Support hashing a certificate directory (#96)

* Add the method to return either a certification file or a directory of certficates
* Support hashing a certificate directory 

---------

Signed-off-by: Ivan Rogach <[email protected]>

3rd_party/cert_rehash/c_rehash.hpp

@@ -0,0 +1,310 @@
+/* c_rehash.c - Create hash symlinks for certificates
+ * C implementation based on the original Perl and shell versions
+ *
+ * Copyright (c) 2013-2014 Timo Teräs <[email protected]>
+ * All rights reserved.
+ *
+ * This software is licensed under the MIT License.
+ * Full license available at: http://opensource.org/licenses/MIT
+ */
+
+#include <dirent.h>
+#include <limits.h>
+#include <stdio.h>
+#include <string.h>
+#include <sys/stat.h>
+#include <unistd.h>
+
+#include <openssl/evp.h>
+#include <openssl/pem.h>
+#include <openssl/x509.h>
+
+#include <everest/logging.hpp>
+
+#define MAX_COLLISIONS 256
+#define countof(x)     (sizeof(x) / sizeof(x[0]))
+
+namespace evse_security {
+
+struct entry_info {
+    struct entry_info* next;
+    char* filename;
+    unsigned short old_id;
+    unsigned char need_symlink;
+    unsigned char digest[EVP_MAX_MD_SIZE];
+};
+
+struct bucket_info {
+    struct bucket_info* next;
+    struct entry_info *first_entry, *last_entry;
+    unsigned int hash;
+    unsigned short type;
+    unsigned short num_needed;
+};
+
+enum Type {
+    TYPE_CERT = 0,
+    TYPE_CRL
+};
+
+static const char* symlink_extensions[] = {"", "r"};
+static const char* file_extensions[] = {"pem", "crt", "cer", "crl"};
+
+static int evpmdsize;
+static const EVP_MD* evpmd;
+
+static struct bucket_info* hash_table[257];
+
+static void bit_set(unsigned char* set, unsigned bit) {
+    set[bit / 8] |= 1 << (bit % 8);
+}
+
+static int bit_isset(unsigned char* set, unsigned bit) {
+    return set[bit / 8] & (1 << (bit % 8));
+}
+
+static void add_entry(int type, unsigned int hash, const char* filename, const unsigned char* digest, int need_symlink,
+                      unsigned short old_id) {
+    struct bucket_info* bi;
+    struct entry_info *ei, *found = NULL;
+    unsigned int ndx = (type + hash) % countof(hash_table);
+
+    for (bi = hash_table[ndx]; bi; bi = bi->next)
+        if (bi->type == type && bi->hash == hash)
+            break;
+    if (!bi) {
+        bi = (bucket_info*)(calloc(1, sizeof(*bi)));
+        if (!bi)
+            return;
+        bi->next = hash_table[ndx];
+        bi->type = type;
+        bi->hash = hash;
+        hash_table[ndx] = bi;
+    }
+
+    for (ei = bi->first_entry; ei; ei = ei->next) {
+        if (digest && memcmp(digest, ei->digest, evpmdsize) == 0) {
+            EVLOG_warning << "Skipping duplicate certificate in file " << std::string(filename);
+            return;
+        }
+        if (!strcmp(filename, ei->filename)) {
+            found = ei;
+            if (!digest)
+                break;
+        }
+    }
+    ei = found;
+    if (!ei) {
+        if (bi->num_needed >= MAX_COLLISIONS)
+            return;
+        ei = (entry_info*)(calloc(1, sizeof(*ei)));
+        if (!ei)
+            return;
+
+        ei->old_id = ~0;
+        ei->filename = strdup(filename);
+        if (bi->last_entry)
+            bi->last_entry->next = ei;
+        if (!bi->first_entry)
+            bi->first_entry = ei;
+        bi->last_entry = ei;
+    }
+
+    if (old_id < ei->old_id)
+        ei->old_id = old_id;
+    if (need_symlink && !ei->need_symlink) {
+        ei->need_symlink = 1;
+        bi->num_needed++;
+        memcpy(ei->digest, digest, evpmdsize);
+    }
+}
+
+static int handle_symlink(const char* filename, const char* fullpath) {
+    static char xdigit[] = {0,  1,  2,  3,  4,  5,  6,  7,  8,  9,  -1, -1, -1, -1, -1, -1, -1, 10, 11,
+                            12, 13, 14, 15, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+                            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 10, 11, 12, 13, 14, 15};
+    char linktarget[NAME_MAX], *endptr;
+    unsigned int hash = 0;
+    unsigned char ch;
+    int i, type, id;
+    ssize_t n;
+
+    for (i = 0; i < 8; i++) {
+        ch = filename[i] - '0';
+        if (ch >= countof(xdigit) || xdigit[ch] < 0)
+            return -1;
+        hash <<= 4;
+        hash += xdigit[ch];
+    }
+    if (filename[i++] != '.')
+        return -1;
+    for (type = countof(symlink_extensions) - 1; type > 0; type--)
+        if (strcasecmp(symlink_extensions[type], &filename[i]) == 0)
+            break;
+    i += strlen(symlink_extensions[type]);
+
+    id = strtoul(&filename[i], &endptr, 10);
+    if (*endptr != 0)
+        return -1;
+
+    n = readlink(fullpath, linktarget, sizeof(linktarget));
+    if (n >= sizeof(linktarget) || n < 0)
+        return -1;
+    linktarget[n] = 0;
+
+    EVLOG_debug << "Found existing symlink " << std::string(filename) << " for " << hash << " (" << type
+                << "), certname " << std::string(linktarget, strlen(linktarget));
+    add_entry(type, hash, linktarget, NULL, 0, id);
+    return 0;
+}
+
+static int handle_certificate(const char* filename, const char* fullpath) {
+    STACK_OF(X509_INFO) * inf;
+    X509_INFO* x;
+    BIO* b;
+    const char* ext;
+    unsigned char digest[EVP_MAX_MD_SIZE];
+    X509_NAME* name = NULL;
+    int i, type, ret = -1;
+
+    ext = strrchr(filename, '.');
+    if (ext == NULL)
+        return 0;
+    for (i = 0; i < countof(file_extensions); i++) {
+        if (strcasecmp(file_extensions[i], ext + 1) == 0)
+            break;
+    }
+    if (i >= countof(file_extensions))
+        return -1;
+
+    b = BIO_new_file(fullpath, "r");
+    if (!b)
+        return -1;
+    inf = PEM_X509_INFO_read_bio(b, NULL, NULL, NULL);
+    BIO_free(b);
+    if (!inf)
+        return -1;
+
+    if (sk_X509_INFO_num(inf) == 1) {
+        x = sk_X509_INFO_value(inf, 0);
+        if (x->x509) {
+            type = TYPE_CERT;
+            name = X509_get_subject_name(x->x509);
+            X509_digest(x->x509, evpmd, digest, NULL);
+        } else if (x->crl) {
+            type = TYPE_CRL;
+            name = X509_CRL_get_issuer(x->crl);
+            X509_CRL_digest(x->crl, evpmd, digest, NULL);
+        }
+        if (name)
+            add_entry(type, X509_NAME_hash(name), filename, digest, 1, ~0);
+    } else {
+        EVLOG_warning << std::string(filename) << " does not contain exactly one certificate or CRL: skipping";
+    }
+
+    sk_X509_INFO_pop_free(inf, X509_INFO_free);
+
+    return ret;
+}
+
+static int hash_dir(const char* dirname) {
+    struct bucket_info *bi, *nextbi;
+    struct entry_info *ei, *nextei;
+    struct dirent* de;
+    struct stat st;
+    unsigned char idmask[MAX_COLLISIONS / 8];
+    int i, n, nextid, buflen, ret = -1;
+    const char* pathsep;
+    char* buf;
+    DIR* d;
+
+    evpmd = EVP_sha1();
+    evpmdsize = EVP_MD_size(evpmd);
+
+    if (access(dirname, R_OK | W_OK | X_OK) != 0) {
+        EVLOG_error << "Access denied '" << std::string(dirname) << "'";
+        return -1;
+    }
+
+    buflen = strlen(dirname);
+    pathsep = (buflen && dirname[buflen - 1] == '/') ? "" : "/";
+    buflen += NAME_MAX + 2;
+    buf = (char*)(malloc(buflen));
+    if (buf == NULL)
+        goto err;
+
+    EVLOG_debug << "Doing " << std::string(dirname);
+    d = opendir(dirname);
+    if (!d)
+        goto err;
+
+    while ((de = readdir(d)) != NULL) {
+        if (snprintf(buf, buflen, "%s%s%s", dirname, pathsep, de->d_name) >= buflen)
+            continue;
+        if (lstat(buf, &st) < 0)
+            continue;
+        if (S_ISLNK(st.st_mode) && handle_symlink(de->d_name, buf) == 0)
+            continue;
+        if (strcmp(buf, "/etc/ssl/certs/ca-certificates.crt") == 0) {
+            /* Ignore the /etc/ssl/certs/ca-certificates.crt file */
+            EVLOG_debug << "Skipping /etc/ssl/certs/ca-certificates.crt file";
+            continue;
+        }
+        handle_certificate(de->d_name, buf);
+    }
+    closedir(d);
+
+    for (i = 0; i < countof(hash_table); i++) {
+        for (bi = hash_table[i]; bi; bi = nextbi) {
+            nextbi = bi->next;
+            EVLOG_debug << "Type " << bi->type << " hash " << bi->hash << " num entries " << bi->num_needed << ":";
+
+            nextid = 0;
+            memset(idmask, 0, (bi->num_needed + 7) / 8);
+            for (ei = bi->first_entry; ei; ei = ei->next)
+                if (ei->old_id < bi->num_needed)
+                    bit_set(idmask, ei->old_id);
+
+            for (ei = bi->first_entry; ei; ei = nextei) {
+                nextei = ei->next;
+                EVLOG_debug << "\t(old_id " << ei->old_id << ", need_symlink " << static_cast<int>(ei->need_symlink)
+                            << ") Cert " << std::string(ei->filename, strlen(ei->filename)) << ":";
+
+                if (ei->old_id < bi->num_needed) {
+                    /* Link exists, and is used as-is */
+                    snprintf(buf, buflen, "%08x.%s%d", bi->hash, symlink_extensions[bi->type], ei->old_id);
+                    EVLOG_debug << "link " << std::string(ei->filename, strlen(ei->filename)) << " -> "
+                                << std::string(buf, strlen(buf));
+                } else if (ei->need_symlink) {
+                    /* New link needed (it may replace something) */
+                    while (bit_isset(idmask, nextid))
+                        nextid++;
+
+                    snprintf(buf, buflen, "%s%s%n%08x.%s%d", dirname, pathsep, &n, bi->hash,
+                             symlink_extensions[bi->type], nextid);
+                    EVLOG_debug << "link " << std::string(ei->filename, strlen(ei->filename)) << " -> "
+                                << std::string(buf + n, strlen(buf + n));
+                    unlink(buf);
+                    symlink(ei->filename, buf);
+                } else {
+                    /* Link to be deleted */
+                    snprintf(buf, buflen, "%s%s%n%08x.%s%d", dirname, pathsep, &n, bi->hash,
+                             symlink_extensions[bi->type], ei->old_id);
+                    EVLOG_debug << "unlink " << std::string(buf + n, strlen(buf + n));
+                    unlink(buf);
+                }
+                free(ei->filename);
+                free(ei);
+            }
+            free(bi);
+        }
+        hash_table[i] = NULL;
+    }
+
+    ret = 0;
+err:
+    free(buf);
+    return ret;
+}
+
+} // namespace evse_security

CMakeLists.txt

@@ -77,6 +77,11 @@ if (EVSE_SECURITY_INSTALL)
         PATTERN "detail" EXCLUDE
     )
 
+    install(
+        DIRECTORY 3rd_party/
+        TYPE INCLUDE
+    )
+
     evc_setup_package(
         NAME everest-evse_security
         NAMESPACE everest

include/evse_security/evse_security.hpp

@@ -227,6 +227,13 @@ class EvseSecurity {
     /// @return CA certificate file
     std::string get_verify_file(CaCertificateType certificate_type);
 
+    /// @brief Retrieves the PEM formatted CA bundle location for the given \p certificate_type It is not recommended to
+    /// add the SUBCAs to any root certificate bundle, but to leave them in the leaf file. Returns either file
+    /// or directory where the certificates are located. In the case of directory, does also rehashing the directory.
+    /// @param certificate_type
+    /// @return CA certificate location
+    std::string get_verify_location(CaCertificateType certificate_type);
+
     /// @brief An extension of 'get_verify_file' with error handling included
     GetCertificateInfoResult get_ca_certificate_info(CaCertificateType certificate_type);
 

lib/evse_security/CMakeLists.txt

@@ -28,6 +28,7 @@ endif()
 target_include_directories(evse_security
     PUBLIC
         $<BUILD_INTERFACE:${PROJECT_SOURCE_DIR}/include>
+        $<BUILD_INTERFACE:${PROJECT_SOURCE_DIR}/3rd_party>
         $<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}>
 )
 

lib/evse_security/evse_security.cpp

@@ -12,6 +12,8 @@
 #include <set>
 #include <stdio.h>
 
+#include <cert_rehash/c_rehash.hpp>
+
 #include <evse_security/certificate/x509_bundle.hpp>
 #include <evse_security/certificate/x509_hierarchy.hpp>
 #include <evse_security/certificate/x509_wrapper.hpp>
@@ -1555,6 +1557,36 @@ std::string EvseSecurity::get_verify_file(CaCertificateType certificate_type) {
     return {};
 }
 
+std::string EvseSecurity::get_verify_location(CaCertificateType certificate_type) {
+
+    std::lock_guard<std::mutex> guard(EvseSecurity::security_mutex);
+
+    try {
+        // Support bundle files, in case the certificates contain
+        // multiple entries (should be 3) as per the specification
+        X509CertificateBundle verify_location(this->ca_bundle_path_map.at(certificate_type), EncodingFormat::PEM);
+
+        const auto location_path = verify_location.get_path();
+
+        EVLOG_info << "Requesting certificate location: ["
+                   << conversions::ca_certificate_type_to_string(certificate_type) << "] location:" << location_path;
+
+        if (!verify_location.empty() &&
+            (!verify_location.is_using_directory() || hash_dir(location_path.c_str()) == 0)) {
+            return location_path;
+        }
+
+    } catch (const CertificateLoadException& e) {
+        EVLOG_error << "Could not obtain verify location, wrong format for certificate: "
+                    << this->ca_bundle_path_map.at(certificate_type) << " with error: " << e.what();
+    }
+
+    EVLOG_error << "Could not find any CA certificate for: "
+                << conversions::ca_certificate_type_to_string(certificate_type);
+
+    return {};
+}
+
 int EvseSecurity::get_leaf_expiry_days_count(LeafCertificateType certificate_type) {
     std::lock_guard<std::mutex> guard(EvseSecurity::security_mutex);