Add simple ASN.1 utils for DSA signature DER.

Adds simple utility functions to allow both the default and fips providers to
encode and decode DSA-Sig-Value and ECDSA-Sig-Value (DSA_SIG and ECDSA_SIG
structures) to/from ASN.1 DER without requiring those providers to have a
dependency on the asn1 module.

Reviewed-by: Paul Dale <paul.dale@oracle.com>
Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/9111)

8 files changed, 665 insertions, 16 deletions

diff --git a/crypto/asn1_dsa.c b/crypto/asn1_dsa.c
new file mode 100644
index 0000000000..bb7f87a80c
--- /dev/null
+++ b/crypto/asn1_dsa.c
@@ -0,0 +1,321 @@
+/*
+ * Copyright 2019 The OpenSSL Project Authors. All Rights Reserved.
+ *
+ * Licensed under the Apache License 2.0 (the "License").  You may not use
+ * this file except in compliance with the License.  You can obtain a copy
+ * in the file LICENSE in the source distribution or at
+ * https://www.openssl.org/source/license.html
+ */
+
+/*
+ * A simple ASN.1 DER encoder/decoder for DSA-Sig-Value and ECDSA-Sig-Value.
+ *
+ * DSA-Sig-Value ::= SEQUENCE {
+ *  r  INTEGER,
+ *  s  INTEGER
+ * }
+ *
+ * ECDSA-Sig-Value ::= SEQUENCE {
+ *  r  INTEGER,
+ *  s  INTEGER
+ * }
+ */
+
+#include <openssl/crypto.h>
+#include <openssl/bn.h>
+#include "internal/asn1_dsa.h"
+
+#define ID_SEQUENCE 0x30
+#define ID_INTEGER 0x02
+
+/*
+ * Outputs the encoding of the length octets for a DER value with a content
+ * length of cont_len bytes to *ppout and, if successful, increments *ppout
+ * past the data just written.
+ *
+ * The maximum supported content length is 65535 (0xffff) bytes.
+ * The maximum returned length in bytes of the encoded output is 3.
+ *
+ * If ppout is NULL then the output size is calculated and returned but no
+ * output is produced.
+ * If ppout is not NULL then *ppout must not be NULL.
+ *
+ * An attempt to produce more than len bytes results in an error.
+ * Returns the number of bytes of output produced (or that would be produced)
+ * or 0 if an error occurs.
+ */
+size_t encode_der_length(size_t cont_len, unsigned char **ppout, size_t len)
+{
+    size_t encoded_len;
+
+    if (cont_len <= 0x7f) {
+        encoded_len = 1;
+    } else if (cont_len <= 0xff) {
+        encoded_len = 2;
+    } else if (cont_len <= 0xffff) {
+        encoded_len = 3;
+    } else {
+        /* Too large for supported length encodings */
+        return 0;
+    }
+    if (encoded_len > len)
+        return 0;
+    if (ppout != NULL) {
+        unsigned char *out = *ppout;
+        switch (encoded_len) {
+        case 2:
+            *out++ = 0x81;
+            break;
+        case 3:
+            *out++ = 0x82;
+            *out++ = (unsigned char)(cont_len >> 8);
+            break;
+        }
+        *out++ = (unsigned char)cont_len;
+        *ppout = out;
+    }
+    return encoded_len;
+}
+
+/*
+ * Outputs the DER encoding of a positive ASN.1 INTEGER to *ppout and, if
+ * successful, increments *ppout past the data just written.
+ *
+ * If n is negative then an error results.
+ * If ppout is NULL then the output size is calculated and returned but no
+ * output is produced.
+ * If ppout is not NULL then *ppout must not be NULL.
+ *
+ * An attempt to produce more than len bytes results in an error.
+ * Returns the number of bytes of output produced (or that would be produced)
+ * or 0 if an error occurs.
+ */
+size_t encode_der_integer(const BIGNUM *n, unsigned char **ppout, size_t len)
+{
+    unsigned char *out = NULL;
+    unsigned char **pp = NULL;
+    size_t produced;
+    size_t c;
+    size_t cont_len;
+
+    if (len < 1 || BN_is_negative(n))
+        return 0;
+
+    /*
+     * Calculate the ASN.1 INTEGER DER content length for n.
+     * This is the number of whole bytes required to represent n (i.e. rounded
+     * down), plus one.
+     * If n is zero then the content is a single zero byte (length = 1).
+     * If the number of bits of n is a multiple of 8 then an extra zero padding
+     * byte is included to ensure that the value is still treated as positive
+     * in the INTEGER two's complement representation.
+     */
+    cont_len = BN_num_bits(n) / 8 + 1;
+
+    if (ppout != NULL) {
+        out = *ppout;
+        pp = &out;
+        *out++ = ID_INTEGER;
+    }
+    produced = 1;
+    if ((c = encode_der_length(cont_len, pp, len - produced)) == 0)
+        return 0;
+    produced += c;
+    if (cont_len > len - produced)
+        return 0;
+    if (pp != NULL) {
+        if (BN_bn2binpad(n, out, (int)cont_len) != (int)cont_len)
+            return 0;
+        out += cont_len;
+        *ppout = out;
+    }
+    produced += cont_len;
+    return produced;
+}
+
+/*
+ * Outputs the DER encoding of a DSA-Sig-Value or ECDSA-Sig-Value to *ppout
+ * and increments *ppout past the data just written.
+ *
+ * If ppout is NULL then the output size is calculated and returned but no
+ * output is produced.
+ * If ppout is not NULL then *ppout must not be NULL.
+ *
+ * An attempt to produce more than len bytes results in an error.
+ * Returns the number of bytes of output produced (or that would be produced)
+ * or 0 if an error occurs.
+ */
+size_t encode_der_dsa_sig(const BIGNUM *r, const BIGNUM *s,
+                          unsigned char **ppout, size_t len)
+{
+    unsigned char *out = NULL;
+    unsigned char **pp = NULL;
+    size_t produced;
+    size_t c;
+    size_t r_der_len;
+    size_t s_der_len;
+    size_t cont_len;
+
+    if (len < 1
+            || (r_der_len = encode_der_integer(r, NULL, SIZE_MAX)) == 0
+            || (s_der_len = encode_der_integer(s, NULL, SIZE_MAX)) == 0)
+        return 0;
+
+    cont_len = r_der_len + s_der_len;
+
+    if (ppout != NULL) {
+        out = *ppout;
+        pp = &out;
+        *out++ = ID_SEQUENCE;
+    }
+    produced = 1;
+    if ((c = encode_der_length(cont_len, pp, len - produced)) == 0)
+        return 0;
+    produced += c;
+    if ((c = encode_der_integer(r, pp, len - produced)) == 0)
+        return 0;
+    produced += c;
+    if ((c = encode_der_integer(s, pp, len - produced)) == 0)
+        return 0;
+    produced += c;
+    if (pp != NULL)
+        *ppout = out;
+    return produced;
+}
+
+/*
+ * Decodes the DER length octets at *ppin, stores the decoded length to
+ * *pcont_len and, if successful, increments *ppin past the data that was
+ * consumed.
+ *
+ * pcont_len, ppin and *ppin must not be NULL.
+ *
+ * An attempt to consume more than len bytes results in an error.
+ * Returns the number of bytes of input consumed or 0 if an error occurs.
+ */
+size_t decode_der_length(size_t *pcont_len, const unsigned char **ppin,
+                         size_t len)
+{
+    const unsigned char *in = *ppin;
+    size_t consumed;
+    size_t n;
+
+    if (len < 1)
+        return 0;
+    n = *in++;
+    consumed = 1;
+    if (n > 0x7f) {
+        if (n == 0x81 && len - consumed >= 1) {
+            n = *in++;
+            if (n <= 0x7f)
+                return 0; /* Not DER. */
+            ++consumed;
+        } else if (n == 0x82 && len - consumed >= 2) {
+            n = *in++ << 8;
+            n |= *in++;
+            if (n <= 0xff)
+                return 0; /* Not DER. */
+            consumed += 2;
+        } else {
+            return 0; /* Too large, invalid, or not DER. */
+        }
+    }
+    *pcont_len = n;
+    *ppin = in;
+    return consumed;
+}
+
+/*
+ * Decodes a single ASN.1 INTEGER value from *ppin, which must be DER encoded,
+ * updates n with the decoded value, and, if successful, increments *ppin past
+ * the data that was consumed.
+ *
+ * The BIGNUM, n, must have already been allocated by calling BN_new().
+ * ppin and *ppin must not be NULL.
+ *
+ * An attempt to consume more than len bytes results in an error.
+ * Returns the number of bytes of input consumed or 0 if an error occurs.
+ *
+ * If the buffer is supposed to only contain a single INTEGER value with no
+ * trailing garbage then it is up to the caller to verify that all bytes
+ * were consumed.
+ */
+size_t decode_der_integer(BIGNUM *n, const unsigned char **ppin, size_t len)
+{
+    const unsigned char *in = *ppin;
+    size_t consumed;
+    size_t c;
+    size_t cont_len;
+
+    if (len < 1 || n == NULL || *in++ != ID_INTEGER)
+        return 0;
+    consumed = 1;
+    if ((c = decode_der_length(&cont_len, &in, len - consumed)) == 0)
+        return 0;
+    consumed += c;
+    /* Check for a positive INTEGER with valid content encoding and decode. */
+    if (cont_len > len - consumed || cont_len < 1 || (in[0] & 0x80) != 0
+            || (cont_len >= 2 && in[0] == 0 && (in[1] & 0x80) == 0)
+            || BN_bin2bn(in, (int)cont_len, n) == NULL)
+        return 0;
+    in += cont_len;
+    consumed += cont_len;
+    *ppin = in;
+    return consumed;
+}
+
+static size_t decode_dsa_sig_content(BIGNUM *r, BIGNUM *s,
+                                     const unsigned char **ppin, size_t len)
+{
+    const unsigned char *in = *ppin;
+    size_t consumed = 0;
+    size_t c;
+
+    if ((c = decode_der_integer(r, &in, len - consumed)) == 0)
+        return 0;
+    consumed += c;
+    if ((c = decode_der_integer(s, &in, len - consumed)) == 0)
+        return 0;
+    consumed += c;
+    *ppin = in;
+    return consumed;
+}
+
+/*
+ * Decodes a single DSA-Sig-Value or ECDSA-Sig-Value from *ppin, which must be
+ * DER encoded, updates r and s with the decoded values, and increments *ppin
+ * past the data that was consumed.
+ *
+ * The BIGNUMs, r and s, must have already been allocated by calls to BN_new().
+ * ppin and *ppin must not be NULL.
+ *
+ * An attempt to consume more than len bytes results in an error.
+ * Returns the number of bytes of input consumed or 0 if an error occurs.
+ *
+ * If the buffer is supposed to only contain a single [EC]DSA-Sig-Value with no
+ * trailing garbage then it is up to the caller to verify that all bytes
+ * were consumed.
+ */
+size_t decode_der_dsa_sig(BIGNUM *r, BIGNUM *s, const unsigned char **ppin,
+                          size_t len)
+{
+    const unsigned char *in = *ppin;
+    size_t consumed;
+    size_t c;
+    size_t cont_len;
+
+    if (len < 1 || *in++ != ID_SEQUENCE)
+        return 0;
+    consumed = 1;
+    if ((c = decode_der_length(&cont_len, &in, len - consumed)) == 0)
+        return 0;
+    consumed += c;
+    if (cont_len > len - consumed
+            || (c = decode_dsa_sig_content(r, s, &in, cont_len)) == 0
+            || c != cont_len)
+        return 0;
+    consumed += c;
+    *ppin = in;
+    return consumed;
+}
+
diff --git a/crypto/build.info b/crypto/build.info
index fccca08153..b82978e1c7 100644
--- a/crypto/build.info
+++ b/crypto/build.info
@@ -75,11 +75,10 @@ SOURCE[../libcrypto]=$UTIL_COMMON \
         mem.c mem_sec.c mem_str.c mem_dbg.c \
         cversion.c info.c cpt_err.c ebcdic.c uid.c o_time.c o_dir.c \
         o_fopen.c getenv.c o_init.c o_fips.c init.c trace.c provider.c \
-        $UPLINKSRC
+        asn1_dsa.c $UPLINKSRC
 DEFINE[../libcrypto]=$UTIL_DEFINE $UPLINKDEF
 SOURCE[../providers/fips]=$UTIL_COMMON
 DEFINE[../providers/fips]=$UTIL_DEFINE
-        
 
 
 DEPEND[cversion.o]=buildinf.h
diff --git a/crypto/dsa/dsa_asn1.c b/crypto/dsa/dsa_asn1.c
index acf80c651a..1c7e8c86bd 100644
--- a/crypto/dsa/dsa_asn1.c
+++ b/crypto/dsa/dsa_asn1.c
@@ -13,13 +13,7 @@
 #include <openssl/asn1.h>
 #include <openssl/asn1t.h>
 #include <openssl/rand.h>
-
-ASN1_SEQUENCE(DSA_SIG) = {
-        ASN1_SIMPLE(DSA_SIG, r, CBIGNUM),
-        ASN1_SIMPLE(DSA_SIG, s, CBIGNUM)
-} static_ASN1_SEQUENCE_END(DSA_SIG)
-
-IMPLEMENT_ASN1_ENCODE_FUNCTIONS_fname(DSA_SIG, DSA_SIG, DSA_SIG)
+#include "internal/asn1_dsa.h"
 
 DSA_SIG *DSA_SIG_new(void)
 {
@@ -38,6 +32,62 @@ void DSA_SIG_free(DSA_SIG *sig)
     OPENSSL_free(sig);
 }
 
+DSA_SIG *d2i_DSA_SIG(DSA_SIG **psig, const unsigned char **ppin, long len)
+{
+    DSA_SIG *sig;
+
+    if (len < 0)
+        return NULL;
+    if (psig != NULL && *psig != NULL) {
+        sig = *psig;
+    } else {
+        sig = DSA_SIG_new();
+        if (sig == NULL)
+            return NULL;
+    }
+    if (sig->r == NULL)
+        sig->r = BN_new();
+    if (sig->s == NULL)
+        sig->s = BN_new();
+    if (decode_der_dsa_sig(sig->r, sig->s, ppin, (size_t)len) == 0) {
+        if (psig == NULL || *psig == NULL)
+            DSA_SIG_free(sig);
+        return NULL;
+    }
+    if (psig != NULL && *psig == NULL)
+        *psig = sig;
+    return sig;
+}
+
+int i2d_DSA_SIG(const DSA_SIG *sig, unsigned char **ppout)
+{
+    unsigned char *buf = NULL;
+    unsigned char *tmp;
+    unsigned char **pp = NULL;
+    size_t len;
+    size_t encoded_len;
+
+    if (ppout != NULL && *ppout == NULL) {
+        if ((len = encode_der_dsa_sig(sig->r, sig->s, NULL, SIZE_MAX)) == 0)
+            return -1;
+        buf = OPENSSL_malloc(len);
+        if (buf == NULL)
+            return -1;
+        tmp = buf;
+        pp = &tmp;
+    } else {
+        len = SIZE_MAX;
+        pp = ppout;
+    }
+    if ((encoded_len = encode_der_dsa_sig(sig->r, sig->s, pp, len)) == 0) {
+        OPENSSL_free(buf);
+        return -1;
+    }
+    if (buf != NULL)
+        *ppout = buf;
+    return (int)encoded_len;
+}
+
 void DSA_SIG_get0(const DSA_SIG *sig, const BIGNUM **pr, const BIGNUM **ps)
 {
     if (pr != NULL)
diff --git a/crypto/ec/ec_asn1.c b/crypto/ec/ec_asn1.c
index 35ff9488f3..57de90d367 100644
--- a/crypto/ec/ec_asn1.c
+++ b/crypto/ec/ec_asn1.c
@@ -13,6 +13,7 @@
 #include <openssl/asn1t.h>
 #include <openssl/objects.h>
 #include "internal/nelem.h"
+#include "internal/asn1_dsa.h"
 
 int EC_GROUP_get_basis_type(const EC_GROUP *group)
 {
@@ -1137,14 +1138,8 @@ int i2o_ECPublicKey(const EC_KEY *a, unsigned char **out)
     return buf_len;
 }
 
-ASN1_SEQUENCE(ECDSA_SIG) = {
-        ASN1_SIMPLE(ECDSA_SIG, r, CBIGNUM),
-        ASN1_SIMPLE(ECDSA_SIG, s, CBIGNUM)
-} static_ASN1_SEQUENCE_END(ECDSA_SIG)
-
 DECLARE_ASN1_FUNCTIONS(ECDSA_SIG)
 DECLARE_ASN1_ENCODE_FUNCTIONS_name(ECDSA_SIG, ECDSA_SIG)
-IMPLEMENT_ASN1_ENCODE_FUNCTIONS_fname(ECDSA_SIG, ECDSA_SIG, ECDSA_SIG)
 
 ECDSA_SIG *ECDSA_SIG_new(void)
 {
@@ -1163,6 +1158,62 @@ void ECDSA_SIG_free(ECDSA_SIG *sig)
     OPENSSL_free(sig);
 }
 
+ECDSA_SIG *d2i_ECDSA_SIG(ECDSA_SIG **psig, const unsigned char **ppin, long len)
+{
+    ECDSA_SIG *sig;
+
+    if (len < 0)
+        return NULL;
+    if (psig != NULL && *psig != NULL) {
+        sig = *psig;
+    } else {
+        sig = ECDSA_SIG_new();
+        if (sig == NULL)
+            return NULL;
+    }
+    if (sig->r == NULL)
+        sig->r = BN_new();
+    if (sig->s == NULL)
+        sig->s = BN_new();
+    if (decode_der_dsa_sig(sig->r, sig->s, ppin, (size_t)len) == 0) {
+        if (psig == NULL || *psig == NULL)
+            ECDSA_SIG_free(sig);
+        return NULL;
+    }
+    if (psig != NULL && *psig == NULL)
+        *psig = sig;
+    return sig;
+}
+
+int i2d_ECDSA_SIG(const ECDSA_SIG *sig, unsigned char **ppout)
+{
+    unsigned char *buf = NULL;
+    unsigned char *tmp;
+    unsigned char **pp = NULL;
+    size_t len;
+    size_t encoded_len;
+
+    if (ppout != NULL && *ppout == NULL) {
+        if ((len = encode_der_dsa_sig(sig->r, sig->s, NULL, SIZE_MAX)) == 0)
+            return -1;
+        buf = OPENSSL_malloc(len);
+        if (buf == NULL)
+            return -1;
+        tmp = buf;
+        pp = &tmp;
+    } else {
+        len = SIZE_MAX;
+        pp = ppout;
+    }
+    if ((encoded_len = encode_der_dsa_sig(sig->r, sig->s, pp, len)) == 0) {
+        OPENSSL_free(buf);
+        return -1;
+    }
+    if (buf != NULL)
+        *ppout = buf;
+    return (int)encoded_len;
+}
+
 void ECDSA_SIG_get0(const ECDSA_SIG *sig, const BIGNUM **pr, const BIGNUM **ps)
 {
     if (pr != NULL)
diff --git a/crypto/include/internal/asn1_dsa.h b/crypto/include/internal/asn1_dsa.h
new file mode 100644
index 0000000000..7c720a1733
--- /dev/null
+++ b/crypto/include/internal/asn1_dsa.h
@@ -0,0 +1,23 @@
+/*
+ * Copyright 2019 The OpenSSL Project Authors. All Rights Reserved.
+ *
+ * Licensed under the Apache License 2.0 (the "License").  You may not use
+ * this file except in compliance with the License.  You can obtain a copy
+ * in the file LICENSE in the source distribution or at
+ * https://www.openssl.org/source/license.html
+ */
+
+#ifndef HEADER_ASN1_DSA_H
+# define HEADER_ASN1_DSA_H
+
+size_t encode_der_length(size_t cont_len, unsigned char **ppout, size_t len);
+size_t encode_der_integer(const BIGNUM *n, unsigned char **ppout, size_t len);
+size_t encode_der_dsa_sig(const BIGNUM *r, const BIGNUM *s,
+                          unsigned char **ppout, size_t len);
+size_t decode_der_length(size_t *pcont_len, const unsigned char **ppin,
+                         size_t len);
+size_t decode_der_integer(BIGNUM *n, const unsigned char **ppin, size_t len);
+size_t decode_der_dsa_sig(BIGNUM *r, BIGNUM *s, const unsigned char **ppin,
+                          size_t len);
+
+#endif
diff --git a/test/asn1_dsa_internal_test.c b/test/asn1_dsa_internal_test.c
new file mode 100644
index 0000000000..a62f5e4cd4
--- /dev/null
+++ b/test/asn1_dsa_internal_test.c
@@ -0,0 +1,184 @@
+/*
+ * Copyright 2019 The OpenSSL Project Authors. All Rights Reserved.
+ *
+ * Licensed under the Apache License 2.0 (the "License").  You may not use
+ * this file except in compliance with the License.  You can obtain a copy
+ * in the file LICENSE in the source distribution or at
+ * https://www.openssl.org/source/license.html
+ */
+
+#include <stdio.h>
+#include <string.h>
+
+#include <openssl/bn.h>
+#include "internal/asn1_dsa.h"
+#include "testutil.h"
+
+static unsigned char t_dsa_sig[] = {
+    0x30, 0x06,                  /* SEQUENCE tag + length */
+    0x02, 0x01, 0x01,            /* INTEGER tag + length + content */
+    0x02, 0x01, 0x02             /* INTEGER tag + length + content */
+};
+
+static unsigned char t_dsa_sig_extra[] = {
+    0x30, 0x06,                  /* SEQUENCE tag + length */
+    0x02, 0x01, 0x01,            /* INTEGER tag + length + content */
+    0x02, 0x01, 0x02,            /* INTEGER tag + length + content */
+    0x05, 0x00                   /* NULL tag + length */
+};
+
+static unsigned char t_dsa_sig_msb[] = {
+    0x30, 0x08,                  /* SEQUENCE tag + length */
+    0x02, 0x02, 0x00, 0x81,      /* INTEGER tag + length + content */
+    0x02, 0x02, 0x00, 0x82       /* INTEGER tag + length + content */
+};
+
+static unsigned char t_dsa_sig_two[] = {
+    0x30, 0x08,                  /* SEQUENCE tag + length */
+    0x02, 0x02, 0x01, 0x00,      /* INTEGER tag + length + content */
+    0x02, 0x02, 0x02, 0x00       /* INTEGER tag + length + content */
+};
+
+/*
+ * Badly coded ASN.1 INTEGER zero wrapped in a sequence along with another
+ * (valid) INTEGER.
+ */
+static unsigned char t_invalid_int_zero[] = {
+    0x30, 0x05,                  /* SEQUENCE tag + length */
+    0x02, 0x00,                  /* INTEGER tag + length */
+    0x02, 0x01, 0x2a             /* INTEGER tag + length */
+};
+
+/*
+ * Badly coded ASN.1 INTEGER (with leading zeros) wrapped in a sequence along
+ * with another (valid) INTEGER.
+ */
+static unsigned char t_invalid_int[] = {
+    0x30, 0x07,                  /* SEQUENCE tag + length */
+    0x02, 0x02, 0x00, 0x7f,      /* INTEGER tag + length */
+    0x02, 0x01, 0x2a             /* INTEGER tag + length */
+};
+
+/*
+ * Negative ASN.1 INTEGER wrapped in a sequence along with another
+ * (valid) INTEGER.
+ */
+static unsigned char t_neg_int[] = {
+    0x30, 0x06,                  /* SEQUENCE tag + length */
+    0x02, 0x01, 0xaa,            /* INTEGER tag + length */
+    0x02, 0x01, 0x2a             /* INTEGER tag + length */
+};
+
+static unsigned char t_trunc_der[] = {
+    0x30, 0x08,                  /* SEQUENCE tag + length */
+    0x02, 0x02, 0x00, 0x81,      /* INTEGER tag + length */
+    0x02, 0x02, 0x00             /* INTEGER tag + length */
+};
+
+static unsigned char t_trunc_seq[] = {
+    0x30, 0x07,                  /* SEQUENCE tag + length */
+    0x02, 0x02, 0x00, 0x81,      /* INTEGER tag + length */
+    0x02, 0x02, 0x00, 0x82       /* INTEGER tag + length */
+};
+
+static int test_decode(void)
+{
+    int rv = 0;
+    BIGNUM *r;
+    BIGNUM *s;
+    const unsigned char *pder;
+
+    r = BN_new();
+    s = BN_new();
+
+    /* Positive tests */
+    pder = t_dsa_sig;
+    if (decode_der_dsa_sig(r, s, &pder, sizeof(t_dsa_sig)) == 0
+            || !TEST_ptr_eq(pder, (t_dsa_sig + sizeof(t_dsa_sig)))
+            || !TEST_BN_eq_word(r, 1) || !TEST_BN_eq_word(s, 2)) {
+        TEST_info("asn1_dsa test_decode: t_dsa_sig failed");
+        goto fail;
+    }
+
+    BN_clear(r);
+    BN_clear(s);
+    pder = t_dsa_sig_extra;
+    if (decode_der_dsa_sig(r, s, &pder, sizeof(t_dsa_sig_extra)) == 0
+            || !TEST_ptr_eq(pder,
+                            (t_dsa_sig_extra + sizeof(t_dsa_sig_extra) - 2))
+            || !TEST_BN_eq_word(r, 1) || !TEST_BN_eq_word(s, 2)) {
+        TEST_info("asn1_dsa test_decode: t_dsa_sig_extra failed");
+        goto fail;
+    }
+
+    BN_clear(r);
+    BN_clear(s);
+    pder = t_dsa_sig_msb;
+    if (decode_der_dsa_sig(r, s, &pder, sizeof(t_dsa_sig_msb)) == 0
+            || !TEST_ptr_eq(pder, (t_dsa_sig_msb + sizeof(t_dsa_sig_msb)))
+            || !TEST_BN_eq_word(r, 0x81) || !TEST_BN_eq_word(s, 0x82)) {
+        TEST_info("asn1_dsa test_decode: t_dsa_sig_msb failed");
+        goto fail;
+    }
+
+    BN_clear(r);
+    BN_clear(s);
+    pder = t_dsa_sig_two;
+    if (decode_der_dsa_sig(r, s, &pder, sizeof(t_dsa_sig_two)) == 0
+            || !TEST_ptr_eq(pder, (t_dsa_sig_two + sizeof(t_dsa_sig_two)))
+            || !TEST_BN_eq_word(r, 0x100) || !TEST_BN_eq_word(s, 0x200)) {
+        TEST_info("asn1_dsa test_decode: t_dsa_sig_two failed");
+        goto fail;
+    }
+
+    /* Negative tests */
+    pder = t_invalid_int_zero;
+    if (decode_der_dsa_sig(r, s, &pder, sizeof(t_invalid_int_zero)) != 0) {
+        TEST_info("asn1_dsa test_decode: Expected t_invalid_int_zero to fail");
+        goto fail;
+    }
+
+    BN_clear(r);
+    BN_clear(s);
+    pder = t_invalid_int;
+    if (decode_der_dsa_sig(r, s, &pder, sizeof(t_invalid_int)) != 0) {
+        TEST_info("asn1_dsa test_decode: Expected t_invalid_int to fail");
+        goto fail;
+    }
+
+    BN_clear(r);
+    BN_clear(s);
+    pder = t_neg_int;
+    if (decode_der_dsa_sig(r, s, &pder, sizeof(t_neg_int)) != 0) {
+        TEST_info("asn1_dsa test_decode: Expected t_neg_int to fail");
+        goto fail;
+    }
+
+    BN_clear(r);
+    BN_clear(s);
+    pder = t_trunc_der;
+    if (decode_der_dsa_sig(r, s, &pder, sizeof(t_trunc_der)) != 0) {
+        TEST_info("asn1_dsa test_decode: Expected fail t_trunc_der");
+        goto fail;
+    }
+
+    BN_clear(r);
+    BN_clear(s);
+    pder = t_trunc_seq;
+    if (decode_der_dsa_sig(r, s, &pder, sizeof(t_trunc_seq)) != 0) {
+        TEST_info("asn1_dsa test_decode: Expected fail t_trunc_seq");
+        goto fail;
+    }
+
+    rv = 1;
+fail:
+    BN_free(r);
+    BN_free(s);
+    return rv;
+}
+
+int setup_tests(void)
+{
+    ADD_TEST(test_decode);
+    return 1;
+}
diff --git a/test/build.info b/test/build.info
index f5b802da4d..a61c0ce2be 100644
--- a/test/build.info
+++ b/test/build.info
@@ -469,7 +469,8 @@ IF[{- !$disabled{tests} -}]
     PROGRAMS{noinst}=asn1_internal_test modes_internal_test x509_internal_test \
                      tls13encryptiontest wpackettest ctype_internal_test \
                      rdrand_sanitytest property_test \
-                     rsa_sp800_56b_test bn_internal_test
+                     rsa_sp800_56b_test bn_internal_test \
+                     asn1_dsa_internal_test
 
     IF[{- !$disabled{poly1305} -}]
       PROGRAMS{noinst}=poly1305_internal_test
@@ -561,6 +562,10 @@ IF[{- !$disabled{tests} -}]
     SOURCE[bn_internal_test]=bn_internal_test.c
     INCLUDE[bn_internal_test]=.. ../include ../crypto/include ../crypto/bn ../apps/include
     DEPEND[bn_internal_test]=../libcrypto.a libtestutil.a
+
+    SOURCE[asn1_dsa_internal_test]=asn1_dsa_internal_test.c
+    INCLUDE[asn1_dsa_internal_test]=.. ../include ../apps/include ../crypto/include
+    DEPEND[asn1_dsa_internal_test]=../libcrypto.a libtestutil.a
   ENDIF
 
   IF[{- !$disabled{mdc2} -}]
diff --git a/test/recipes/03-test_internal_asn1_dsa.t b/test/recipes/03-test_internal_asn1_dsa.t
new file mode 100644
index 0000000000..ecacac73cb
--- /dev/null
+++ b/test/recipes/03-test_internal_asn1_dsa.t
@@ -0,0 +1,16 @@
+#! /usr/bin/env perl
+# Copyright 2019 The OpenSSL Project Authors. All Rights Reserved.
+#
+# Licensed under the Apache License 2.0 (the "License").  You may not use
+# this file except in compliance with the License.  You can obtain a copy
+# in the file LICENSE in the source distribution or at
+# https://www.openssl.org/source/license.html
+
+use strict;
+use OpenSSL::Test;              # get 'plan'
+use OpenSSL::Test::Simple;
+use OpenSSL::Test::Utils;
+
+setup("test_internal_asn1_dsa");
+
+simple_test("test_internal_asn1_dsa", "asn1_dsa_internal_test");