Re: [PATCH v2 1/5] misc-progs: addonctrl: Add support for 'Services' metadata

[Robin Roevens <robin.roevens@disroot.org>]

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Hi Michael

Thanks again for the review and comments.

Michael Tremer schreef op vr 07-10-2022 om 16:01 [+0100]:
> Hello again,
> 
> > On 6 Oct 2022, at 18:59, Robin Roevens <robin.roevens(a)disroot.org>
> > wrote:
> > 
> > * Addonctrl will now check in addon metadata for the exact
> > initscript
> >  names (Services). If more than one initscript is defined for an
> > addon,
> >  the requested action will be performed on all listed initscripts.
> > * Added posibility to perform action on a specific initscript of an
> >  addon instead of on all initscripts of the addon.
> > * New action 'list-services' to display a list of services related
> > to
> >  an addon.
> > * New action 'boot-status' to display wether service(s) are enabled
> >  to start on boot or not.
> > * More error checking and cleaner error reporting to user
> > * General cleanup and code restructuring to avoid code duplication
> > * Updated and made usage instructions more verbose.
> > 
> > Fixes: Bug#12935
> > Signed-off-by: Robin Roevens <robin.roevens(a)disroot.org>
> > ---
> > src/misc-progs/addonctrl.c | 397 +++++++++++++++++++++++++++++++---
> > ---
> > 1 file changed, 336 insertions(+), 61 deletions(-)
> > 
> > diff --git a/src/misc-progs/addonctrl.c b/src/misc-
> > progs/addonctrl.c
> > index 14b4b1325..1687aac19 100644
> > --- a/src/misc-progs/addonctrl.c
> > +++ b/src/misc-progs/addonctrl.c
> > @@ -10,71 +10,346 @@
> > #include <string.h>
> > #include <unistd.h>
> > #include <sys/types.h>
> > +#include <sys/stat.h>
> > #include <fcntl.h>
> > +#include <dirent.h>
> > +#include <fnmatch.h>
> > +#include <errno.h>
> > #include "setuid.h"
> > 
> > #define BUFFER_SIZE 1024
> > 
> > +const char *enabled_path = "/etc/rc.d/rc3.d";
> > +const char *disabled_path = "/etc/rc.d/rc3.d/off";
> > +
> > +char errormsg[BUFFER_SIZE] = "";
> > +const char *usage = 
> > +    "Usage\n"
> > +    "  addonctrl <addon>
> > (start|stop|restart|reload|enable|disable|status|boot-status|list-
> > services) [<service>]\n"
> > +    "\n"
> > +    "Options:\n"
> > +    "  <addon>\t\tName of the addon to control\n"
> > +    "  <service>\t\tSpecific service of the addon to control
> > (optional)\n"
> > +    "  \t\t\tBy default the requested action is performed on all
> > related services. See also 'list-services'.\n"
> > +    "  start\t\t\tStart service(s) of the addon\n"
> > +    "  stop\t\t\tStop service(s) of the addon\n"
> > +    "  restart\t\tRestart service(s) of the addon\n"
> > +    "  enable\t\tEnable service(s) of the addon to start at
> > boot\n"
> > +    "  disable\t\tDisable service(s) of the addon to start at
> > boot\n"
> > +    "  status\t\tDisplay current state of addon service(s)\n"
> > +    "  boot-status\t\tDisplay wether service(s) is enabled on boot
> > or not\n"
> > +    "  list-services\t\tDisplay a list of services related to the
> > addon";
> > +
> > +// Find a file <path> using <filepattern> as glob pattern. 
> > +// Returns the found filename or NULL if not found
> > +char *find_file_in_dir(const char *path, const char *filepattern) 
> > +{
> > +    struct dirent *entry;
> > +    DIR *dp;
> > +    char *found = NULL;
> > +
> > +    if ((dp = opendir(path)) != NULL) {
> > +        while(found == NULL && (entry = readdir(dp)) != NULL)
> > +            if (fnmatch(filepattern, entry->d_name, FNM_PATHNAME)
> > == 0)
> > +                found = strdup(entry->d_name);
> > +
> > +        closedir(dp);
> > +    }
> > +
> > +    return found;
> > +}
> > +
> > +// Reads Services metadata for <addon>.
> > +// Returns pointer to array of strings containing the services for
> > <addon> 
> > +// and sets <servicescnt> to the number of found services
> > +char **get_addon_services(const char *addon, int *servicescnt,
> > const char *filter) {
> > +    const char *metafile_prefix = "/opt/pakfire/db/installed/meta-
> > ";
> > +    const char *metadata_key = "Services";
> > +    const char *keyvalue_delim = ":";
> > +    const char *service_delim = " ";
> > +    char *token;
> > +    char **services = NULL;
> > +    char *service;
> > +    char *line = NULL;
> > +    size_t line_len = 0;
> > +    int i = 0;
> > +    char *metafile;
> > + 
> > +    if (addon == NULL) {
> > +        errno = EINVAL;
> > +        return NULL;
> > +    }
> > +
> > +    if (asprintf(&metafile, "%s%s", metafile_prefix, addon) == -1)
> > {
> > +        errno = ENOMEM;
> > +        return NULL;
> > +    }
> 
> You should initialise metafile with NULL before passing it to
> asprintf().

I'm not sure why? I can't find any information on why it should be
initialized to NULL as it is passed to malloc, which doesn't seem to
require it to be NULL beforehand. Or at least I didn't find any
documentation stating as such.

What I did find is that many implementations of C leave the string in
undefined state when it was unable to malloc. While others (like GNU)
set it to NULL explicitly if malloc fails.

But since I check the return value of asprintf, I never read or touch
the returned string, undefined or not, so I didn't think it was
required.

But I'll initialize them. It's probably indeed the safest to do anyway.

> 
> asprintf() will automatically set errno, actually.

Ok. I was not sure as the manpage for asprintf does not mention that
while the manpage for for example strdup does mention that explicitly.
And I have investigated the source of asprintf, and it does not set
errno when there is a problem with malloc.. 
But now I found that malloc itself actually sets errno. So it will
indeed be set by asprintf too as that calls malloc.
So I'll remove all my setting of ENOMEM.

> 
> > +
> > +    FILE *fp = fopen(metafile,"r");
> > +    if (fp != NULL) {
> 
> Just FYI, I like writing this check as “if (!fp)” because it is a a
> lot shorter...

It seems there are 2 camps about this, one just writes what you like to
write, while the other argues it is more clear that you are working
with pointers by explicitly checking against NULL.

But if you think that is unnecessary I'll change it.
Should I change all my other checks against NULL also? Or only the
filepointer ? 

> 
> > +        // Get initscript(s) for addon from meta-file
> > +        while (getline(&line, &line_len, fp) != -1 && services ==
> > NULL) {
> > +            // Strip newline
> > +            char *newline = strchr(line, '\n');
> > +            if (newline) *newline = 0;
> 
> Yes, this will cut off the trailing newline.
> 
> > +
> > +            // Parse key/value and look for required key.
> > +            token = strtok(line, keyvalue_delim);
> > +            if (token != NULL && strcmp(token, metadata_key) == 0)
> > {
> > +                token = strtok(NULL, keyvalue_delim);
> > +                if (token != NULL) {
> > +                    // Put each service in services array
> > +                    service = strtok(token, service_delim);
> > +                    while (service != NULL) {
> > +                        // if filter is set, only select filtered
> > service
> > +                        if ((filter != NULL && strcmp(filter,
> > service) == 0) || 
> > +                            filter == NULL) {
> > +                            services = reallocarray(services ,i+1
> > ,sizeof (char *));
> > +                            if (services != NULL)
> > +                                services[i++] = strdup(service);
> 
> Technically you could check whether strdup() was successful, but I
> would accept this version.

Indeed, I forgot. As you gave enough comments to need a new version of
the patchset, I'll include this too anyway. :-)

> 
> > +                            else 
> > +                                break;
> > +                        }
> > +                        service = strtok(NULL, service_delim);
> > +                    }
> > +                }
> > +            }
> > +        }
> > +
> > +        free(line);
> 
> Are you sure that line will always be non-NULL?
> 
> What happens if you read an empty file and getline() exists
> immediately without ever allocating a buffer?

You are right. Not sure what will happen then. So I'll check if 'line'
is not NULL before trying to free it.

> 
> > +        fclose(fp);
> > +    }  else {
> > +        snprintf(errormsg, BUFFER_SIZE - 1, "Addon '%s' not
> > found.\n\n%s", addon, usage);
> > +    }
> > +
> > +    free(metafile);
> > +    *servicescnt = i;
> > +    return services;
> > +}
> > +
> > +// Calls initscript <service> with parameter <action>
> > +int initscript_action(const char *service, const char *action) {
> > +    const char *initd_path = "/etc/rc.d/init.d";
> > +    char *initscript;
> 
> Same here. Please initialise it.
> 
> > +    char *argv[] = {
> > +        action,
> > +        NULL
> > +    };
> > +    int r = 0;
> > +
> > +    if ((r = asprintf(&initscript, "%s/%s", initd_path, service))
> > != -1) {
> > +        r = run(initscript, argv);
> > +        free(initscript);
> > +    } else {
> > +        errno = ENOMEM;
> > +    }
> 
> This could look slightly cleaner as:
> 
> …
> 
> r = asprintf(&initscript, ….);
> if (r > 0) {
>   r = run(initscript, argv);
> }
> 
> if (initscript)
>   free(initscript);
> 
> return r;
> 
> Maybe… I don’t know.

Yes, indeed, as I don't have to set ENOMEM

> 
> > +
> > +    return r; 
> > +}
> > +
> > +// Move an initscript with filepattern from <src_path> to
> > <dest_path>
> > +// Returns:
> > +//   -1: Error during move or memory allocation. Details in errno
> > +//   0: Success
> > +//   1: file was not moved, but is already in <dest_path>
> > +//   2: file does not exist in either in <src_path> or <dest_path>
> > +int move_initscript_by_pattern(const char *src_path, const char
> > *dest_path, const char *filepattern) {
> > +    char *src = NULL;
> > +    char *dest = NULL;
> > +    int r = 1;
> > +    char *filename = NULL;
> > +
> > +    if ((filename = find_file_in_dir(src_path, filepattern)) !=
> > NULL) {
> > +        if ((r = asprintf(&src, "%s/%s", src_path, filename)) != -
> > 1 &&
> > +            (r = asprintf(&dest, "%s/%s", dest_path, filename) !=
> > -1)) {
> > +            // move initscript
> > +            r = rename(src, dest);
> > +        } else {
> > +            errno = ENOMEM;
> > +        }
> > +
> > +        if (src != NULL)
> > +            free(src);
> > +        if (dest != NULL)
> > +            free(dest);
> > +    } else {
> > +        if ((filename = find_file_in_dir(dest_path, filepattern))
> > == NULL) 
> > +            r = 2;
> > +    }
> > +
> > +    if (filename != NULL)
> > +        free(filename);
> > +
> > +    return r;
> > +}
> > +
> > +// Enable/Disable addon service(s) by moving initscript symlink
> > from/to disabled_path
> > +int toggle_service(const char *service, const char *action) {
> > +    const char *src_path, *dest_path;
> > +    char *filepattern; 
> 
> Init to NULL.
> 
> > +    int r = 0;
> > +    
> > +    if (asprintf(&filepattern, "S??%s", service) == -1) {
> > +        errno = ENOMEM;
> > +        return -1;
> > +    }
> > +
> > +    if (strcmp(action, "enable") == 0) {
> > +        src_path = disabled_path;
> > +        dest_path = enabled_path;
> > +    } else {
> > +        src_path = enabled_path;
> > +        dest_path = disabled_path;
> > +    }
> > +
> > +    // Ensure disabled_path exists
> > +    errno = 0;
> > +    if (mkdir(disabled_path, S_IRWXU + S_IRGRP + S_IXGRP + S_IROTH
> > + S_IXOTH) == -1 && errno != EEXIST) {
> > +        r = 1;
> > +        snprintf(errormsg, BUFFER_SIZE -1, "Error creating %s.
> > (Error: %d)", disabled_path, errno);
> > +    } else {
> > +        r = move_initscript_by_pattern(src_path, dest_path,
> > filepattern);
> > +        if (r == -1 ) {
> > +            r = 1;
> > +            snprintf(errormsg, BUFFER_SIZE - 1, "Could not %s %s.
> > (Error: %d)", action, service, errno);
> > +        } else if (r == 1) {
> > +            snprintf(errormsg, BUFFER_SIZE - 1, "Service %s is
> > already %sd. Skipping...", service, action);
> > +        } else if (r == 2) {
> > +            snprintf(errormsg, BUFFER_SIZE - 1, "Unable to %s
> > service %s. (Service has no valid symlink in %s).", action,
> > service, src_path);
> > +        }
> > +    }
> > +
> > +    free(filepattern);
> > +    
> > +    return r;
> > +}
> > +
> > +// Print to stdout wether <service> is enabled or disabled on boot
> > +// Prints <service> as Not available when initscript is not found
> > +// in either enabled_path or disabled_path.
> > +void print_boot_status(char *service) {
> > +    char *filepattern;
> 
> NULL. How does this even run without it?
> 
> > +    if (asprintf(&filepattern, "S??%s", service) == -1) {
> > +        errno = ENOMEM;
> > +        return;
> > +    }
> > +
> > +    if (find_file_in_dir(enabled_path, filepattern) != NULL) 
> > +        fprintf(stdout, "%s is enabled on boot.\n", service);
> > +    else if (find_file_in_dir(disabled_path, filepattern) != NULL)
> > +        fprintf(stdout, "%s is disabled on boot.\n", service);
> > +    else
> > +        fprintf(stdout, "%s is not available for boot. (Service
> > has no valid symlink in either %s or %s).\n", service,
> > enabled_path, disabled_path);
> > +
> > +    free(filepattern);
> > +}
> > +
> > int main(int argc, char *argv[]) {
> > -       char command[BUFFER_SIZE];
> > -
> > -       if (!(initsetuid()))
> > -               exit(1);
> > -
> > -       if (argc < 3) {
> > -               fprintf(stderr, "\nMissing arguments.\n\naddonctrl
> > addon (start|stop|restart|reload|enable|disable)\n\n");
> > -               exit(1);
> > -       }
> > -
> > -       const char* name = argv[1];
> > -
> > -       if (strlen(name) > 32) {
> > -           fprintf(stderr, "\nString to large.\n\naddonctrl addon
> > (start|stop|restart|reload|enable|disable)\n\n");
> > -           exit(1);
> > -       }
> > -
> > -       // Check if the input argument is valid
> > -       if (!is_valid_argument_alnum(name)) {
> > -               fprintf(stderr, "Invalid add-on name: %s\n", name);
> > -               exit(2);
> > -       }
> > -
> > -       sprintf(command, "/opt/pakfire/db/installed/meta-%s",
> > name);
> > -       FILE *fp = fopen(command,"r");
> > -       if ( fp ) {
> > -           fclose(fp);
> > -       } else {
> > -           fprintf(stderr, "\nAddon '%s' not found.\n\naddonctrl
> > addon (start|stop|restart|reload|status|enable|disable)\n\n",
> > name);
> > -           exit(1);
> > -       }
> > -
> > -       if (strcmp(argv[2], "start") == 0) {
> > -               snprintf(command, BUFFER_SIZE - 1,
> > "/etc/rc.d/init.d/%s start", name);
> > -               safe_system(command);
> > -       } else if (strcmp(argv[2], "stop") == 0) {
> > -               snprintf(command, BUFFER_SIZE - 1,
> > "/etc/rc.d/init.d/%s stop", name);
> > -               safe_system(command);
> > -       } else if (strcmp(argv[2], "restart") == 0) {
> > -               snprintf(command, BUFFER_SIZE - 1,
> > "/etc/rc.d/init.d/%s restart", name);
> > -               safe_system(command);
> > -       } else if (strcmp(argv[2], "reload") == 0) {
> > -               snprintf(command, BUFFER_SIZE - 1,
> > "/etc/rc.d/init.d/%s reload", name);
> > -               safe_system(command);
> > -       } else if (strcmp(argv[2], "status") == 0) {
> > -               snprintf(command, BUFFER_SIZE - 1,
> > "/etc/rc.d/init.d/%s status", name);
> > -               safe_system(command);
> > -       } else if (strcmp(argv[2], "enable") == 0) {
> > -               snprintf(command, BUFFER_SIZE - 1, "mv -f
> > /etc/rc.d/rc3.d/off/S??%s /etc/rc.d/rc3.d" , name);
> > -               safe_system(command);
> > -       } else if (strcmp(argv[2], "disable") == 0) {
> > -               snprintf(command, BUFFER_SIZE - 1, "mkdir -p
> > /etc/rc.d/rc3.d/off");
> > -               safe_system(command);
> > -               snprintf(command, BUFFER_SIZE - 1, "mv -f
> > /etc/rc.d/rc3.d/S??%s /etc/rc.d/rc3.d/off" , name);
> > -               safe_system(command);
> > -       } else {
> > -               fprintf(stderr, "\nBad argument given.\n\naddonctrl
> > addon (start|stop|restart|reload|enable|disable)\n\n");
> > -               exit(1);
> > -       }
> > -
> > -       return 0;
> > +    char **services = NULL;
> > +    int servicescnt = 0;
> > +    char *addon = argv[1];
> > +    char *action = argv[2];
> > +    char *service_filter = NULL;
> > +    int r = 0;
> > +
> > +    if (!(initsetuid()))
> > +        exit(1);
> > +
> > +    if (argc < 3) {
> > +        fprintf(stderr, "\nMissing arguments.\n\n%s\n\n", usage);
> > +        exit(1);
> > +    }
> > +
> > +    if (argc == 4 && strcmp(action, "list-services") != 0)
> > +        service_filter = argv[3];
> > +
> > +    if (strlen(addon) > 32) {
> > +        fprintf(stderr, "\nString too large.\n\n%s\n\n", usage);
> > +        exit(1);
> > +    }
> > +
> > +    // Check if the input argument is valid
> > +    if (!is_valid_argument_alnum(addon)) {
> > +        fprintf(stderr, "Invalid add-on name: %s.\n", addon);
> > +        exit(2);
> > +    }
> > +
> > +    // Get initscript name(s) from addon metadata
> > +    errno = 0;
> 
> There is usually no need to reset this.

I noticed before, during testing, that, since I do an mkdir in
toggle_service, but ignore the error if it is EEXIST, that later in the
code after using other functions that could produce errno, errno keeps
the value EEXIST if those functions just succeed.
And as get_addon_services could return NULL when there are no services
but could also return NULL due to an error with errno set.
However when no error occurred and the EEXIST error is still in errno,
the code would falsely conclude that services is NULL due to an error.
So now for safety, I make sure it is set to 0 before I call
get_addon_services.

> 
> > +    services = get_addon_services(addon, &servicescnt,
> > service_filter);
> > +    if (services == NULL || *services == 0) {
> > +        if (errno != 0)
> 
> This is not reliable error checking. The function should return a
> defined value if an error has occurred (e.g. NULL) and an error is
> detected, that error should be handled.
> 
> So in this case:
> 
>   services = get_addon_services(…);
>   if (!services) {
>     printf(“ERROR: …\”);
> 
>   }
> 
>   … Other code, on success…
> 
> Now, NULL is not a very good indicator because your problem might be
> that an error has been found and therefore the function aborted, or
> that there is actually no services available for this package.
> 
> You could handle this by setting errno to something like ENOENT (No
> such file or directory) and handle that separately:
> 
>   services = get_addon_services(…);
>   if (!services) {
>     switch (errno) {
>       case ENOENT:
>         DO SOMETHING;
>         Break;
> 
>       default:
>         printf(“ERROR: …\”);
>         DO SOMETING ELSE
>   }

I'm not sure why it is not reliable?

I had thought about setting errno before; but I saw it being strongly
discouraged in many discussions on the web; unless you where writing an
actual system library. So I went for my own 'errormsg'; And I check if
errno is set for system errors, if not, check my own errormsg for
function errors. If both are clear, services is NULL due to no
services.  (which could then be due to an invalid filter, or just no
services for the addon)

> 
> Finally, instead of printing the errno number in the error message,
> you can use %m (without any argument) which will be automatically
> converted into something human readable.

Are you sure? As I found this:
> The %m directive is not portable, use %s mapped to an argument of
> strerror(errno) (or a version of strerror_r) instead. 
here:
https://www.gnu.org/software/gnulib/manual/html_node/asprintf.html

> 
> > +            fprintf(stderr, "\nSystem error occured. (Error:
> > %d)\n\n", errno);
> > +        else if (strcmp(errormsg, "") != 0)
> > +            fprintf(stderr, "\n%s\n\n", errormsg);
> > +        else if (service_filter != NULL)
> > +            fprintf(stderr, "\nNo service '%s' found for addon
> > '%s'. Use 'list-services' to get a list of available
> > services\n\n%s\n\n", service_filter, addon, usage);
> > +        else
> > +            fprintf(stderr, "\nAddon '%s' has no services.\n\n",
> > addon);
> > +        exit(1);
> > +    }
> > +
> > +    // Handle requested action
> > +    if (strcmp(action, "start") == 0 ||
> > +        strcmp(action, "stop") == 0 ||
> > +        strcmp(action, "restart") == 0 ||
> > +        strcmp(action, "reload") == 0 ||
> > +        strcmp(action, "status") == 0) {
> > +
> > +        errno = 0;
> > +        for(int i = 0; i < servicescnt; i++) {
> > +            if (initscript_action(services[i], action) != 0) {
> > +                r = 1;
> > +                if (errno != 0) 
> > +                    fprintf(stderr, "\nSystem error occured.
> > (Error: %d)\n\n", errno);
> > +                    break;
> > +            }
> > +        }
> > +
> > +    } else if (strcmp(action, "enable") == 0 ||
> > +               strcmp(action, "disable") == 0) {
> > +
> > +        errno = 0;
> > +        for(int i = 0; i < servicescnt; i++) {
> > +            if (toggle_service(services[i], action) == 0) {
> > +                fprintf(stdout, "%sd service %s\n", action,
> > services[i]);
> 
> If you want to just print something, just use printf.

Ok

> 
> > +            } else if (errno != 0) {
> > +                r = 1;
> > +                fprintf(stderr, "\nSystem error occured. (Error:
> > %d)\n\n", errno);
> > +                break;
> > +            } else {
> > +                r = 1;
> > +                fprintf(stderr, "\n%s\n\n", errormsg);
> > +            }
> > +        }
> > +
> > +    } else if (strcmp(action, "boot-status") == 0) {
> > +        errno = 0;
> > +        for(int i = 0; i < servicescnt; i++) {
> > +            print_boot_status(services[i]);
> > +            if (errno != 0) {
> > +                r = 1;
> > +                fprintf(stderr, "\nSystem error occured. (Error:
> > %d)\n\n", errno);
> > +                break;
> > +            }
> > +        }
> > +    
> > +    } else if (strcmp(action, "list-services") == 0) {
> > +        fprintf(stdout, "\nServices for addon %s:\n", addon);
> > +        for(int i = 0; i < servicescnt; i++) {
> > +            fprintf(stdout, "  %s\n", services[i]);
> > +        }
> > +        fprintf(stdout, "\n");
> > +
> > +    } else {
> > +        fprintf(stderr, "\nBad argument given.\n\n%s\n\n", usage);
> > +        r = 1;
> > +    }
> > +
> > +    // Cleanup
> > +    for(int i = 0; i < servicescnt; i++) 
> > +        free(services[i]);
> > +    free(services);
> > +
> > +    return r;
> > }
> 
> Otherwise, this looks a lot better since the last version :)

Thanks. I'm learning a lot.

Robin

> 
> -Michael
> 
> > -- 
> > 2.37.3
> > 
> > 
> > -- 
> > Dit bericht is gescanned op virussen en andere gevaarlijke
> > inhoud door MailScanner en lijkt schoon te zijn.
> > 
> 
> 

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