docs/manual/developer/mod_example_2.c

/*
 * mod_example_2.c: Example module for Apache HTTP Server 2.4
 * This module calculates and displays MD5 or SHA1 digests of files.
 */

#include "httpd.h"
#include "http_config.h"
#include "http_protocol.h"
#include "ap_config.h"
#include "apr_md5.h"
#include "apr_sha1.h"
#include "apr_file_io.h"
#include "apr_tables.h"

static int example_handler(request_rec *r)
{
    int rc, exists;
    apr_finfo_t finfo;
    apr_file_t *file;
    char *filename;
    char buffer[256];
    apr_size_t readBytes;
    int n;
    apr_table_t *GET;
    apr_array_header_t *POST;
    const char *digestType;


    /* Check that the "example-handler" handler is being called. */
    if (!r->handler || strcmp(r->handler, "example-handler")) return (DECLINED);

    /* Figure out which file is being requested by removing the .sum from it */
    filename = apr_pstrdup(r->pool, r->filename);
    filename[strlen(filename)-4] = 0; /* Cut off the last 4 characters. */

    /* Figure out if the file we request a sum on exists and isn't a directory */
    rc = apr_stat(&finfo, filename, APR_FINFO_MIN, r->pool);
    if (rc == APR_SUCCESS) {
        exists =
        (
            (finfo.filetype != APR_NOFILE)
        &&  !(finfo.filetype & APR_DIR)
        );
        if (!exists) return HTTP_NOT_FOUND; /* Return a 404 if not found. */
    }
    /* If apr_stat failed, we're probably not allowed to check this file. */
    else return HTTP_FORBIDDEN;

    /* Parse the GET and, optionally, the POST data sent to us */

    ap_args_to_table(r, &GET);
    ap_parse_form_data(r, NULL, &POST, -1, 8192);

    /* Set the appropriate content type */
    ap_set_content_type(r, "text/html");

    /* Print a title and some general information */
    ap_rprintf(r, "<h2>Information on %s:</h2>", filename);
    ap_rprintf(r, "<b>Size:</b> %" APR_OFF_T_FMT " bytes<br/>", finfo.size);

    /* Get the digest type the client wants to see */
    digestType = apr_table_get(GET, "digest");
    if (!digestType) digestType = "MD5";


    rc = apr_file_open(&file, filename, APR_READ, APR_OS_DEFAULT, r->pool);
    if (rc == APR_SUCCESS) {

        /* Are we trying to calculate the MD5 or the SHA1 digest? */
        if (!strcasecmp(digestType, "md5")) {
            /* Calculate the MD5 sum of the file */
            union {
                char      chr[16];
                uint32_t  num[4];
            } digest;
            apr_md5_ctx_t md5;
            apr_md5_init(&md5);
            readBytes = 256;
            while ( apr_file_read(file, buffer, &readBytes) == APR_SUCCESS ) {
                apr_md5_update(&md5, buffer, readBytes);
            }
            apr_md5_final(digest.chr, &md5);

            /* Print out the MD5 digest */
            ap_rputs("<b>MD5: </b><code>", r);
            for (n = 0; n < APR_MD5_DIGESTSIZE/4; n++) {
                ap_rprintf(r, "%08x", digest.num[n]);
            }
            ap_rputs("</code>", r);
            /* Print a link to the SHA1 version */
            ap_rputs("<br/><a href='?digest=sha1'>View the SHA1 hash instead</a>", r);
        }
        else {
            /* Calculate the SHA1 sum of the file */
            union {
                char      chr[20];
                uint32_t  num[5];
            } digest;
            apr_sha1_ctx_t sha1;
            apr_sha1_init(&sha1);
            readBytes = 256;
            while ( apr_file_read(file, buffer, &readBytes) == APR_SUCCESS ) {
                apr_sha1_update(&sha1, buffer, readBytes);
            }
            apr_sha1_final(digest.chr, &sha1);

            /* Print out the SHA1 digest */
            ap_rputs("<b>SHA1: </b><code>", r);
            for (n = 0; n < APR_SHA1_DIGESTSIZE/4; n++) {
                ap_rprintf(r, "%08x", digest.num[n]);
            }
            ap_rputs("</code>", r);

            /* Print a link to the MD5 version */
            ap_rputs("<br/><a href='?digest=md5'>View the MD5 hash instead</a>", r);
        }
        apr_file_close(file);

    }
    /* Let the server know that we responded to this request. */
    return OK;
}

static void register_hooks(apr_pool_t *pool)
{
    /* Create a hook in the request handler, so we get called when a request arrives */
    ap_hook_handler(example_handler, NULL, NULL, APR_HOOK_LAST);
}

AP_DECLARE_MODULE(example) =
{
    STANDARD20_MODULE_STUFF,
    NULL,
    NULL,
    NULL,
    NULL,
    NULL,
    register_hooks   /* Our hook registering function */
};