💾 Archived View for gmn.clttr.info › sources › cgmnlm.git › tree › src › tofu.c.txt captured on 2023-03-20 at 18:53:41.
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#include <assert.h> #include <bearssl.h> #include <errno.h> #include <gmni/gmni.h> #include <gmni/tofu.h> #include <libgen.h> #include <limits.h> #include <stdint.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include "util.h" static void xt_start_chain(const br_x509_class **ctx, const char *server_name) { struct x509_tofu_context *cc = (struct x509_tofu_context *)(void *)ctx; cc->server_name = server_name; cc->err = 0; cc->pkey = NULL; } static void xt_start_cert(const br_x509_class **ctx, uint32_t length) { struct x509_tofu_context *cc = (struct x509_tofu_context *)(void *)ctx; if (cc->err != 0 || cc->pkey) { return; } if (length == 0) { cc->err = BR_ERR_X509_TRUNCATED; return; } br_x509_decoder_init(&cc->decoder, NULL, NULL); br_sha512_init(&cc->sha512); } static void xt_append(const br_x509_class **ctx, const unsigned char *buf, size_t len) { struct x509_tofu_context *cc = (struct x509_tofu_context *)(void *)ctx; if (cc->err != 0 || cc->pkey) { return; } br_x509_decoder_push(&cc->decoder, buf, len); int err = br_x509_decoder_last_error(&cc->decoder); if (err != 0 && err != BR_ERR_X509_TRUNCATED) { cc->err = err; } br_sha512_update(&cc->sha512, buf, len); } static void xt_end_cert(const br_x509_class **ctx) { struct x509_tofu_context *cc = (struct x509_tofu_context *)(void *)ctx; if (cc->err != 0) { return; } int err = br_x509_decoder_last_error(&cc->decoder); if (err != 0 && err != BR_ERR_X509_TRUNCATED) { cc->err = err; return; } cc->pkey = br_x509_decoder_get_pkey(&cc->decoder); br_sha512_out(&cc->sha512, &cc->hash); } static unsigned xt_end_chain(const br_x509_class **ctx) { struct x509_tofu_context *cc = (struct x509_tofu_context *)(void *)ctx; if (cc->err != 0) { return (unsigned)cc->err; } if (!cc->pkey) { return BR_ERR_X509_EMPTY_CHAIN; } char fingerprint[512 / 8 * 3]; for (size_t i = 0; i < sizeof(cc->hash); ++i) { snprintf(&fingerprint[i * 3], 4, "%02X%s", cc->hash[i], i + 1 == sizeof(cc->hash) ? "" : ":"); } enum tofu_error error = TOFU_UNTRUSTED_CERT; struct known_host *host = cc->store->known_hosts; while (host) { if (strcmp(host->host, cc->server_name) != 0) { goto next; } if (strcmp(host->fingerprint, fingerprint) == 0) { // Valid match in known hosts return 0; } error = TOFU_FINGERPRINT_MISMATCH; break; next: host = host->next; } switch (cc->store->callback(error, fingerprint, host, cc->store->cb_data)) { case TOFU_ASK: assert(0); // Invariant case TOFU_FAIL: return BR_ERR_X509_NOT_TRUSTED; case TOFU_TRUST_ONCE: // No further action necessary return 0; case TOFU_TRUST_ALWAYS:; FILE *f = fopen(cc->store->known_hosts_path, "a"); if (!f) { fprintf(stderr, "Error opening %s for writing: %s\n", cc->store->known_hosts_path, strerror(errno)); break; }; fprintf(f, "%s %s %s\n", cc->server_name, "SHA-512", fingerprint); fclose(f); host = calloc(1, sizeof(struct known_host)); host->host = strdup(cc->server_name); host->fingerprint = strdup(fingerprint); host->lineno = ++cc->store->lineno; host->next = cc->store->known_hosts; cc->store->known_hosts = host; return 0; } assert(0); // Unreachable } static const br_x509_pkey * xt_get_pkey(const br_x509_class *const *ctx, unsigned *usages) { struct x509_tofu_context *cc = (struct x509_tofu_context *)(void *)ctx; if (cc->err != 0) { return NULL; } if (usages) { // XXX: BearSSL doesn't pull the usages out of the X.509 for us *usages = BR_KEYTYPE_KEYX | BR_KEYTYPE_SIGN; } return cc->pkey; } const br_x509_class xt_vtable = { sizeof(struct x509_tofu_context), xt_start_chain, xt_start_cert, xt_append, xt_end_cert, xt_end_chain, xt_get_pkey, }; static void x509_init_tofu(struct x509_tofu_context *ctx, struct gemini_tofu *store) { ctx->vtable = &xt_vtable; ctx->store = store; } void gemini_tofu_init(struct gemini_tofu *tofu, tofu_callback_t *cb, void *cb_data) { const struct pathspec paths[] = { {.var = "GMNIDATA", .path = "/%s"}, {.var = "XDG_DATA_HOME", .path = "/gmni/%s"}, {.var = "HOME", .path = "/.local/share/gmni/%s"} }; char *path_fmt = getpath(paths, sizeof(paths) / sizeof(paths[0])); char dname[PATH_MAX+1]; size_t n = 0; n = snprintf(tofu->known_hosts_path, sizeof(tofu->known_hosts_path), path_fmt, "known_hosts"); free(path_fmt); assert(n < sizeof(tofu->known_hosts_path)); posix_dirname(tofu->known_hosts_path, dname); if (mkdirs(dname, 0755) != 0) { fprintf(stderr, "Error creating directory %s: %s\n", dname, strerror(errno)); return; } tofu->callback = cb; tofu->cb_data = cb_data; tofu->known_hosts = NULL; x509_init_tofu(&tofu->x509_ctx, tofu); br_x509_minimal_context _; // Discarded br_ssl_client_init_full(&tofu->sc, &_, NULL, 0); br_ssl_engine_set_x509(&tofu->sc.eng, &tofu->x509_ctx.vtable); br_ssl_engine_set_buffer(&tofu->sc.eng, &tofu->iobuf, sizeof(tofu->iobuf), 1); FILE *f = fopen(tofu->known_hosts_path, "r"); if (!f) { return; } n = 0; int lineno = 1; char *line = NULL; while (getline(&line, &n, f) != -1) { int ln = strlen(line); if (line[ln-1] == '\n') { line[ln-1] = 0; } struct known_host *host = calloc(1, sizeof(struct known_host)); char *tok = strtok(line, " "); assert(tok); host->host = strdup(tok); tok = strtok(NULL, " "); assert(tok); if (strcmp(tok, "SHA-512") != 0) { free(host->host); free(host); continue; } tok = strtok(NULL, " "); assert(tok); host->fingerprint = strdup(tok); host->lineno = lineno++; host->next = tofu->known_hosts; tofu->known_hosts = host; } free(line); fclose(f); } void gemini_tofu_finish(struct gemini_tofu *tofu) { struct known_host *host = tofu->known_hosts; while (host) { struct known_host *tmp = host; host = host->next; free(tmp->host); free(tmp->fingerprint); free(tmp); } }