AIX chroot fix

CHANGELOG.md

@@ -50,6 +50,7 @@ This release focuses on analysisd scalability and broader stability. Key enhance
 - @atomicturtle - [PR 2238](https://github.com/ossec/ossec-hids/pull/2238) - Fix false dpkg install alert when removing packages
 - @atomicturtle - [PR 2239](https://github.com/ossec/ossec-hids/pull/2239) - Fix msauth Enterprise Admins false positives and negatives
 - @atomicturtle - [PR 2240](https://github.com/ossec/ossec-hids/pull/2240) - Fix Postfix rule 3331 false positive on postscreen client ports
+- @atomicturtle - [PR 2243](https://github.com/ossec/ossec-hids/pull/2243) - Fix AIX agent entropy failure after chroot by keeping OS RNG usable
 
 
 **OSSEC changelog (4.1.0) <support@atomicorp.com>**

src/addagent/manage_agents.c

@@ -14,7 +14,6 @@
 #include "manage_agents.h"
 #include "os_crypto/md5/md5_op.h"
 #include "external/cJSON/cJSON.h"
-#include <openssl/rand.h>
 #include <stdlib.h>
 
 /* Global variables */
@@ -366,7 +365,7 @@ int add_agent(int json_output)
             char rand_hex[129];
 
             /* Generate cryptographically secure random bytes */
-            if (!RAND_bytes(random_data, sizeof(random_data))) {
+            if (!randombytes_try(random_data, sizeof(random_data))) {
                 if (json_output) {
                     cJSON *json_root = cJSON_CreateObject();
                     cJSON_AddNumberToObject(json_root, "error", 75);

src/addagent/manage_keys.c

@@ -8,7 +8,6 @@
  */
 
 #include "manage_agents.h"
-#include <openssl/rand.h>
 #include "os_crypto/md5/md5_op.h"
 #include "external/cJSON/cJSON.h"
 #include <stdlib.h>
@@ -324,6 +323,7 @@ int k_extract(const char *cmdextract, int json_output)
 int k_bulkload(const char *cmdbulk)
 {
     int i = 1;
+    int status = 0;
     FILE *fp, *infp;
     char str1[STR_SIZE + 1];
     char str2[STR_SIZE + 1];
@@ -443,38 +443,43 @@ int k_bulkload(const char *cmdbulk)
         }
 #endif
 
-    /* Cryptographically secure random number generation */
-    unsigned char random_data[64];
-    char rand_hex[129];
-
-    if (!RAND_bytes(random_data, sizeof(random_data))) {
-        merror("Failed to generate secure random data for agent key");
-        return 0;
-    }
+        /* Cryptographically secure random number generation */
+        unsigned char random_data[64];
+        char rand_hex[129];
 
-    /* Hex encode the random data */
-    for(i=0; i<64; i++) {
-        sprintf(&rand_hex[i*2], "%02x", random_data[i]);
-    }
+        if (!randombytes_try(random_data, sizeof(random_data))) {
+            merror("Failed to generate secure random data for agent key");
+            fclose(fp);
+            status = 1;
+            goto cleanup;
+        }
 
-    /* First key component: name + ID + random data */
-    snprintf(str1, STR_SIZE, "%s%s%s", name, id, rand_hex);
-    OS_MD5_Str(str1, md1);
+        /* Hex encode the random data */
+        for (i = 0; i < 64; i++) {
+            sprintf(&rand_hex[i * 2], "%02x", random_data[i]);
+        }
+
+        /* First key component: name + ID + random data */
+        snprintf(str1, STR_SIZE, "%s%s%s", name, id, rand_hex);
+        OS_MD5_Str(str1, md1);
 
-    /* Second key component: IP + name + random data (offset) */
-    snprintf(str2, STR_SIZE, "%s%s%s", ip, name, rand_hex + 64);
-    OS_MD5_Str(str2, md2);
+        /* Second key component: IP + name + random data (offset) */
+        snprintf(str2, STR_SIZE, "%s%s%s", ip, name, rand_hex + 64);
+        OS_MD5_Str(str2, md2);
 
-    fprintf(fp, "%s %s %s %s%s\n", id, name, ip, md1, md2);
+        fprintf(fp, "%s %s %s %s%s\n", id, name, ip, md1, md2);
         fclose(fp);
 
         printf(AGENT_ADD, id);
         restart_necessary = 1;
 
 cleanup:
         free(c_ip.ip);
+        if (status != 0) {
+            break;
+        }
     };
 
     fclose(infp);
-    return (0);
+    return (status);
 }

src/headers/randombytes.h

@@ -1,8 +1,11 @@
 #ifndef __RANDOMBYTES_H
 #define __RANDOMBYTES_H
 
+#include <stddef.h>
+
 void randombytes(void *ptr, size_t length);
+/** Fill buffer with OS entropy. Returns 1 on success, 0 on failure (no exit). */
+int randombytes_try(void *ptr, size_t length);
 void srandom_init(void);
 
 #endif
-

src/os_crypto/aes/aes_op.c

@@ -18,29 +18,35 @@
 #include <openssl/evp.h>
 #include <openssl/err.h>
 #include "aes_op.h"
+#include "randombytes.h"
 
 typedef unsigned char uchar;
 
 
-#include <openssl/rand.h>
-
 int OS_AES_Str(const char *input, char *output, const char *charkey,
               long size, short int action)
 {
     unsigned char iv[16];
 
     if(action == OS_ENCRYPT)
     {
-        /* Generate Random IV */
-        if (!RAND_bytes(iv, sizeof(iv))) {
-            return 0; // Error
+        /* Per-message random IV via OS entropy (FD kept across chroot). */
+        if (!randombytes_try(iv, sizeof(iv))) {
+            return 0;
         }
 
         /* Prepend IV to output */
         memcpy(output, iv, 16);
 
         /* Encrypt content after the IV */
-        return 16 + encrypt_AES((const uchar *)input, (int)size, (uchar *)charkey, iv, (uchar *)output + 16);
+        {
+            int aes_len = encrypt_AES((const uchar *)input, (int)size, (uchar *)charkey, iv,
+                                      (uchar *)output + 16);
+            if (aes_len == 0) {
+                return 0;
+            }
+            return 16 + aes_len;
+        }
     }
     else
     {

src/os_crypto/shared/msgs.c

@@ -13,7 +13,6 @@
 #include "os_crypto/md5/md5_op.h"
 #include "os_crypto/blowfish/bf_op.h"
 #include "os_crypto/aes/aes_op.h"
-#include <openssl/rand.h>
 #include <sys/stat.h>
 
 /* Helper for File_Inode */
@@ -544,10 +543,15 @@ size_t CreateSecMSG(const keystore *keys, const char *msg, size_t msg_length, ch
             return 0; // OS_INVALID
     }
 
-    /* Random number, take only 5 chars ~= 2^16=65536*/
-    if (!RAND_bytes((unsigned char *)&rand1, sizeof(rand1))) {
-        merror("RAND_bytes failed");
-        return(0);
+    /* Random number, take only 5 chars ~= 2^16=65536.
+     * Entropy via randombytes_try: pre-chroot /dev/urandom FD on Unix,
+     * arc4random on OpenBSD, CryptoAPI (CRYPT_VERIFYCONTEXT) on Windows.
+     * Avoids OpenSSL RAND_bytes, which re-opens /dev/urandom by path after
+     * chroot and fails on AIX and similar platforms without getrandom().
+     */
+    if (!randombytes_try(&rand1, sizeof(rand1))) {
+        merror("randombytes failed");
+        return (0);
     }
 
     _tmpmsg[OS_MAXSTR + 1] = '\0';
@@ -643,6 +647,14 @@ size_t CreateSecMSG(const keystore *keys, const char *msg, size_t msg_length, ch
         (long) cmp_size,
         OS_ENCRYPT,crypto_method);
 
+    /* Blowfish returns 1; AES returns ciphertext length. Zero means failure
+     * (e.g. AES IV entropy unavailable).
+     */
+    if (!crypto_length) {
+        merror("encryption failed");
+        return (0);
+    }
+
     if(cmp_size < crypto_length)
         cmp_size = crypto_length;