Allow arbitrary-length PAM messages

The PAM standard allows for messages of any length to be returned
to the client. We were discarding all messages of length greater
than 255. This patch dynamically allocates the message buffers so
we can pass the complete message.

This resolves https://fedorahosted.org/sssd/ticket/432

7 files changed, 55 insertions, 43 deletions

diff --git a/src/providers/child_common.c b/src/providers/child_common.c
index 2ad0f04e..b9802557 100644
--- a/src/providers/child_common.c
+++ b/src/providers/child_common.c
@@ -149,9 +149,8 @@ struct tevent_req *read_pipe_send(TALLOC_CTX *mem_ctx,
     if (req == NULL) return NULL;
 
     state->fd = fd;
-    state->buf = talloc_array(state, uint8_t, MAX_CHILD_MSG_SIZE);
+    state->buf = NULL;
     state->len = 0;
-    if (state->buf == NULL) goto fail;
 
     fde = tevent_add_fd(ev, state, fd, TEVENT_FD_READ,
                         read_pipe_handler, req);
@@ -176,6 +175,7 @@ static void read_pipe_handler(struct tevent_context *ev,
                                                     struct read_pipe_state);
     ssize_t size;
     errno_t err;
+    uint8_t buf[CHILD_MSG_CHUNK];
 
     if (flags & TEVENT_FD_WRITE) {
         DEBUG(1, ("read_pipe_done called with TEVENT_FD_WRITE,"
@@ -185,8 +185,8 @@ static void read_pipe_handler(struct tevent_context *ev,
     }
 
     size = read(state->fd,
-                state->buf + state->len,
-                MAX_CHILD_MSG_SIZE - state->len);
+                buf,
+                CHILD_MSG_CHUNK);
     if (size == -1) {
         err = errno;
         if (err == EAGAIN || err == EINTR) {
@@ -198,13 +198,17 @@ static void read_pipe_handler(struct tevent_context *ev,
         return;
 
     } else if (size > 0) {
-        state->len += size;
-        if (state->len > MAX_CHILD_MSG_SIZE) {
-            DEBUG(1, ("read to much, this should never happen.\n"));
-            tevent_req_error(req, EINVAL);
+        state->buf = talloc_realloc(state, state->buf, uint8_t,
+                                    state->len + size);
+        if(!state->buf) {
+            tevent_req_error(req, ENOMEM);
             return;
         }
 
+        safealign_memcpy(&state->buf[state->len], buf,
+                         size, &state->len);
+        return;
+
     } else if (size == 0) {
         DEBUG(6, ("EOF received, client finished\n"));
         tevent_req_done(req);
diff --git a/src/providers/child_common.h b/src/providers/child_common.h
index a441df3c..0b2081d2 100644
--- a/src/providers/child_common.h
+++ b/src/providers/child_common.h
@@ -33,12 +33,11 @@
 #include "util/util.h"
 
 #define IN_BUF_SIZE         512
-#define MAX_CHILD_MSG_SIZE  255
+#define CHILD_MSG_CHUNK     256
 
 struct response {
-    size_t max_size;
-    size_t size;
     uint8_t *buf;
+    size_t size;
 };
 
 struct io_buffer {
diff --git a/src/providers/krb5/krb5_auth.c b/src/providers/krb5/krb5_auth.c
index ce3aacd8..880930a1 100644
--- a/src/providers/krb5/krb5_auth.c
+++ b/src/providers/krb5/krb5_auth.c
@@ -1091,7 +1091,7 @@ static void krb5_child_done(struct tevent_req *req)
                                                 *msg_len));
 
     if ((p + *msg_len) != len) {
-        DEBUG(1, ("message format error.\n"));
+        DEBUG(1, ("message format error [%d] != [%d].\n", p+*msg_len, len));
         goto done;
     }
 
diff --git a/src/providers/krb5/krb5_child.c b/src/providers/krb5/krb5_child.c
index 86242ef3..620e4d14 100644
--- a/src/providers/krb5/krb5_child.c
+++ b/src/providers/krb5/krb5_child.c
@@ -247,27 +247,15 @@ done:
     return kerr;
 }
 
-static struct response *init_response(TALLOC_CTX *mem_ctx) {
-    struct response *r;
-    r = talloc(mem_ctx, struct response);
-    r->buf = talloc_size(mem_ctx, MAX_CHILD_MSG_SIZE);
-    if (r->buf == NULL) {
-        DEBUG(1, ("talloc_size failed.\n"));
-        return NULL;
-    }
-    r->max_size = MAX_CHILD_MSG_SIZE;
-    r->size = 0;
-
-    return r;
-}
-
 static errno_t pack_response_packet(struct response *resp, int status, int type,
                                     size_t len, const uint8_t *data)
 {
     size_t p = 0;
 
-    if ((3*sizeof(int32_t) + len +1) > resp->max_size) {
-        DEBUG(1, ("response message too big.\n"));
+    resp->buf = talloc_array(resp, uint8_t,
+                             3*sizeof(int32_t) + len);
+    if (!resp->buf) {
+        DEBUG(1, ("Insufficient memory to create message.\n"));
         return ENOMEM;
     }
 
@@ -293,9 +281,9 @@ static struct response *prepare_response_message(struct krb5_req *kr,
     size_t user_resp_len;
     uint8_t *user_resp;
 
-    resp = init_response(kr);
+    resp = talloc_zero(kr, struct response);
     if (resp == NULL) {
-        DEBUG(1, ("init_response failed.\n"));
+        DEBUG(1, ("Initializing response failed.\n"));
         return NULL;
     }
 
@@ -321,7 +309,6 @@ static struct response *prepare_response_message(struct krb5_req *kr,
             talloc_zfree(msg);
         }
     } else {
-
         if (user_error_message != NULL) {
             ret = pack_user_info_chpass_error(kr, user_error_message,
                                               &user_resp_len, &user_resp);
diff --git a/src/providers/ldap/ldap_child.c b/src/providers/ldap/ldap_child.c
index 069fbcfe..6a78ca01 100644
--- a/src/providers/ldap/ldap_child.c
+++ b/src/providers/ldap/ldap_child.c
@@ -97,6 +97,11 @@ static int pack_buffer(struct response *r, int result, const char *msg)
     len = strlen(msg);
     r->size = 2 * sizeof(uint32_t) + len;
 
+    r->buf = talloc_array(r, uint8_t, r->size);
+    if(!r->buf) {
+        return ENOMEM;
+    }
+
     /* result */
     SAFEALIGN_SET_UINT32(&r->buf[p], result, &p);
 
@@ -265,12 +270,7 @@ static int prepare_response(TALLOC_CTX *mem_ctx,
     r = talloc_zero(mem_ctx, struct response);
     if (!r) return ENOMEM;
 
-    r->buf = talloc_size(mem_ctx, MAX_CHILD_MSG_SIZE);
-    if (r->buf == NULL) {
-        DEBUG(1, ("talloc_size failed.\n"));
-        return ENOMEM;
-    }
-    r->max_size = MAX_CHILD_MSG_SIZE;
+    r->buf = NULL;
     r->size = 0;
 
     if (kerr == 0) {
diff --git a/src/sss_client/pam_sss.c b/src/sss_client/pam_sss.c
index 07ed4e72..6059dfaa 100644
--- a/src/sss_client/pam_sss.c
+++ b/src/sss_client/pam_sss.c
@@ -588,7 +588,8 @@ static int user_info_chpass_error(pam_handle_t *pamh, size_t buflen,
 {
     int ret;
     uint32_t msg_len;
-    char user_msg[256];
+    char *user_msg;
+    size_t bufsize = 0;
 
     if (buflen < 2* sizeof(uint32_t)) {
         D(("User info response data is too short"));
@@ -602,19 +603,35 @@ static int user_info_chpass_error(pam_handle_t *pamh, size_t buflen,
         return PAM_BUF_ERR;
     }
 
-    ret = snprintf(user_msg, sizeof(user_msg), "%s%s%.*s",
+    bufsize = strlen(_("Password change failed. ")) + 1;
+
+    if (msg_len > 0) {
+        bufsize += strlen(_("Server message: ")) + msg_len;
+    }
+
+    user_msg = (char *)malloc(sizeof(char) * bufsize);
+    if (!user_msg) {
+       D(("Out of memory."));
+       return PAM_SYSTEM_ERR;
+    }
+
+    ret = snprintf(user_msg, bufsize, "%s%s%.*s",
                    _("Password change failed. "),
                    msg_len > 0 ? _("Server message: ") : "",
                    msg_len,
                    msg_len > 0 ? (char *)(buf + 2 * sizeof(uint32_t)) : "" );
-    if (ret < 0 || ret >= sizeof(user_msg)) {
+    if (ret < 0 || ret > bufsize) {
         D(("snprintf failed."));
+
+        free(user_msg);
         return PAM_SYSTEM_ERR;
     }
 
     ret = do_pam_conversation(pamh, PAM_TEXT_INFO, user_msg, NULL, NULL);
+    free(user_msg);
     if (ret != PAM_SUCCESS) {
         D(("do_pam_conversation failed."));
+
         return PAM_SYSTEM_ERR;
     }
 
diff --git a/src/util/user_info_msg.c b/src/util/user_info_msg.c
index 547e3bb7..505b03d9 100644
--- a/src/util/user_info_msg.c
+++ b/src/util/user_info_msg.c
@@ -33,6 +33,7 @@ errno_t pack_user_info_chpass_error(TALLOC_CTX *mem_ctx,
     uint32_t resp_type = SSS_PAM_USER_INFO_CHPASS_ERROR;
     size_t err_len;
     uint8_t *resp;
+    size_t p;
 
     err_len = strlen(user_error_message);
     *resp_len = 2 * sizeof(uint32_t) + err_len;
@@ -42,9 +43,13 @@ errno_t pack_user_info_chpass_error(TALLOC_CTX *mem_ctx,
         return ENOMEM;
     }
 
-    memcpy(resp, &resp_type, sizeof(uint32_t));
-    memcpy(resp + sizeof(uint32_t), &err_len, sizeof(uint32_t));
-    memcpy(resp + 2 * sizeof(uint32_t), user_error_message, err_len);
+    p = 0;
+    SAFEALIGN_SET_UINT32(&resp[p], resp_type, &p);
+    SAFEALIGN_SET_UINT32(&resp[p], err_len, &p);
+    safealign_memcpy(&resp[p], user_error_message, err_len, &p);
+    if (p != *resp_len) {
+        DEBUG(0, ("Size mismatch\n"));
+    }
 
     *_resp = resp;
     return EOK;