cfengine-3.17.0/libpromises/verify_vars.c

/*
  Copyright 2020 Northern.tech AS

  This file is part of CFEngine 3 - written and maintained by Northern.tech AS.

  This program is free software; you can redistribute it and/or modify it
  under the terms of the GNU General Public License as published by the
  Free Software Foundation; version 3.

  This program is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with this program; if not, write to the Free Software
  Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA

  To the extent this program is licensed as part of the Enterprise
  versions of CFEngine, the applicable Commercial Open Source License
  (COSL) may apply to this file if you as a licensee so wish it. See
  included file COSL.txt.
*/

#include <verify_vars.h>

#include <actuator.h>
#include <attributes.h>
#include <regex.h>      /* CompileRegex,StringMatchFullWithPrecompiledRegex */
#include <buffer.h>
#include <misc_lib.h>
#include <fncall.h>
#include <rlist.h>
#include <conversion.h>
#include <expand.h>
#include <scope.h>
#include <promises.h>
#include <vars.h>
#include <matching.h>
#include <syntax.h>
#include <audit.h>
#include <string_lib.h>
#include <cleanup.h>

typedef struct
{
    bool should_converge;
    bool ok_redefine;
    bool drop_undefined;
    Constraint *cp_save; // e.g. string => "foo"
} ConvergeVariableOptions;


static ConvergeVariableOptions CollectConvergeVariableOptions(EvalContext *ctx, const Promise *pp);
static bool Epimenides(EvalContext *ctx, const char *ns, const char *scope, const char *var, Rval rval, int level);
static bool CompareRval(const void *rval1_item, RvalType rval1_type, const void *rval2_item, RvalType rval2_type);

static bool IsLegalVariableName(EvalContext *ctx, const Promise *pp)
{
    const char *var_name = pp->promiser;

    /* TODO: remove at some point (global, leaked), but for now
     * this offers an attractive speedup. */
    static pcre *rx = NULL;
    if (!rx)
    {
        /* \200-\377 is there for multibyte unicode characters */
        rx = CompileRegex("[a-zA-Z0-9_\200-\377.]+(\\[.+\\])*"); /* Known leak, see TODO. */
    }

    if (!StringMatchFullWithPrecompiledRegex(rx, var_name))
    {
        return false;
    }

    char *bracket = strchr(var_name, '[');
    char *dot = strchr(var_name, '.');
    /* we only care about variable name prefix, not dots inside array keys */
    if ((dot != NULL) && ((bracket == NULL) || (dot < bracket)))
    {
        /* detect and prevent remote bundle variable injection (CFE-1915) */
        char *prefix = xstrndup(var_name, dot - var_name);
        const Bundle *cur_bundle = PromiseGetBundle(pp);

        if (!StringEqual(prefix, cur_bundle->name))
        {
            Log(LOG_LEVEL_VERBOSE,
                "Variable '%s' may be attempted to be injected into a remote bundle",
                var_name);
            if (StringSetContains(EvalContextGetBundleNames(ctx), prefix))
            {
                Log(LOG_LEVEL_ERR, "Remote bundle variable injection detected!");
                free(prefix);
                return false;
            }
            /* the conflicting bundle may be defined later, we need to remember
             * this promise as potentially dangerous */
            EvalContextPushRemoteVarPromise(ctx, prefix, pp->org_pp);
        }
        free(prefix);
    }

    return true;
}

// TODO why not printing that new definition is skipped?
// TODO what with ifdefined?

PromiseResult VerifyVarPromise(EvalContext *ctx, const Promise *pp,
                               ARG_UNUSED void *param)
{
    ConvergeVariableOptions opts = CollectConvergeVariableOptions(ctx, pp);

    Log(LOG_LEVEL_DEBUG, "Evaluating vars promise: %s", pp->promiser);
    LogDebug(LOG_MOD_VARS,
             "ok_redefine=%d, drop_undefined=%d, should_converge=%d",
             opts.ok_redefine, opts.drop_undefined, opts.should_converge);

    if (!opts.should_converge)
    {
        LogDebug(LOG_MOD_VARS,
                 "Skipping vars promise because should_converge=false");
        return PROMISE_RESULT_NOOP;
    }

//    opts.drop_undefined = true;         /* always remove @{unresolved_list} */

    Attributes a = ZeroAttributes;
    // More consideration needs to be given to using these
    //a.transaction = GetTransactionConstraints(pp);

    /* Warn if promise locking was used with a promise that doesn't support it
     * (which applies to all of 'vars', 'meta' and 'defaults' promises handled
     * by this code).
     * (Only do this in the first pass in cf-promises, we don't have to repeat
     * the warning over and over.) */
    if (EvalContextGetPass(ctx) == 0 && THIS_AGENT_TYPE == AGENT_TYPE_COMMON)
    {
        int ifelapsed = PromiseGetConstraintAsInt(ctx, "ifelapsed", pp);
        if (ifelapsed != CF_NOINT)
        {
            Log(LOG_LEVEL_WARNING,
                "ifelapsed attribute specified in action body for %s promise '%s',"
                " but %s promises do not support promise locking",
                pp->parent_section->promise_type, pp->promiser,
                pp->parent_section->promise_type);
        }
        int expireafter = PromiseGetConstraintAsInt(ctx, "expireafter", pp);
        if (expireafter != CF_NOINT)
        {
            Log(LOG_LEVEL_WARNING,
                "expireafter attribute specified in action body for %s promise '%s',"
                " but %s promises do not support promise locking",
                pp->parent_section->promise_type, pp->promiser,
                pp->parent_section->promise_type);
        }
    }

    a.classes = GetClassDefinitionConstraints(ctx, pp);

    VarRef *ref = VarRefParseFromBundle(pp->promiser, PromiseGetBundle(pp));
    if (strcmp("meta", pp->parent_section->promise_type) == 0)
    {
        VarRefSetMeta(ref, true);
    }

    DataType existing_value_type = CF_DATA_TYPE_NONE;
    const void *existing_value;
    if (IsExpandable(pp->promiser))
    {
        existing_value = NULL;
    }
    else
    {
        existing_value = EvalContextVariableGet(ctx, ref, &existing_value_type);
    }

    Rval rval = opts.cp_save->rval;
    PromiseResult result;

    if (rval.item != NULL || rval.type == RVAL_TYPE_LIST)
    {
        DataType data_type = DataTypeFromString(opts.cp_save->lval);

        if (opts.cp_save->rval.type == RVAL_TYPE_FNCALL)
        {
            FnCall *fp = RvalFnCallValue(rval);
            const FnCallType *fn = FnCallTypeGet(fp->name);
            if (!fn)
            {
                assert(false && "Canary: should have been caught before this point");
                FatalError(ctx, "While setting variable '%s' in bundle '%s', unknown function '%s'",
                           pp->promiser, PromiseGetBundle(pp)->name, fp->name);
            }

            if (fn->dtype != DataTypeFromString(opts.cp_save->lval))
            {
                FatalError(ctx, "While setting variable '%s' in bundle '%s', variable declared type '%s' but function '%s' returns type '%s'",
                           pp->promiser, PromiseGetBundle(pp)->name, opts.cp_save->lval,
                           fp->name, DataTypeToString(fn->dtype));
            }

            if (existing_value_type != CF_DATA_TYPE_NONE)
            {
                // Already did this
                VarRefDestroy(ref);
                return PROMISE_RESULT_NOOP;
            }

            FnCallResult res = FnCallEvaluate(ctx, PromiseGetPolicy(pp), fp, pp);

            if (res.status == FNCALL_FAILURE)
            {
                /* We do not assign variables to failed fn calls */
                if (EvalContextGetPass(ctx) == CF_DONEPASSES-1) {
                    // If we still fail at last pass, make a log
                    Log(LOG_LEVEL_VERBOSE, "While setting variable '%s' in bundle '%s', function '%s' failed - skipping",
                                       pp->promiser, PromiseGetBundle(pp)->name, fp->name);
                }
                RvalDestroy(res.rval);
                VarRefDestroy(ref);
                return PROMISE_RESULT_NOOP;
            }
            else
            {
                rval = res.rval;
            }
        }
        else
        {
            Buffer *conv = BufferNew();
            bool malformed = false, misprint = false;

            if (strcmp(opts.cp_save->lval, "int") == 0)
            {
                long int asint = IntFromString(opts.cp_save->rval.item);
                if (asint == CF_NOINT)
                {
                    malformed = true;
                }
                else if (0 > BufferPrintf(conv, "%ld", asint))
                {
                    misprint = true;
                }
                else
                {
                    rval = RvalNew(BufferData(conv), opts.cp_save->rval.type);
                }
            }
            else if (strcmp(opts.cp_save->lval, "real") == 0)
            {
                double real_value;
                if (!DoubleFromString(opts.cp_save->rval.item, &real_value))
                {
                    malformed = true;
                }
                else if (0 > BufferPrintf(conv, "%lf", real_value))
                {
                    misprint = true;
                }
                else
                {
                    rval = RvalNew(BufferData(conv), opts.cp_save->rval.type);
                }
            }
            else
            {
                rval = RvalCopy(opts.cp_save->rval);
            }
            BufferDestroy(conv);

            if (malformed)
            {
                /* Arises when opts->cp_save->rval.item isn't yet expanded. */
                /* Has already been logged by *FromString */
                VarRefDestroy(ref);
                return PROMISE_RESULT_FAIL;
            }
            else if (misprint)
            {
                /* Even though no problems with memory allocation can
                 * get here, there might be other problems. */
                UnexpectedError("Problems writing to buffer");
                VarRefDestroy(ref);
                return PROMISE_RESULT_FAIL;
            }
            else if (rval.type == RVAL_TYPE_LIST)
            {
                Rlist *rval_list = RvalRlistValue(rval);
                RlistFlatten(ctx, &rval_list);
                rval.item = rval_list;
            }
        }

        if (Epimenides(ctx, PromiseGetBundle(pp)->ns, PromiseGetBundle(pp)->name, pp->promiser, rval, 0))
        {
            Log(LOG_LEVEL_ERR, "Variable '%s' contains itself indirectly - an unkeepable promise", pp->promiser);
            DoCleanupAndExit(EXIT_FAILURE);
        }
        else
        {
            /* See if the variable needs recursively expanding again */

            Rval returnval = EvaluateFinalRval(ctx, PromiseGetPolicy(pp), ref->ns, ref->scope, rval, true, pp);

            RvalDestroy(rval);

            // freed before function exit
            rval = returnval;
        }

        /* If variable did resolve but we're not allowed to modify it. */
        /* ok_redefine: only on second iteration, else we ignore broken promises. TODO wat? */
        if (existing_value_type != CF_DATA_TYPE_NONE &&
            !opts.ok_redefine)
        {
            if (!CompareRval(existing_value, DataTypeToRvalType(existing_value_type),
                             rval.item, rval.type))
            {
                switch (rval.type)
                {
                    /* TODO redefinition shouldn't be mentioned. Maybe handle like normal variable definition/ */
                case RVAL_TYPE_SCALAR:
                    Log(LOG_LEVEL_VERBOSE, "V: Skipping redefinition of constant scalar '%s': from '%s' to '%s'",
                        pp->promiser, (const char *)existing_value, RvalScalarValue(rval));
                    PromiseRef(LOG_LEVEL_VERBOSE, pp);
                    break;

                case RVAL_TYPE_LIST:
                {
                    Log(LOG_LEVEL_VERBOSE, "V: Skipping redefinition of constant list '%s'", pp->promiser);
                    Writer *w = StringWriter();
                    RlistWrite(w, existing_value);
                    char *oldstr = StringWriterClose(w);
                    Log(LOG_LEVEL_DEBUG, "Old value:         %s", oldstr);
                    free(oldstr);

                    w = StringWriter();
                    RlistWrite(w, rval.item);
                    char *newstr = StringWriterClose(w);
                    Log(LOG_LEVEL_DEBUG, "Skipped new value: %s", newstr);
                    free(newstr);

                    PromiseRef(LOG_LEVEL_VERBOSE, pp);
                }
                break;

                case RVAL_TYPE_CONTAINER:
                case RVAL_TYPE_FNCALL:
                case RVAL_TYPE_NOPROMISEE:
                    break;
                }
            }

            RvalDestroy(rval);
            VarRefDestroy(ref);
            return PROMISE_RESULT_NOOP;
        }

        if (IsCf3VarString(pp->promiser))
        {
            // Unexpanded variables, we don't do anything with
            RvalDestroy(rval);
            VarRefDestroy(ref);
            return PROMISE_RESULT_NOOP;
        }

        if (!IsLegalVariableName(ctx, pp))
        {
            Log(LOG_LEVEL_ERR, "Variable identifier '%s' is not legal", pp->promiser);
            PromiseRef(LOG_LEVEL_ERR, pp);
            RvalDestroy(rval);
            VarRefDestroy(ref);
            return PROMISE_RESULT_NOOP;
        }

        if (rval.type == RVAL_TYPE_LIST)
        {
            if (opts.drop_undefined)
            {
                Rlist *stripped = RvalRlistValue(rval);
                Rlist *entry = stripped;
                while (entry)
                {
                    Rlist *delete_me = NULL;
                    if (IsNakedVar(RlistScalarValue(entry), '@'))
                    {
                        delete_me = entry;
                    }
                    entry = entry->next;
                    RlistDestroyEntry(&stripped, delete_me);
                }
                rval.item = stripped;
            }

            for (const Rlist *rp = RvalRlistValue(rval); rp; rp = rp->next)
            {
                if (rp->val.type != RVAL_TYPE_SCALAR)
                {
                    // Cannot assign variable because value is a list containing a non-scalar item
                    VarRefDestroy(ref);
                    RvalDestroy(rval);
                    return PROMISE_RESULT_NOOP;
                }
            }
        }

        if (ref->num_indices > 0)
        {
            if (data_type == CF_DATA_TYPE_CONTAINER)
            {
                char *lval_str = VarRefToString(ref, true);
                Log(LOG_LEVEL_ERR, "Cannot assign a container to an indexed variable name '%s'. Should be assigned to '%s' instead",
                    lval_str, ref->lval);
                free(lval_str);
                VarRefDestroy(ref);
                RvalDestroy(rval);
                return PROMISE_RESULT_NOOP;
            }
            else
            {
                DataType existing_type;
                VarRef *base_ref = VarRefCopyIndexless(ref);
                if (EvalContextVariableGet(ctx, ref, &existing_type) && existing_type == CF_DATA_TYPE_CONTAINER)
                {
                    char *lval_str = VarRefToString(ref, true);
                    char *base_ref_str = VarRefToString(base_ref, true);
                    Log(LOG_LEVEL_ERR, "Cannot assign value to indexed variable name '%s', because a container is already assigned to the base name '%s'",
                        lval_str, base_ref_str);
                    free(lval_str);
                    free(base_ref_str);
                    VarRefDestroy(base_ref);
                    VarRefDestroy(ref);
                    RvalDestroy(rval);
                    return PROMISE_RESULT_NOOP;
                }
                VarRefDestroy(base_ref);
            }
        }


        DataType required_datatype = DataTypeFromString(opts.cp_save->lval);
        if (rval.type != DataTypeToRvalType(required_datatype))
        {
            char *ref_str = VarRefToString(ref, true);
            char *value_str = RvalToString(rval);
            Log(LOG_LEVEL_ERR, "Variable '%s' expected a variable of type '%s', but was given incompatible value '%s'",
                ref_str, DataTypeToString(required_datatype), value_str);
            PromiseRef(LOG_LEVEL_ERR, pp);

            free(ref_str);
            free(value_str);
            VarRefDestroy(ref);
            RvalDestroy(rval);
            return PROMISE_RESULT_FAIL;
        }

        /* WRITE THE VARIABLE AT LAST. */
        bool success = EvalContextVariablePut(ctx, ref, rval.item, required_datatype, "source=promise");

        if (!success)
        {
            Log(LOG_LEVEL_VERBOSE,
                "Unable to converge %s.%s value (possibly empty or infinite regression)",
                ref->scope, pp->promiser);
            PromiseRef(LOG_LEVEL_VERBOSE, pp);

            VarRefDestroy(ref);
            RvalDestroy(rval);
            return PROMISE_RESULT_FAIL;
        }

        Rlist *promise_meta = PromiseGetConstraintAsList(ctx, "meta", pp);
        if (promise_meta)
        {
            StringSet *class_meta = EvalContextVariableTags(ctx, ref);
            Buffer *print;
            for (const Rlist *rp = promise_meta; rp; rp = rp->next)
            {
                StringSetAdd(class_meta, xstrdup(RlistScalarValue(rp)));
                print = StringSetToBuffer(class_meta, ',');
                Log(LOG_LEVEL_DEBUG,
                    "Added tag %s to class %s, tags now [%s]",
                    RlistScalarValue(rp), pp->promiser, BufferData(print));
                BufferDestroy(print);
            }
        }

        result = PROMISE_RESULT_NOOP;
    }
    else
    {
        Log(LOG_LEVEL_ERR, "Variable %s has no promised value", pp->promiser);
        Log(LOG_LEVEL_ERR, "Rule from %s at/before line %zu", PromiseGetBundle(pp)->source_path, opts.cp_save->offset.line);
        result = PROMISE_RESULT_FAIL;
    }

    /*
     * FIXME: Variable promise are exempt from normal evaluation logic still, so
     * they are not pushed to evaluation stack before being evaluated. Due to
     * this reason, we cannot call cfPS here to set classes, as it will error
     * out with ProgrammingError.
     *
     * In order to support 'classes' body for variables as well, we call
     * ClassAuditLog explicitly.
     */
    ClassAuditLog(ctx, pp, &a, result);

    VarRefDestroy(ref);
    RvalDestroy(rval);

    return result;
}

static bool CompareRval(const void *rval1_item, RvalType rval1_type,
                        const void *rval2_item, RvalType rval2_type)
{
    if (rval1_type != rval2_type)
    {
        return false;
    }

    switch (rval1_type)
    {
    case RVAL_TYPE_SCALAR:

        if (IsCf3VarString(rval1_item) || IsCf3VarString(rval2_item))
        {
            return false;          // inconclusive
        }

        if (strcmp(rval1_item, rval2_item) != 0)
        {
            return false;
        }

        break;

    case RVAL_TYPE_LIST:
        return RlistEqual(rval1_item, rval2_item);

    case RVAL_TYPE_FNCALL:
        return false;

    default:
        return false;
    }

    return true;
}

static bool Epimenides(EvalContext *ctx, const char *ns, const char *scope, const char *var, Rval rval, int level)
{
    switch (rval.type)
    {
    case RVAL_TYPE_SCALAR:

        if (StringContainsVar(RvalScalarValue(rval), var))
        {
            Log(LOG_LEVEL_ERR, "Scalar variable '%s' contains itself (non-convergent) '%s'", var, RvalScalarValue(rval));
            return true;
        }

        if (IsCf3VarString(RvalScalarValue(rval)))
        {
            Buffer *exp = BufferNew();
            ExpandScalar(ctx, ns, scope, RvalScalarValue(rval), exp);

            if (strcmp(BufferData(exp), RvalScalarValue(rval)) == 0)
            {
                BufferDestroy(exp);
                return false;
            }

            if (level > 3)
            {
                BufferDestroy(exp);
                return false;
            }

            if (Epimenides(ctx, ns, scope, var, (Rval) { BufferGet(exp), RVAL_TYPE_SCALAR}, level + 1))
            {
                BufferDestroy(exp);
                return true;
            }

            BufferDestroy(exp);
        }

        break;

    case RVAL_TYPE_LIST:
        for (const Rlist *rp = RvalRlistValue(rval); rp != NULL; rp = rp->next)
        {
            if (Epimenides(ctx, ns, scope, var, rp->val, level))
            {
                return true;
            }
        }
        break;

    case RVAL_TYPE_CONTAINER:
    case RVAL_TYPE_FNCALL:
    case RVAL_TYPE_NOPROMISEE:
        return false;
    }

    return false;
}

/**
 * @brief Collects variable constraints controlling how the promise should be converged
 */
static ConvergeVariableOptions CollectConvergeVariableOptions(EvalContext *ctx, const Promise *pp)
{
    ConvergeVariableOptions opts;
    opts.drop_undefined = false;
    opts.cp_save = NULL;                             /* main variable value */
    /* By default allow variable redefinition, use "policy" constraint
     * to override. */
    opts.ok_redefine = true;
    /* Main return value: becomes true at the end of the function. */
    opts.should_converge = false;

    if (!IsDefinedClass(ctx, pp->classes))
    {
        return opts;
    }

    int num_values = 0;
    for (size_t i = 0; i < SeqLength(pp->conlist); i++)
    {
        Constraint *cp = SeqAt(pp->conlist, i);

        if (strcmp(cp->lval, "comment") == 0)
        {
            // Comments don't affect convergence
            // Unclear why this is in the constraint list in the first place?
            continue;
        }
        else if (cp->rval.item == NULL && cp->rval.type != RVAL_TYPE_LIST)
        {
            // No right value, considered empty
            continue;
        }
        else if (strcmp(cp->lval, "ifvarclass") == 0 ||
                 strcmp(cp->lval, "if")         == 0)
        {
            switch (cp->rval.type)
            {
            case RVAL_TYPE_SCALAR:
                if (!IsDefinedClass(ctx, cp->rval.item))
                {
                    return opts;
                }

                break;

            case RVAL_TYPE_FNCALL:
            {
                bool excluded = false;

                /* eval it: e.g. ifvarclass => not("a_class") */

                Rval res = FnCallEvaluate(ctx, PromiseGetPolicy(pp), cp->rval.item, pp).rval;

                /* Don't continue unless function was evaluated properly */
                if (res.type != RVAL_TYPE_SCALAR)
                {
                    RvalDestroy(res);
                    return opts;
                }

                excluded = !IsDefinedClass(ctx, res.item);

                RvalDestroy(res);

                if (excluded)
                {
                    return opts;
                }
            }
            break;

            default:
                Log(LOG_LEVEL_ERR, "Invalid if/ifvarclass type '%c': should be string or function", cp->rval.type);
            }
        }
        else if (strcmp(cp->lval, "policy") == 0)
        {
            if (strcmp(cp->rval.item, "ifdefined") == 0)
            {
                opts.drop_undefined = true;
            }
            else if (strcmp(cp->rval.item, "constant") == 0)
            {
                opts.ok_redefine = false;
            }
        }
        else if (DataTypeFromString(cp->lval) != CF_DATA_TYPE_NONE)
        {
            num_values++;
            opts.cp_save = cp;
        }
    }

    if (opts.cp_save == NULL)
    {
        Log(LOG_LEVEL_WARNING, "Incomplete vars promise: %s",
            pp->promiser);
        PromiseRef(LOG_LEVEL_INFO, pp);
        return opts;
    }

    if (num_values > 2)
    {
        Log(LOG_LEVEL_ERR,
            "Variable '%s' breaks its own promise with multiple (%d) values",
            pp->promiser, num_values);
        PromiseRef(LOG_LEVEL_ERR, pp);
        return opts;
    }

    /* All constraints look OK, and classes are defined. Move forward with
     * this promise. */
    opts.should_converge = true;

    return opts;
}