Revert "Implement runtime check on libcrypto linkage (awslabs#186)" (a…

…wslabs#191)

**Issue**:
The libcrypto runtime check isn't working with latest [AWS-LC-FIPS-2.0.13](https://github.com/aws/aws-lc/releases/tag/AWS-LC-FIPS-2.0.13) release. It's not returning the expected version string.

AWS-LC is working on a fix here: aws/aws-lc#1689

**Description of changes:**
This reverts commit 0cdbf2b.

We'll bring this check right back once AWS-LC-FIPS has this fix in its latest release (on Github, and internally at Amazon).

It seems simpler to remove the check entirely, and bring it back once things are working. Vs patching it now, and then patching it again, and then we have all these different versions of aws-lc/aws-c-cal that aren't compatible...

source/unix/openssl_platform_init.c

@@ -22,10 +22,6 @@
 #define OPENSSL_SUPPRESS_DEPRECATED
 #include <openssl/crypto.h>
 
-#if defined(OPENSSL_IS_AWSLC)
-#    include <openssl/service_indicator.h>
-#endif
-
 static struct openssl_hmac_ctx_table hmac_ctx_table;
 static struct openssl_evp_md_ctx_table evp_md_ctx_table;
 
@@ -559,47 +555,6 @@ static enum aws_libcrypto_version s_resolve_libcrypto_lib(void) {
     return AWS_LIBCRYPTO_NONE;
 }
 
-/* Validate at runtime that we're linked against the same libcrypto we compiled against. */
-static void s_validate_libcrypto_linkage(void) {
-    /* NOTE: the choice of stack buffer size is somewhat arbitrary. it's
-     * possible, but unlikely, that libcrypto version strings may exceed this in
-     * the future. we guard against buffer overflow by limiting write size in
-     * snprintf with the size of the buffer itself. if libcrypto version strings
-     * do eventually exceed the chosen size, this runtime check will fail and
-     * will need to be addressed by increasing buffer size.*/
-    char expected_version[64] = {0};
-#if defined(OPENSSL_IS_AWSLC)
-    /* get FIPS mode at runtime becuase headers don't give any indication of
-     * AWS-LC's FIPSness at aws-c-cal compile time. version number can still be
-     * captured at preprocess/compile time from AWSLC_VERSION_NUMBER_STRING.*/
-    const char *mode = FIPS_mode() ? "AWS-LC FIPS" : "AWS-LC";
-    snprintf(expected_version, sizeof(expected_version), "%s %s", mode, AWSLC_VERSION_NUMBER_STRING);
-#elif defined(OPENSSL_IS_BORINGSSL)
-    snprintf(expected_version, sizeof(expected_version), "BoringSSL");
-#elif defined(OPENSSL_IS_OPENSSL)
-    snprintf(expected_version, sizeof(expected_version), OPENSSL_VERSION_TEXT);
-#elif !defined(BYO_CRYPTO)
-#    error Unsupported libcrypto!
-#endif
-    const char *runtime_version = SSLeay_version(SSLEAY_VERSION);
-    AWS_LOGF_DEBUG(
-        AWS_LS_CAL_LIBCRYPTO_RESOLVE,
-        "Compiled with libcrypto %s, linked to libcrypto %s",
-        expected_version,
-        runtime_version);
-#if defined(OPENSSL_IS_OPENSSL)
-    /* Validate that the string "AWS-LC" doesn't appear in OpenSSL version str. */
-    AWS_FATAL_ASSERT(strstr("AWS-LC", expected_version) == NULL);
-    AWS_FATAL_ASSERT(strstr("AWS-LC", runtime_version) == NULL);
-    /* Validate both expected and runtime versions begin with OpenSSL's version str prefix. */
-    const char *openssl_prefix = "OpenSSL ";
-    AWS_FATAL_ASSERT(strncmp(openssl_prefix, expected_version, strlen(openssl_prefix)) == 0);
-    AWS_FATAL_ASSERT(strncmp(openssl_prefix, runtime_version, strlen(openssl_prefix)) == 0);
-#else
-    AWS_FATAL_ASSERT(strcmp(expected_version, runtime_version) == 0 && "libcrypto mislink");
-#endif
-}
-
 static enum aws_libcrypto_version s_resolve_libcrypto(void) {
     /* Try to auto-resolve against what's linked in/process space */
     AWS_LOGF_DEBUG(AWS_LS_CAL_LIBCRYPTO_RESOLVE, "searching process and loaded modules");
@@ -628,8 +583,6 @@ static enum aws_libcrypto_version s_resolve_libcrypto(void) {
         result = s_resolve_libcrypto_lib();
     }
 
-    s_validate_libcrypto_linkage();
-
     return result;
 }