Premier commit.

Trois programmes:
	- authKeysPg génère un fichier .authorized_keys à partir de la BDD
	- pam_oath_key est un module PAM demandant un mot de passe otp selon la clé de connection SSH utilisée
	- bash-gitonly est un «shell» qui execute les commandes transmises par SSH, uniquement reliées à git et en vérifiant les permissions
This commit is contained in:
Mysaa Java 2021-05-03 22:29:20 +02:00
commit 04d63fd09f
7 changed files with 608 additions and 0 deletions

4
.gitignore vendored Normal file
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auth-keys-gen
bash-gitonly
*.so
*.o

3
.gitmodules vendored Normal file
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[submodule "nargv"]
path = nargv
url = https://github.com/hypersoft/nargv

20
Makefile Normal file
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.PHONY: all install
all: bash-gitonly pam_oath_key.so auth-keys-gen
nargv/argvt.o: nargv/nargv.c
gcc -c nargv/nargv.c -o nargv/argvt.o
bash-gitonly: nargv/argvt.o bash-gitonly.c
gcc bash-gitonly.c nargv/argvt.o -I . -o bash-gitonly
pam_oath_key.so: pam_oath_key.c
gcc pam_oath_key.c -I/usr/system/include/ -I/usr/server/postgresql/include/ -L/usr/server/postgresql/lib/ -L/usr/libraries/lib/ -shared -lpam -lpq -loath -fPIC -o pam_oath_key.so
auth-keys-gen: authKeysPg.c
gcc authKeysPg.c -o auth-keys-gen -L/usr/server/postgresql/lib -I/usr/server/postgresql/include -lpq
install: all
cp pam_oath_key.so /lib/security
cp bash-gitonly /srv/git/bin
cp auth-keys-gen /srv/etc/

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authKeysPg.c Normal file
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#include <stdio.h>
#include <stdlib.h>
#include "libpq-fe.h"
#include <string.h>
static void
exit_nicely(PGconn *conn)
{
PQfinish(conn);
exit(1);
}
int
main(int argc, char **argv)
{
PGconn *conn;
PGresult *res;
int nFields;
int j,i;
/*
char *password;
const char *passFileName = "/srv/bdd/pipi-system.pass";
FILE *passFile;
passFile = fopen(passFileName, "r");
fgets(password,127,passFile);
fclose(passFile);
printf("%-15s",password);
const char *connfirst = "dbname='pipi-system' user=pipiadmin password=";
//int lgt = strlen(connfirst) + strlen(password);
char * conninfo = (char *) malloc(256);
strcpy(conninfo,connfirst);
strcat(conninfo,password);
/* Crée une connexion à la base de données */
char *conninfo = "dbname='pipi-system' user=pipiadmin password='oaelEAAZH3Pr+hej43NnISY+RqkDpl09EHqzWu4XGQWUkG/Tkb+an2Triybhog/lkb/NRYK6b277duP0d3MF'";
conn = PQconnectdb(conninfo);
/* Vérifier que la connexion au backend a été faite avec succès */
if (PQstatus(conn) != CONNECTION_OK)
{
fprintf(stderr, "Connection to database failed: %s", PQerrorMessage(conn));
exit_nicely(conn);
}
/* Initialise un search path sûr, pour qu'un utilisateur
malveillant ne puisse prendre le contrôle. */
res = PQexec(conn,
"SELECT pg_catalog.set_config('search_path', '', false)");
if (PQresultStatus(res) != PGRES_TUPLES_OK)
{
fprintf(stderr, "SET failed: %s", PQerrorMessage(conn));
PQclear(res);
exit_nicely(conn);
}
/*
* Il faut libérer PGresult avec PQclear dès que l'on en a plus besoin pour
* éviter les fuites de mémoire.
*/
PQclear(res);
//res = PQprepare(conn,"GettingAllLoginGitUsersInfo","SELECT * FROM $1",1,NULL);
//const char * tablename = "git-users";
//res = PQexecPrepared(conn,"GettingAllLoginGitUsersInfo",1,"git-users",NULL,NULL,0);
res = PQexec(conn,"SELECT * FROM login.\"git-users\"");
/* affiche d'abord les noms des attributs */
nFields = PQnfields(res);
fprintf(stderr, PQerrorMessage(conn));
/* puis affiche les lignes */
for (i = 0; i < PQntuples(res); i++)
{
printf("ssh-ed25519 %s\n",PQgetvalue(res,i,3));
//printf("environment=\"GIT_USER_UID=%s\" ssh-ed25519 %s\n",PQgetvalue(res, i, 1),PQgetvalue(res,i,3));
}
PQclear(res);
/* ferme la connexion à la base et nettoie */
PQfinish(conn);
return 0;
}

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bash-gitonly.c Normal file
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#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include "nargv/nargv.h"
#include <unistd.h> /* for fork */
#include <sys/types.h> /* for pid_t */
#include <sys/wait.h> /* for wait */
#define ANSI_COLOR_GREEN "\x1b[32m"
#define ANSI_COLOR_RESET "\x1b[0m"
#define AUTHORIZED_SHELL_COMMAND "bash-gitonly"
#define AUTHORIZED_COMMANDS "git-receive-pack","git-upload-pack","git-upload-archive"
#define AUTHORIZED_COMMANDS_COUNT 3
#define COMMANDS_PATH "/bin/"
#define MAX_FULL_EXECFILENAME_LENGTH 24
char* isCmdAuthorized(char* cmd){
const char* authorizedCommands[] = {AUTHORIZED_COMMANDS};
for (int i=0; i<AUTHORIZED_COMMANDS_COUNT-1;i++){
char * curseur = cmd;
const char * reader = authorizedCommands[i];
while(*curseur!=' ' && *curseur != '\0' && *curseur==*reader){
curseur++;
reader++;
}
if(*curseur == ' ' || *curseur == '\0')
return curseur;
}
return NULL;
}
int main(int argc, char **argv, char **envp)
{
fprintf(stderr,"Printing environnement: \n");
for (char **env = envp; *env != 0; env++)
{
char *thisEnv = *env;
fprintf(stderr,"%s\n", thisEnv);
}
int counter;
for(counter=0; counter<argc; counter++)
printf("argv[%2d]: %s\n",counter,argv[counter]);
const char* sshcmdname = "/bin/bash-gitonly";
const char* sshcmdflags = "-c";
// Ce bout de code est ultra-restrictif et risque de planter si SSH change. Le message sera alors reconaissable.
if(argc !=3 || (strcmp(argv[0],AUTHORIZED_SHELL_COMMAND)!=0 && strcmp(argv[0],COMMANDS_PATH AUTHORIZED_SHELL_COMMAND)) || strcmp(argv[1],sshcmdflags)!=0){
fprintf(stderr, ANSI_COLOR_GREEN "Pas de bash ici, il vous faut un «vrai» accès SSH" ANSI_COLOR_RESET "\n");
return 1;
}
// Verification que la commande envoyée est bien une commande git
char* sshCommandEnd = isCmdAuthorized(argv[2]);
if(sshCommandEnd == NULL){
fprintf(stderr, ANSI_COLOR_GREEN "Wow ! ce canal est réservé aux commandes de données git, pour le reste, utilisez un «vrai» accès SSH" ANSI_COLOR_RESET "\n");
return 1;
}
// Récupération de l'utilisateur
// Récupération du repo et du droit d'accès demandés
// Récupération de l'autorisation auprès du serveur Pgsql
// On effectue la commande.
char execFilename[MAX_FULL_EXECFILENAME_LENGTH] = COMMANDS_PATH;
*sshCommandEnd = '\0';
strcat(execFilename, argv[2]);
*sshCommandEnd = ' ';
const char* sshArgs = sshCommandEnd+1;
NARGV* subargv = nargv_parse(argv[2]);
fprintf(stderr,"Trying to parse '%s': %i args\n",sshArgs,subargv->argc);
fprintf(stderr,"Error code: %i\n",subargv->error_code);
for(int i = 0;i<subargv->argc;i++){
fprintf(stderr,"%02d -> %s\n",i,subargv->argv[i]);
}
if (subargv->error_code) {
fprintf(stderr,"nargv parse error: %i: %s: at input column %i\n",
subargv->error_code, subargv->error_message, subargv->error_index);
return 2;
}
pid_t pid=fork();
if (pid==0) { /* child process */
//static char *argv[]={"echo","Foo is my name.",NULL};
execve(execFilename, subargv->argv, (char *const []){NULL});
exit(127); /* only if execv fails */
}
else { /* pid!=0; parent process */
waitpid(pid,0,0); /* wait for child to exit */
}
nargv_free(subargv);
return 0;
}

1
nargv Submodule

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Subproject commit c022a75fad52e297bdb6ab98f026e58f516def00

376
pam_oath_key.c Normal file
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#include "liboath/oath.h"
#include "libpq-fe.h"
#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>
#include <ctype.h>
// These #defines must be present according to PAM documentation.
#define PAM_SM_AUTH
//#define PAM_SM_ACCOUNT
//#define PAM_SM_SESSION
//#define PAM_SM_PASSWORD
#include <security/pam_appl.h>
#include <security/pam_modules.h>
// Les fonctions de debug
#define D(x) do {\
printf("[%s:%s(%d)] ", __FILE__, __FUNCTION__, __LINE__);\
printf x;\
printf("\n");\
} while (0)
#define DBG(x) if (cfg.debug) {\
D(x);\
}
#define PAM_EXTERN extern
// Static options
#define BDD_PASS_FILE "/srv/bdd/pipi-system.pass"
#define BDD_CONN_LENGTH 255
#define MIN_OTP_LEN 6
#define DEFAULT_OTP_LEN 6
#define MAX_OTP_LEN 8
#define OTP_SECRET_LEN 32
#define SSH_AUTH_INFO_LEN 1024
struct cfg {
int debug;
int digits;
int window;
};
static void
parse_cfg(int flags, int argc,
const char ** argv, struct cfg * cfg) {
int i;
cfg -> debug = 0;
cfg -> digits = 6;
cfg -> window = 5;
for (i = 0; i < argc; i++) {
if (strcmp(argv[i], "debug") == 0)
cfg -> debug = 1;
if (strncmp(argv[i], "digits=", 7) == 0)
cfg -> digits = atoi(argv[i] + 7);
if (strncmp(argv[i], "window=", 7) == 0)
cfg -> window = atoi(argv[i] + 7);
}
if (MIN_OTP_LEN > cfg -> digits || cfg -> digits > MAX_OTP_LEN) {
D(("La longueur du code otp doit être entre %i et %i. Valeur invalide: digits=%i",MIN_OTP_LEN,MAX_OTP_LEN, cfg -> digits));
}
if (cfg -> debug) {
D(("called."));
D(("flags %d argc %d", flags, argc));
for (i = 0; i < argc; i++)
D(("argv[%d]=%s", i, argv[i]));
D(("debug=%d", cfg -> debug));
D(("digits=%d", cfg -> digits));
D(("window=%d", cfg -> window));
}
}
char * strtokk(char * str,const char cutter) {
while((*str != cutter) && (*str != '\0'))
str++;
bool strEnd = (*str == '\0');
*str = '\0';
if(!strEnd)
str++;
return str;
}
char hexCharReader(char hex){
if('0'<=hex && hex<='9')
return hex-'0';
else
return hex-'a'+10;
}
void hexToBytes(char * str, char arr[]){
int pos = 0;
while(*str != '\0'){
char b1 = hexCharReader(*str);
str++;
char b0 = hexCharReader(*str);
str++;
arr[pos] = b1<<4 | b0;
pos++;
}
return;
}
PAM_EXTERN int
pam_sm_authenticate(pam_handle_t * pamh, int flags, int argc, const char ** argv) {
int retval, rc;
const char * user = NULL;
const char * password = NULL;
char otp[MAX_OTP_LEN + 1];
int password_len = 0;
struct pam_conv * conv;
struct pam_message * pmsg[1], msg[1];
struct pam_response * resp;
int nargs = 1;
struct cfg cfg;
char * query_prompt = NULL;
char * onlypasswd = strdup(""); /* empty passwords never match */
PGconn *conn;
PGresult *res;
int nFields;
char * oathSecret;
/***** Parsing config *****/
parse_cfg(flags, argc, argv, & cfg);
/***** Getting User *****/
retval = pam_get_user(pamh, &user, NULL);
if (retval != PAM_SUCCESS) {
DBG(("Could not get PAM user: %s", pam_strerror(pamh, retval)));
goto done;
}
DBG(("We got the user: %s", user));
/****** Getting ssh key ******/
/* Retrieve SSH authentication information. */
char * ssh_auth_info_ret = (char *)pam_getenv(pamh, "SSH_AUTH_INFO_0");
char ssh_auth_info [SSH_AUTH_INFO_LEN];
ssh_auth_info_ret = "pubkey ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIKXQt1YWjKCsjcsFW7o1hdjAB/qxWBwesAeV0RcBeW0I";
strcpy(ssh_auth_info,ssh_auth_info_ret);
if (!ssh_auth_info || !*ssh_auth_info) {
DBG(("No SSH auth info, du coup on ignore"));
return PAM_IGNORE;
}
const char delim = ' ';
char * authType = ssh_auth_info;
char * sshKeyType = strtokk(ssh_auth_info, delim);
char * sshKeyVal = strtokk(sshKeyType, delim);
DBG(("Authentification Type: '%s'", authType));
DBG(("Authentification KeyType: '%s'", sshKeyType));
DBG(("Authentification KeyVal: '%s'", sshKeyVal));
rc = oath_init();
if (rc != OATH_OK) {
DBG(("oath_init() failed (%d)", rc));
retval = PAM_AUTHINFO_UNAVAIL;
goto done;
}
/****** Get oath secret from database ******/
char connInfo[BDD_CONN_LENGTH] = "dbname='pipi-system' user=pipiadmin password='";
char lastAp = '\'';
FILE *dbPassFile;
char ch;
int pos = strlen(connInfo);
dbPassFile = fopen(BDD_PASS_FILE,"r");
if (dbPassFile == NULL) {
DBG(("Cannot open file %s, on peut pas se connecter à la base de données\n", BDD_PASS_FILE));
retval = PAM_AUTHINFO_UNAVAIL;
goto done;
}
while (feof(dbPassFile))
{
connInfo[pos] = fgetc(dbPassFile);
pos++;
}
fclose(dbPassFile);
connInfo[pos] = '\'';
conn = PQconnectdb(connInfo);
/* Vérifier que la connexion au backend a été faite avec succès */
if (PQstatus(conn) != CONNECTION_OK) {
DBG(("Connection to database failed: %s", PQerrorMessage(conn)));
retval = PAM_AUTH_ERR;
goto done;
}
res = PQexec(conn,
"SELECT pg_catalog.set_config('search_path', '', false)");
if (PQresultStatus(res) != PGRES_TUPLES_OK) {
DBG(("SET failed: %s", PQerrorMessage(conn)));
PQclear(res);
retval = PAM_AUTH_ERR;
goto done;
}
DBG(("Initialisation de la base de données efféctuée"));
PQclear(res);
const char *paramValues[2];
paramValues[0] = sshKeyType;
paramValues[1] = sshKeyVal;
res = PQexecParams(conn, "SELECT \"oathPrivate\" FROM login.git WHERE \"sshKeyType\"=$1 AND \"sshPubKey\"=$2",2,NULL,paramValues,NULL,NULL,1);
if (PQresultStatus(res) != PGRES_TUPLES_OK) {
DBG(("SET failed: %s", PQerrorMessage(conn)));
PQclear(res);
retval = PAM_AUTH_ERR;
goto done;
}
nFields = PQntuples(res);
if(nFields!=1){
DBG(("Aucun code secret oath trouvé pour la clé '%s'", sshKeyVal));
PQclear(res);
retval = PAM_AUTH_ERR;
goto done;
}
oathSecret=PQgetvalue(res, 0, 0);
DBG(("On a récupéré le code secret : %s",oathSecret));
PQclear(res);
PQfinish(conn);
/*** Parsing hex to byte array ***/
char oathSecretBin[OTP_SECRET_LEN];
int oathSecretBinLen = OTP_SECRET_LEN+1;
oath_hex2bin(oathSecret,oathSecretBin,&oathSecretBinLen);
/****** Asking for password ******/
retval = pam_get_item(pamh, PAM_CONV, (const void ** ) & conv);
if (retval != PAM_SUCCESS) {
DBG(("get conv returned error: %s", pam_strerror(pamh, retval)));
goto done;
}
pmsg[0] = & msg[0];
{
const char * query_template = "One-time password (OATH) for `%s': ";
size_t len = strlen(query_template) + strlen(user);
size_t wrote;
query_prompt = malloc(len);
if (!query_prompt) {
retval = PAM_BUF_ERR;
goto done;
}
wrote = snprintf(query_prompt, len, query_template, user);
if (wrote < 0 || wrote >= len) {
retval = PAM_BUF_ERR;
goto done;
}
msg[0].msg = query_prompt;
}
msg[0].msg_style = PAM_PROMPT_ECHO_OFF;
resp = NULL;
retval = conv -> conv(nargs, (const struct pam_message ** ) pmsg, &
resp, conv -> appdata_ptr);
free(query_prompt);
query_prompt = NULL;
if (retval != PAM_SUCCESS) {
DBG(("conv returned error: %s", pam_strerror(pamh, retval)));
goto done;
}
DBG(("conv returned: %s", resp -> resp));
password = resp -> resp;
if (password)
password_len = strlen(password);
else {
DBG(("Could not read password"));
retval = PAM_AUTH_ERR;
goto done;
}
if (password_len < MIN_OTP_LEN) {
DBG(("OTP too short: %s", password));
retval = PAM_AUTH_ERR;
goto done;
} else if (password_len < cfg.digits) {
DBG(("OTP shorter than digits=%d: %s", cfg.digits, password));
retval = PAM_AUTH_ERR;
goto done;
} else if (password_len > MAX_OTP_LEN) {
DBG(("OTP too long (and no digits=): %s", password));
retval = PAM_AUTH_ERR;
goto done;
} else {
strcpy(otp, password);
password = NULL;
}
DBG(("Pouf ! OTP: %s", otp ? otp : "(null)"));
/****** Validation du mot de passe oath ******/
{
time_t last_otp;
time_t jetzt = 0;
time(&jetzt);
int timeStep = 30;
DBG(("Validating oath secret %s of length %i at time %ld",oathSecret,oathSecretBinLen, jetzt));
char cdex[32];
rc = oath_totp_validate(oathSecretBin, oathSecretBinLen, jetzt, timeStep, 0, cfg.window, otp);
}
if (rc == OATH_INVALID_OTP) {
DBG(("One-time password not authorized to login as user '%s'", user));
retval = PAM_AUTH_ERR;
goto done;
}
retval = PAM_SUCCESS;
/****** Terminé ! ******/
done:
oath_done();
free(query_prompt);
free(onlypasswd);
DBG(("Terminé ! [%s]", pam_strerror(pamh, retval)));
return retval;
}
PAM_EXTERN
int pam_sm_setcred(pam_handle_t *pamh,int flags,int argc
,const char **argv)
{
return PAM_SUCCESS;
}