schemas.c

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/*
 * Copyright 2004-2023 the Pacemaker project contributors
 *
 * The version control history for this file may have further details.
 *
 * This source code is licensed under the GNU Lesser General Public License
 * version 2.1 or later (LGPLv2.1+) WITHOUT ANY WARRANTY.
 */

#include <crm_internal.h>

#include <stdio.h>
#include <string.h>
#include <dirent.h>
#include <errno.h>
#include <sys/stat.h>
#include <stdarg.h>

#include <libxml/relaxng.h>
#include <libxslt/xslt.h>
#include <libxslt/transform.h>
#include <libxslt/security.h>
#include <libxslt/xsltutils.h>

#include <crm/msg_xml.h>
#include <crm/common/xml.h>
#include <crm/common/xml_internal.h>  /* PCMK__XML_LOG_BASE */

typedef struct {
    unsigned char v[2];
} schema_version_t;

#define SCHEMA_ZERO { .v = { 0, 0 } }

#define schema_scanf(s, prefix, version, suffix) \
    sscanf((s), prefix "%hhu.%hhu" suffix, &((version).v[0]), &((version).v[1]))

#define schema_strdup_printf(prefix, version, suffix) \
    crm_strdup_printf(prefix "%u.%u" suffix, (version).v[0], (version).v[1])

typedef struct {
    xmlRelaxNGPtr rng;
    xmlRelaxNGValidCtxtPtr valid;
    xmlRelaxNGParserCtxtPtr parser;
} relaxng_ctx_cache_t;

enum schema_validator_e {
    schema_validator_none,
    schema_validator_rng
};

struct schema_s {
    char *name;
    char *transform;
    void *cache;
    enum schema_validator_e validator;
    int after_transform;
    schema_version_t version;
    char *transform_enter;
    bool transform_onleave;
};

static struct schema_s *known_schemas = NULL;
static int xml_schema_max = 0;
static bool silent_logging = FALSE;

static void
xml_log(int priority, const char *fmt, ...)
G_GNUC_PRINTF(2, 3);

static void
xml_log(int priority, const char *fmt, ...)
{
    va_list ap;

    va_start(ap, fmt);
    if (silent_logging == FALSE) {
        /* XXX should not this enable dechunking as well? */
        PCMK__XML_LOG_BASE(priority, FALSE, 0, NULL, fmt, ap);
    }
    va_end(ap);
}

static int
xml_latest_schema_index(void)
{
    // @COMPAT: pacemaker-next is deprecated since 2.1.5
    return xml_schema_max - 3; // index from 0, ignore "pacemaker-next"/"none"
}

static int
xml_minimum_schema_index(void)
{
    static int best = 0;
    if (best == 0) {
        int lpc = 0;

        best = xml_latest_schema_index();
        for (lpc = best; lpc > 0; lpc--) {
            if (known_schemas[lpc].version.v[0]
                < known_schemas[best].version.v[0]) {
                return best;
            } else {
                best = lpc;
            }
        }
        best = xml_latest_schema_index();
    }
    return best;
}

const char *
xml_latest_schema(void)
{
    return get_schema_name(xml_latest_schema_index());
}

static inline bool
version_from_filename(const char *filename, schema_version_t *version)
{
    int rc = schema_scanf(filename, "pacemaker-", *version, ".rng");

    return (rc == 2);
}

static int
schema_filter(const struct dirent *a)
{
    int rc = 0;
    schema_version_t version = SCHEMA_ZERO;

    if (strstr(a->d_name, "pacemaker-") != a->d_name) {
        /* crm_trace("%s - wrong prefix", a->d_name); */

    } else if (!pcmk__ends_with_ext(a->d_name, ".rng")) {
        /* crm_trace("%s - wrong suffix", a->d_name); */

    } else if (!version_from_filename(a->d_name, &version)) {
        /* crm_trace("%s - wrong format", a->d_name); */

    } else {
        /* crm_debug("%s - candidate", a->d_name); */
        rc = 1;
    }

    return rc;
}

static int
schema_sort(const struct dirent **a, const struct dirent **b)
{
    schema_version_t a_version = SCHEMA_ZERO;
    schema_version_t b_version = SCHEMA_ZERO;

    if (!version_from_filename(a[0]->d_name, &a_version)
        || !version_from_filename(b[0]->d_name, &b_version)) {
        // Shouldn't be possible, but makes static analysis happy
        return 0;
    }

    for (int i = 0; i < 2; ++i) {
        if (a_version.v[i] < b_version.v[i]) {
            return -1;
        } else if (a_version.v[i] > b_version.v[i]) {
            return 1;
        }
    }
    return 0;
}

static void
add_schema(enum schema_validator_e validator, const schema_version_t *version,
           const char *name, const char *transform,
           const char *transform_enter, bool transform_onleave,
           int after_transform)
{
    int last = xml_schema_max;
    bool have_version = FALSE;

    xml_schema_max++;
    known_schemas = pcmk__realloc(known_schemas,
                                  xml_schema_max * sizeof(struct schema_s));
    CRM_ASSERT(known_schemas != NULL);
    memset(known_schemas+last, 0, sizeof(struct schema_s));
    known_schemas[last].validator = validator;
    known_schemas[last].after_transform = after_transform;

    for (int i = 0; i < 2; ++i) {
        known_schemas[last].version.v[i] = version->v[i];
        if (version->v[i]) {
            have_version = TRUE;
        }
    }
    if (have_version) {
        known_schemas[last].name = schema_strdup_printf("pacemaker-", *version, "");
    } else {
        CRM_ASSERT(name);
        schema_scanf(name, "%*[^-]-", known_schemas[last].version, "");
        known_schemas[last].name = strdup(name);
    }

    if (transform) {
        known_schemas[last].transform = strdup(transform);
    }
    if (transform_enter) {
        known_schemas[last].transform_enter = strdup(transform_enter);
    }
    known_schemas[last].transform_onleave = transform_onleave;
    if (after_transform == 0) {
        after_transform = xml_schema_max;  /* upgrade is a one-way */
    }
    known_schemas[last].after_transform = after_transform;

    if (known_schemas[last].after_transform < 0) {
        crm_debug("Added supported schema %d: %s",
                  last, known_schemas[last].name);

    } else if (known_schemas[last].transform) {
        crm_debug("Added supported schema %d: %s (upgrades to %d with %s.xsl)",
                  last, known_schemas[last].name,
                  known_schemas[last].after_transform,
                  known_schemas[last].transform);

    } else {
        crm_debug("Added supported schema %d: %s (upgrades to %d)",
                  last, known_schemas[last].name,
                  known_schemas[last].after_transform);
    }
}

static int
add_schema_by_version(const schema_version_t *version, int next,
                      bool transform_expected)
{
    bool transform_onleave = FALSE;
    int rc = pcmk_rc_ok;
    struct stat s;
    char *xslt = NULL,
         *transform_upgrade = NULL,
         *transform_enter = NULL;

    /* prologue for further transform_expected handling */
    if (transform_expected) {
        /* check if there's suitable "upgrade" stylesheet */
        transform_upgrade = schema_strdup_printf("upgrade-", *version, );
        xslt = pcmk__xml_artefact_path(pcmk__xml_artefact_ns_legacy_xslt,
                                       transform_upgrade);
    }

    if (!transform_expected) {
        /* jump directly to the end */

    } else if (stat(xslt, &s) == 0) {
        /* perhaps there's also a targeted "upgrade-enter" stylesheet */
        transform_enter = schema_strdup_printf("upgrade-", *version, "-enter");
        free(xslt);
        xslt = pcmk__xml_artefact_path(pcmk__xml_artefact_ns_legacy_xslt,
                                       transform_enter);
        if (stat(xslt, &s) != 0) {
            /* or initially, at least a generic one */
            crm_debug("Upgrade-enter transform %s.xsl not found", xslt);
            free(xslt);
            free(transform_enter);
            transform_enter = strdup("upgrade-enter");
            xslt = pcmk__xml_artefact_path(pcmk__xml_artefact_ns_legacy_xslt,
                                           transform_enter);
            if (stat(xslt, &s) != 0) {
                crm_debug("Upgrade-enter transform %s.xsl not found, either", xslt);
                free(xslt);
                xslt = NULL;
            }
        }
        /* xslt contains full path to "upgrade-enter" stylesheet */
        if (xslt != NULL) {
            /* then there should be "upgrade-leave" counterpart (enter->leave) */
            memcpy(strrchr(xslt, '-') + 1, "leave", sizeof("leave") - 1);
            transform_onleave = (stat(xslt, &s) == 0);
            free(xslt);
        } else {
            free(transform_enter);
            transform_enter = NULL;
        }

    } else {
        crm_err("Upgrade transform %s not found", xslt);
        free(xslt);
        free(transform_upgrade);
        transform_upgrade = NULL;
        next = -1;
        rc = ENOENT;
    }

    add_schema(schema_validator_rng, version, NULL,
               transform_upgrade, transform_enter, transform_onleave, next);

    free(transform_upgrade);
    free(transform_enter);

    return rc;
}

static void
wrap_libxslt(bool finalize)
{
    static xsltSecurityPrefsPtr secprefs;
    int ret = 0;

    /* security framework preferences */
    if (!finalize) {
        CRM_ASSERT(secprefs == NULL);
        secprefs = xsltNewSecurityPrefs();
        ret = xsltSetSecurityPrefs(secprefs, XSLT_SECPREF_WRITE_FILE,
                                   xsltSecurityForbid)
              | xsltSetSecurityPrefs(secprefs, XSLT_SECPREF_CREATE_DIRECTORY,
                                     xsltSecurityForbid)
              | xsltSetSecurityPrefs(secprefs, XSLT_SECPREF_READ_NETWORK,
                                     xsltSecurityForbid)
              | xsltSetSecurityPrefs(secprefs, XSLT_SECPREF_WRITE_NETWORK,
                                     xsltSecurityForbid);
        if (ret != 0) {
            return;
        }
    } else {
        xsltFreeSecurityPrefs(secprefs);
        secprefs = NULL;
    }

    /* cleanup only */
    if (finalize) {
        xsltCleanupGlobals();
    }
}

void
crm_schema_init(void)
{
    int lpc, max;
    char *base = pcmk__xml_artefact_root(pcmk__xml_artefact_ns_legacy_rng);
    struct dirent **namelist = NULL;
    const schema_version_t zero = SCHEMA_ZERO;

    wrap_libxslt(false);

    max = scandir(base, &namelist, schema_filter, schema_sort);
    if (max < 0) {
        crm_notice("scandir(%s) failed: %s (%d)", base, strerror(errno), errno);
        free(base);

    } else {
        free(base);
        for (lpc = 0; lpc < max; lpc++) {
            bool transform_expected = FALSE;
            int next = 0;
            schema_version_t version = SCHEMA_ZERO;

            if (!version_from_filename(namelist[lpc]->d_name, &version)) {
                // Shouldn't be possible, but makes static analysis happy
                crm_err("Skipping schema '%s': could not parse version",
                        namelist[lpc]->d_name);
                continue;
            }
            if ((lpc + 1) < max) {
                schema_version_t next_version = SCHEMA_ZERO;

                if (version_from_filename(namelist[lpc+1]->d_name, &next_version)
                        && (version.v[0] < next_version.v[0])) {
                    transform_expected = TRUE;
                }

            } else {
                next = -1;
            }
            if (add_schema_by_version(&version, next, transform_expected)
                    == ENOENT) {
                break;
            }
        }

        for (lpc = 0; lpc < max; lpc++) {
            free(namelist[lpc]);
        }
        free(namelist);
    }

    // @COMPAT: Deprecated since 2.1.5
    add_schema(schema_validator_rng, &zero, "pacemaker-next",
               NULL, NULL, FALSE, -1);

    add_schema(schema_validator_none, &zero, PCMK__VALUE_NONE,
               NULL, NULL, FALSE, -1);
}

static gboolean
validate_with_relaxng(xmlDocPtr doc, xmlRelaxNGValidityErrorFunc error_handler, void *error_handler_context, const char *relaxng_file,
                      relaxng_ctx_cache_t **cached_ctx)
{
    int rc = 0;
    gboolean valid = TRUE;
    relaxng_ctx_cache_t *ctx = NULL;

    CRM_CHECK(doc != NULL, return FALSE);
    CRM_CHECK(relaxng_file != NULL, return FALSE);

    if (cached_ctx && *cached_ctx) {
        ctx = *cached_ctx;

    } else {
        crm_debug("Creating RNG parser context");
        ctx = calloc(1, sizeof(relaxng_ctx_cache_t));

        ctx->parser = xmlRelaxNGNewParserCtxt(relaxng_file);
        CRM_CHECK(ctx->parser != NULL, goto cleanup);

        if (error_handler) {
            xmlRelaxNGSetParserErrors(ctx->parser,
                                      (xmlRelaxNGValidityErrorFunc) error_handler,
                                      (xmlRelaxNGValidityWarningFunc) error_handler,
                                      error_handler_context);
        } else {
            xmlRelaxNGSetParserErrors(ctx->parser,
                                      (xmlRelaxNGValidityErrorFunc) fprintf,
                                      (xmlRelaxNGValidityWarningFunc) fprintf,
                                      stderr);
        }

        ctx->rng = xmlRelaxNGParse(ctx->parser);
        CRM_CHECK(ctx->rng != NULL,
                  crm_err("Could not find/parse %s", relaxng_file);
                  goto cleanup);

        ctx->valid = xmlRelaxNGNewValidCtxt(ctx->rng);
        CRM_CHECK(ctx->valid != NULL, goto cleanup);

        if (error_handler) {
            xmlRelaxNGSetValidErrors(ctx->valid,
                                     (xmlRelaxNGValidityErrorFunc) error_handler,
                                     (xmlRelaxNGValidityWarningFunc) error_handler,
                                     error_handler_context);
        } else {
            xmlRelaxNGSetValidErrors(ctx->valid,
                                     (xmlRelaxNGValidityErrorFunc) fprintf,
                                     (xmlRelaxNGValidityWarningFunc) fprintf,
                                     stderr);
        }
    }

    rc = xmlRelaxNGValidateDoc(ctx->valid, doc);
    if (rc > 0) {
        valid = FALSE;

    } else if (rc < 0) {
        crm_err("Internal libxml error during validation");
    }

  cleanup:

    if (cached_ctx) {
        *cached_ctx = ctx;

    } else {
        if (ctx->parser != NULL) {
            xmlRelaxNGFreeParserCtxt(ctx->parser);
        }
        if (ctx->valid != NULL) {
            xmlRelaxNGFreeValidCtxt(ctx->valid);
        }
        if (ctx->rng != NULL) {
            xmlRelaxNGFree(ctx->rng);
        }
        free(ctx);
    }

    return valid;
}

void
crm_schema_cleanup(void)
{
    int lpc;
    relaxng_ctx_cache_t *ctx = NULL;

    for (lpc = 0; lpc < xml_schema_max; lpc++) {

        switch (known_schemas[lpc].validator) {
            case schema_validator_none: // not cached
                break;
            case schema_validator_rng: // cached
                ctx = (relaxng_ctx_cache_t *) known_schemas[lpc].cache;
                if (ctx == NULL) {
                    break;
                }
                if (ctx->parser != NULL) {
                    xmlRelaxNGFreeParserCtxt(ctx->parser);
                }
                if (ctx->valid != NULL) {
                    xmlRelaxNGFreeValidCtxt(ctx->valid);
                }
                if (ctx->rng != NULL) {
                    xmlRelaxNGFree(ctx->rng);
                }
                free(ctx);
                known_schemas[lpc].cache = NULL;
                break;
        }
        free(known_schemas[lpc].name);
        free(known_schemas[lpc].transform);
        free(known_schemas[lpc].transform_enter);
    }
    free(known_schemas);
    known_schemas = NULL;

    wrap_libxslt(true);
}

static gboolean
validate_with(xmlNode *xml, int method, xmlRelaxNGValidityErrorFunc error_handler, void* error_handler_context)
{
    gboolean valid = FALSE;
    char *file = NULL;
    struct schema_s *schema = NULL;
    relaxng_ctx_cache_t **cache = NULL;

    if (method < 0) {
        return FALSE;
    }

    schema = &(known_schemas[method]);
    if (schema->validator == schema_validator_none) {
        return TRUE;
    }

    if (pcmk__str_eq(schema->name, "pacemaker-next", pcmk__str_none)) {
        crm_warn("The pacemaker-next schema is deprecated and will be removed "
                 "in a future release.");
    }

    file = pcmk__xml_artefact_path(pcmk__xml_artefact_ns_legacy_rng,
                                   schema->name);

    crm_trace("Validating with %s (type=%d)",
              pcmk__s(file, "missing schema"), schema->validator);
    switch (schema->validator) {
        case schema_validator_rng:
            cache = (relaxng_ctx_cache_t **) &(schema->cache);
            valid = validate_with_relaxng(xml->doc, error_handler, error_handler_context, file, cache);
            break;
        default:
            crm_err("Unknown validator type: %d",
                    known_schemas[method].validator);
            break;
    }

    free(file);
    return valid;
}

static bool
validate_with_silent(xmlNode *xml, int method)
{
    bool rc, sl_backup = silent_logging;
    silent_logging = TRUE;
    rc = validate_with(xml, method, (xmlRelaxNGValidityErrorFunc) xml_log, GUINT_TO_POINTER(LOG_ERR));
    silent_logging = sl_backup;
    return rc;
}

static void
dump_file(const char *filename)
{

    FILE *fp = NULL;
    int ch, line = 0;

    CRM_CHECK(filename != NULL, return);

    fp = fopen(filename, "r");
    if (fp == NULL) {
        crm_perror(LOG_ERR, "Could not open %s for reading", filename);
        return;
    }

    fprintf(stderr, "%4d ", ++line);
    do {
        ch = getc(fp);
        if (ch == EOF) {
            putc('\n', stderr);
            break;
        } else if (ch == '\n') {
            fprintf(stderr, "\n%4d ", ++line);
        } else {
            putc(ch, stderr);
        }
    } while (1);

    fclose(fp);
}

gboolean
validate_xml_verbose(const xmlNode *xml_blob)
{
    int fd = 0;
    xmlDoc *doc = NULL;
    xmlNode *xml = NULL;
    gboolean rc = FALSE;
    char *filename = NULL;

    filename = crm_strdup_printf("%s/cib-invalid.XXXXXX", pcmk__get_tmpdir());

    umask(S_IWGRP | S_IWOTH | S_IROTH);
    fd = mkstemp(filename);
    write_xml_fd(xml_blob, filename, fd, FALSE);

    dump_file(filename);

    doc = xmlReadFile(filename, NULL, 0);
    xml = xmlDocGetRootElement(doc);
    rc = validate_xml(xml, NULL, FALSE);
    free_xml(xml);

    unlink(filename);
    free(filename);

    return rc;
}

gboolean
validate_xml(xmlNode *xml_blob, const char *validation, gboolean to_logs)
{
    return pcmk__validate_xml(xml_blob, validation, to_logs ? (xmlRelaxNGValidityErrorFunc) xml_log : NULL, GUINT_TO_POINTER(LOG_ERR));
}

gboolean
pcmk__validate_xml(xmlNode *xml_blob, const char *validation, xmlRelaxNGValidityErrorFunc error_handler, void* error_handler_context)
{
    int version = 0;

    CRM_CHECK((xml_blob != NULL) && (xml_blob->doc != NULL), return FALSE);

    if (validation == NULL) {
        validation = crm_element_value(xml_blob, XML_ATTR_VALIDATION);
    }

    if (validation == NULL) {
        int lpc = 0;
        bool valid = FALSE;

        for (lpc = 0; lpc < xml_schema_max; lpc++) {
            if (validate_with(xml_blob, lpc, NULL, NULL)) {
                valid = TRUE;
                crm_xml_add(xml_blob, XML_ATTR_VALIDATION,
                            known_schemas[lpc].name);
                crm_info("XML validated against %s", known_schemas[lpc].name);
                if(known_schemas[lpc].after_transform == 0) {
                    break;
                }
            }
        }

        return valid;
    }

    version = get_schema_version(validation);
    if (strcmp(validation, PCMK__VALUE_NONE) == 0) {
        return TRUE;
    } else if (version < xml_schema_max) {
        return validate_with(xml_blob, version, error_handler, error_handler_context);
    }

    crm_err("Unknown validator: %s", validation);
    return FALSE;
}

static void
cib_upgrade_err(void *ctx, const char *fmt, ...)
G_GNUC_PRINTF(2, 3);

/* With this arrangement, an attempt to identify the message severity
   as explicitly signalled directly from XSLT is performed in rather
   a smart way (no reliance on formatting string + arguments being
   always specified as ["%s", purposeful_string], as it can also be
   ["%s: %s", some_prefix, purposeful_string] etc. so every argument
   pertaining %s specifier is investigated), and if such a mark found,
   the respective level is determined and, when the messages are to go
   to the native logs, the mark itself gets dropped
   (by the means of string shift).

   NOTE: whether the native logging is the right sink is decided per
         the ctx parameter -- NULL denotes this case, otherwise it
         carries a pointer to the numeric expression of the desired
         target logging level (messages with higher level will be
         suppressed)

   NOTE: on some architectures, this string shift may not have any
         effect, but that's an acceptable tradeoff

   The logging level for not explicitly designated messages
   (suspicious, likely internal errors or some runaways) is
   LOG_WARNING.
 */
static void
cib_upgrade_err(void *ctx, const char *fmt, ...)
{
    va_list ap, aq;
    char *arg_cur;

    bool found = FALSE;
    const char *fmt_iter = fmt;
    uint8_t msg_log_level = LOG_WARNING;  /* default for runaway messages */
    const unsigned * log_level = (const unsigned *) ctx;
    enum {
        escan_seennothing,
        escan_seenpercent,
    } scan_state = escan_seennothing;

    va_start(ap, fmt);
    va_copy(aq, ap);

    while (!found && *fmt_iter != '\0') {
        /* while casing schema borrowed from libqb:qb_vsnprintf_serialize */
        switch (*fmt_iter++) {
        case '%':
            if (scan_state == escan_seennothing) {
                scan_state = escan_seenpercent;
            } else if (scan_state == escan_seenpercent) {
                scan_state = escan_seennothing;
            }
            break;
        case 's':
            if (scan_state == escan_seenpercent) {
                scan_state = escan_seennothing;
                arg_cur = va_arg(aq, char *);
                if (arg_cur != NULL) {
                    switch (arg_cur[0]) {
                    case 'W':
                        if (!strncmp(arg_cur, "WARNING: ",
                                     sizeof("WARNING: ") - 1)) {
                            msg_log_level = LOG_WARNING;
                        }
                        if (ctx == NULL) {
                            memmove(arg_cur, arg_cur + sizeof("WARNING: ") - 1,
                                    strlen(arg_cur + sizeof("WARNING: ") - 1) + 1);
                        }
                        found = TRUE;
                        break;
                    case 'I':
                        if (!strncmp(arg_cur, "INFO: ",
                                     sizeof("INFO: ") - 1)) {
                            msg_log_level = LOG_INFO;
                        }
                        if (ctx == NULL) {
                            memmove(arg_cur, arg_cur + sizeof("INFO: ") - 1,
                                    strlen(arg_cur + sizeof("INFO: ") - 1) + 1);
                        }
                        found = TRUE;
                        break;
                    case 'D':
                        if (!strncmp(arg_cur, "DEBUG: ",
                                     sizeof("DEBUG: ") - 1)) {
                            msg_log_level = LOG_DEBUG;
                        }
                        if (ctx == NULL) {
                            memmove(arg_cur, arg_cur + sizeof("DEBUG: ") - 1,
                                    strlen(arg_cur + sizeof("DEBUG: ") - 1) + 1);
                        }
                        found = TRUE;
                        break;
                    }
                }
            }
            break;
        case '#': case '-': case ' ': case '+': case '\'': case 'I': case '.':
        case '0': case '1': case '2': case '3': case '4':
        case '5': case '6': case '7': case '8': case '9':
        case '*':
            break;
        case 'l':
        case 'z':
        case 't':
        case 'j':
        case 'd': case 'i':
        case 'o':
        case 'u':
        case 'x': case 'X':
        case 'e': case 'E':
        case 'f': case 'F':
        case 'g': case 'G':
        case 'a': case 'A':
        case 'c':
        case 'p':
            if (scan_state == escan_seenpercent) {
                (void) va_arg(aq, void *);  /* skip forward */
                scan_state = escan_seennothing;
            }
            break;
        default:
            scan_state = escan_seennothing;
            break;
        }
    }

    if (log_level != NULL) {
        /* intention of the following offset is:
           cibadmin -V -> start showing INFO labelled messages */
        if (*log_level + 4 >= msg_log_level) {
            vfprintf(stderr, fmt, ap);
        }
    } else {
        PCMK__XML_LOG_BASE(msg_log_level, TRUE, 0, "CIB upgrade: ", fmt, ap);
    }

    va_end(aq);
    va_end(ap);
}

static xmlNode *
apply_transformation(xmlNode *xml, const char *transform, gboolean to_logs)
{
    char *xform = NULL;
    xmlNode *out = NULL;
    xmlDocPtr res = NULL;
    xsltStylesheet *xslt = NULL;

    xform = pcmk__xml_artefact_path(pcmk__xml_artefact_ns_legacy_xslt,
                                    transform);

    /* for capturing, e.g., what's emitted via <xsl:message> */
    if (to_logs) {
        xsltSetGenericErrorFunc(NULL, cib_upgrade_err);
    } else {
        xsltSetGenericErrorFunc(&crm_log_level, cib_upgrade_err);
    }

    xslt = xsltParseStylesheetFile((pcmkXmlStr) xform);
    CRM_CHECK(xslt != NULL, goto cleanup);

    res = xsltApplyStylesheet(xslt, xml->doc, NULL);
    CRM_CHECK(res != NULL, goto cleanup);

    xsltSetGenericErrorFunc(NULL, NULL);  /* restore default one */

    out = xmlDocGetRootElement(res);

  cleanup:
    if (xslt) {
        xsltFreeStylesheet(xslt);
    }

    free(xform);

    return out;
}

static xmlNode *
apply_upgrade(xmlNode *xml, const struct schema_s *schema, gboolean to_logs)
{
    bool transform_onleave = schema->transform_onleave;
    char *transform_leave;
    xmlNode *upgrade = NULL,
            *final = NULL;

    if (schema->transform_enter) {
        crm_debug("Upgrading %s-style configuration, pre-upgrade phase with %s.xsl",
                  schema->name, schema->transform_enter);
        upgrade = apply_transformation(xml, schema->transform_enter, to_logs);
        if (upgrade == NULL) {
            crm_warn("Upgrade-enter transformation %s.xsl failed",
                     schema->transform_enter);
            transform_onleave = FALSE;
        }
    }
    if (upgrade == NULL) {
        upgrade = xml;
    }

    crm_debug("Upgrading %s-style configuration, main phase with %s.xsl",
              schema->name, schema->transform);
    final = apply_transformation(upgrade, schema->transform, to_logs);
    if (upgrade != xml) {
        free_xml(upgrade);
        upgrade = NULL;
    }

    if (final != NULL && transform_onleave) {
        upgrade = final;
        /* following condition ensured in add_schema_by_version */
        CRM_ASSERT(schema->transform_enter != NULL);
        transform_leave = strdup(schema->transform_enter);
        /* enter -> leave */
        memcpy(strrchr(transform_leave, '-') + 1, "leave", sizeof("leave") - 1);
        crm_debug("Upgrading %s-style configuration, post-upgrade phase with %s.xsl",
                  schema->name, transform_leave);
        final = apply_transformation(upgrade, transform_leave, to_logs);
        if (final == NULL) {
            crm_warn("Upgrade-leave transformation %s.xsl failed", transform_leave);
            final = upgrade;
        } else {
            free_xml(upgrade);
        }
        free(transform_leave);
    }

    return final;
}

const char *
get_schema_name(int version)
{
    if (version < 0 || version >= xml_schema_max) {
        return "unknown";
    }
    return known_schemas[version].name;
}

int
get_schema_version(const char *name)
{
    int lpc = 0;

    if (name == NULL) {
        name = PCMK__VALUE_NONE;
    }
    for (; lpc < xml_schema_max; lpc++) {
        if (pcmk__str_eq(name, known_schemas[lpc].name, pcmk__str_casei)) {
            return lpc;
        }
    }
    return -1;
}

/* set which validation to use */
int
update_validation(xmlNode **xml_blob, int *best, int max, gboolean transform,
                  gboolean to_logs)
{
    xmlNode *xml = NULL;
    char *value = NULL;
    int max_stable_schemas = xml_latest_schema_index();
    int lpc = 0, match = -1, rc = pcmk_ok;
    int next = -1;  /* -1 denotes "inactive" value */
    xmlRelaxNGValidityErrorFunc error_handler = 
        to_logs ? (xmlRelaxNGValidityErrorFunc) xml_log : NULL;

    CRM_CHECK(best != NULL, return -EINVAL);
    *best = 0;

    CRM_CHECK((xml_blob != NULL) && (*xml_blob != NULL)
              && ((*xml_blob)->doc != NULL),
              return -EINVAL);

    xml = *xml_blob;
    value = crm_element_value_copy(xml, XML_ATTR_VALIDATION);

    if (value != NULL) {
        match = get_schema_version(value);

        lpc = match;
        if (lpc >= 0 && transform == FALSE) {
            *best = lpc++;

        } else if (lpc < 0) {
            crm_debug("Unknown validation schema");
            lpc = 0;
        }
    }

    if (match >= max_stable_schemas) {
        /* nothing to do */
        free(value);
        *best = match;
        return pcmk_ok;
    }

    while (lpc <= max_stable_schemas) {
        crm_debug("Testing '%s' validation (%d of %d)",
                  known_schemas[lpc].name ? known_schemas[lpc].name : "<unset>",
                  lpc, max_stable_schemas);

        if (validate_with(xml, lpc, error_handler, GUINT_TO_POINTER(LOG_ERR)) == FALSE) {
            if (next != -1) {
                crm_info("Configuration not valid for schema: %s",
                         known_schemas[lpc].name);
                next = -1;
            } else {
                crm_trace("%s validation failed",
                          known_schemas[lpc].name ? known_schemas[lpc].name : "<unset>");
            }
            if (*best) {
                /* we've satisfied the validation, no need to check further */
                break;
            }
            rc = -pcmk_err_schema_validation;

        } else {
            if (next != -1) {
                crm_debug("Configuration valid for schema: %s",
                          known_schemas[next].name);
                next = -1;
            }
            rc = pcmk_ok;
        }

        if (rc == pcmk_ok) {
            *best = lpc;
        }

        if (rc == pcmk_ok && transform) {
            xmlNode *upgrade = NULL;
            next = known_schemas[lpc].after_transform;

            if (next <= lpc) {
                /* There is no next version, or next would regress */
                crm_trace("Stopping at %s", known_schemas[lpc].name);
                break;

            } else if (max > 0 && (lpc == max || next > max)) {
                crm_trace("Upgrade limit reached at %s (lpc=%d, next=%d, max=%d)",
                          known_schemas[lpc].name, lpc, next, max);
                break;

            } else if (known_schemas[lpc].transform == NULL
                       /* possibly avoid transforming when readily valid
                          (in general more restricted when crossing the major
                          version boundary, as X.0 "transitional" version is
                          expected to be more strict than it's successors that
                          may re-allow constructs from previous major line) */
                       || validate_with_silent(xml, next)) {
                crm_debug("%s-style configuration is also valid for %s",
                           known_schemas[lpc].name, known_schemas[next].name);

                lpc = next;

            } else {
                crm_debug("Upgrading %s-style configuration to %s with %s.xsl",
                           known_schemas[lpc].name, known_schemas[next].name,
                           known_schemas[lpc].transform);

                upgrade = apply_upgrade(xml, &known_schemas[lpc], to_logs);
                if (upgrade == NULL) {
                    crm_err("Transformation %s.xsl failed",
                            known_schemas[lpc].transform);
                    rc = -pcmk_err_transform_failed;

                } else if (validate_with(upgrade, next, error_handler, GUINT_TO_POINTER(LOG_ERR))) {
                    crm_info("Transformation %s.xsl successful",
                             known_schemas[lpc].transform);
                    lpc = next;
                    *best = next;
                    free_xml(xml);
                    xml = upgrade;
                    rc = pcmk_ok;

                } else {
                    crm_err("Transformation %s.xsl did not produce a valid configuration",
                            known_schemas[lpc].transform);
                    crm_log_xml_info(upgrade, "transform:bad");
                    free_xml(upgrade);
                    rc = -pcmk_err_schema_validation;
                }
                next = -1;
            }
        }

        if (transform == FALSE || rc != pcmk_ok) {
            /* we need some progress! */
            lpc++;
        }
    }

    if (*best > match && *best) {
        crm_info("%s the configuration from %s to %s",
                   transform?"Transformed":"Upgraded",
                   value ? value : "<none>", known_schemas[*best].name);
        crm_xml_add(xml, XML_ATTR_VALIDATION, known_schemas[*best].name);
    }

    *xml_blob = xml;
    free(value);
    return rc;
}

gboolean
cli_config_update(xmlNode **xml, int *best_version, gboolean to_logs)
{
    gboolean rc = TRUE;
    const char *value = crm_element_value(*xml, XML_ATTR_VALIDATION);
    char *const orig_value = strdup(value == NULL ? "(none)" : value);

    int version = get_schema_version(value);
    int orig_version = version;
    int min_version = xml_minimum_schema_index();

    if (version < min_version) {
        // Current configuration schema is not acceptable, try to update
        xmlNode *converted = NULL;

        converted = copy_xml(*xml);
        update_validation(&converted, &version, 0, TRUE, to_logs);

        value = crm_element_value(converted, XML_ATTR_VALIDATION);
        if (version < min_version) {
            // Updated configuration schema is still not acceptable

            if (version < orig_version || orig_version == -1) {
                // We couldn't validate any schema at all
                if (to_logs) {
                    pcmk__config_err("Cannot upgrade configuration (claiming "
                                     "schema %s) to at least %s because it "
                                     "does not validate with any schema from "
                                     "%s to %s",
                                     orig_value,
                                     get_schema_name(min_version),
                                     get_schema_name(orig_version),
                                     xml_latest_schema());
                } else {
                    fprintf(stderr, "Cannot upgrade configuration (claiming "
                                    "schema %s) to at least %s because it "
                                    "does not validate with any schema from "
                                    "%s to %s\n",
                                    orig_value,
                                    get_schema_name(min_version),
                                    get_schema_name(orig_version),
                                    xml_latest_schema());
                }
            } else {
                // We updated configuration successfully, but still too low
                if (to_logs) {
                    pcmk__config_err("Cannot upgrade configuration (claiming "
                                     "schema %s) to at least %s because it "
                                     "would not upgrade past %s",
                                     orig_value,
                                     get_schema_name(min_version),
                                     pcmk__s(value, "unspecified version"));
                } else {
                    fprintf(stderr, "Cannot upgrade configuration (claiming "
                                    "schema %s) to at least %s because it "
                                    "would not upgrade past %s\n",
                                    orig_value,
                                    get_schema_name(min_version),
                                    pcmk__s(value, "unspecified version"));
                }
            }

            free_xml(converted);
            converted = NULL;
            rc = FALSE;

        } else {
            // Updated configuration schema is acceptable
            free_xml(*xml);
            *xml = converted;

            if (version < xml_latest_schema_index()) {
                if (to_logs) {
                    pcmk__config_warn("Configuration with schema %s was "
                                      "internally upgraded to acceptable (but "
                                      "not most recent) %s",
                                      orig_value, get_schema_name(version));
                }
            } else {
                if (to_logs) {
                    crm_info("Configuration with schema %s was internally "
                             "upgraded to latest version %s",
                             orig_value, get_schema_name(version));
                }
            }
        }

    } else if (version >= get_schema_version(PCMK__VALUE_NONE)) {
        // Schema validation is disabled
        if (to_logs) {
            pcmk__config_warn("Schema validation of configuration is disabled "
                              "(enabling is encouraged and prevents common "
                              "misconfigurations)");

        } else {
            fprintf(stderr, "Schema validation of configuration is disabled "
                            "(enabling is encouraged and prevents common "
                            "misconfigurations)\n");
        }
    }

    if (best_version) {
        *best_version = version;
    }

    free(orig_value);
    return rc;
}