core-d08ae9eff/libpromises/fncall.c

/*
  Copyright 2021 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 <fncall.h>

#include <eval_context.h>
#include <files_names.h>
#include <expand.h>
#include <vars.h>
#include <evalfunction.h>
#include <policy.h>
#include <string_lib.h>
#include <promises.h>
#include <syntax.h>
#include <audit.h>
#include <cleanup.h>

#define SIMULATE_SAFE_META_TAG "simulate_safe"

/******************************************************************/
/* Argument propagation                                           */
/******************************************************************/

/*

When formal parameters are passed, they should be literal strings, i.e.
values (check for this). But when the values are received the
receiving body should state only variable names without literal quotes.
That way we can feed in the received parameter name directly in as an lvalue

e.g.
       access => myaccess("$(person)"),

       body files myaccess(user)

leads to Hash Association (lval,rval) => (user,"$(person)")

*/

/******************************************************************/

Rlist *NewExpArgs(EvalContext *ctx, const Policy *policy, const FnCall *fp, const FnCallType *fp_type)
{
    // Functions with delayed evaluation will call this themselves later
    if (fp_type && fp_type->options & FNCALL_OPTION_DELAYED_EVALUATION)
    {
        return RlistCopy(fp->args);
    }

    const FnCallType *fn = FnCallTypeGet(fp->name);
    if (fn == NULL)
    {
        FatalError(ctx, "Function call '%s' has unknown type", fp->name);
    }
    else
    {
        int len = RlistLen(fp->args);

        if (!(fn->options & FNCALL_OPTION_VARARG))
        {
            if (len != FnNumArgs(fn))
            {
                Log(LOG_LEVEL_ERR, "Arguments to function '%s' do not tally. Expected %d not %d",
                      fp->name, FnNumArgs(fn), len);
                PromiseRef(LOG_LEVEL_ERR, fp->caller);
                DoCleanupAndExit(EXIT_FAILURE);
            }
        }
    }

    Rlist *expanded_args = NULL;
    for (const Rlist *rp = fp->args; rp != NULL; rp = rp->next)
    {
        Rval rval;

        if (rp->val.type == RVAL_TYPE_FNCALL)
        {
            FnCall *subfp = RlistFnCallValue(rp);
            rval = FnCallEvaluate(ctx, policy, subfp, fp->caller).rval;
        }
        else
        {
            rval = ExpandPrivateRval(ctx, NULL, NULL, rp->val.item, rp->val.type);
            assert(rval.item);
        }

        /*

          Collect compound values into containers only if the function
          supports it.

          Functions without FNCALL_OPTION_COLLECTING don't collect
          Rlist elements. So in the policy, you call
          and(splitstring("a b")) and it ends up as and("a", "b").
          This expansion happens once per FnCall, not for all
          arguments.

          Functions with FNCALL_OPTION_COLLECTING instead collect all
          the results of a FnCall into a single JSON array object. It
          requires functions to expect it, but it's the only
          reasonable way to preserve backwards compatibility for
          functions like and() and allow nesting of calls to functions
          that take and return compound data types.

        */
        RlistAppendAllTypes(&expanded_args, rval.item, rval.type,
                            (fn->options & FNCALL_OPTION_COLLECTING));
        RvalDestroy(rval);
    }

    return expanded_args;
}

/*******************************************************************/

bool FnCallIsBuiltIn(Rval rval)
{
    FnCall *fp;

    if (rval.type != RVAL_TYPE_FNCALL)
    {
        return false;
    }

    fp = (FnCall *) rval.item;

    if (FnCallTypeGet(fp->name))
    {
        return true;
    }
    else
    {
        return false;
    }
}

/*******************************************************************/

FnCall *FnCallNew(const char *name, Rlist *args)
{
    FnCall *fp = xmalloc(sizeof(FnCall));

    fp->name = xstrdup(name);
    fp->args = args;

    return fp;
}

/*******************************************************************/

FnCall *FnCallCopyRewriter(const FnCall *f, JsonElement *map)
{
    return FnCallNew(f->name, RlistCopyRewriter(f->args, map));
}

FnCall *FnCallCopy(const FnCall *f)
{
    return FnCallCopyRewriter(f, NULL);
}

/*******************************************************************/

void FnCallDestroy(FnCall *fp)
{
    if (fp)
    {
        free(fp->name);
        RlistDestroy(fp->args);
    }
    free(fp);
}

unsigned FnCallHash(const FnCall *fp, unsigned seed)
{
    unsigned hash = StringHash(fp->name, seed);
    return RlistHash(fp->args, hash);
}


FnCall *ExpandFnCall(const EvalContext *ctx, const char *ns, const char *scope, const FnCall *f)
{
    FnCall *result = NULL;
    if (IsCf3VarString(f->name))
    {
        // e.g. usebundle => $(m)(arg0, arg1);
        Buffer *buf = BufferNewWithCapacity(CF_MAXVARSIZE);
        ExpandScalar(ctx, ns, scope, f->name, buf);

        result = FnCallNew(BufferData(buf), ExpandList(ctx, ns, scope, f->args, false));
        BufferDestroy(buf);
    }
    else
    {
        result = FnCallNew(f->name, ExpandList(ctx, ns, scope, f->args, false));
    }

    return result;
}

void FnCallWrite(Writer *writer, const FnCall *call)
{
    WriterWrite(writer, call->name);
    WriterWriteChar(writer, '(');

    for (const Rlist *rp = call->args; rp != NULL; rp = rp->next)
    {
        switch (rp->val.type)
        {
        case RVAL_TYPE_SCALAR:
            ScalarWrite(writer, RlistScalarValue(rp), true);
            break;

        case RVAL_TYPE_FNCALL:
            FnCallWrite(writer, RlistFnCallValue(rp));
            break;

        default:
            WriterWrite(writer, "(** Unknown argument **)\n");
            break;
        }

        if (rp->next != NULL)
        {
            WriterWriteChar(writer, ',');
        }
    }

    WriterWriteChar(writer, ')');
}

/*******************************************************************/

static FnCallResult CallFunction(EvalContext *ctx, const Policy *policy, const FnCall *fp, const Rlist *expargs)
{
    const Rlist *rp = fp->args;
    const FnCallType *fncall_type = FnCallTypeGet(fp->name);
    if (fncall_type == NULL)
    {
        FatalError(ctx, "Function call '%s' has unknown type", fp->name);
    }

    int argnum = 0;
    for (argnum = 0; rp != NULL && fncall_type->args[argnum].pattern != NULL; argnum++)
    {
        if (rp->val.type != RVAL_TYPE_FNCALL)
        {
            /* Nested functions will not match to lval so don't bother checking */
            SyntaxTypeMatch err = CheckConstraintTypeMatch(fp->name, rp->val,
                                                           fncall_type->args[argnum].dtype,
                                                           fncall_type->args[argnum].pattern, 1);
            if (err != SYNTAX_TYPE_MATCH_OK && err != SYNTAX_TYPE_MATCH_ERROR_UNEXPANDED)
            {
                FatalError(ctx, "In function '%s', error in variable '%s', '%s'", fp->name, (const char *)rp->val.item, SyntaxTypeMatchToString(err));
            }
        }

        rp = rp->next;
    }

    if (argnum != RlistLen(expargs) && !(fncall_type->options & FNCALL_OPTION_VARARG))
    {
        char *args_str = RlistToString(expargs);
        Log(LOG_LEVEL_ERR, "Argument template mismatch handling function %s(%s)", fp->name, args_str);
        free(args_str);

        rp = expargs;
        for (int i = 0; i < argnum; i++)
        {
            if (rp != NULL)
            {
                char *rval_str = RvalToString(rp->val);
                Log(LOG_LEVEL_ERR, "  arg[%d] range %s\t %s ", i, fncall_type->args[i].pattern, rval_str);
                free(rval_str);
            }
            else
            {
                Log(LOG_LEVEL_ERR, "  arg[%d] range %s\t ? ", i, fncall_type->args[i].pattern);
            }
        }

        FatalError(ctx, "Bad arguments");
    }

    return (*fncall_type->impl) (ctx, policy, fp, expargs);
}

FnCallResult FnCallEvaluate(EvalContext *ctx, const Policy *policy, FnCall *fp, const Promise *caller)
{
    assert(ctx != NULL);
    assert(policy != NULL);
    assert(fp != NULL);
    fp->caller = caller;

    if (!EvalContextGetEvalOption(ctx, EVAL_OPTION_EVAL_FUNCTIONS))
    {
        Log(LOG_LEVEL_VERBOSE, "Skipping function '%s', because evaluation was turned off in the evaluator",
            fp->name);
        return (FnCallResult) { FNCALL_FAILURE, { FnCallCopy(fp), RVAL_TYPE_FNCALL } };
    }

    const FnCallType *fp_type = FnCallTypeGet(fp->name);

    if (!fp_type)
    {
        if (caller)
        {
            Log(LOG_LEVEL_ERR, "No such FnCall '%s' in promise '%s' near line %zu",
                  fp->name, PromiseGetBundle(caller)->source_path, caller->offset.line);
        }
        else
        {
            Log(LOG_LEVEL_ERR, "No such FnCall '%s', context info unavailable", fp->name);
        }

        return (FnCallResult) { FNCALL_FAILURE, { FnCallCopy(fp), RVAL_TYPE_FNCALL } };
    }

    const bool skip_unsafe_function_calls = ((EVAL_MODE == EVAL_MODE_SIMULATE_MANIFEST) ||
                                             (EVAL_MODE == EVAL_MODE_SIMULATE_MANIFEST_FULL) ||
                                             (EVAL_MODE == EVAL_MODE_SIMULATE_DIFF));

    Rlist *caller_meta = PromiseGetConstraintAsList(ctx, "meta", caller);
    if (skip_unsafe_function_calls &&
        ((fp_type->options & FNCALL_OPTION_UNSAFE) != 0) &&
        !RlistContainsString(caller_meta, SIMULATE_SAFE_META_TAG))
    {
        Log(LOG_LEVEL_WARNING, "Not calling unsafe function '%s' in simulate mode", fp->name);
        return (FnCallResult) { FNCALL_FAILURE, { FnCallCopy(fp), RVAL_TYPE_FNCALL } };
    }

    Rlist *expargs = NewExpArgs(ctx, policy, fp, fp_type);

    Writer *fncall_writer = NULL;
    const char *fncall_string = "";
    if (LogGetGlobalLevel() >= LOG_LEVEL_DEBUG)
    {
        fncall_writer = StringWriter();
        FnCallWrite(fncall_writer, fp);
        fncall_string = StringWriterData(fncall_writer);
    }

    // Check if arguments are resolved, except for delayed evaluation functions
    if ( ! (fp_type->options & FNCALL_OPTION_DELAYED_EVALUATION) &&
         RlistIsUnresolved(expargs))
    {
        // Special case where a three argument ifelse call must
        // be allowed to have undefined variables.
        if (strcmp(fp->name, "ifelse") == 0 &&
            expargs->val.type != RVAL_TYPE_FNCALL &&
            RlistLen(expargs) == 3)
        {
                Log(LOG_LEVEL_DEBUG, "Allowing ifelse() function evaluation even"
                    " though its arguments contain unresolved variables: %s",
                    fncall_string);
        }
        else
        {
            if (LogGetGlobalLevel() >= LOG_LEVEL_DEBUG)
            {
                Log(LOG_LEVEL_DEBUG, "Skipping function evaluation for now,"
                    " arguments contain unresolved variables: %s",
                    fncall_string);
                WriterClose(fncall_writer);
            }
            RlistDestroy(expargs);
            return (FnCallResult) { FNCALL_FAILURE, { FnCallCopy(fp), RVAL_TYPE_FNCALL } };
        }
    }

    /* Call functions in promises with 'ifelapsed => "0"' (e.g. with
     * 'action => immediate') [ENT-7478] */
    const int if_elapsed = PromiseGetConstraintAsInt(ctx, "ifelapsed", caller);
    if (if_elapsed != 0)
    {
        Rval cached_rval;
        if ((fp_type->options & FNCALL_OPTION_CACHED) && EvalContextFunctionCacheGet(ctx, fp, expargs, &cached_rval))
        {
            if (LogGetGlobalLevel() >= LOG_LEVEL_DEBUG)
            {
                Log(LOG_LEVEL_DEBUG,
                    "Using previously cached result for function: %s",
                    fncall_string);
                WriterClose(fncall_writer);
            }
            Writer *w = StringWriter();
            FnCallWrite(w, fp);
            WriterClose(w);
            RlistDestroy(expargs);

            return (FnCallResult) { FNCALL_SUCCESS, RvalCopy(cached_rval) };
        }
    }

    if (LogGetGlobalLevel() >= LOG_LEVEL_DEBUG)
    {
        Log(LOG_LEVEL_DEBUG, "Evaluating function: %s%s",
            fncall_string, (if_elapsed == 0) ? " (because of ifelapsed => \"0\")" : "");
        WriterClose(fncall_writer);
    }

    FnCallResult result = CallFunction(ctx, policy, fp, expargs);

    if (result.status == FNCALL_FAILURE)
    {
        RlistDestroy(expargs);
        RvalDestroy(result.rval);
        return (FnCallResult) { FNCALL_FAILURE, { FnCallCopy(fp), RVAL_TYPE_FNCALL } };
    }

    if (fp_type->options & FNCALL_OPTION_CACHED)
    {
        Writer *w = StringWriter();
        FnCallWrite(w, fp);
        Log(LOG_LEVEL_VERBOSE, "Caching result for function '%s'", StringWriterData(w));
        WriterClose(w);

        EvalContextFunctionCachePut(ctx, fp, expargs, &result.rval);
    }

    RlistDestroy(expargs);

    return result;
}

/*******************************************************************/

const FnCallType *FnCallTypeGet(const char *name)
{
    int i;

    for (i = 0; CF_FNCALL_TYPES[i].name != NULL; i++)
    {
        if (strcmp(CF_FNCALL_TYPES[i].name, name) == 0)
        {
            return CF_FNCALL_TYPES + i;
        }
    }

    return NULL;
}