fix memory corruption caused by use-after-free
[oweals/ucert.git] / ucert.c
diff --git a/ucert.c b/ucert.c
index 7be2f8f0691ad809f0f8851e3251c6c1a289ef3c..49d39e9fa58c226aad93d1d48694609b86145b48 100644 (file)
--- a/ucert.c
+++ b/ucert.c
@@ -48,6 +48,13 @@ static enum {
 
 static bool quiet;
 
+/*
+ * ucert structure
+ * |               BLOB                    |
+ * |    SIGNATURE    |       PAYLOAD       |
+ * |                 |[ BLOBMSG CONTAINER ]|
+ * |                 |[[T,i,v,e,f,pubkey ]]|
+ */
 enum cert_attr {
        CERT_ATTR_SIGNATURE,
        CERT_ATTR_PAYLOAD,
@@ -93,11 +100,13 @@ static const struct blobmsg_policy cert_payload_policy[CERT_PL_ATTR_MAX] = {
        [CERT_PL_ATTR_KEY_FINGERPRINT] = { .name = "fingerprint", .type = BLOBMSG_TYPE_STRING },
 };
 
+/* list to store certificate chain at runtime */
 struct cert_object {
        struct list_head list;
        struct blob_attr *cert[CERT_ATTR_MAX];
 };
 
+/* write buffer to file */
 static int write_file(const char *filename, void *buf, size_t len, bool append) {
        FILE *f;
        size_t outlen;
@@ -111,6 +120,7 @@ static int write_file(const char *filename, void *buf, size_t len, bool append)
        return (outlen == len);
 }
 
+/* load certfile into list */
 static int cert_load(const char *certfile, struct list_head *chain) {
        FILE *f;
        struct blob_attr *certtb[CERT_ATTR_MAX];
@@ -146,8 +156,15 @@ static int cert_load(const char *certfile, struct list_head *chain) {
                else
                        pos += blob_pad_len(bufpt);
 
+               if (!certtb[CERT_ATTR_SIGNATURE])
+                       /* no signature -> drop */
+                       break;
+
                cobj = calloc(1, sizeof(*cobj));
-               memcpy(cobj->cert, &certtb, sizeof(certtb));
+               cobj->cert[CERT_ATTR_SIGNATURE] = blob_memdup(certtb[CERT_ATTR_SIGNATURE]);
+               if (certtb[CERT_ATTR_PAYLOAD])
+                       cobj->cert[CERT_ATTR_PAYLOAD] = blob_memdup(certtb[CERT_ATTR_PAYLOAD]);
+
                list_add_tail(&cobj->list, chain);
                ret += pret;
                bufpt = blob_next(bufpt);
@@ -157,6 +174,7 @@ static int cert_load(const char *certfile, struct list_head *chain) {
        return (ret <= 0);
 }
 
+/* append signature to certfile */
 static int cert_append(const char *certfile, const char *sigfile) {
        FILE *fs;
        char filebuf[CERT_BUF_LEN];
@@ -181,6 +199,7 @@ static int cert_append(const char *certfile, const char *sigfile) {
        return ret;
 }
 
+/* verify the signature of a single chain element */
 static int cert_verify_blob(struct blob_attr *cert[CERT_ATTR_MAX],
                       const char *pubkeyfile, const char *pubkeydir) {
        int i;
@@ -219,6 +238,7 @@ static int cert_verify_blob(struct blob_attr *cert[CERT_ATTR_MAX],
        return ret;
 }
 
+/* verify cert chain (and message) */
 static int chain_verify(const char *msgfile, const char *pubkeyfile,
                        const char *pubkeydir, struct list_head *chain) {
        struct cert_object *cobj;
@@ -226,6 +246,7 @@ static int chain_verify(const char *msgfile, const char *pubkeyfile,
        struct blob_attr *payloadtb[CERT_PL_ATTR_MAX];
        char tmpdir[] = "/tmp/ucert-XXXXXX";
        char chainedpubkey[256] = {0};
+       char chainedfp[17] = {0};
        char extsigfile[256] = {0};
        int ret = 1;
        int checkmsg = 0;
@@ -295,6 +316,19 @@ static int chain_verify(const char *msgfile, const char *pubkeyfile,
                                   blobmsg_data(payloadtb[CERT_PL_ATTR_PUBKEY]),
                                   blobmsg_data_len(payloadtb[CERT_PL_ATTR_PUBKEY]),
                                   false);
+
+                       if (usign_f_pubkey(chainedfp, chainedpubkey)) {
+                               if (!quiet)
+                                       fprintf(stderr, "cannot get fingerprint for chained key\n");
+                               ret = 2;
+                               goto clean_and_return;
+                       }
+                       if (pubkeydir && _usign_key_is_revoked(chainedfp, pubkeydir)) {
+                               if (!quiet)
+                                       fprintf(stderr, "key %s has been revoked!\n", chainedfp);
+                               ret = 4;
+                               goto clean_and_return;
+                       }
                } else {
                /* blob doesn't have payload, verify message using signature */
                        if (msgfile) {
@@ -324,6 +358,7 @@ clean_and_return:
        return ret | checkmsg;
 }
 
+/* dump single chain element to console */
 static void cert_dump_blob(struct blob_attr *cert[CERT_ATTR_MAX]) {
        int i;
 
@@ -344,6 +379,7 @@ static void cert_dump_blob(struct blob_attr *cert[CERT_ATTR_MAX]) {
        }
 }
 
+/* dump certfile to console */
 static int cert_dump(const char *certfile) {
        struct cert_object *cobj;
        static LIST_HEAD(certchain);
@@ -363,6 +399,7 @@ static int cert_dump(const char *certfile) {
        return 0;
 }
 
+/* issue an auth certificate for pubkey */
 static int cert_issue(const char *certfile, const char *pubkeyfile, const char *seckeyfile) {
        struct blob_buf certbuf;
        struct blob_buf payloadbuf;
@@ -454,11 +491,97 @@ static int cert_issue(const char *certfile, const char *pubkeyfile, const char *
        return 0;
 }
 
-static int cert_process_revoker(const char *certfile) {
-       fprintf(stderr, "not implemented\n");
-       return 1;
+/* process revoker certificate */
+static int cert_process_revoker(const char *certfile, const char *pubkeydir) {
+       static LIST_HEAD(certchain);
+       struct cert_object *cobj;
+       struct blob_attr *containertb[CERT_CT_ATTR_MAX];
+       struct blob_attr *payloadtb[CERT_PL_ATTR_MAX];
+       struct stat st;
+       struct timeval tv;
+       uint64_t validfrom;
+       uint32_t certtype;
+       char *fingerprint;
+       char rfname[512];
+
+       int ret;
+
+       if (cert_load(certfile, &certchain)) {
+               fprintf(stderr, "cannot parse cert\n");
+               return 1;
+       }
+
+       list_for_each_entry(cobj, &certchain, list) {
+               /* blob has payload, verify that using signature */
+               if (!cobj->cert[CERT_ATTR_PAYLOAD])
+                       return 2;
+               ret = cert_verify_blob(cobj->cert, NULL, pubkeydir);
+               if (ret)
+                       return ret;
+
+               blobmsg_parse(cert_cont_policy,
+                             ARRAY_SIZE(cert_cont_policy),
+                             containertb,
+                             blob_data(cobj->cert[CERT_ATTR_PAYLOAD]),
+                             blob_len(cobj->cert[CERT_ATTR_PAYLOAD]));
+               if (!containertb[CERT_CT_ATTR_PAYLOAD]) {
+                       fprintf(stderr, "no ucert in signed payload\n");
+                       return 2;
+               }
+
+               blobmsg_parse(cert_payload_policy,
+                             ARRAY_SIZE(cert_payload_policy),
+                             payloadtb,
+                             blobmsg_data(containertb[CERT_CT_ATTR_PAYLOAD]),
+                             blobmsg_data_len(containertb[CERT_CT_ATTR_PAYLOAD]));
+
+               if (!payloadtb[CERT_PL_ATTR_CERTTYPE] ||
+                   !payloadtb[CERT_PL_ATTR_VALIDFROMTIME] ||
+                   !payloadtb[CERT_PL_ATTR_KEY_FINGERPRINT]) {
+                       fprintf(stderr, "missing mandatory ucert attributes\n");
+                       return 2;
+               }
+
+               certtype = blobmsg_get_u32(payloadtb[CERT_PL_ATTR_CERTTYPE]);
+               validfrom = blobmsg_get_u64(payloadtb[CERT_PL_ATTR_VALIDFROMTIME]);
+               fingerprint = blobmsg_get_string(payloadtb[CERT_PL_ATTR_KEY_FINGERPRINT]);
+
+               if (certtype != CERTTYPE_REVOKE) {
+                       fprintf(stderr, "wrong certificate type\n");
+                       return 2;
+               }
+
+               gettimeofday(&tv, NULL);
+               if (tv.tv_sec < validfrom) {
+                       return 3;
+               }
+
+               snprintf(rfname, sizeof(rfname)-1, "%s/%s", pubkeydir, fingerprint);
+               /* check if entry in pubkeydir exists */
+               if (stat(rfname, &st) == 0) {
+                       if (_usign_key_is_revoked(fingerprint, pubkeydir)) {
+                               if (!quiet)
+                                       fprintf(stdout, "existing revoker deadlink for key %s\n", fingerprint);
+                               continue;
+                       };
+
+                       /* remove any other entry */
+                       if (unlink(rfname))
+                               return -1;
+               }
+
+               ret = symlink(".revoked.", rfname);
+               if (ret)
+                       return ret;
+
+               if (!quiet)
+                       fprintf(stdout, "created revoker deadlink for key %s\n", fingerprint);
+       };
+
+       return ret;
 }
 
+/* load and verify certfile (and message) */
 static int cert_verify(const char *certfile, const char *pubkeyfile, const char *pubkeydir, const char *msgfile) {
        static LIST_HEAD(certchain);
 
@@ -470,16 +593,17 @@ static int cert_verify(const char *certfile, const char *pubkeyfile, const char
        return chain_verify(msgfile, pubkeyfile, pubkeydir, &certchain);
 }
 
+/* output help */
 static int usage(const char *cmd)
 {
        fprintf(stderr,
                "Usage: %s <command> <options>\n"
                "Commands:\n"
                "  -A:                  append signature (needs -c and -x)\n"
-               "  -D:                  dump\n"
+               "  -D:                  dump (needs -c)\n"
                "  -I:                  issue cert and revoker (needs -c and -p and -s)\n"
-               "  -R:                  process revoker certificate (needs -c)\n"
-               "  -V:                  verify (needs -c and -p|-P)\n"
+               "  -R:                  process revoker certificate (needs -c and -P)\n"
+               "  -V:                  verify (needs -c and -p|-P, may have -m)\n"
                "Options:\n"
                "  -c <file>:           certificate file\n"
                "  -m <file>:           message file (verify only)\n"
@@ -493,6 +617,7 @@ static int usage(const char *cmd)
        return 1;
 }
 
+/* parse command line options and call functions */
 int main(int argc, char *argv[]) {
        int ch;
        const char *msgfile = NULL;
@@ -506,39 +631,63 @@ int main(int argc, char *argv[]) {
        while ((ch = getopt(argc, argv, "ADIRVc:m:p:P:qs:x:")) != -1) {
                switch (ch) {
                case 'A':
+                       if (cmd != CMD_NONE)
+                               return usage(argv[0]);
                        cmd = CMD_APPEND;
                        break;
                case 'D':
+                       if (cmd != CMD_NONE)
+                               return usage(argv[0]);
                        cmd = CMD_DUMP;
                        break;
                case 'I':
+                       if (cmd != CMD_NONE)
+                               return usage(argv[0]);
                        cmd = CMD_ISSUE;
                        break;
                case 'R':
+                       if (cmd != CMD_NONE)
+                               return usage(argv[0]);
                        cmd = CMD_REVOKE;
                        break;
                case 'V':
+                       if (cmd != CMD_NONE)
+                               return usage(argv[0]);
                        cmd = CMD_VERIFY;
                        break;
                case 'c':
+                       if (certfile || cmd == CMD_NONE)
+                               return usage(argv[0]);
                        certfile = optarg;
                        break;
                case 'm':
+                       if (msgfile || cmd != CMD_VERIFY)
+                               return usage(argv[0]);
                        msgfile = optarg;
                        break;
                case 'p':
+                       if (pubkeyfile || (cmd != CMD_VERIFY && cmd != CMD_ISSUE) || cmd == CMD_NONE)
+                               return usage(argv[0]);
                        pubkeyfile = optarg;
                        break;
                case 'P':
+                       if (pubkeydir || (cmd != CMD_VERIFY && cmd != CMD_REVOKE) || cmd == CMD_NONE)
+                               return usage(argv[0]);
                        pubkeydir = optarg;
                        break;
                case 'q':
+                       if (quiet || cmd == CMD_NONE)
+                               return usage(argv[0]);
                        quiet = true;
                        break;
                case 's':
+                       if (seckeyfile || cmd != CMD_ISSUE || cmd == CMD_NONE)
+                               return usage(argv[0]);
                        seckeyfile = optarg;
                        break;
                case 'x':
+                       if (sigfile || cmd != CMD_APPEND || cmd == CMD_NONE)
+                               return usage(argv[0]);
                        sigfile = optarg;
                        break;
                default:
@@ -563,8 +712,8 @@ int main(int argc, char *argv[]) {
                else
                        return usage(argv[0]);
        case CMD_REVOKE:
-               if (certfile)
-                       return cert_process_revoker(certfile);
+               if (certfile && pubkeydir)
+                       return cert_process_revoker(certfile, pubkeydir);
                else
                        return usage(argv[0]);
        case CMD_VERIFY: