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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-07 14:22:51 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-07 14:22:51 +0000 |
commit | 9ada0093e92388590c7368600ca4e9e3e376f0d0 (patch) | |
tree | a56fe41110023676d7082028cbaa47ca4b6e6164 /libpamc/test/modules/pam_secret.c | |
parent | Initial commit. (diff) | |
download | pam-upstream/1.5.2.tar.xz pam-upstream/1.5.2.zip |
Adding upstream version 1.5.2.upstream/1.5.2upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to '')
-rw-r--r-- | libpamc/test/modules/pam_secret.c | 669 |
1 files changed, 669 insertions, 0 deletions
diff --git a/libpamc/test/modules/pam_secret.c b/libpamc/test/modules/pam_secret.c new file mode 100644 index 0000000..f1c74c6 --- /dev/null +++ b/libpamc/test/modules/pam_secret.c @@ -0,0 +1,669 @@ +/* + * $Id$ + * + * Copyright (c) 1999 Andrew G. Morgan <morgan@linux.kernel.org> + */ + +/* + * WARNING: AS WRITTEN THIS CODE IS NOT SECURE. THE MD5 IMPLEMENTATION + * NEEDS TO BE INTEGRATED MORE NATIVELY. + */ + +#include <fcntl.h> +#include <pwd.h> +#include <stdio.h> +#include <string.h> +#include <sys/types.h> +#include <sys/stat.h> + +#include <security/pam_modules.h> +#include <security/pam_client.h> +#include <security/_pam_macros.h> + +/* + * This is a sample module that demonstrates the use of binary prompts + * and how they can be used to implement sophisticated authentication + * schemes. + */ + +struct ps_state_s { + int retval; /* last retval returned by the authentication fn */ + int state; /* what state the module was in when it + returned incomplete */ + + char *username; /* the name of the local user */ + + char server_cookie[33]; /* storage for 32 bytes of server cookie */ + char client_cookie[33]; /* storage for 32 bytes of client cookie */ + + char *secret_data; /* pointer to <NUL> terminated secret_data */ + int invalid_secret; /* indication of whether the secret is valid */ + + pamc_bp_t current_prompt; /* place to store the current prompt */ + pamc_bp_t current_reply; /* place to receive the reply prompt */ +}; + +#define PS_STATE_ID "PAM_SECRET__STATE" +#define PS_AGENT_ID "secret@here" +#define PS_STATE_DEAD 0 +#define PS_STATE_INIT 1 +#define PS_STATE_PROMPT1 2 +#define PS_STATE_PROMPT2 3 + +#define MAX_LEN_HOSTNAME 512 +#define MAX_FILE_LINE_LEN 1024 + +/* + * Routine for generating 16*8 bits of random data represented in ASCII hex + */ + +static int generate_cookie(unsigned char *buffer_33) +{ + static const char hexarray[] = "0123456789abcdef"; + int i, fd; + + /* fill buffer_33 with 32 hex characters (lower case) + '\0' */ + fd = open("/dev/urandom", O_RDONLY); + if (fd < 0) { + D(("failed to open /dev/urandom")); + return 0; + } + read(fd, buffer_33 + 16, 16); + close(fd); + + /* expand top 16 bytes into 32 nibbles */ + for (i=0; i<16; ++i) { + buffer_33[2*i ] = hexarray[(buffer_33[16+i] & 0xf0)>>4]; + buffer_33[2*i+1] = hexarray[(buffer_33[16+i] & 0x0f)]; + } + + buffer_33[32] = '\0'; + + return 1; +} + +/* + * XXX - This is a hack, and is fundamentally insecure. Its subject to + * all sorts of attacks not to mention the fact that all our secrets + * will be displayed on the command line for someone doing 'ps' to + * see. This is just for programming convenience in this instance, it + * needs to be replaced with the md5 code. Although I am loath to + * add yet another instance of md5 code to the Linux-PAM source code. + * [Need to think of a cleaner way to do this for the distribution as + * a whole...] + */ + +#define COMMAND_FORMAT "/bin/echo -n '%s|%s|%s'|/usr/bin/md5sum -" + +int create_digest(const char *d1, const char *d2, const char *d3, + char *buffer_33) +{ + int length; + char *buffer; + FILE *pipe; + + length = strlen(d1)+strlen(d2)+strlen(d3)+sizeof(COMMAND_FORMAT); + buffer = malloc(length); + if (buffer == NULL) { + D(("out of memory")); + return 0; + } + + sprintf(buffer, COMMAND_FORMAT, d1,d2,d3); + + D(("executing pipe [%s]", buffer)); + pipe = popen(buffer, "r"); + memset(buffer, 0, length); + free(buffer); + + if (pipe == NULL) { + D(("failed to launch pipe")); + return 0; + } + + if (fgets(buffer_33, 33, pipe) == NULL) { + D(("failed to read digest")); + return 0; + } + + if (strlen(buffer_33) != 32) { + D(("digest was not 32 chars")); + return 0; + } + + fclose(pipe); + + D(("done [%s]", buffer_33)); + + return 1; +} + +/* + * method to attempt to instruct the application's conversation function + */ + +static int converse(pam_handle_t *pamh, struct ps_state_s *new) +{ + int retval; + struct pam_conv *conv; + + D(("called")); + + retval = pam_get_item(pamh, PAM_CONV, (const void **) &conv); + if (retval == PAM_SUCCESS) { + struct pam_message msg; + struct pam_response *single_reply; + const struct pam_message *msg_ptr; + + memset(&msg, 0, sizeof(msg)); + msg.msg_style = PAM_BINARY_PROMPT; + msg.msg = (const char *) new->current_prompt; + msg_ptr = &msg; + + single_reply = NULL; + retval = conv->conv(1, &msg_ptr, &single_reply, conv->appdata_ptr); + if (retval == PAM_SUCCESS) { + if ((single_reply == NULL) || (single_reply->resp == NULL)) { + retval == PAM_CONV_ERR; + } else { + new->current_reply = (pamc_bp_t) single_reply->resp; + single_reply->resp = NULL; + } + } + + if (single_reply) { + free(single_reply); + } + } + +#ifdef PAM_DEBUG + if (retval == PAM_SUCCESS) { + D(("reply has length=%d and control=%u", + PAM_BP_LENGTH(new->current_reply), + PAM_BP_CONTROL(new->current_reply))); + } + D(("returning %s", pam_strerror(pamh, retval))); +#endif + + return retval; +} + +/* + * identify the secret in question + */ + +#define SECRET_FILE_FORMAT "%s/.secret@here" + +char *identify_secret(char *identity, const char *user) +{ + struct passwd *pwd; + char *temp; + FILE *secrets; + int length_id; + + pwd = getpwnam(user); + if ((pwd == NULL) || (pwd->pw_dir == NULL)) { + D(("user [%s] is not known", user)); + return NULL; + } + + length_id = strlen(pwd->pw_dir) + sizeof(SECRET_FILE_FORMAT); + temp = malloc(length_id); + if (temp == NULL) { + D(("out of memory")); + pwd = NULL; + return NULL; + } + + sprintf(temp, SECRET_FILE_FORMAT, pwd->pw_dir); + pwd = NULL; + + D(("opening key file [%s]", temp)); + secrets = fopen(temp, "r"); + memset(temp, 0, length_id); + + if (secrets == NULL) { + D(("failed to open key file")); + return NULL; + } + + length_id = strlen(identity); + temp = malloc(MAX_FILE_LINE_LEN); + + for (;;) { + char *secret = NULL; + + if (fgets(temp, MAX_FILE_LINE_LEN, secrets) == NULL) { + fclose(secrets); + return NULL; + } + + D(("cf[%s][%s]", identity, temp)); + if (memcmp(temp, identity, length_id)) { + continue; + } + + D(("found entry")); + fclose(secrets); + + for (secret=temp+length_id; *secret; ++secret) { + if (!(*secret == ' ' || *secret == '\n' || *secret == '\t')) { + break; + } + } + + memmove(temp, secret, MAX_FILE_LINE_LEN-(secret-(temp+length_id))); + secret = temp; + + for (; *secret; ++secret) { + if (*secret == ' ' || *secret == '\n' || *secret == '\t') { + break; + } + } + + if (*secret) { + *secret = '\0'; + } + + D(("secret found [%s]", temp)); + + return temp; + } + + /* NOT REACHED */ +} + +/* + * function to perform the two message authentication process + * (with support for event driven conversation functions) + */ + +static int auth_sequence(pam_handle_t *pamh, + const struct ps_state_s *old, struct ps_state_s *new) +{ + const char *rhostname; + const char *rusername; + int retval; + + retval = pam_get_item(pamh, PAM_RUSER, (const void **) &rusername); + if ((retval != PAM_SUCCESS) || (rusername == NULL)) { + D(("failed to obtain an rusername")); + new->state = PS_STATE_DEAD; + return PAM_AUTH_ERR; + } + + retval = pam_get_item(pamh, PAM_RHOST, (const void **) &rhostname); + if ((retval != PAM_SUCCESS) || (rhostname == NULL)) { + D(("failed to identify local hostname: ", pam_strerror(pamh, retval))); + new->state = PS_STATE_DEAD; + return PAM_AUTH_ERR; + } + + D(("switch on new->state=%d [%s@%s]", new->state, rusername, rhostname)); + switch (new->state) { + + case PS_STATE_INIT: + { + const char *user = NULL; + + retval = pam_get_user(pamh, &user, NULL); + + if ((retval == PAM_SUCCESS) && (user == NULL)) { + D(("success but no username?")); + new->state = PS_STATE_DEAD; + retval = PAM_USER_UNKNOWN; + } + + if (retval != PAM_SUCCESS) { + if (retval == PAM_CONV_AGAIN) { + retval = PAM_INCOMPLETE; + } else { + new->state = PS_STATE_DEAD; + } + D(("state init failed: %s", pam_strerror(pamh, retval))); + return retval; + } + + /* nothing else in this 'case' can be retried */ + + new->username = strdup(user); + if (new->username == NULL) { + D(("out of memory")); + new->state = PS_STATE_DEAD; + return PAM_BUF_ERR; + } + + if (! generate_cookie(new->server_cookie)) { + D(("problem generating server cookie")); + new->state = PS_STATE_DEAD; + return PAM_ABORT; + } + + new->current_prompt = NULL; + PAM_BP_RENEW(&new->current_prompt, PAM_BPC_SELECT, + sizeof(PS_AGENT_ID) + strlen(rusername) + 1 + + strlen(rhostname) + 1 + 32); + sprintf(PAM_BP_WDATA(new->current_prompt), + PS_AGENT_ID "/%s@%s|%.32s", rusername, rhostname, + new->server_cookie); + + /* note, the BP is guaranteed by the spec to be <NUL> terminated */ + D(("initialization packet [%s]", PAM_BP_DATA(new->current_prompt))); + + /* fall through */ + new->state = PS_STATE_PROMPT1; + + D(("fall through to state_prompt1")); + } + + case PS_STATE_PROMPT1: + { + int i, length; + + /* send {secret@here/jdoe@client.host|<s_cookie>} */ + retval = converse(pamh, new); + if (retval != PAM_SUCCESS) { + if (retval == PAM_CONV_AGAIN) { + D(("conversation failed to complete")); + return PAM_INCOMPLETE; + } else { + new->state = PS_STATE_DEAD; + return retval; + } + } + + if (retval != PAM_SUCCESS) { + D(("failed to read ruser@rhost")); + new->state = PS_STATE_DEAD; + return PAM_AUTH_ERR; + } + + /* expect to receive the following {<seqid>|<a_cookie>} */ + if (new->current_reply == NULL) { + D(("converstation returned [%s] but gave no reply", + pam_strerror(pamh, retval))); + new->state = PS_STATE_DEAD; + return PAM_CONV_ERR; + } + + /* find | */ + length = PAM_BP_LENGTH(new->current_reply); + for (i=0; i<length; ++i) { + if (PAM_BP_RDATA(new->current_reply)[i] == '|') { + break; + } + } + if (i >= length) { + D(("malformed response (no |) of length %d", length)); + new->state = PS_STATE_DEAD; + return PAM_CONV_ERR; + } + if ((length - ++i) != 32) { + D(("cookie is incorrect length (%d,%d) %d != 32", + length, i, length-i)); + new->state = PS_STATE_DEAD; + return PAM_CONV_ERR; + } + + /* copy client cookie */ + memcpy(new->client_cookie, PAM_BP_RDATA(new->current_reply)+i, 32); + + /* generate a prompt that is length(seqid) + length(|) + 32 long */ + PAM_BP_RENEW(&new->current_prompt, PAM_BPC_OK, i+32); + /* copy the head of the response prompt */ + memcpy(PAM_BP_WDATA(new->current_prompt), + PAM_BP_RDATA(new->current_reply), i); + PAM_BP_RENEW(&new->current_reply, 0, 0); + + /* look up the secret */ + new->invalid_secret = 0; + + if (new->secret_data == NULL) { + char *ruser_rhost; + + ruser_rhost = malloc(strlen(rusername)+2+strlen(rhostname)); + if (ruser_rhost == NULL) { + D(("out of memory")); + new->state = PS_STATE_DEAD; + return PAM_BUF_ERR; + } + sprintf(ruser_rhost, "%s@%s", rusername, rhostname); + new->secret_data = identify_secret(ruser_rhost, new->username); + + memset(ruser_rhost, 0, strlen(ruser_rhost)); + free(ruser_rhost); + } + + if (new->secret_data == NULL) { + D(("secret not found for user")); + new->invalid_secret = 1; + + /* need to make up a secret */ + new->secret_data = malloc(32 + 1); + if (new->secret_data == NULL) { + D(("out of memory")); + new->state = PS_STATE_DEAD; + return PAM_BUF_ERR; + } + if (! generate_cookie(new->secret_data)) { + D(("what's up - no fake cookie generated?")); + new->state = PS_STATE_DEAD; + return PAM_ABORT; + } + } + + /* construct md5[<client_cookie>|<server_cookie>|<secret_data>] */ + if (! create_digest(new->client_cookie, new->server_cookie, + new->secret_data, + PAM_BP_WDATA(new->current_prompt)+i)) { + D(("md5 digesting failed")); + new->state = PS_STATE_DEAD; + return PAM_ABORT; + } + + /* prompt2 is now constructed - fall through to send it */ + } + + case PS_STATE_PROMPT2: + { + /* send {<seqid>|md5[<client_cookie>|<server_cookie>|<secret_data>]} */ + retval = converse(pamh, new); + if (retval != PAM_SUCCESS) { + if (retval == PAM_CONV_AGAIN) { + D(("conversation failed to complete")); + return PAM_INCOMPLETE; + } else { + new->state = PS_STATE_DEAD; + return retval; + } + } + + /* After we complete this section, we should not be able to + recall this authentication function. So, we force all + future calls into the weeds. */ + + new->state = PS_STATE_DEAD; + + /* expect reply:{md5[<secret_data>|<server_cookie>|<client_cookie>]} */ + + { + int cf; + char expectation[33]; + + if (!create_digest(new->secret_data, new->server_cookie, + new->client_cookie, expectation)) { + new->state = PS_STATE_DEAD; + return PAM_ABORT; + } + + cf = strcmp(expectation, PAM_BP_RDATA(new->current_reply)); + memset(expectation, 0, sizeof(expectation)); + if (cf || new->invalid_secret) { + D(("failed to authenticate")); + return PAM_AUTH_ERR; + } + } + + D(("correctly authenticated :)")); + return PAM_SUCCESS; + } + + default: + new->state = PS_STATE_DEAD; + + case PS_STATE_DEAD: + + D(("state is currently dead/unknown")); + return PAM_AUTH_ERR; + } + + fprintf(stderr, "pam_secret: this should not be reached\n"); + return PAM_ABORT; +} + +static void clean_data(pam_handle_t *pamh, void *datum, int error_status) +{ + struct ps_state_s *data = datum; + + D(("liberating datum=%p", datum)); + + if (data) { + D(("renew prompt")); + PAM_BP_RENEW(&data->current_prompt, 0, 0); + D(("renew reply")); + PAM_BP_RENEW(&data->current_reply, 0, 0); + D(("overwrite datum")); + memset(data, 0, sizeof(struct ps_state_s)); + D(("liberate datum")); + free(data); + } + + D(("done.")); +} + +/* + * front end for the authentication function + */ + +int pam_sm_authenticate(pam_handle_t *pamh, int flags, + int argc, const char **argv) +{ + int retval; + struct ps_state_s *new_data; + const struct ps_state_s *old_data; + + D(("called")); + + new_data = calloc(1, sizeof(struct ps_state_s)); + if (new_data == NULL) { + D(("out of memory")); + return PAM_BUF_ERR; + } + new_data->retval = PAM_SUCCESS; + + retval = pam_get_data(pamh, PS_STATE_ID, (const void **) &old_data); + if (retval == PAM_SUCCESS) { + new_data->state = old_data->state; + memcpy(new_data->server_cookie, old_data->server_cookie, 32); + memcpy(new_data->client_cookie, old_data->client_cookie, 32); + if (old_data->username) { + new_data->username = strdup(old_data->username); + } + if (old_data->secret_data) { + new_data->secret_data = strdup(old_data->secret_data); + } + if (old_data->current_prompt) { + int length; + + length = PAM_BP_LENGTH(old_data->current_prompt); + PAM_BP_RENEW(&new_data->current_prompt, + PAM_BP_CONTROL(old_data->current_prompt), length); + PAM_BP_FILL(new_data->current_prompt, 0, length, + PAM_BP_RDATA(old_data->current_prompt)); + } + /* don't need to duplicate current_reply */ + } else { + old_data = NULL; + new_data->state = PS_STATE_INIT; + } + + D(("call auth_sequence")); + new_data->retval = auth_sequence(pamh, old_data, new_data); + D(("returned from auth_sequence")); + + retval = pam_set_data(pamh, PS_STATE_ID, new_data, clean_data); + if (retval != PAM_SUCCESS) { + D(("unable to store new_data")); + } else { + retval = new_data->retval; + } + + old_data = new_data = NULL; + + D(("done (%d)", retval)); + return retval; +} + +/* + * front end for the credential setting function + */ + +#define AUTH_SESSION_TICKET_ENV_FORMAT "AUTH_SESSION_TICKET=" + +int pam_sm_setcred(pam_handle_t *pamh, int flags, + int argc, const char **argv) +{ + int retval; + const struct ps_state_s *old_data; + + D(("called")); + + /* XXX - need to pay attention to the various flavors of call */ + + /* XXX - need provide an option to turn this feature on/off: if + other modules want to supply an AUTH_SESSION_TICKET, we should + leave it up to the admin which module dominiates. */ + + retval = pam_get_data(pamh, PS_STATE_ID, (const void **) &old_data); + if (retval != PAM_SUCCESS) { + D(("no data to base decision on")); + return PAM_AUTH_ERR; + } + + /* + * If ok, export a derived shared secret session ticket to the + * client's PAM environment - the ticket has the form + * + * AUTH_SESSION_TICKET = + * md5[<server_cookie>|<secret_data>|<client_cookie>] + * + * This is a precursor to supporting a spoof resistant trusted + * path mechanism. This shared secret ticket can be used to add + * a hard-to-guess checksum to further authentication data. + */ + + retval = old_data->retval; + if (retval == PAM_SUCCESS) { + char envticket[sizeof(AUTH_SESSION_TICKET_ENV_FORMAT)+32]; + + memcpy(envticket, AUTH_SESSION_TICKET_ENV_FORMAT, + sizeof(AUTH_SESSION_TICKET_ENV_FORMAT)); + + if (! create_digest(old_data->server_cookie, old_data->secret_data, + old_data->client_cookie, + envticket+sizeof(AUTH_SESSION_TICKET_ENV_FORMAT)-1 + )) { + D(("unable to generate a digest for session ticket")); + return PAM_ABORT; + } + + D(("putenv[%s]", envticket)); + retval = pam_putenv(pamh, envticket); + memset(envticket, 0, sizeof(envticket)); + } + + old_data = NULL; + D(("done (%d)", retval)); + + return retval; +} |