcs11:", token_uri_escaped);
+        if (!id)
+                return log_oom();
+
+        for (unsigned tries = 0; tries < 3; tries++) {
+                _cleanup_strv_free_erase_ char **passwords = NULL;
+                char **i, *e;
+
+                e = getenv("PIN");
+                if (e) {
+                        passwords = strv_new(e);
+                        if (!passwords)
+                                return log_oom();
+
+                        string_erase(e);
+                        if (unsetenv("PIN") < 0)
+                                return log_error_errno(errno, "Failed to unset $PIN: %m");
+                } else {
+                        _cleanup_free_ char *text = NULL;
+
+                        if (FLAGS_SET(token_info->flags, CKF_USER_PIN_FINAL_TRY))
+                                r = asprintf(&text,
+                                             "Please enter correct PIN for security token '%s' in order to unlock %s (final try):",
+                                             token_label, friendly_name);
+                        else if (FLAGS_SET(token_info->flags, CKF_USER_PIN_COUNT_LOW))
+                                r = asprintf(&text,
+                                             "PIN has been entered incorrectly previously, please enter correct PIN for security token '%s' in order to unlock %s:",
+                                             token_label, friendly_name);
+                        else if (tries == 0)
+                                r = asprintf(&text,
+                                             "Please enter PIN for security token '%s' in order to unlock %s:",
+                                             token_label, friendly_name);
+                        else
+                                r = asprintf(&text,
+                                             "Please enter PIN for security token '%s' in order to unlock %s (try #%u):",
+                                             token_label, friendly_name, tries+1);
+                        if (r < 0)
+                                return log_oom();
+
+                        /* We never cache PINs, simply because it's fatal if we use wrong PINs, since usually there are only 3 tries */
+                        r = ask_password_auto(text, icon_name, id, keyname, until, 0, &passwords);
+                        if (r < 0)
+                                return log_error_errno(r, "Failed to query PIN for security token '%s': %m", token_label);
+                }
+
+                STRV_FOREACH(i, passwords) {
+                        rv = m->C_Login(session, CKU_USER, (CK_UTF8CHAR*) *i, strlen(*i));
+                        if (rv == CKR_OK)  {
+
+                                if (ret_used_pin) {
+                                        char *c;
+
+                                        c = strdup(*i);
+                                        if (!c)
+                                                return log_oom();
+
+                                        *ret_used_pin = c;
+                                }
+
+                                log_info("Successfully logged into security token '%s'.", token_label);
+                                return 0;
+                        }
+                        if (rv == CKR_PIN_LOCKED)
+                                return log_error_errno(SYNTHETIC_ERRNO(EPERM),
+                                                       "PIN has been locked, please reset PIN of security token '%s'.", token_label);
+                        if (!IN_SET(rv, CKR_PIN_INCORRECT, CKR_PIN_LEN_RANGE))
+                                return log_error_errno(SYNTHETIC_ERRNO(EIO),
+                                                       "Failed to log into security token '%s': %s", token_label, p11_kit_strerror(rv));
+
+                        /* Referesh the token info, so that we can prompt knowing the new flags if they changed. */
+                        rv = m->C_GetTokenInfo(slotid, &updated_token_info);
+                        if (rv != CKR_OK)
+                                return log_error_errno(SYNTHETIC_ERRNO(EIO),
+                                                       "Failed to acquire updated security token information for slot %lu: %s",
+                                                       slotid, p11_kit_strerror(rv));
+
+                        token_info = &updated_token_info;
+                        log_notice("PIN for token '%s' is incorrect, please try again.", token_label);
+                }
+        }
+
+        return log_error_errno(SYNTHETIC_ERRNO(EPERM), "Too many attempts to log into token '%s'.", token_label);
+}
+
+int pkcs11_token_find_x509_certificate(
+                CK_FUNCTION_LIST *m,
+                CK_SESSION_HANDLE session,
+                P11KitUri *search_uri,
+                CK_OBJECT_HANDLE *ret_object) {
+
+        bool found_class = false, found_certificate_type = false;
+        _cleanup_free_ CK_ATTRIBUTE *attributes_buffer = NULL;
+        CK_ULONG n_attributes, a, n_objects;
+        CK_ATTRIBUTE *attributes = NULL;
+        CK_OBJECT_HANDLE objects[2];
+        CK_RV rv, rv2;
+
+        assert(m);
+        assert(search_uri);
+        assert(ret_object);
+
+        attributes = p11_kit_uri_get_attributes(search_uri, &n_attributes);
+        for (a = 0; a < n_attributes; a++) {
+
+                /* We use the URI's included match attributes, but make them more strict. This allows users
+                 * to specify a token URL instead of an object URL and the right thing should happen if
+                 * there's only one suitable key on the token. */
+
+                switch (attributes[a].type) {
+
+                case CKA_CLASS: {
+                        CK_OBJECT_CLASS c;
+
+                        if (attributes[a].ulValueLen != sizeof(c))
+                                return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Invalid PKCS#11 CKA_CLASS attribute size.");
+
+                        memcpy(&c, attributes[a].pValue, sizeof(c));
+                        if (c != CKO_CERTIFICATE)
+                                return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Selected PKCS#11 object is not an X.509 certificate, refusing.");
+
+                        found_class = true;
+                        break;
+                }
+
+                case CKA_CERTIFICATE_TYPE: {
+                        CK_CERTIFICATE_TYPE t;
+
+                        if (attributes[a].ulValueLen != sizeof(t))
+                                return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Invalid PKCS#11 CKA_CERTIFICATE_TYPE attribute size.");
+
+                        memcpy(&t, attributes[a].pValue, sizeof(t));
+                        if (t != CKC_X_509)
+                                return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Selected PKCS#11 object is not an X.509 certificate, refusing.");
+
+                        found_certificate_type = true;
+                        break;
+                }}
+        }
+
+        if (!found_class || !found_certificate_type) {
+                /* Hmm, let's slightly extend the attribute list we search for */
+
+                attributes_buffer = new(CK_ATTRIBUTE, n_attributes + !found_class + !found_certificate_type);
+                if (!attributes_buffer)
+                        return log_oom();
+
+                memcpy(attributes_buffer, attributes, sizeof(CK_ATTRIBUTE) * n_attributes);
+
+                if (!found_class) {
+                        static const CK_OBJECT_CLASS class = CKO_CERTIFICATE;
+
+                        attributes_buffer[n_attributes++] = (CK_ATTRIBUTE) {
+                                .type = CKA_CLASS,
+                                .pValue = (CK_OBJECT_CLASS*) &class,
+                                .ulValueLen = sizeof(class),
+                        };
+                }
+
+                if (!found_certificate_type) {
+                        static const CK_CERTIFICATE_TYPE type = CKC_X_509;
+
+                        attributes_buffer[n_attributes++] = (CK_ATTRIBUTE) {
+                                .type = CKA_CERTIFICATE_TYPE,
+                                .pValue = (CK_CERTIFICATE_TYPE*) &type,
+                                .ulValueLen = sizeof(type),
+                        };
+                }
+
+                attributes = attributes_buffer;
+        }
+
+        rv = m->C_FindObjectsInit(session, attributes, n_attributes);
+        if (rv != CKR_OK)
+                return log_error_errno(SYNTHETIC_ERRNO(EIO),
+                                       "Failed to initialize object find call: %s", p11_kit_strerror(rv));
+
+        rv = m->C_FindObjects(session, objects, ELEMENTSOF(objects), &n_objects);
+        rv2 = m->C_FindObjectsFinal(session);
+        if (rv != CKR_OK)
+                return log_error_errno(SYNTHETIC_ERRNO(EIO),
+                                       "Failed to find objects: %s", p11_kit_strerror(rv));
+        if (rv2 != CKR_OK)
+                return log_error_errno(SYNTHETIC_ERRNO(EIO),
+                                       "Failed to finalize object find call: %s", p11_kit_strerror(rv));
+        if (n_objects == 0)
+                return log_error_errno(SYNTHETIC_ERRNO(ENOENT),
+                                       "Failed to find selected X509 certificate on token.");
+        if (n_objects > 1)
+                return log_error_errno(SYNTHETIC_ERRNO(ENOTUNIQ),
+                                       "Configured URI matches multiple certificates, refusing.");
+
+        *ret_object = objects[0];
+        return 0;
+}
+
+#if HAVE_OPENSSL
+int pkcs11_token_read_x509_certificate(
+                CK_FUNCTION_LIST *m,
+                CK_SESSION_HANDLE session,
+                CK_OBJECT_HANDLE object,
+                X509 **ret_cert) {
+
+        _cleanup_free_ void *buffer = NULL;
+        _cleanup_free_ char *t = NULL;
+        CK_ATTRIBUTE attribute = {
+                .type = CKA_VALUE
+        };
+        CK_RV rv;
+        _cleanup_(X509_freep) X509 *x509 = NULL;
+        X509_NAME *name = NULL;
+        const unsigned char *p;
+
+        rv = m->C_GetAttributeValue(session, object, &attribute, 1);
+        if (rv != CKR_OK)
+                return log_error_errno(SYNTHETIC_ERRNO(EIO),
+                                       "Failed to read X.509 certificate size off token: %s", p11_kit_strerror(rv));
+
+        buffer = malloc(attribute.ulValueLen);
+        if (!buffer)
+                return log_oom();
+
+        attribute.pValue = buffer;
+
+        rv = m->C_GetAttributeValue(session, object, &attribute, 1);
+        if (rv != CKR_OK)
+                return log_error_errno(SYNTHETIC_ERRNO(EIO),
+                                       "Failed to read X.509 certificate data off token: %s", p11_kit_strerror(rv));
+
+        p = attribute.pValue;
+        x509 = d2i_X509(NULL, &p, attribute.ulValueLen);
+        if (!x509)
+                return log_error_errno(SYNTHETIC_ERRNO(EBADMSG), "Failed parse X.509 certificate.");
+
+        name = X509_get_subject_name(x509);
+        if (!name)
+                return log_error_errno(SYNTHETIC_ERRNO(EBADMSG), "Failed to acquire X.509 subject name.");
+
+        t = X509_NAME_oneline(name, NULL, 0);
+        if (!t)
+                return log_error_errno(SYNTHETIC_ERRNO(EIO), "Failed to format X.509 subject name as string.");
+
+        log_debug("Using X.509 certificate issued for '%s'.", t);
+
+        *ret_cert = TAKE_PTR(x509);
+        return 0;
+}
+#endif
+
+int pkcs11_token_find_private_key(
+                CK_FUNCTION_LIST *m,
+                CK_SESSION_HANDLE session,
+                P11KitUri *search_uri,
+                CK_OBJECT_HANDLE *ret_object) {
+
+        bool found_decrypt = false, found_class = false, found_key_type = false;
+        _cleanup_free_ CK_ATTRIBUTE *attributes_buffer = NULL;
+        CK_ULONG n_attributes, a, n_objects;
+        CK_ATTRIBUTE *attributes = NULL;
+        CK_OBJECT_HANDLE objects[2];
+        CK_RV rv, rv2;
+
+        assert(m);
+        assert(search_uri);
+        assert(ret_object);
+
+        attributes = p11_kit_uri_get_attributes(search_uri, &n_attributes);
+        for (a = 0; a < n_attributes; a++) {
+
+                /* We use the URI's included match attributes, but make them more strict. This allows users
+                 * to specify a token URL instead of an object URL and the right thing should happen if
+                 * there's only one suitable key on the token. */
+
+                switch (attributes[a].type) {
+
+                case CKA_CLASS: {
+                        CK_OBJECT_CLASS c;
+
+                        if (attributes[a].ulValueLen != sizeof(c))
+                                return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Invalid PKCS#11 CKA_CLASS attribute size.");
+
+                        memcpy(&c, attributes[a].pValue, sizeof(c));
+                        if (c != CKO_PRIVATE_KEY)
+                                return log_error_errno(SYNTHETIC_ERRNO(EINVAL),
+                                                       "Selected PKCS#11 object is not a private key, refusing.");
+
+                        found_class = true;
+                        break;
+                }
+
+                case CKA_DECRYPT: {
+                        CK_BBOOL b;
+
+                        if (attributes[a].ulValueLen != sizeof(b))
+                                return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Invalid PKCS#11 CKA_DECRYPT attribute size.");
+
+                        memcpy(&b, attributes[a].pValue, sizeof(b));
+                        if (!b)
+                                return log_error_errno(SYNTHETIC_ERRNO(EINVAL),
+                                                       "Selected PKCS#11 object is not suitable for decryption, refusing.");
+
+                        found_decrypt = true;
+                        break;
+                }
+
+                case CKA_KEY_TYPE: {
+                        CK_KEY_TYPE t;
+
+                        if (attributes[a].ulValueLen != sizeof(t))
+                                return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Invalid PKCS#11 CKA_KEY_TYPE attribute size.");
+
+                        memcpy(&t, attributes[a].pValue, sizeof(t));
+                        if (t != CKK_RSA)
+                                return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Selected PKCS#11 object is not an RSA key, refusing.");
+
+                        found_key_type = true;
+                        break;
+                }}
+        }
+
+        if (!found_decrypt || !found_class || !found_key_type) {
+                /* Hmm, let's slightly extend the attribute list we search for */
+
+                attributes_buffer = new(CK_ATTRIBUTE, n_attributes + !found_decrypt + !found_class + !found_key_type);
+                if (!attributes_buffer)
+                        return log_oom();
+
+                memcpy(attributes_buffer, attributes, sizeof(CK_ATTRIBUTE) * n_attributes);
+
+                if (!found_decrypt) {
+                        static const CK_BBOOL yes = true;
+
+                        attributes_buffer[n_attributes++] = (CK_ATTRIBUTE) {
+                                .type = CKA_DECRYPT,
+                                .pValue = (CK_BBOOL*) &yes,
+                                .ulValueLen = sizeof(yes),
+                        };
+                }
+
+                if (!found_class) {
+                        static const CK_OBJECT_CLASS class = CKO_PRIVATE_KEY;
+
+                        attributes_buffer[n_attributes++] = (CK_ATTRIBUTE) {
+                                .type = CKA_CLASS,
+                                .pValue = (CK_OBJECT_CLASS*) &class,
+                                .ulValueLen = sizeof(class),
+                        };
+                }
+
+                if (!found_key_type) {
+                        static const CK_KEY_TYPE type = CKK_RSA;
+
+                        attributes_buffer[n_attributes++] = (CK_ATTRIBUTE) {
+                                .type = CKA_KEY_TYPE,
+                                .pValue = (CK_KEY_TYPE*) &type,
+                                .ulValueLen = sizeof(type),
+                        };
+                }
+
+                attributes = attributes_buffer;
+        }
+
+        rv = m->C_FindObjectsInit(session, attributes, n_attributes);
+        if (rv != CKR_OK)
+                return log_error_errno(SYNTHETIC_ERRNO(EIO),
+                                       "Failed to initialize object find call: %s", p11_kit_strerror(rv));
+
+        rv = m->C_FindObjects(session, objects, ELEMENTSOF(objects), &n_objects);
+        rv2 = m->C_FindObjectsFinal(session);
+        if (rv != CKR_OK)
+                return log_error_errno(SYNTHETIC_ERRNO(EIO),
+                                       "Failed to find objects: %s", p11_kit_strerror(rv));
+        if (rv2 != CKR_OK)
+                return log_error_errno(SYNTHETIC_ERRNO(EIO),
+                                       "Failed to finalize object find call: %s", p11_kit_strerror(rv));
+        if (n_objects == 0)
+                return log_error_errno(SYNTHETIC_ERRNO(ENOENT),
+                                       "Failed to find selected private key suitable for decryption on token.");
+        if (n_objects > 1)
+                return log_error_errno(SYNTHETIC_ERRNO(ENOTUNIQ),
+                                       "Configured private key URI matches multiple keys, refusing.");
+
+        *ret_object = objects[0];
+        return 0;
+}
+
+int pkcs11_token_decrypt_data(
+                CK_FUNCTION_LIST *m,
+                CK_SESSION_HANDLE session,
+                CK_OBJECT_HANDLE object,
+                const void *encrypted_data,
+                size_t encrypted_data_size,
+                void **ret_decrypted_data,
+                size_t *ret_decrypted_data_size) {
+
+        static const CK_MECHANISM mechanism = {
+                 .mechanism = CKM_RSA_PKCS
+        };
+        _cleanup_(erase_and_freep) CK_BYTE *dbuffer = NULL;
+        CK_ULONG dbuffer_size = 0;
+        CK_RV rv;
+
+        assert(m);
+        assert(encrypted_data);
+        assert(encrypted_data_size > 0);
+        assert(ret_decrypted_data);
+        assert(ret_decrypted_data_size);
+
+        rv = m->C_DecryptInit(session, (CK_MECHANISM*) &mechanism, object);
+        if (rv != CKR_OK)
+                return log_error_errno(SYNTHETIC_ERRNO(EIO),
+                                       "Failed to initialize decryption on security token: %s", p11_kit_strerror(rv));
+
+        dbuffer_size = encrypted_data_size; /* Start with something reasonable */
+        dbuffer = malloc(dbuffer_size);
+        if (!dbuffer)
+                return log_oom();
+
+        rv = m->C_Decrypt(session, (CK_BYTE*) encrypted_data, encrypted_data_size, dbuffer, &dbuffer_size);
+        if (rv == CKR_BUFFER_TOO_SMALL) {
+                erase_and_free(dbuffer);
+
+                dbuffer = malloc(dbuffer_size);
+                if (!dbuffer)
+                        return log_oom();
+
+                rv = m->C_Decrypt(session, (CK_BYTE*) encrypted_data, encrypted_data_size, dbuffer, &dbuffer_size);
+        }
+        if (rv != CKR_OK)
+                return log_error_errno(SYNTHETIC_ERRNO(EIO),
+                                       "Failed to decrypt key on security token: %s", p11_kit_strerror(rv));
+
+        log_info("Successfully decrypted key with security token.");
+
+        *ret_decrypted_data = TAKE_PTR(dbuffer);
+        *ret_decrypted_data_size = dbuffer_size;
+        return 0;
+}
+
+int pkcs11_token_acquire_rng(
+                CK_FUNCTION_LIST *m,
+                CK_SESSION_HANDLE session) {
+
+        _cleanup_free_ void *buffer = NULL;
+        _cleanup_close_ int fd = -1;
+        size_t rps;
+        CK_RV rv;
+        int r;
+
+        assert(m);
+
+        /* While we are at it, let's read some RNG data from the PKCS#11 token and pass it to the kernel
+         * random pool. This should be cheap if we are talking to the device already. Note that we don't
+         * credit any entropy, since we don't know about the quality of the pkcs#11 token's RNG. Why bother
+         * at all? There are two sides to the argument whether to generate private keys on tokens or on the
+         * host. By crediting some data from the token RNG to the host's pool we at least can say that any
+         * key generated from it is at least as good as both sources individually. */
+
+        rps = random_pool_size();
+
+        buffer = malloc(rps);
+        if (!buffer)
+                return log_oom();
+
+        rv = m->C_GenerateRandom(session, buffer, rps);
+        if (rv != CKR_OK)
+                return log_debug_errno(SYNTHETIC_ERRNO(EOPNOTSUPP),
+                                       "Failed to generate RNG data on security token: %s", p11_kit_strerror(rv));
+
+        fd = open("/dev/urandom", O_WRONLY|O_CLOEXEC|O_NOCTTY);
+        if (fd < 0)
+                return log_debug_errno(errno, "Failed to open /dev/urandom for writing: %m");
+
+        r = loop_write(fd, buffer, rps, false);
+        if (r < 0)
+                return log_debug_errno(r, "Failed to write PKCS#11 acquired random data to /dev/urandom: %m");
+
+        log_debug("Successfully written %zu bytes random data acquired via PKCS#11 to kernel random pool.", rps);
+
+        return 0;
+}
+
+static int token_process(
+                CK_FUNCTION_LIST *m,
+                CK_SLOT_ID slotid,
+                const CK_SLOT_INFO *slot_info,
+                const CK_TOKEN_INFO *token_info,
+                P11KitUri *search_uri,
+                pkcs11_find_token_callback_t callback,
+                void *userdata) {
+
+        _cleanup_free_ char *token_label = NULL;
+        CK_SESSION_HANDLE session;
+        CK_RV rv;
+        int r;
+
+        assert(m);
+        assert(slot_info);
+        assert(token_info);
+
+        token_label = pkcs11_token_label(token_info);
+        if (!token_label)
+                return log_oom();
+
+        rv = m->C_OpenSession(slotid, CKF_SERIAL_SESSION, NULL, NULL, &session);
+        if (rv != CKR_OK)
+                return log_error_errno(SYNTHETIC_ERRNO(EIO),
+                                       "Failed to create session for security token '%s': %s", token_label, p11_kit_strerror(rv));
+
+        if (callback)
+                r = callback(m, session, slotid, slot_info, token_info, search_uri, userdata);
+        else
+                r = 1; /* if not callback was specified, just say we found what we were looking for */
+
+        rv = m->C_CloseSession(session);
+        if (rv != CKR_OK)
+                log_warning("Failed to close session on PKCS#11 token, ignoring: %s", p11_kit_strerror(rv));
+
+        return r;
+}
+
+static int slot_process(
+                CK_FUNCTION_LIST *m,
+                CK_SLOT_ID slotid,
+                P11KitUri *search_uri,
+                pkcs11_find_token_callback_t callback,
+                void *userdata) {
+
+        _cleanup_(p11_kit_uri_freep) P11KitUri* slot_uri = NULL, *token_uri = NULL;
+        _cleanup_free_ char *token_uri_string = NULL;
+        CK_TOKEN_INFO token_info;
+        CK_SLOT_INFO slot_info;
+        int uri_result;
+        CK_RV rv;
+
+        assert(m);
+
+        /* We return -EAGAIN for all failures we can attribute to a specific slot in some way, so that the
+         * caller might try other slots before giving up. */
+
+        rv = m->C_GetSlotInfo(slotid, &slot_info);
+        if (rv != CKR_OK) {
+                log_warning("Failed to acquire slot info for slot %lu, ignoring slot: %s", slotid, p11_kit_strerror(rv));
+                return -EAGAIN;
+        }
+
+        slot_uri = uri_from_slot_info(&slot_info);
+        if (!slot_uri)
+                return log_oom();
+
+        if (DEBUG_LOGGING) {
+                _cleanup_free_ char *slot_uri_string = NULL;
+
+                uri_result = p11_kit_uri_format(slot_uri, P11_KIT_URI_FOR_ANY, &slot_uri_string);
+                if (uri_result != P11_KIT_URI_OK) {
+                        log_warning("Failed to format slot URI, ignoring slot: %s", p11_kit_uri_message(uri_result));
+                        return -EAGAIN;
+                }
+
+                log_debug("Found slot with URI %s", slot_uri_string);
+        }
+
+        rv = m->C_GetTokenInfo(slotid, &token_info);
+        if (rv == CKR_TOKEN_NOT_PRESENT) {
+                return log_debug_errno(SYNTHETIC_ERRNO(EAGAIN),
+                                       "Token not present in slot, ignoring.");
+        } else if (rv != CKR_OK) {
+                log_warning("Failed to acquire token info for slot %lu, ignoring slot: %s", slotid, p11_kit_strerror(rv));
+                return -EAGAIN;
+        }
+
+        token_uri = uri_from_token_info(&token_info);
+        if (!token_uri)
+                return log_oom();
+
+        uri_result = p11_kit_uri_format(token_uri, P11_KIT_URI_FOR_ANY, &token_uri_string);
+        if (uri_result != P11_KIT_URI_OK) {
+                log_warning("Failed to format slot URI: %s", p11_kit_uri_message(uri_result));
+                return -EAGAIN;
+        }
+
+        if (search_uri && !p11_kit_uri_match_token_info(search_uri, &token_info))
+                return log_debug_errno(SYNTHETIC_ERRNO(EAGAIN),
+                                       "Found non-matching token with URI %s.",
+                                       token_uri_string);
+
+        log_debug("Found matching token with URI %s.", token_uri_string);
+
+        return token_process(
+                        m,
+                        slotid,
+                        &slot_info,
+                        &token_info,
+                        search_uri,
+                        callback,
+                        userdata);
+}
+
+static int module_process(
+                CK_FUNCTION_LIST *m,
+                P11KitUri *search_uri,
+                pkcs11_find_token_callback_t callback,
+                void *userdata) {
+
+        _cleanup_free_ char *name = NULL, *module_uri_string = NULL;
+        _cleanup_(p11_kit_uri_freep) P11KitUri* module_uri = NULL;
+        _cleanup_free_ CK_SLOT_ID *slotids = NULL;
+        CK_ULONG n_slotids = 0;
+        int uri_result;
+        CK_INFO info;
+        size_t k;
+        CK_RV rv;
+        int r;
+
+        assert(m);
+
+        /* We ignore most errors from modules here, in order to skip over faulty modules: one faulty module
+         * should not have the effect that we don't try the others anymore. We indicate such per-module
+         * failures with -EAGAIN, which let's the caller try the next module. */
+
+        name = p11_kit_module_get_name(m);
+        if (!name)
+                return log_oom();
+
+        log_debug("Trying PKCS#11 module %s.", name);
+
+        rv = m->C_GetInfo(&info);
+        if (rv != CKR_OK) {
+                log_warning("Failed to get info on PKCS#11 module, ignoring module: %s", p11_kit_strerror(rv));
+                return -EAGAIN;
+        }
+
+        module_uri = uri_from_module_info(&info);
+        if (!module_uri)
+                return log_oom();
+
+        uri_result = p11_kit_uri_format(module_uri, P11_KIT_URI_FOR_ANY, &module_uri_string);
+        if (uri_result != P11_KIT_URI_OK) {
+                log_warning("Failed to format module URI, ignoring module: %s", p11_kit_uri_message(uri_result));
+                return -EAGAIN;
+        }
+
+        log_debug("Found module with URI %s", module_uri_string);
+
+        rv = pkcs11_get_slot_list_malloc(m, &slotids, &n_slotids);
+        if (rv != CKR_OK) {
+                log_warning("Failed to get slot list, ignoring module: %s", p11_kit_strerror(rv));
+                return -EAGAIN;
+        }
+        if (n_slotids == 0)
+                return log_debug_errno(SYNTHETIC_ERRNO(EAGAIN),
+                                       "This module has no slots? Ignoring module.");
+
+        for (k = 0; k < n_slotids; k++) {
+                r = slot_process(
+                                m,
+                                slotids[k],
+                                search_uri,
+                                callback,
+                                userdata);
+                if (r != -EAGAIN)
+                        return r;
+        }
+
+        return -EAGAIN;
+}
+
+int pkcs11_find_token(
+                const char *pkcs11_uri,
+                pkcs11_find_token_callback_t callback,
+                void *userdata) {
+
+        _cleanup_(p11_kit_modules_finalize_and_releasep) CK_FUNCTION_LIST **modules = NULL;
+        _cleanup_(p11_kit_uri_freep) P11KitUri *search_uri = NULL;
+        int r;
+
+        /* Execute the specified callback for each matching token found. If nothing is found returns
+         * -EAGAIN. Logs about all errors, except for EAGAIN, which the caller has to log about. */
+
+        if (pkcs11_uri) {
+                r = uri_from_string(pkcs11_uri, &search_uri);
+                if (r < 0)
+                        return log_error_errno(r, "Failed to parse PKCS#11 URI '%s': %m", pkcs11_uri);
+        }
+
+        modules = p11_kit_modules_load_and_initialize(0);
+        if (!modules)
+                return log_error_errno(SYNTHETIC_ERRNO(EIO), "Failed to initialize pkcs11 modules");
+
+        for (CK_FUNCTION_LIST **i = modules; *i; i++) {
+                r = module_process(
+                                *i,
+                                search_uri,
+                                callback,
+                                userdata);
+                if (r != -EAGAIN)
+                        return r;
+        }
+
+        return -EAGAIN;
+}
+
+#endif