Firefox for Android custom addons hack

ff-addons.c

#include <sys/socket.h>
#include <sys/un.h>
#include <stdio.h>
#include <stdlib.h>
#include <dirent.h>
#include <unistd.h>
#include <stddef.h>

void write_request(int fd, const char* c)
{
    dprintf(fd, "%d:%s", strlen(c), c);
}

void read_response(char** p, size_t* psz, int fd)
{
    size_t sz = 0;
    char c;
    for(;;)
    {
        read(fd, &c, 1);
        if(c == ':')
            break;
        sz = 10 * sz + c - '0';
    }
    size_t cur = *psz;
    while(cur <= sz)
    {
        cur *= 2;
        if(!cur)
            cur = 1;
    }
    if(cur != *psz)
    {
        *psz = cur;
        *p = realloc(*p, *psz);
    }
    char* pp = *p;
    while(sz > 0)
    {
        ssize_t chk = read(fd, pp, sz);
        if(chk <= 0)
            break;
        pp += chk;
        sz -= chk;
    }
    *pp++ = 0;
}

int main(int argc, const char** argv)
{
    setbuf(stdout, NULL);
    if(argc != 2)
    {
        printf("usage: ff-addons <addon_dir>\n");
        return 1;
    }
    int sock = socket(AF_UNIX, SOCK_STREAM, 0);
    struct sockaddr_un un = {
        .sun_family = AF_UNIX,
        .sun_path = "\0org.mozilla.fenix/firefox-debugger-socket",
    };
    printf("connecting to debug... ");
    while(connect(sock, (struct sockaddr*)&un, offsetof(struct sockaddr_un, sun_path) + strlen(un.sun_path+1) + 1));
    printf("ok\n");
    char* p = 0;
    size_t sz = 0;
    read_response(&p, &sz, sock);
    printf("< %s\n", p);
    char* out1 = "{\"to\": \"root\", \"type\": \"getRoot\"}";
    printf("> %s\n", out1);
    write_request(sock, out1);
    read_response(&p, &sz, sock);
    printf("< %s\n", p);
    char* pp = strstr(p, "\"addonsActor\":");
    if(!pp)
        return 1;
    pp += 14;
    while(*pp != '"')
        pp++;
    char* ppp = pp+1;
    while(*ppp != '"')
    {
        if(*ppp == '\\')
            ppp++;
        ppp++;
    }
    *++ppp = 0;
    char* addons_actor = pp;
    size_t addons_actor_size = ppp - pp;
    DIR* d = opendir(argv[1]);
    struct dirent* de;
    while((de = readdir(d)))
    {
        if(de->d_name[0] == '.' && (!de->d_name[1] || (de->d_name[1] == '.' && !de->d_name[2])))
            continue;
        printf("installing %s\n", de->d_name);
        char path[strlen(argv[1])+strlen(de->d_name)+2];
        sprintf(path, "%s/%s", argv[1], de->d_name);
        char escaped[strlen(path)*2+1];
        char* p1 = escaped;
        for(char* i = path; *i; i++)
        {
            switch(*i)
            {
            case '\b':
                *p1++ = '\\';
                *p1++ = 'b';
                break;
            case '\f':
                *p1++ = '\\';
                *p1++ = 'r';
                break;
            case '\n':
                *p1++ = '\\';
                *p1++ = 'n';
                break;
            case '\r':
                *p1++ = '\\';
                *p1++ = 'r';
                break;
            case '\t':
                *p1++ = '\\';
                *p1++ = 't';
                break;
            case '"':
            case '\\':
                *p1++ = '\\';
                *p1++ = *i;
                break;
            default:
                *p1++ = *i;
            }
        }
        *p1++ = 0;
        char out3[addons_actor_size+(p1-escaped)+80];
        sprintf(out3, "{\"to\": %s, \"type\": \"installTemporaryAddon\", \"addonPath\": \"%s\"}", addons_actor, escaped);
        printf("> %s\n", out3);
        write_request(sock, out3);
        read_response(&p, &sz, sock);
        printf("< %s\n", p);
    }
    close(sock);
    return 0;
}

install.sh

# build c file with android ndk, and run this as root
# org.mozilla.fenix is for ff nightly, replace with org.mozilla.firefox for normal one
# you also need to enable remote debugging in ff settings
# then you can put xpis into /data/data/org.mozilla.fenix/files/addon_sideload
# and they will be loaded on each app start; swipe it off the alt-tab screen to force a restart
mkdir /data/data/org.mozilla.fenix/files/addon_sideload
cp ff-addons /data/data/org.mozilla.fenix/lib/
setprop wrap.org.mozilla.fenix 'p=/data/data/org.mozilla.fenix; $p/lib/ff-addons $p/files/addon_sideload & '