/*

 * fuzz.c: Common functions for fuzzing.

 *

 * See Copyright for the status of this software.

 */

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include <sys/stat.h>

#include <libxml/hash.h>

#include <libxml/parser.h>

#include <libxml/parserInternals.h>

#include <libxml/tree.h>

#include <libxml/xmlIO.h>

#include "fuzz.h"

typedef struct {

    const char *data;

    size_t size;

} xmlFuzzEntityInfo;

/* Single static instance for now */

static struct {

    /* Original data */

    const char *data;

    size_t size;

    /* Remaining data */

    const char *ptr;

    size_t remaining;

    /* Buffer for unescaped strings */

    char *outBuf;

    char *outPtr; /* Free space at end of buffer */

    xmlHashTablePtr entities; /* Maps URLs to xmlFuzzEntityInfos */

    /* The first entity is the main entity. */

    const char *mainUrl;

    xmlFuzzEntityInfo *mainEntity;

} fuzzData;

/**

 * xmlFuzzErrorFunc:

 *

 * An error function that simply discards all errors.

 */

void

xmlFuzzErrorFunc(void *ctx ATTRIBUTE_UNUSED, const char *msg ATTRIBUTE_UNUSED,

                 ...) {

}

/**

 * xmlFuzzDataInit:

 *

 * Initialize fuzz data provider.

 */

void

xmlFuzzDataInit(const char *data, size_t size) {

    fuzzData.data = data;

    fuzzData.size = size;

    fuzzData.ptr = data;

    fuzzData.remaining = size;

    fuzzData.outBuf = xmlMalloc(size + 1);

    fuzzData.outPtr = fuzzData.outBuf;

    fuzzData.entities = xmlHashCreate(8);

    fuzzData.mainUrl = NULL;

    fuzzData.mainEntity = NULL;

}

/**

 * xmlFuzzDataFree:

 *

 * Cleanup fuzz data provider.

 */

void

xmlFuzzDataCleanup(void) {

    xmlFree(fuzzData.outBuf);

    xmlHashFree(fuzzData.entities, xmlHashDefaultDeallocator);

}

/**

 * xmlFuzzReadInt:

 * @size:  size of string in bytes

 *

 * Read an integer from the fuzz data.

 */

int

xmlFuzzReadInt(void) {

    int ret;

    if (fuzzData.remaining < sizeof(int))

        return(0);

    memcpy(&ret, fuzzData.ptr, sizeof(int));

    fuzzData.ptr += sizeof(int);

    fuzzData.remaining -= sizeof(int);

    return ret;

}

/**

 * xmlFuzzReadRemaining:

 * @size:  size of string in bytes

 *

 * Read remaining bytes from fuzz data.

 */

const char *

xmlFuzzReadRemaining(size_t *size) {

    const char *ret = fuzzData.ptr;

    *size = fuzzData.remaining;

    fuzzData.ptr += fuzzData.remaining;

    fuzzData.remaining = 0;

    return(ret);

}

/*

 * xmlFuzzWriteString:

 * @out:  output file

 * @str:  string to write

 *

 * Write a random-length string to file in a format similar to

 * FuzzedDataProvider. Backslash followed by newline marks the end of the

 * string. Two backslashes are used to escape a backslash.

 */

void

xmlFuzzWriteString(FILE *out, const char *str) {

    for (; *str; str++) {

        int c = (unsigned char) *str;

        putc(c, out);

        if (c == '\\')

            putc(c, out);

    }

    putc('\\', out);

    putc('\n', out);

}

/**

 * xmlFuzzReadString:

 * @size:  size of string in bytes

 *

 * Read a random-length string from the fuzz data.

 *

 * The format is similar to libFuzzer's FuzzedDataProvider but treats

 * backslash followed by newline as end of string. This makes the fuzz data

 * more readable. A backslash character is escaped with another backslash.

 *

 * Returns a zero-terminated string or NULL if the fuzz data is exhausted.

 */

const char *

xmlFuzzReadString(size_t *size) {

    const char *out = fuzzData.outPtr;

    while (fuzzData.remaining > 0) {

        int c = *fuzzData.ptr++;

        fuzzData.remaining--;

        if ((c == '\\') && (fuzzData.remaining > 0)) {

            int c2 = *fuzzData.ptr;

            if (c2 == '\n') {

                fuzzData.ptr++;

                fuzzData.remaining--;

                *size = fuzzData.outPtr - out;

                *fuzzData.outPtr++ = '\0';

                return(out);

            }

            if (c2 == '\\') {

                fuzzData.ptr++;

                fuzzData.remaining--;

            }

        }

        *fuzzData.outPtr++ = c;

    }

    if (fuzzData.outPtr > out) {

        *size = fuzzData.outPtr - out;

        *fuzzData.outPtr++ = '\0';

        return(out);

    }

    *size = 0;

    return(NULL);

}

/**

 * xmlFuzzReadEntities:

 *

 * Read entities like the main XML file, external DTDs, external parsed

 * entities from fuzz data.

 */

void

xmlFuzzReadEntities(void) {

    size_t num = 0;

    while (1) {

        const char *url, *entity;

        size_t urlSize, entitySize;

        xmlFuzzEntityInfo *entityInfo;

        url = xmlFuzzReadString(&urlSize);

        if (url == NULL) break;

        entity = xmlFuzzReadString(&entitySize);

        if (entity == NULL) break;

        if (xmlHashLookup(fuzzData.entities, (xmlChar *)url) == NULL) {

            entityInfo = xmlMalloc(sizeof(xmlFuzzEntityInfo));

            if (entityInfo == NULL)

                break;

            entityInfo->data = entity;

            entityInfo->size = entitySize;

            xmlHashAddEntry(fuzzData.entities, (xmlChar *)url, entityInfo);

            if (num == 0) {

                fuzzData.mainUrl = url;

                fuzzData.mainEntity = entityInfo;

            }

            num++;

        }

    }

}

/**

 * xmlFuzzMainUrl:

 *

 * Returns the main URL.

 */

const char *

xmlFuzzMainUrl(void) {

    return(fuzzData.mainUrl);

}

/**

 * xmlFuzzMainEntity:

 * @size:  size of the main entity in bytes

 *

 * Returns the main entity.

 */

const char *

xmlFuzzMainEntity(size_t *size) {

    if (fuzzData.mainEntity == NULL)

        return(NULL);

    *size = fuzzData.mainEntity->size;

    return(fuzzData.mainEntity->data);

}

/**

 * xmlFuzzEntityLoader:

 *

 * The entity loader for fuzz data.

 */

xmlParserInputPtr

xmlFuzzEntityLoader(const char *URL, const char *ID ATTRIBUTE_UNUSED,

                    xmlParserCtxtPtr ctxt) {

    xmlParserInputPtr input;

    xmlFuzzEntityInfo *entity;

    if (URL == NULL)

        return(NULL);

    entity = xmlHashLookup(fuzzData.entities, (xmlChar *) URL);

    if (entity == NULL)

        return(NULL);

    input = xmlNewInputStream(ctxt);

    input->filename = NULL;

    input->buf = xmlParserInputBufferCreateMem(entity->data, entity->size,

                                               XML_CHAR_ENCODING_NONE);

    if (input->buf == NULL) {

        xmlFreeInputStream(input);

        return(NULL);

    }

    input->base = input->cur = xmlBufContent(input->buf->buffer);

    input->end = input->base + entity->size;

    return input;

}

/**

 * xmlFuzzExtractStrings:

 *

 * Extract C strings from input data. Use exact-size allocations to detect

 * potential memory errors.

 */

size_t

xmlFuzzExtractStrings(const char *data, size_t size, char **strings,

                      size_t numStrings) {

    const char *start = data;

    const char *end = data + size;

    size_t i = 0, ret;

    while (i < numStrings) {

        size_t strSize = end - start;

        const char *zero = memchr(start, 0, strSize);

        if (zero != NULL)

            strSize = zero - start;

        strings[i] = xmlMalloc(strSize + 1);

        memcpy(strings[i], start, strSize);

        strings[i][strSize] = '\0';

        i++;

        if (zero != NULL)

            start = zero + 1;

        else

            break;

    }

    ret = i;

    while (i < numStrings) {

        strings[i] = NULL;

        i++;

    }

    return(ret);

}

char *

xmlSlurpFile(const char *path, size_t *sizeRet) {

    FILE *file;

    struct stat statbuf;

    char *data;

    size_t size;

    if ((stat(path, &statbuf) != 0) || (!S_ISREG(statbuf.st_mode)))

        return(NULL);

    size = statbuf.st_size;

    file = fopen(path, "rb");

    if (file == NULL)

        return(NULL);

    data = xmlMalloc(size + 1);

    if (data != NULL) {

        if (fread(data, 1, size, file) != size) {

            xmlFree(data);

            data = NULL;

        } else {

            data[size] = 0;

            if (sizeRet != NULL)

                *sizeRet = size;

        }

    }

    fclose(file);

    return(data);

}